Building with Hardwood by DETAIL

Building with

Hardwood Konrad Merz Anne Niemann Stefan Torno

∂ Practice

Authors Konrad Merz Anne Niemann Stefan Torno With contributions from: Hermann Kaufmann (Preface) Markus Lechner (High-Performance Materials with Potential for the Future) Stefan Winter (High-Performance Materials with Potential for the Future)

Editorial Services Editing, layout and copy-editing: Steffi Lenzen (project management and Example Builds texts); Claudia Fuchs (Example Builds), Jana Rackwitz (theory chapters); Sandra Leitte (Proofreading German edition), Charlotte Petereit (Editorial Assistant) Cover design following a concept by Kai Meyer, Munich Drawings: Rana Aminian, Ralph Donhauser, Sandra Gunnermann, Martin Hämmel, Ursula Sparakowski Translation into English: Susanne Hauger, New York (US) Copy-editing (English edition): Stefan Widdess, Berlin (DE) Proofreading (English edition): Meriel Clemett, Bromborough (GB)

This work is subject to copyright. The rights arising from this copyright are reserved, especially the rights of translation, reprinting, presentation, extraction of illustrations and tables, broadcasting, microfilming or reproduction by any other means, and storage in data-processing systems, either in whole or in part. Reproduction of this work, or of parts thereof, even on an individual basis, is permitted only under the provisions of the copyright law in its current version. This is always subject to remuneration. Infringements are subject to the legal sanctions of copyright law. This reference book takes into consideration the terms valid at the time of the editorial deadline and the state of the art at this point in time. Legal claims cannot be derived from the content of this book. We assume no liability for any errors or omissions.

Typesetting & production: Simone Soesters Printed by: Grafisches Centrum Cuno GmbH & Co. KG, Calbe 1st edition, 2021 Paper: Peydur lissé (cover), Profibulk (content)

A German edition of this book is also available (ISBN 978-3-95553-504-9). Bibliographical information of the German National Library The German National Library lists this publication in the German National Bibliography; detailed bibliographical data is available on the Internet at http://dnb.d-nb.de. DETAIL Business Information GmbH Messerschmittstr. 4, 80992 Munich, Germany Tel: +49 89 381620-0 detail-online.com

Contents

Preface

Yesterday – Today – Tomorrow The Historical Use of Hardwood as a Building Material Hardwood in Modern Timber Construction 11 Outlook and Relevance 15

Forest Management Background

High-performance Materials with Potential for the Future New Developments and Improvements in Structural Hardwood Products Bonding of Hardwoods 21 Connections 21 Durability and Moisture 22 Joinery and Processing 22 Regulations for Use 23

Wood Species

Hardwood Construction Products Sawn Lumber and Finger-Jointed Solid Wood 30 Glued Laminated Timber and Hybrid Glulam 33 Beechwood Laminated Veneer Lumber 35 Engineered Timber Products of Hardwood 37 Information on Use 39 Durability 41 Emissions 43

Building with Hardwood Reasons for Using Hardwood 45 Hardwood Products in Use 47 Connections 52

Example Builds Ten Real-life Examples

104

Appendix Authors 105 Approvals, Standards 106 Bibliography, Links 107 Picture Credits 108 Acknowledgements 109 Subject Index 110

Authors’ note for the international edition of the DETAIL Praxis publication Building with Hardwood:

This book deals mainly with regulations in Germany and Europe. There are several reasons for this. The existing high proportion of hardwood and its expected increase due to an active restructuring of the forests has reinforced the desire to put the material to sensible use. This goal has led to the relatively rapid development – compared to that in the case of softwood – of a research environment focusing on the potential suitability of hardwood for timber construction. Critical factors were the already historically documented high strength and stiffness properties of hardwood, and the fact that Europe’s construction sector was a large consumer of timber. In other words, there was also an economically attractive sales market. This development continues to this day. In addition, research is expected to significantly expand the application possibilities of wood in the construction sector as a whole – owing to the socially and culturally increasing significance of timber engineering. Thanks to the system of European standardisation and the building legislation in individual countries, research findings were put into practice relatively quickly and the first products and applications were developed. Although the field of structural hardwood construction is still of manageable size, it is steadily increasing, especially as efforts to improve and develop new products continue in research and development as well as in industry. From a global perspective, though countries with traditionally high timber construction rates such as Canada and the United States also use hardwood for construction, their applications, building methods and products differ from those in Europe. Wood is used for the most part in one and two-storey residential buildings of timber frame construction, so that on the one hand, the demands on the performance of the products are not very 4

high, and on the other – especially for the framing timbers – the wood most commonly employed is softwood. In addition to the framing timbers, wood composite materials in panel form (plywood, OSB) are used, some of which are made of hardwood. Overall, however, hardwoods are used mainly in interior finishing and rarely for the support structure. This book can be viewed as a “general case study”. The showcased products and key figures, and the possibilities that they represent, can often be transferred to other wood types, situations and countries. Individual adjustments will be required, such as the determination of characteristic values for new wood species, as well as the reconciliation among regionally varying rules and regulations. However, this in turn could give rise to further benefits, for example the use of even stronger timber varieties. So please consider this book as a welcome encouragement to you to become active in the “application of hardwoods in construction”. The Authors

Preface

Increasingly, construction is becoming a question of raw materials, because the demand for space and thus for building materials will continue to grow rapidly worldwide. The modern world has forgotten that the earth possesses a huge, constantly growing reservoir of raw materials that are also very suitable for building. For a hundred years, research and development focused mainly on modern

materials, while timber, once the most important building material, was virtually forgotten. Renewable materials represent a source of hope, as they symbolise a commitment to solving the pressing issues of the future having to do with essential decarbonisation and the growing shortage of resources in the construction sector. The increasing demand for timber

constructions is unmistakable evidence of a renaissance in this oldest of building materials. Coniferous or softwood is and will likely remain the primary material for building applications because it has superbly well-suited properties and is easy to work with. Compared to hardwood, it is more economical because the yield from the regular, straight-growing tree trunks is significantly greater. On the other hand, depending on the type of tree, valuable hardwood is available in large quantities, but is currently too often under-utilised as a material, too often burned or wasted in the manufacture of short-lived products. The reasons for this are alleged disadvantages in processing (due to the hardness of the material), greater drying costs as well as the lack of dimensional stability of the products. That must and will change. The outstanding properties of hardwood can lead to the optimisation of existing timber materials or to completely new products. Thanks to developments such as laminated veneer lumber produced from beech, for the first time in history the second most common species of tree in Central Europe can now be used in timber construction. Hardwood allows for amazingly slender and aesthetic constructions that are very economical. Material combinations of softwood and hardwood will also open up new structural and design options in architecture. This book presents the status quo for building with hardwood. It is intended to stimulate new ideas and contribute to a future in which the increasing demand for ecological and climate-neutral construction can rely on a broader palette of available tree species.

Hermann Kaufmann 5

High-Performance Materials with Potential for the Future Markus Lechner, Stefan Winter, Stefan Torno

Wood is the world’s leading biogenic building material and, from a current perspective, one of the key materials for developing sustainable solutions for building in the future. It can make a significant contribution to the necessary reduction in carbon emissions and the targeted use of renewable raw materials. The challenge of the future is to build faster, for more people, with fewer renewable resources, on less land and with lower emissions. This will require highperformance timber materials. Current research and development projects are often focused on increasing strength characteristics. High-performance materials with potential for the future, however, must have multidimensional properties. This includes, for example, a selfextinguishing feature in the event of fire or a reduction in VOC emissions into interior spaces. Compared to modern softwood timber products, those made of hardwood are still relatively new. Accordingly, based especially on experiences from early applications, there is still a significant need for research and development. This is the case even though hardwood has been used for a long time, in axe handles and oak beams, and of course for making furniture.

