Di song 160

Site Visit Report - Wood

Professor: Dana BUNTROCK Student: Di (Carina) SONG

GSI : Benjamin Michael Lueck Student No: 23300523

Background: The building is located in 1995-1999 El Dorado Ave, Berkeley, where is the intersection of El Dorado, Sutter and Hopkins, and it is considered as a landmark that should be kept according to the renovation regulation of the city of Berkeley.

In this case, 50% of the structure of the original house was being kept in order to being regarded as renovation rather than demolition. Thus in this stage, the prescribed building codes that applied to this building are slightly different to those applied to newly built buildings.

Now the renovated building is built as a commercial office (B 1 building). This will restrict the height of the building, its setback from street, its fire resistance level and the construction type.

The main supporting system of the building is concrete veneer that combines traditional wood frame and steel system, which aims to strength the seismic issue. The undergoing trade, when I was first on site on 10/02/2012, was the timber framing, while the second time on 20/02/2012, was window installation.

I paid attention to the temporary utilities on site such as the waste deposit location, temporary electricity panel, water supply and chemical toilet facility. Also, different types of wood are used as different structures according to their characters and properties. Wood grades are labeled on the wood as we can trace back the properties of the wood easily. Nailing and spacing are two other issues that I especially concerned, as they not only response to the soil type, ground movement but seismic consideration.

The building uses special design on its west-facade shear wall and a complex combination of different roofing system. To obtain environmental sustainability, it was also rated by LEEDS, which leads to more budgets.

In this report, I will split the activities that I observed into three phases: 1. preconstruction phase which is the documentation process that concentrates on related legislations, regulations and prescribed building code; 2.construction phase which includes constructing of foundation, vertical building frame, subfloor system and roof trusses, applying insulations, membrane and vapor barrier system, installing roof and utilities; attentions are paid on material properties and selection This report will explore the legislation progress in phase one, discuss the materials, construction methods and equipment in phase two.

Preconstruction phase  Administrative procedures The construction of this house has being lasts for 5 years since 2007. Complex legislation procedures chuck the construction process of this building. The building is to be designed according to prescribed building codes that establish minimum requirements for building design and construction.

Building codes that is involved in this house could be IBC, ASTM, related health codes, energy codes, fire codes and also, local zoning ordinances. Local authorities might issue the building permission at the first stage and control the design of the house in the context of surrounding area.

For example, the city of Berkeley do not allow the building to be demolished, as the architect of this building said, ‘they regard this building as a landmark.’ Also, in light of Berkeley’s aim of reducing the amount of landfill, not demolishing the building help to reduce the amount of waste generated in the process of excavation process. Thus the building was renovated rather than rebuilt.

The design of a house involves with many professions and trades. The house I visited is built under a lump sum contract with a fix budget of $3.7million. Builders estimate their cost by listing the construction activities in a chronologically manner. The owner pays a fixed fee regardless of how much the project actually costs. In this case, we can see that the construction work, trades and labors would have been well defined at the time it started.

The banker will come over to survey and issue the process of the construction every 2 weeks, then they will give out of 5% of the project fees for further construction. .

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Building site preparation

o Setback, temporary utilities and basic service connection Before construction, it is important to plan the access routes and storage location so that trucks are easy to drive into the site, heavy equipment are easy to load on the soil, pegs won’t be moved accidentally, and construction activity is not disrupted.

The site is well organized for construction. Pickup trucks and vans can easily park on around the site, and the waste pile stacks in the corner of the lot.

Boundary lines is set up by the surveyors and is be fenced by the builders.

Temporary utilities are installed on site, e.g.: chemical toilet, tar plumping machine.

Generally, temporary facilities such as water electricity are also needed on site for construction equipment and certain construction process such as concrete mixing and curing.

However, in the case of renovation rather than demolition, water and electricity supply are already on site before the workers come into site. Thus, there is no need to contact with city council in signing up new lines.

Construction phase  Foundation: Slab on Grade Construction of a foundation helps to transmit the weight of the building into the earth. The foundation of this building is slab on grade.

