ArchDoc: Vaulting system and roof trusses of the choir Saint John the Evangelist Church, Park Abbey by Sofia Marin

ArchDOC 2021 - G R O U P B

Vaulting system and roof trusses of the choir Saint John the Evangelist Church, Park Abbey FACILITATORS Christian Ouimet Pieter-Jan de Vos

STUDENTS

Hannah Mathew Komal Nandrekar Marjolein Schut Sofía Marín

Group B: Vaulting system and roof trusses of the choir of the Saint John the Evangelist Church, Park Abbey Hannah Mathew (Architect), Komal Nandrekar (Architect), Marjolein Schut (Historian and Conflict studies) & Sofía Marín (Architect) ArchDOC team: Christian Ouimet, Pieter-Jan de Vos

Table of contents

I N T R O D U C T I O N H I S T O R Y O F T H E S I T E S I T E & S C O P E O F W O R K M E T H O D O L O G Y D O C U M E N T A T I O N - P L A N D O C U M E N T A T I O N - R E F L E C T E D R O O F P L A N DOCUMENTATION - SECTION A-A’ DOCUMENTATION - SECTION B-B’ DOCUMENTATION - DETAILS D O C U M E N T A T I O N - O B S E R V A T I O N S B U I L D I N G A R C H E O L O G Y S I G N I F I C A N C E / C O N S E R V A T I O N F I N A L R E M A R K S T E A M - W H O W E A R E I M A G E I N D E X B I B L I O G R A P H Y

1 3 5 7 13 14 19 20 23 26 29 33 34 35 37 38

INTRODUCTION

Park Abbey is a Norbertine abbey located just southeast of the city of Leuven, Belgium. The abbey was founded in 1129, when Godfrey I the Bearded, Duke of Brabant, donated his game park to the Nortbertines. The exact location of our survey is the roof structure of the abbey church: the Saint-John-the-Evangelist Church. The earliest history of the church dates back to 1131, when the first canons built a small roman chapel for their services. Later, in 1228, the larger stone church in Romanesque style was erected and remained relatively untouched until 1626 when the choir was extended, and the apse was rounded. In 1729 abbot de Waerseggere embarked on the largest building campaign in the history of the abbey, and both the lay-out of the church and the interior were adjusted to better suit the tastes of that time (e.g., the baroque main altar stems from that campaign). Park Abbey is one of the best-preserved abbeys in Belgium, and the wealth that the Norbertines enjoyed at times throughout the almost 900 years of history is still visible in the complex of buildings today. The abbey is listed as protected architectural heritage by the Government of Flanders, as well as a protected monument and the abbey with its surrounding area are listed as protected cultural and historical landscape. Figure1. Plan of Leuven, 2015, from the Nationaal Geografisch Instituut.

INTRODUCTION

Figure 3. Photograph Park Abbey. October 28th, 2021. Photographer: Sofiía Marín.

Figure 2. Engraving of L.Vostermans, 1669, image from Studio Roma https://www.studioroma.be/wp-content/uploads/2018/11/0046_ill-5. jpg, accessed 16 January 2022. INTRODUCTION

PARK ABBEY TIMELINE

1129

1610

The Church as seen on one of the earliest recordings on engraving by Gramaye.

The abbey was founded when the Duke of Brabant Godfrey I the Bearded donated his game park to the Norbertines.

Figure 5. Park Abbey on an engraving by Gramaye, 1606. Image from Parcum.

The Saint-John-theEvangelist Church was built in Meuse Romanesque Style in 1228.

1228

The Church as seen on a map from the ‘Boschboek’.

1558

1668

Figure 4. Detail showing Park Abbey on a 1560 map by Jacob van Deventer. Image from Studiebureau Archeologie.

HISTORY OF THE SITE

1719-1730

2000

The last great construction campaign, including he expansion of the church (1726 engraving by Sanderus).

The abbey grounds are let to the city of Leuven on a 99 year lease and maintenance work started. The site now houses the PARCUM museum, while other restoration works continue. The work is expected to be completed in 2025.

Figure 7. Park Abbey on a print by Sanderus, 1726, image from Visit Leuven.

Following the French Revolution, the Abbey is dissolved. The church becomes a Parish Church.