New developments and improvements in structural hardwood products Construction with softwood-derived glued laminated and cross-laminated timber has established itself in recent decades with designers and builders. The performance limits of the currently available timber building products are limited on the one hand by their strength, and on the other by their elastic modulus and its associated cross-sectional stiffness. Both properties can be improved on by using hardwood. The applicable 20

calculated strengths of timber building products in beech compared to those in spruce, for example, are two to three times as high. The use of beech can increase stiffness properties by up to 50 %. Two approaches to the development of hardwood-based structural products are possible. In one, the base material of a timber building product can be switched from softwood to hardwood, e.g. glulam, laminated veneer lumber (LVL) or cross-laminated timber (CLT) made of beech, oak and birch. At first glance, this approach is compelling. But the question is whether it is also resource-efficient, i.e. whether it realises the potential of hardwood efficiently. Alternatively, a targeted composition using hardwoods can improve the weaknesses of current softwood timber products. The composite beams in the International House Sydney (Fig. 2) are a good example of this. The maximum building height according to planning regulations and the number of floors desired by the client could not be built with conventional timber construction products. Therefore, a composite beam made of softwood glulam and beech LVL was developed and tested [1]. When cross-laminated timber is used as a panel, its load capacity is usually limited by rolling shear strength. In this case, replacing the transverse layer subject to rolling shear stress with hardwood is an excellent solution (Fig. 3) [2]. Another promising approach is the strengthening of spruce glulam with carefully placed hardwood veneers to create “timber-reinforced timber” (Fig. 1) [3]. The highly anisotropic strength and stiffness properties of glued laminated timber can be homogenised by arranging the veneer layers between the glulam components at angles of 0° and 90°.

High-Performance Materials with Potential for the Future

glued laminated timber

The veneers can also be specifically modified, for example to produce selfextinguishing layers. The combination of hardwood with mineral building materials also offers great potential, for example for timber-concrete composite ceilings. Due to the higher tensile strength of hardwood, the wood layer can be made much thinner. Because this makes a thinner ceiling structure possible, it also enables a better utilisation of room height or an increase in the number of floors for a given building height [4].

hardwood veneers

visible at its joints. In softwood constructions, the limiting conditions of the fastening technology are often decisive in determining member crosssections. Initial investigations indicate that the use of hardwoods makes it possible to transfer greater forces within much smaller spaces. In the case of pin-shaped fasteners such as nails, dowels, screws and bolts, the reason for this are the higher hole-wall and transverse tensile strengths of hardwoods compared to those of softwoods. The load-bearing behaviour of estab-

lished timber fasteners must therefore be carefully researched for use with hardwoods, as in some cases failure mechanisms such as the shearing-off of the connecting means can dominate. Aside from the classic fasteners, new

1 2

Basic composition of timber-reinforced timber with transverse veneer arrangements Composite beams, International House Sydney office building, Sydney (AU) 2016, Tzannes Architects, Structural Design: DesignMake Lendlease Test set-up for determining the rolling shear properties of a triple-ply CLT cross-section construction with a transverse layer of beech

Bonding of hardwoods Glued building components are of great importance in the use of hardwood because sections with growth-related reductions in stiffness and strength can be eliminated, leading to the homogenisation of properties. It is therefore necessary to optimise bonding by redeveloping the adhesives for the gluing of hardwoods as well as those for gluing hardwoods to softwoods in order to make the process faster, technically simpler and thus more cost-effective. Although the current use of phenolic resins (PF, PRF) already makes very reliable bonding possible, this group of adhesives places higher demands on occupational health and safety measures at the plant during product manufacture. Extended testing of other adhesive families, such as PUR, is currently being carried out in various projects [5].

Connections In the field of connection technology, hardwoods offer enormous potential due to their higher density and strength. The quality of a timber construction is

Hardwood Construction Products

An overview of the usability and availability of hardwood construction products is shown in Fig. 4. In general, a distinction must be drawn between the regulations governing the products and the rules for their application. Product regulations contain information about manufacture, quality control and labelling. Usage rules determine which classes of a product can be used in which applications.

Sawn lumber and finger-jointed solid wood 1

The term ‘sawn lumber’ is used as a synonym for the term ‘solid wood’. According to DIN 4074-5, sawn lumber describes a timber product of at least 6-mm thickness, which is produced by sawing or shaving roundwood along the length of the trunk (Fig. 1). Depending on the ratio of cross-section height to cross-section width, as well as the orientation of the cross section in its eventual application (vertical or horizontal), a distinction is made between squared timbers, planks and boards. Finger-jointed solid wood for load-bearing purposes consists of strength-graded timbers that are longitudinally frictionlocked together with other timbers via finger (or comb) joints to form longer units (Fig. 2).

Product characteristics

1 2 3 4

Sawn lumber Finger joints Dimensional tolerance classes for lumber according to EN 336:2013-12 An overview of the regulations for use and availability of hardwood construction products in Germany

Sawn lumber is usually available in thicknesses ranging from 20 mm to 120 mm. The width depends largely on the diameter of the roundwood used. The lengths vary mostly between 2.5 m and 6 m. Thicker squared timbers or beams with cross-sectional dimensions of > 120 mm up to 300 mm and greater lengths are usually only produced on request (primarily because of the difficult drying process and limited availability) and are

therefore only rarely in stock. Regardless of the cross section, the ratios of edge lengths specified in DIN 4074-5:2008-12 must be observed during planning (e.g. for squared timber: w > 40 mm and w ≤ h ≤ 3w), as otherwise a strength classification can lead to erroneous results. In general, hardwood is subject to the dimensional tolerance classes given in EN 336:2013-12 (Fig. 3). However, its applications must be individually defined. Based on DIN 68 365:2008-12, for example, class 1 can be defined for rough-sawn wood and class 2 for planed wood. Usability of sawn lumber

The European harmonised product standard for solid wood and sawn lumber is EN 14 081-1. It regulates structural timber with a rectangular cross section graded according to strength. Roundwood is not regulated by building authorities. The latest version of EN 14 081-1 included in the Official Journal of the European Union (OJEU) is from May 2011. Later versions from 2016 and 2019 are thus currently not officially binding. The OJEU is the Official Journal of the European Union. To be binding on construction authorities, a European harmonised standard must be included and published in the OJEU. EN 14 081 addresses the visual and machine-executed strength grading of softwood and hardwood. Machine grading leads directly to classification into a strength class. Visual grading in the EU is carried out on the basis of national sorting standards. In Germany, the visual sorting standard for hardwood is DIN 4074-5. The national visual grading classes are assigned European strength classes via the “assignment

Hardwood Construction Products

Cross-section dimensions

Dimensional tolerance class 1 2

≤ 100 mm

+3 / -1 mm

± 1 mm

> 100 mm to ≤ 300 mm

+4 / -2 mm

± 1.5 mm

> 300 mm

+5 / -3 mm

± 2 mm

For dimensional tolerances in the longitudinal direction, the following applies: Negative deviations are not permitted, positive deviations must be limited as needed. The reference humidity is ≤ 20 %. In the event of changes in the wood moisture content, the dimensional changes in the transverse direction should be determined as 3 follows: 0.35 % per 1 % moisture change.