Foundation will settle to suit the soil around and adjust to the loads. Before designing a foundation, an examination of the soil type is needed. Site class is determined by the characteristics of the soil, according to IBC table shown below:

Then IBC requires to define the seismic design category for the site, based on occupancy category and spectral response acceleration parameters. According to the table below, Berkeley area belongs to SDC Class D.

Slab on grade rest their slab on ground. The concrete is thickened at its perimeter to provide footings under the exterior wall. This kind of construction method is cheaper than strip footings and it is suitable for clay and flat soil and warm climate zone, as the thermal mass of concrete slab could cool the house.

Reinforcement used on site: ¾’’ steel, 1’grid, 2layers depth of trench: 3’

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Platform framing ( stud)

The timber structure constructed nowadays is an advanced version of wood light framing called platform frame.

It is an elaborated version of old American balloon style that long studs run all to way from roof to foundation, and floor joists are rest on a recessed area into the studs

Advantages of platform framing: -to use shorter and easier handled timber.

-provides platform on which carpenters can work conveniently.

Disadvantages: -more labor and time in construction floor -increase the height of building.

-larger amount of shrinkages in wood -make the interior finish surfaces uneven.

Veneer walls are bolted down to foundation and between the gaps is a layer of water resistance membrane

Toe nailing vertical bottom plate to horizontal one

Bottom plate bolt down to foundation

Frame material:

Frame material: wood and selection

PSL

LVL

Wood product used in visited building

characters

Usage in the visited building

parallel strand lumber

Long, thin strips of veneer glued

1.columns and lintel

together with most of its strips run in one parallel direction. It is

2. some of studs

the heaviest, strongest, and most expensive engineered lumber.

3. blocking between roof joists

Made from thin wood veneer

Roof joist

Laminated veneer lumber

sheet that is glued into thicker

member.

Piece of wood cut into prescribed size

Dimensioned lumber

Roof joist Stud lintel

OSB

Oriented Strand Board

Made of long strands of wood glued into 3-5 layers. In each layer, the strand goes the same direction.

Sheathing board

Blocking

Other than the flat roof truss system which is prefabricated, the other framing works are done on site.

Seasoned plain sawing lumber are used in the stud system. The bottom sills are pressure preservative lumber in which preservation chemicals are forced into the cecullar structure of the wood, so that the service life the wood can be extended. In this building, all the wood that is attached to the concrete shear wall are treated with chemical preservation in pressure.

sealant on side of OSB board resisting water being sucking into the wood.

Frame material: steel and connections The main supporting structure of the building is steel and they are 450 pounds per foot square.

The combination usage of wood and steel increases the strength of the building frame. Wood is one of the best materials for anti-seismic construction since it is of low mass and is relatively less brittle than masonry. Steel can deal with tension well. But the system will only work well when it’s properly connected to its foundation and has adequate shear force resistance.

Also, joints are common structural weakness in dealing with building’s seismic performance. Thus, dense nailing, strong hold-down and bolts all help to integrate different materials together, protecting the building's integrity and enhancing its seismic performance

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2

3

5

1. Roof joist hang across the steel beam 2. Lintel rest on steel caped stud 3. Heavy –duty seismic holddown on PSL stud. Steel plate hold- downs are stronger and tie the full height of the building frame to its foundation.

4. Bottom plate bolt down to concrete and face nailing 5. Toe nailing 30degree angle the stud to bottom plate(sill plate) 6. Conventional foundation anchor bolt with oversize washer 7. Nailing on the sheathing board :every 3’’on horizontal line and every 8’’ on vertical line, double on the edge

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The steel columns are anchor bolted onto the foundation. Before the column was erected, the workers prepare a ‘pocket’ on which a thin layer of leveling plate is placed. Then the base plate of the column would be put on the leveling plate, before workers grouting the column base and bolting it down.

Frame Size, spacing ,bracing system and seismic Despite the studs attached to concrete shear wall are 2x4, the other studs are all 2x6. The length of the stud is of standard size of 12’. Roof truss spans 224’ in the main hall while the size of I joist in the other room is 2x12. The size of sheathing panel is of regular size of 4’x10’ and 4’x12’.