standard” EN 1912 or via assignment reports. Hardwood sawn lumber can currently be graded only visually. DIN 20 000-5 is the application standard associated with EN 14 081-1. There are different versions of DIN 20 000-5, as well. Since only DIN 20 000-5:2012-03 refers to EN 14 081-1:2011-05, which is cited in the OJEU, this is the version currently listed in the Model Administrative Rules on Technical Building Regulations (Muster-Verwaltungsvorschrift Technische Baubestimmungen – MVV TB) for solid wood applications per EN 14 081-1. Consequently, these applications are currently limited to beech and oak. For other wood species, a general construction technique permit or a European technical assessment is required. Wood species

Regulations for use 1)

Availability

Maple

EN 14 081-1 with ZiE 2) / –

–/–

Birch

EN 14 081-1 with ZiE 2) / –

Beech

or a European technical assessment. However, the non-normative regulation of finger-jointed solid hardwood timber other than poplar would be a largely theoretical solution, which would be difficult to implement in the short term. Technical rules and labelling

Applicability of finger-jointed solid wood

The European harmonised standard for finger-jointed solid wood is EN 15 497: 2014-07 and the associated application standard is DIN 20 000-7:2015-08. In addition to softwoods, the only hardwood species both of these standards allow for is poplar. Thus, only poplar may be used for finger-jointed solid timber; other hardwood species require a German national technical approval with a general construction technique permit Glued laminated timber

Laminated veneer lumber Regulations for use

Structural plywood / OSB

Regulations for use

Availability

ZiE

–

ZiE

–

ZiE

–

EN 13 986 with DIN 20 000-1

–/–

x/–

ZiE

–

EN 13 986 with DIN 20 000-1

x/–

EN 14 081-1 with DIN 20 000-5

x/–

abZ / aBG Z-9.1-679

ZiE

–

aBG Z-9.1-838 ETA-14/0354 ETA-18/1018

EN 13 986 with DIN 20 000-1 abZ Z-9.1-841

x/–

European chestnut

EN 14 081-1 with ZiE 2) / –

x/–

ETA-13/0646

ZiE

–

ZiE

–

EN 13 986 with DIN 20 000-1

–/–

Oak

EN 14 081-1 with DIN 20 000-5

x/–

abZ Z-9.1-821 ETA-13/0642

ZiE

–

ZiE

–

EN 13 986 with DIN 20 000-1

–/–

Ash

EN 14 081-1 with ZiE 2) / –

x/–

ZiE

(x)

ZiE

–

ZiE

–

EN 13 986 with DIN 20 000 1

–/–

Eucalyptus

EN 14 081-1 with ZiE 2) / –

–/–

ZiE

(x)

ZiE

–

ZiE

–

EN 13 986 with DIN 20 000 1

–/

Poplar

EN 14 081-1 with ZiE 2) / EN 15 497 with DIN 20 000-7

x/–

EN 14 080 with DIN 20 000-3

(x)

ZiE

–

ZiE

–

EN 13 986 with DIN 20 000-1

x/x

Regulations for use

Cross-laminated timber

The technical regulations listed below are relevant to sawn lumber and fingerjointed solid timber. In each case in the following text, the valid (dated) version is given. • DIN 4074-5: Strength grading of wood – Part 5: Sawn hardwood • DIN 68 800-1: Wood preservation – Part 1: General • DIN 68 800-2: Wood preservation – Part 2: Preventive constructional measures in buildings

Availability

Sawn lumber / finger-jointed solid wood

Application standards The standard series DIN 20 000-x governs the application of European standards in Germany. These application standards specify which regulations of a product can be used for which applications in Germany.

Availability

Regulations for use

Availability

In general, all timber species and the products manufactured from them can be regulated for structural purposes through an individual approval (ZiE). There are various versions of EN 14 081-1. In order to be binding on building authorities, a regulation must be included in the Official Journal of the EU (OJEU). Although EN 14 081-1 has been revised twice since, EN 14 081-1:2011 is still the version cited in the OJEU and is thus binding. There are also different versions of the associated application standard DIN 20 000-5. Since the later versions refer to versions of EN 14 081-1 not cited in the Official Journal of the EU, DIN 20 000-5:2012 remains valid for applications in Germany .

Building with Hardwood

The last two points in particular have a direct influence on the application of hardwoods in bearing structures. Only the dimensions of the hardwood materials available today make their structural use possible to any significant degree. The manufacture of bonded products always follows the progression shredding – sorting – gluing. In this way, the timber is neither modified nor improved, but rather “homogenised”. This can be demonstrated, for example, by comparing solid beech with beech laminated veneer lumber. Homogenisation has a positive effect especially on the determination of the characteristic strength properties, i.e. the properties required for dimensioning, since in this determination the five worst samples of a total of 100 (the 5 % quantile) are decisive. For example, the characteristic tensile strength for beech timber is approx. 20 N/mm2, while for beech laminated veneer lumber it is 60 N/mm2. The stiffness, for which the mean value of all the samples is decisive, the E-module values range from about 15,000 N/mm2 for beech timber to

approximately 17,000 N/m2 for beech laminated veneer lumber of similar size (Fig. 2). The crosswise arrangement of the layers (fibres), especially in materials with a panel format, evens out the properties that depend on the fibre direction (anisotropic characteristics), in particular the tensile and compressive strengths but also swelling and shrinkage due to changes in wood moisture. The following expositions are intended as a snapshot. The developments in this field are very fast-paced, and new products are continually entering the market. Despite this pleasing trend, most hardwoods – with the exception of beech laminated veneer lumber – can be described as niche products. For each planned use of hardwood, therefore, the designer must take care to verify its availability, especially in large quantities, the delivery time and the costs. The same applies to the specifications for dimensioning given in the standards and to the restrictions in the use of company-specific products in the context of public procurement.

Reasons for using hardwood The most important reasons for using hardwood in structural applications are: • slimmer cross sections due to greater strength • material and thus cost savings • appearance, surface • robustness • natural durability The greater strength of hardwood products results in leaner cross sections. This has formal advantages, because it allows for more delicate constructions (Fig. 1). In cases where space is limited (room, girder, lintel heights), larger spans are possible than with softwood products,

and steel beams can also be substituted. Since the cross sections of columns are smaller, openings can be made wider, saving space. In addition to material savings, further secondary cost effects help to justify the use of hardwood. If the focus is on pure material and cost savings, the explicit strengths of hardwood products must be exploited in the structural design in order to ensure a significant reduction in the consumption of materials compared to a solution using softwood. At present, hardwood products are considerably more expensive than comparable products made of softwood. In order to better understand the consid-

Comparison of the section heights (for a given width) of a girder truss with the same geometry and dimensions and identical loads a GL 24h spruce glulam truss b GL 75 beech LVL truss Comparison of characteristic tensile strength and mean stiffness between beech sawn lumber and GL 75 beech laminated veneer lumber beech sawn timber beech laminated veneer lumber

100

25,000

20,000

15,000

10,000

5,000

rigidity [N/mm2]

Most of the hardwoods native to Europe and used in European construction have intrinsically better strength properties and greater rigidity than the native softwoods due to their higher bulk density. Advances in grading, processing and bonding technologies are constantly leading to new product innovations in the form of composite products. This is the only way to make significant use of hardwood in structural applications possible. The primary goals in manufacture are mainly: • better utilisation of roundwood • overcoming the natural geometric limits that arise when processing is restricted to the production of sawn timber (solid wood) • eliminating natural weaknesses

tensile strength [N/mm2]

bending

shear

compression II

tension II

E-modulus

200 (100 %)

64 (32 %)

142 (71 %)

58 (29 %)

60 (30 %)

137 (68 %)

GL 24h spruce glulam

GL 75 beech LVL 3

erations and comparisons below, the following price comparison is used as a very rough guide: • Price of GL 24 spruce glulam: 100 % per unit volume • Price of GL 48 beech glulam: 500 % per unit volume • Price of GL 75 beech LVL: 200 % per unit volume Aside from the reduction of the component dimensions for formal, structural or economic reasons, another decisive factor in choosing hardwood products is their surface, i.e. their appearance or structure. Robustness against mechanical damage or wear is a criterion in favour of hardwood mainly for columns. In general, the resistance of native hardwoods against fungal infestation (rot) is lower than that of softwood. For this reason, the use of hardwood products is often limited to use classes 1 and 2. Oak, European chestnut and black locust are exceptions. The latter, however, has no construction authority approvals. Structural relationships

Hardwood building products are divided into strength classes; for example, sawn hardwood timber is assigned classes D 22 to D 70 (see “Sawn lumber and finger-jointed solid wood”, p. 30ff.) and sawn softwood timber into classes C 14 to C 45. The number in each case corresponds to the characteristic bending strength. A C 24 cross section thus has the same bending strength as a D 24 cross section of the same size. However, a comparison of other material properties relevant to structural design shows differences within the same strength class (Fig. 6). These are small for some parameters and substantial for others. Hardwood has obvious advantages when it comes to its transverse compressive 46

and tensile strengths and bulk density, whilst the E-modulus and tensile strength values for spruce are actually slightly greater than those of hardwood of the same strength class. Correspondingly, the same is true for the strength classes of glued laminated timber (see “Glued laminated timber and hybrid glulam”, p. 33ff.). The importance of the various parameters depends on the application. For example, transverse compression, transverse tension and bulk density are not critical for the dimensioning of rod cross sections (see “Rod-shaped products”), but play an important role in the design ofconnections (see “Connections”, p. 52f.). Performance of hardwood building products

Whenever the performance of softwood and hardwood is compared in the following, the comparisons will be between GL 24h spruce glulam and GL 75 beech laminated veneer lumber (Figs. 4, 5 and 7). There are several reasons for this: As already described, the use of hardwood is particularly suited to applications in which tensile, compressive, transverse compressive and shear strengths are critical to the design. For pure compressive or tensile loads parallel to the fibre, it is more common to use class GL 24h glulam. This is due to the fact that class GL 28h glulam is hardly available, because the roundwood yield of the laminates required for its manufacture is low. As a result, GL 28h is very rarely used. The values of the shear and transverse compressive strengths of all strength classes of glued laminated timber are identical. Beech laminated veneer lumber has the highest values of all hardwood products for most of the characteristic parameters. All other comparisons will therefore fall

within the range spanned by these two products. In addition, beech laminated veneer lumber is currently the most widely used product on the market. The decisive strength and stiffness properties of beech laminated veneer lumber are in some cases significantly higher than those of GL 24 spruce glulam (Fig. 7). This results in significant material savings (Fig. 3). However, depending on the characteristic, these theoretical values must be qualified to ensure that the correct conclusions are drawn for the given application or structural design. In addition to the following general considerations, please refer to the section “Hardwood products in use”. Elastic modulus (E-modulus) The stiffness of a component and its deformation depend on its E-modulus and its planar moment of inertia I (I = (w ≈ h3)/12 for rectangular cross sections). The height of the component enters into the calculation of I as a cubed quantity. If the height of the component is not limited, a smaller E-modulus can be compensated for with a slightly greater cross-sectional area and the associated increase in material expenditure (Fig. 4). On the other hand, for technical reasons (buckling, connections, fire protection) the width cannot be arbitrarily reduced. Conclusion In applications where the stiffness (deformations) of the building components plays a significant role (slender flexural members, panels on curves, etc.), the potential for material savings through the use of hardwood is comparatively low, especially if the height of the components is not limited. Bending strength The bending strength of a building component depends on the bending strength

Building with Hardwood

Comparison of cross sections of the same load capacity subject to different primary stresses; assumptions: use class 1, beam height h = 300 mm, kmod = 0.8, JM = 1.3 Cross sections of the same bending stiffness. A lower E-modulus can be compensated for by a small increase in height. Cross sections of the same bending strength. Compensating for a lower bending strength by an increase in height is unrealistic. Comparison of the strength, stiffness and bulk density values of hardwood normalised to the softwood value of the assigned C-class. Softand hardwood of the same strength class differ especially in tensile and compressive strengths transverse to the fibre and in bulk density. Comparison of the characteristic strengths, the bulk density and the mean value of the E-modulus between GL 24h spruce glulam and GL 75 beech LVL

GL 24h spruce glulam GL 75 beech LVL

137/400 (69 %)

137/455 78%)

Compressive and tensile strength parallel to the fibre For any given cross section, the material savings resulting from greater compressive or tensile strength are inversely proportional to the amount of material used. Therefore, the relationship shown in Fig. 3 applies here, as well. However, the very large material savings must be qualified. For compression members, the slimness must be taken into account in addition to the compressive strength. The proportional relationship therefore applies mainly to short, compact members. In addition, the fire requirements for flexural and compression members (fire-resistant design of the reduced cross section) must be taken into account. For flexural and compression members it is also often not the strength that is decisive in determining the required cross section, but rather the connection at the end of the member.

of the material and the section modulus W (W = (b ≈ h2)/6 for rectangular cross sections). Since the height enters the calculation as a squared quantity, the notes on the E-modulus also apply here to a lesser degree. However, the bending strength of beech laminated veneer lumber is about a factor of 3 greater than that of spruce glulam. For stiffness, the factor is only about 1.5. As Fig. 5 shows, the potential material savings are significant. Conclusion In applications where bending strength is decisive, the potential exists for material savings through the use of hardwood. Shear strength For rectangular cross sections, the material savings from a greater shear strength are inversely proportional to the amount of material used. Therefore, the relationship shown in Fig. 3 applies.

C = coniferous (softwood)

In general, a distinction is made between the rod and plate-like application types. Rod-shaped products

Fig. 8 provides an overview of the main rod-shaped building components. Material properties, availability, dimensions and the corresponding standards are given in the chapter “Hardwood Construction Products” (p. 30ff.). Sawn timber / Solid wood Due to the growth characteristics of hardwood, cutting it produces low yields of the common structural timber cross sections. In addition, its greater strengths

2.5 2 2.0 1.5

0.95

1.4

1.0

0.93

GL 24h spruce glulam

GL 75 beech LVL

Bending fm, k

Tensile II ft, 0, k

19.2

Tensile 90 ft, 90, k

0.5

0.6

Compression II fc, 0, k

59.4 1)

Shear fv, k

3.5

4.5

11,500

16,800

385

730

E-Modulus II E0, mean

0.5

Bulk density pk 1)

bending

tension II compression II

shear

tension

compression

E-modulus bulk density

64/547 (58 %)

Hardwood products in use

D = deciduous (hardwood)

1.5

64/300 (32%)

Conclusion The raw density of hardwood, which is between around 30 % and 70 % greater than that of softwood, gives it significantly greater transverse compressive strength. The correspondingly higher hole-wall strength allows for a reduction in fastening agents or the use of novel products.