2x4 and 2x6 is the common stud size in small timber construction. Considering the main supporting system of the building is steel which is really strong, there is no need to enlarge the stud size to increase seismic performance.

The stud spacing is of standard size of 16’’. In some unimportant area such as garage, local codes might allow for larger spacing in 24’’. Spacing of joist and roof truss corresponds to stud spacing with 16’’ also.

There is no diagonal bracing system in this building as the traditional diagonal bracing will cut notches through into the studs which will reduce the integrity and strength of studs.

16’’

Instead of having diagonal bracing, there are rows of blockings that run allign with each other. Rather than traditionally staggered face nailing, the aligned blockings are toe nailed in 30-degree to studs. The blocking between studs will increse its structual integrety and reduce lateral flexibility.

Sheathing is an important element in timber framing to resist shear forces. The nails that connect the sheathing panel to framing members have little to do with perpendicular forces against walls, but sheathing panel connect frames into a strong unit. Sheathing also act as a furnish surface for building.

The house that was visited use double shear wall system which apply sheathign panels on each side of the stud wall. This will increse its seismic performance.

Roof joist is stabilized by rim joist and blocking.

Steel framing system also helps to synthesis and support the span.

The design of roof system of this building compromises three types of construction. This might be related to its seismic requirement where larger span calls for stronger material and construction method.

In the largest room, the roof construction type is prefabricated flat roof truss. This choice may be due to the limitation of materials. Dimension lumbers that span in such a long distance is very expensive, so this might lead them to choose pre-fab flat truss in this area.

In the room that is just adjacent to the main hall, runs along rows of dimensioned lumbers in the direction that is different from those flat truss. This might be also out of consideration of availability of materials. Long span dimensioned lumber cost much.

In the other room there roof is low with two layers of joist going through. The upper layer is LVL wood while the lower are dimensioned lumbers. There are blocking panels to assist the stability of the joists.

But different roof system within one house might lead to uneven ground movement.

Insulations, water barriers, services and sustainability (LEEDS rating) The building is rated by LEEDS in order to achieve sustainability deisgn.

Considering there are lots of fenestrations in the building, the heat loss would be high if the window is not silled properly or insulation is not applied adequately. In order to achieve higher performance in LEEDS rating ,the building used good quality materials and clever construction methods which adds up 30-35% of the original budget.

Pumping pipes need to be wraped around by insulation materials to prevent heat loss.

The window of the building can operate automatically during night to do natral vetilation.

Window is adequately silled and insulated. Vapour barrier is installed in site when I was paying the second site visit.

Vapour barrier can also be seen between the gap of brick veneer and concrete shear wall. This will prevent the studs from moisture and deflection.

Services will run through the framing system and sometime penestrate into the structure.

Electricity box is fixed to the stud.

Fire Rating , Dry wall, Set back

The dry wall of the building is rates as 1h 15mins.

11’set back from the main road (front) 15’set back from neighbor( back)

Trees that is too near to foundation will cause damage to foudnation.

Conclusion The report was trying to go through the construction trades that has being on site and concentrates on the materials and special construction methods they used for improving seismic performance. The site visit informs me to design house according to prescibed building codes and choose materials wisely. The way they build the west façade shear wall, the way they combine timber frame with steel framing, the way they deal with joints, and especially three different systems of roof all indicates that safety for occupants as well as wisely choosing systems according to needs are two significant issues when designing a house.

Bibliography: Aleen Edward, Fundamentals of building construction materials and methods, Wiley,2009 American forest and paper association,Details for conventional wood construction, 2001 Burden, Ernest E. Illustrated dictionary of building design and construction. New York ,McGraw-Hill, 2005.

Ching, Frank. Hoboken, Building codes illustrated : a guide to understanding the 2006 International building code , New York, Wiley, c2007 Ching, Frank. Hoboken,Building Construction Illustrated, New York John Wiley & Sons, 2008.

Ghosh, S.K, Sesmic design considerations in model codes, S.K. Ghosh Associates,Inc,2000 Gary S. Berman, PE, Structural steel design and construction, Greyhawk North America,LLC Jeff Barr, Preliminary Seismic design analysis,Advanced Technology Solar Telescope,2008