Transverse compression, transverse tension, bulk density Transverse compression, transverse tension and bulk density are particularly

3.0

200/300 (100%)

important in the design of node connections and in the choice of fastening agents (see “Connections”, p. 52f.).

Conclusion The potential for material savings is enormous for flexural and compression members.

Conclusion For applications in which shear strength is decisive (highly stressed single and multiple span girders), the potential for material savings through the use of hardwood is considerable. strength [N/mm2]

200/400 (100%)

GL 24h spruce glulam GL 75 beech LVL

values for use class 1 all values in N/mm2, density in kg/m3

Example Builds

Production Hall in Waldenburg (DE) Hermann Kaufmann + Partner, Schwarzach

Administrative Building in Augsburg (DE) Lattke Architekten, Augsburg

Production Building in Royal Leamington Spa (GB) Waugh Thistle Architects, London Vits∞, Leamington Spa Martin Francis, London

Holiday Home in Büttenhardt (CH) bernath+widmer, Zurich

Administrative Building in Risch-Rotkreuz (CH) Burkard Meyer Architekten, Baden

Museum in Aspen (US) Shigeru Ban Architects, New York

Research Pavilion in Stuttgart (DE) University of Stuttgart Institute for Computational Design and Construction: Achim Menges Institute of Building Structures and Structural Design: Jan Knippers

Parking Garage and Ski School in Innerarosa (CH) Lutz & Buss, Zurich masKarade, Montreuil-sous-Bois

Stand Roof in London (GB) Populous Architects, London

100

Bank Headquarters in Stavanger (NO) Helen & Hard, Stavanger SAAHA, Oslo

Production Hall in Waldenburg

Architecture:

Hermann Kaufmann + Partner, Schwarzach (AT); Building site manager: GAPP GmbH, Munich (DE) Structural Solid construction: engineering: BHM-Ingenieure Engineering & Consulting, Feldkirch (AT); Timber construction: SWG Engineering, Rülzheim (DE) Timber construction: Schlosser Holzbau, Jagstzell (DE)

In order to increase its production capacity, SWG, a company with 230 employees, wanted to expand its current site. The result was an innovative timber building with a production hall 114-m long, almost 97-m wide and 12-m high. A covered bridge connects this with the new three-storey administration and visitors’ pavilion. The production hall is currently considered the world’s largest industrial hall built from laminated veneer lumber and boasts an enormous, yet surprisingly delicate beech roof structure. The roof structure is divided into five bays 20-m wide and separated from one another at

the top like the teeth of a comb, allowing a generous amount of indirect daylight into the building. The bearing structure consists of 82 m-long main trusses of beech laminated veneer lumber that are employed as two-span girders over 40 and 42-m length intervals, respectively, and are supported on a few slender piers of the same material. Secondary truss girders, supported by the main trusses, run in the orthogonal direction. The node points of the truss girders are joinery connections optimised for the hardwood material. The large spans mean that, in some cases, the beams, piers and nodes

must support enormous loads of up to 3 MN. The high density of the material required pre-drilled junctions. The amount of timber required could be kept to a minimum thanks to very precise pre-planning and the exact material-dependent fit. Compared to conventional softwood timber buildings, this led to a material savings of 50 %. Hardwood as a bearing material made this innovative construction possible, and the few slender support pillars guarantee a flexible use of the space. Apart from its environmental advantages, the building contributes to a positive corporate image.

8 b

1 2 6

7 3

Production Hall in Waldenburg

A Floor plans • Sections Scale 1:1,000 B aa C

1 2 3 4 5 6 7 8

Entrance Office Multipurpose room Building services Production Workshop Break room Storage

A Main girder truss of beech laminated veneer lumber Length: 82.18 m Height: 3.80 m Span: 41.94 and 40.24 m B Main pier of beech laminated veneer lumber 2≈ 280/320 mm C Secondary girder truss of beech laminated veneer lumber Length: 18.30 m Height: 1.90 m Span: 18.30 m

“The project clearly shows the benefits of large spans and hardwood connections.”

Anne Niemann interviews Christoph Dünser, Hermann Kaufmann + Partner 11.12.2019

Anne Niemann Had you already had experience with beech laminated veneer lumber? Christoph Dünser Only a little. We had wanted to use this material in a previous project. But at that time, the product was still absolutely new and the company had difficulties with delivery.

AN What was the reason for using hardwood for this project?

CD We wanted to demonstrate what span lengths are possible with timber, and had made our plans with beech laminated veneer lumber in mind from the very beginning. At the time there had been no project that used the material to its limits. What was important to us was that the entire load-bearing construction of the roof be made of beech LVL, not just the most heavily stressed building components. That led to this relatively long-span structure. Together with the structural engineer, we thought about and tested: How far can we push this, up to what limit can we use this material to its fullest?

AN What special features came out of this that were only possible with hardwood? CD A very aesthetic, slim construction was created that corresponds to the proportions of steel or is possibly even trimmer. This is only possible with beech. The high compression forces, especially in the supports and chords, could not have been realised with spruce. In the node construction we used multiple-step joints that are derived from heel notch joints. The transferred forces are huge. However, these connections must be positively locking, otherwise a zippertype failure will occur if the work is not precise. The joining machines are not designed for the enormous weight of the large building components. It was necessary to turn the heavy components by hand, and the precision that is typically expected when shaping spruce could only be achieved after a software update.

AN How and with which arguments were you able to convince the building client to use this material? CD The client, a manufacturer of wood screws, wanted a flagship project in timber. The company wanted to demonstrate that screws can be used for beech even on a large scale. It is a great advantage when the screw manufacturer and its own engineering firm are involved in the design. Because the test engineer suddenly demanded a longer screw for which there was no approval yet. So the company just went ahead and brought it out on the market.

Production Hall in Waldenburg

AN Does it require special knowledge or experience to be able to use hardwood properly? How important is the expertise and support of specialist planners and contractors? CD It was a great advantage that the team was selected in a partnering process, that is, the companies were already involved at the planning stage. This made it possible to eliminate some imponderables right from the start. The joiner had already had experience with beech laminated veneer lumber, albeit not in these dimensions. We all learned a lot during this project. For example, we were afraid that red-hot wood shavings could ignite a fire. The concern was unfounded, but the difficulty of processing beech was a problem in terms of time. Processing beech takes longer than processing spruce. We did include this in our time planning, but it’s good to have some experience with the joining of beech, otherwise things get difficult.

AN Were your expectations of the material confirmed in the course of this project? CD Definitely, yes. The construction ended up being much more slender than we thought in the beginning, and the connections are much more precise. The fear that the priming coats would be a problem was not borne out, because the temporary weather protection worked extremely well. The project clearly shows the benefits of large spans and hardwood connections and I hope it will serve as a model for even bigger or better projects.

AN What particular challenges arose during the planning and construction phases? CD The weather protection of such large constructions is a challenge. The components remain very sensitive to moisture, and these large, long-span support structures demand a speed during assembly that is almost impossible to achieve. The joiner lays out the constructions so quickly that the sheet metal worker can hardly keep up. If one follows the principle that every craftsman is responsible for protecting his own work from the weather, projects of this magnitude are not feasible. Only the close cooperation between sheet metal worker and joiner allowed the problems of weather protection during the assembly to be successfully solved.

AN What direction should the development of building products take? What do you wish for from materials research? CD Beech laminated veneer lumber, for example that of the BauBuche brand, is a relatively new product for which there are only a few fasteners and screws that are officially approved. We will see whether others join in the competition and develop products as well. It will be necessary to design joining machines for the greater weight of beech laminated veneer lumber, so that the usual precision can be guaranteed – especially when the individual components become as large as in our case. On the positive side, contract joinery already exists for beech. This will quickly generate the experience that will form the basis for specifications for future generations of joining machines.

Administrative Building in Augsburg

Architecture: Structural engineering: Timber construction:

Lattke Architekten, Augsburg (DE) bauart Konstruktions GmbH & Co. KG, Munich (DE) Gumpp & Maier, Binswangen (DE)

The new three-storey office building for a software developer in the Swabian city of Augsburg, Germany, is surrounded by trees in the middle of a park. It is designed as a pure timber building and accessed via a central stairwell. The bearing structure is a classic timber frame construction of beech laminated veneer lumber, making extremely slim cross sections possible. The primary beams with dimensions of 20 ≈ 40 cm span the spaces between the 20 ≈ 20 cm pillars. The support intervals are 5.10 m on the north and south sides, with a central corridor 2.40 m wide. Here, a suspended ceiling caches all the building technology for ventilation, heating and cooling. In the lateral wings, ceilings featuring exposed beech laminated veneer lumber beams with cross sections of 12 ≈ 32 cm spaced 85 cm apart dominate the spatial impression. Laid over the beams, a 40-mm thick timber panel made of the same material reinforces the construction. The large spacing of the supports allows for a free and extremely flexible spatial layout. The timber of the pillars and beams was left exposed. Glass and timber also predominate in the interior, contributing to a bright, friendly atmosphere. In the south, 2-m wide balconies prevent direct solar radiation from entering and thus provide the necessary protection from summer heat. The facade features an interplay of closed and open areas. The gable walls and parapets are conceptualised as a timber frame construction, while on the north and south sides a post-and-beam construction in front of the plane of the support pillars allows for full-surface triple glazing. Vertical timber shuttering clads the building and, depending on the opening angle, guarantees generous sightlines in and out as well as the necessary sun protection.

2nd floor

1st floor a

a Ground floor

Administrative Building in Augsburg

Floor plan • Sections Scale 1:400 1 2 3 4 5

Entrance Office Meeting / Seminar Lounge Loggia

5 3

b 7 10

Administrative Building in Risch-Rotkreuz

Vertical sections Scale 1:20 Isometric drawing of a column head: Spruce (light), beech laminated veneer lumber (dark) Isometric drawing of panel construction and assembly system

1 Roof construction: 80 mm extensive green roof substrate 20 mm drainage mat double-layer sealing membrane 200 mm PUR thermal insulation 35 – 95 mm tapered EPS thermal insulation vapour barrier timber-concrete composite slab: 120 mm reinforced concrete slab and 160/300 mm girder, spruce glulam 300 mm ceiling cooling / ventilation system 2 textile sun shade 3 triple glazing in timber-aluminium frame 4 5 mm aluminum composite facade cladding aluminium substructure timber frame construction: housewrap 18 mm gypsum fibreboard 15 mm gypsum fibreboard 60/280 mm solid spruce timber posts, interspersed with mineral wool thermal insulation vapour barrier 15 mm gypsum fibreboard 18 mm gypsum fibreboard 18 mm spruce / fir three-layer board 5 160/300 mm facade-plane girder, spruce glulam 6 340/340 mm facade-plane column, spruce glulam 7 Floor construction: carpet; 150 mm cavity floor 60 mm cement subfloor 20 mm mineral wool impact sound insulation separating layer timber-concrete composite ceiling: 120 mm reinforced concrete slab and 160/300 mm girder, spruce glulam 300 mm ceiling cooling / ventilation system 8 480/340 mm girder, beech laminated veneer lumber 9 340/340 mm column, beech laminated veneer lumber 10 Grouting mortar and centering pin 11 20 mm steel plate

Research Pavilion in Stuttgart

Architecture:

Structural engineering:

Implementation:

Institute for Computational Design and Construction, University of Stuttgart (DE): Achim Menges Institute of Building Structures and Structural Design, University of Stuttgart (DE): Jan Knippers Students of the participating institutes

This pavilion’s almost weightless appearance demonstrates what can be achieved if different disciplines work together interactively. The scientific research project, which was carried out on the university campus in the middle of Stuttgart city centre, is based on the concept of finding a geometry that optimally exploits the potential of the material and at the same time fulfils the highest of architectural design requirements. The result is a filigree, complex structure made of thin timber bands that makes use of a special characteristic of plywood: elasticity through the internal stress of the material. The pavilion consists of 80 birch strips only 6.5 mm in thickness, joined together via simple plug-in connections and screws. Bending the 10-m long strips places the self-stabilising construction under intrinsic tension. As a result, the actually quite soft plywood strips combine to form a rigid structure. The geometry of the pavilion is derived from 40 pairs of 80 segment arcs arranged next to one another so that the components under tensile and bending stress mutually maintain each other’s shapes. The interconnection of computer-based design, simulation and production processes allowed the exact bending and load-bearing behaviour of the individual timber strips to be simulated and rated.

Research Pavilion in Stuttgart

Computer-based information model A gravel bed and tension band B ribs C pairs of strips part 2 D pairs of strips part 1

Authors

Konrad Merz

Anne Niemann

Stefan Torno

Chartered engineer

Architect

Forester

1984 Degree in Civil Engineering, University of Applied Sciences and Arts, Northwestern Switzerland (CH) 1995 Degree in Industrial Engineering 1984 –1986 Project manager at a glulam manufacturer 1986 –1990 Research assistant at the Laboratory for Timber Constructions, EPF Lausanne (CH) 1990 –1993 Senior structural engineer, MacMillan Bloedel Research, Vancouver (CA) since 1994, managing director at merz kley partner, Dornbirn (AT) /Altenrhein (CH) since 2015, academic director at the University of Art and Design Linz (AT)

1996 – 2002 Studies in architecture at the Technical University of Munich (DE) and ETSA Madrid (ES) 2001 Visiting researcher at the Jacob Blaustein Institutes for Desert Research (IL) 2003 – 2009 Partner at Niemann Ingrisch Architekten, Munich 2006 Villa Massimo German Academy in Rome: Scholarship at Casa Baldi, Olevano Romano (IT) 2008 – 2011, 2014 Grading assistant at the Professorship of Architectural Design and Timber Construction, Technical University of Munich (DE) 2009 – 2013 Partner at m8architekten, Munich (DE) 2014 – 2019 Research associate at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich (DE) since 2017, Research associate at the Chair of Architectural Design and Construction, Prof. Florian Nagler, Technical University of Munich (DE) 2018 Teaching appointment at Augsburg University of Applied Sciences (DE) in the “Energy-Efficient Planning and Building” study programme

1997– 2003 Forestry studies at Dresden University of Technology (DE) 2004 – 2006 Preparatory training for the senior forest management service in Bavaria 2007– 2015 Research associate at Holzforschung München (TUM Research Laboratory Wood), Technical University of Munich (DE), active in research and teaching since 2015 Manager of the “Hardwood” and “Bio-economics” divisions at Cluster-Initiative Forst und Holz in Bayern gGmbH (Forestry and wood cluster Bavaria), Munich (DE)

105

Picture Credits

The authors and the publisher would like to extend their sincere thanks to everyone who assisted in the production of this book by providing images, granting permission to reproduce their work and supplying other information. All drawings in this publication are produced in-house, those in the Example Builds section are based on the architects’ plans. Unattributed photos come from the architects’ archives or from the archive of Detail magazine. Despite our efforts, we have been unable to identify the copyright holders of some of the photographs and images. However, their copyright claim remains unaffected. In these cases, we ask to be notified.

Cover

Column of beech glued laminated timber; extension of the Bavarian State Institute of Forestry, Freising Photo: Ralf Rosin Introductory Photos to Sections

Page 4: Arbour of oak glulam with oak planking; Agricultural centre, Salez (CH) 2018, Andy Senn Architektur, structural engineering: merz kley partner Photo: Seraina Wirz Page 6: Internal bearing structure, St. Josef Parish Church, Holzkirchen (DE) 2018, Eberhard Wimmer Architekten, structural engineering: Sailer Stepan & Partner Photo: Andreas Gabriel Page 24: Lumber production in a hardwood sawmill Photo: Tobias Kromke / Pollmeier Massivholz Page 44: Braced trusses of beech laminated veneer lumber, Elobau production hall, Probstzella (DE) 2016, F64 Architekten, structural engineering: merz kley partner Photo: peters-fotodesign.com Page 54: Roof structure of the Aspen Art Museum (US), Shigeru Ban Architects, New York, structural engineering: KL&A, Golden, Création Holz Hermann Blumer and SJB Kempter Fitze, Herisau Photo: Michael Moran Page 104: Headquarters of euregon AG, Augsburg (DE), 2017, Lattke Architekten, structural engineering: bauart Konstruktions GmbH & Co. KG Photo: Eckhart Matthäus

108

Preface

Page 5 Seraina Wirz Yesterday – Today – Tomorrow

Page 6 Andreas Gabriel 1 Zorzi, A. (1981). Venice. Munich, Amber-Verlag 2 Dcoetzee, Wikimedia Commons, Public Domain, URL: https://en.wikipedia.org/ wiki/The_Woodcutter_and_the_Trees 3 Bedal, K. and Back, M.: Unter Dach und Fach. Bad Windsheim, loan from Fränkisches Freilandmuseum 2002 4 after: Niemz, Peter; Sonderegger, Walter: Holzphysik. Physik des Holzes und der Holzwerkstoffe. Munich 2017 5 TU Berlin Architecture Museum 6 BuzzWikimedia, Wikimedia Commons, PD-old, URL: https://de.wikipedia.org/ wiki/Vierungsturm_von_Notre-Dame_ de_Paris#/ media/File:Charpente.fleche. Notre.Dame.Paris.2.png 7 construction images /Alamy Stock Photo 8 Thonet GmbH, C. Meyer 9 Ralf Rosin 10 after: Thünen Institute for International Forestry and Forest Economics, Thünen impact analysis 11 robertharding /Alamy Stock Photo 12 JøMa, Wikimedia Commons, licensed under Creative Commons AttributionShare Alike 4.0 International, URL: https://de.wikipedia.org/wiki/Stabkirche_Urnes#/media/ 13 Bauhaus Archive Berlin / © VG Bild-Kunst, Bonn 2017, Photo: Carl Rogge 14 a Sailer Stepan & Partner GmbH 14 b sblumer ZT GmbH Graz 15 Peter Bennetts 16 Khaloian Sarnaghi A., Rais A., Kovryga A., Gard W. F., van de Kuilen J. W. G.. (2020) “Yield optimization and surface image-based strength prediction of beech.” European Journal of Wood and Wood Products. https://doi.org/10.1007/s00107-02001571-4 17 after: Krackler, Verena; Niemz, Peter: “Schwierigkeiten und Chancen in der Laubholzverarbeitung; Teil 1: Bestandssituation, Eigenschaften und Verarbeitung von Laubholz am Beispiel der Schweiz”. In: Holztechnologie 52, 2/2011

18 a 18 b 19 20 21 22 23 24

bauen + wohnen 12/1985 bauen + wohnen 12/1985 Pollmeier Massivholz GmbH & Co. KG Richard Davies Roman Keller Nelson Kon Judith Stichtenoth 2001 image: Richard Davies 2002 image: Richard Learoyd 2008 image: AHEC 2009 image: Production hall Bodegas Vega Sicilia; VIGAM – oak glulam – Elaborados y Fabricados Gámiz; timber construction executed by TRC Estructuras de madera 2010 image: Roland Bernath 2011 image: Christian Schittiich 2012 image: Roman Keller 2013 image: Blumer-Lehmann AG 2014 image: Laura Egger 2015 image: Jost&Bayer 2016 image: www.peters-fotodesign.com 2017 image: Michael Moran 2018 image: Südostschweiz / Theo Gstöhl 2019 image: Sindre Ellingsen 2020 image: Visualisation Hermann Kaufmann + Partner

Forest Management Background

Ralf Rosin

High-Performance Materials with Potential for the Future

1 2 3

4 5 6

author’s own illustration, Markus Lechner Rensteph Thompson – HESS TIMBER, Kleinheubach Simon Aicher / MPA Stuttgart: European hardwoods for the building sector, page 77, image 46 SWG Schraubenwerk Gaisbach GmbH, Waldenburg Blumer-Lehmann AG Didier Boy de la Tour

Wood Species

Page 24 Tobias Kromke / Pollmeier Massivholz Page 26 – 29 Ralf Rosin (all photos) Hardwood Construction Products

1 2

Stefan Torno Stefan Torno

3 – 6 author’s own representation 7 Ralf Rosin 8 Ralf Rosin 9 author’s own representation 10 a Ralf Rosin 10 b Ralf Rosin 11 Ralf Rosin 12 author’s own representation 13 SWISS KRONO 14 –16 author’s own representation 17 Koch & Schulte GmbH & Co. KG 18 Siegfried Mäser 19 author’s own representation 20 a Ralf Rosin 20 b Ralf Rosin 21 Roland Bernath Building with Hardwood

Page 44: Michael Christian Peters; peters-fotodesign.com 1 – 8 author’s own representation 9 RADON photography / Norman Radon 10 Ralf Rosin 11 author’s own representation 12 a HILDEBRAND (blue architects until 2018) & Ruprecht Architekten 12 b ETH Zurich, Institute of Structural Engineering 13 Hermann Kaufmann + Partner 15 Christian Grass 16 a – d merz kley partner 17 Hüsser Holzleimbau 18 Hüsser Holzleimbau 19, 20 author’s own representation 21 Dav Stewart 22 Holzbau Amann 23 Hüsser Holzleimbau 24 SWG Schraubenwerk Gaisbach GmbH, Waldenburg 25 x-fix.at Example Builds

Page 54 Pages 57– 59: Page 60:

Michael Moran Roland Wehinger SWG Schraubenwerk Gaisbach GmbH, photo: Dominik Rau Page 61 top, bottom: SWG Schraubenwerk Gaisbach GmbH – production division Page 61 centre: Hermann Kaufmann Architekten Pages 63 – 67 top: Eckhart Matthäus Page 67 bottom: Frank Lattke

Pages 68 –71: Dirk Lindner Pages 72 –75: Roland Bernath Page 77: Roger Frei Page 78 top, centre: ERNE AG Holzbau, CH – Laufenburg, photo: Andreas Koger Page 78 bottom: Markus Bertschi Page 79 top right: ERNE AG Holzbau, CH – Laufenburg, photo: Roger Frei Page 79 bottom: Roger Frei Page 81 left: HESS TIMBER, Markus Golinski Page 81 centre: Markus Bertschi Page 81 right: ERNE AG Holzbau, CH – Laufenburg, photo: Roger Frei Pages 82 – 84 top: Michael Moran Page 84 B: Gregory Kingsley Page 85: Michael Moran Page 86: Axel Menges Page 87: Andrea Lautenschlager Page 88 top left: Simon Schleicher Page 88 top right: Roland Halbe Page 88 bottom: Axel Menges Page 89 left: Christopher Robeller Page 89 centre: Karola Dierichs Page 89 right: Axel Menges Pages 90 – 93: Lutz & Buss Architekten, photo: Daniele Portamone Page 94: Lutz & Buss Architekten Page 95: neue holzbau AG Pages 96 – 97: AHEC, photo: Jon Cardwell Page 98 top: Arup Page 98 bottom left: LEICHT Structural engineering and specialist consulting GmbH Page 98 bottom right AHEC, photo: Jon Cardwell Page 99 top left: HESS TIMBER Page 99 top right, bottom: AHEC, photo: Jon Cardwell Pages 100 –102: Sindre Ellingsen Page 103 top: Helen & Hard Architects Page 103 centre: Moelven Limtre AS Page 103 bottom: Sindre Ellingsen

Acknowledgements The authors would like to thank the following people for their contributions to the book, valuable suggestions and diligent proofreading: Prof. Hermann Kaufmann, TUM Markus Lechner, TUM Dr.-Ing. Tobias Wiegand, Studiengemeinschaft Holzleimbau (Council of Timber Technology) Prof. Dr. Stefan Winter, TUM Prof. Stefan Krötsch, HTWG Konstanz Prof. Kurt Schwaner

Appendix

Page 104

Eckhart Matthäus

109

Subject Index

A acetylation 22 adhesives 21, 33, 37 allgemeine Bauartengenehmigung (aBG) 25, 31ff. allgemeine bauaufsichtliche Zulassung (abZ) 25, 31ff. American hardwoods 14f., 96ff. application norms / instructions 31f., 39f. ash 13, 28, 90ff. availability of raw materials 23 availability 30f. B bar dowels beams - hybrid beams beech bending strength birch Bohlenständerbau branch structure bulk density butt joints

52 34f., 48 48ff. 9f., 27, 35f. 47 26, 82ff., 86ff. 72ff. 12 21, 26ff., 34ff. 45 53

C chemical wood modification 22 cities 7 climate change 14, 18 columns 50 - hinged pillars 50 component dimensions 46 composite beam 20 compression members 50 compression strength 47, 60, 90 connecting agent 21f., 53 connections 21f., 52ff., 66 - joinery connections 53 construction products of hardwood 23, 30ff. construction sector 19 construction, bearing structure 11, 45ff. cross-laminated timber (CLT) 7, 15ff., 20, 31ff. cross-section dimensions 30f. 110

D deforestation 18f. design 51 dimensional stability 22 dimensional tolerance classes 30ff. dimethylol dihydroy ethylene urea (DMDHEU) 22 domes 8 dowels 52 durability 22, 41f., 45 E elastic modulus 20, 46 emissions 20, 43 engineered timber products of hardwood 11, 37ff. eucalyptus 15, 29 European chestnut 13, 27 European Technical Assessment (ETA) 25, 31ff. extreme weather phenomena 12, 16f. F fastener 21f., 53 Federal Forest Inventory 16f. Federal State building regulations 23 finger-jointed solid timber 30ff. finger-jointing 30 flexural members 48, 50 forest conversion 18f. forest management 18f. fuel 9f. furfurylation 22 G general construction technique permit (aBG) 25, 31ff. glued laminated timber (glulam) 7, 12f., 16f., 20, 23, 31ff., 46ff. glulam beams 34 grade 32 H half-timbered construction 8 hardwood as a building material 7 hardwood products 12ff., 20, 23, 32, 35, 47ff.

high-performance materials hinged pillar history hybrid beam hybrid glulam hydrophobisation I impregnation - pressure impregnation indoor air quality Intrallam LSL (laminated strand lumber) joinery technology joining techniques

20ff. 50 7ff., 18 48ff. 33ff. 41

22 10 20, 43 14, 50 22f. 22f.

L laminated strand lumber (LSL) 14, 51 laminated veneer lumber (LVL) 13, 16f., 20, 31ff., 35, 46ff. laminates 34 leaching 41 load-bearing behaviour 21 M maple 26 marking 31, 35ff., 39 material properties 46 mixed forest 18f. Model Administrative Rules on Technical Building Regulations (MVV TB) 31 modern timber construction 11, 23 moisture 22 moulded laminated timber 48 Muster-Verwaltungsvorschrift Technische Baubestimmung (MVV TB) 31 N nails 52 national technical approval (abZ) 25, 31ff. national technical regulation 23 node 12, 22, 50, 59 notched joints 53 O oak OSB

7ff., 28 31, 38f., 41, 51

P panels 51f. panel-shaped products 50ff. phenolic resins 21 piles 7f. plywood 31, 38f., 51, 82ff., 86ff. poplar 29, 33 post-and-beam facade 49f., 62ff. post-and-plank construction (see Bohlenständerbau) processing 11, 22f. product characteristics 30, 33, 35, 37, 39

structural timber products

R railway sleepers raw wood regulations for use resistance reuse rod rod-shaped products roof structures roofs roundwood

timber industry timber research timber-concrete composite ceiling 21, 76ff. timber-concrete hybrid construction 76ff. timber-reinforced timber 20f. timber-to-timber connections 52 trunkwood share 12f. truss 11, 45, 50f. tulipwood 14ff., 50 use classes 40f., 42, 46ff.

10 10f., 19 30f. 46 9 47f. 47ff. 8f. 8 30

S sawn lumber 30ff., 45ff. screws 52 self-extinguishing feature 20 service class 42 service life 8 shear strength 47 shrinkage and swelling 22 solid wood 30, 45, 48 sorting standard 30 Southern blue gum (see eucalyptus) space frames 50 span length 60 species diversity 18f. squared timber 30 stem growth 12 stiffness 20, 34ff., 47, 80 strength characteristics 20, 45, 80 strength classes 30ff., 46 structural parameters 41 structural plywood 31

12ff., 20, 23, 32, 35, 39, 47ff. bearing structure, construction 11, 45ff., 60 synthetic resins 22 T technical rules tensile strength tension member timber church timber framework construction

V Venice Vitruvius W weather protection weather wood ash wood energy wood gas carburettor wood moisture content wood protection wood species

35 47, 90 50 11f. 62ff., 76ff., 100ff. 14, 19 19

7 7

22, 39ff., 41, 61 13 9 10 9 40f. 22, 39ff. 25ff.

111