1797

Figure 6. Detail from country map showing Park Abbey, 1665, from Joris en Willem Subil. Image from Studio Roma.

The Abbey is re-established.

1836

HISTORY

Figure 8. Park Abbey on a painting by Van Gobbelschroy, 1836, image from Visit Leuven.

SITE & SCOPE OF WORK

GROUP B Figure 9. Aerial photo of Park Abbey. @Google Earth

The location of our survey is the vaulting system and roof trusses of the choir of the Saint-John-the-Evangelist’s church of Park Abbey. After the first inspection of our site on day 1 we identified the following deliverables for our remaining 3 days on the Abbey: 1. 2. 3. 4. 5.

Plan of the roof over the choir and the transept. Plan of the vaults over the choir. Cross section of the roof cutting over the choir, the transept and, the bell. Detail of one of the type roof trusses. Additional cross section (depending on time and how much data is recorded).

At the start of the week and the assignment, the focus was on the practical implications of documentation and becoming familiar with the recording equipment. However, the site’s significance became clear to us as the week progressed, and we worked on the recording. This process made us realize the importance of recognizing what should be recorded, informing our decision-making as the week progressed. Please see also our conclusion for our assessment of the significance and the state of conservation.

SITE & SCOPE OF WORK

Figure 10. Section of Park Abbey Church. Taken from “ArchDOC Topics and Groups_2021-2022”.

Figure 11. Park Abbey outside church south façade. Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021.

SCOPE OF WORK

Figure 12. Park Abbey outside church north façade. Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021.

METHODOLOGY

When first coming into the site, we understood that the biggest challenge would be capturing all the information needed to deliver our agreed products while only having access to the wooden bridge in the middle of the room. We had a group meeting on how to approach such a big area in limited conditions of light and space while being only four people. The facilitators, Christian Ouimet and Pieter-Jan De Vos, helped us plan which tools would be helpful for each deliverable agreeing that a holistic approach (using both laser scan and a total station) would be necessary to get full coverage of the site. We made a list of what type of digital tools and experience each team member had. We divided the group in two: Pieter-Jan oversaw the total station set-up and the laser scan and, Christian supervised photogrammetry and record photography. 7

Figurs 13 to 15. Group B surveying the roof of Park Abbey Church. Photograph taken by Pieter-Jan de Vos. October 2021

METHODOLOGY

Plan Reflected Ceiling Plan

Section A-A’

Section B-B’

Truss model Joinery detail Building chronology

0 Total station

20 Hand measurements

40 Lasser scann

Observation

80 Record photography

100

Photogrammetry

Figure 16. Chart of the percentages of each technique used to produce the deliverables for the survey of Park Abbey Church. Image produced by Group B. @ArchDoc 2021. METHODOLOGY

D O C U M E NTATI O N TOTAL STATION +

R E C O R D I N G STRATE GY + D RAW I N G PR O C E S S

CAD SURVEY

Figure 17. Placement of the Total Station at the roof of Park Abbey Church. Image produced by Group B. @ArchDoc 2021.

Thanks to the wooden runway, the Total Station could be set on a stable place which guaranteed a good-enough sight to the targets. These were placed around the vaults the space and used to coordinate data obtained by photogrammetry and laser scanning.

Figures 20 and 21. Photographs showing various control points around the roof of Park Abbey Church. Photos taken by Christian Ouimet. October 2021

Figure 19. Wireframe drawing made with Total Station and AutoCAD. Image produced by Group B. @ArchDoc 2021.

Figure 18. Control points. Image produced by Group B. @ArchDoc 2021.

Figure 22. Group B at the roof Park Abbey Church. Photo taken by Marjolein Schut, October 2021.

METHODOLOGY

AutoCAD was directly connected to the Total Station. Using this method an overall drawing of truss Nº3 was made.

Figure 23. Scan of truss Nº3 at the roof of Park Abbey Church. Scan done by Aziliz Vandesande. October 2021.

A laser scan was done using FARO X130 on the roof. Both, the point cloud obtained from the scan and the wireframe obtained with the Total Station, were used in AutoCAD for the final drawings.

LASER SCANNING

Figures 24 and 25. Placement of the FARO X130 3D scanner at the roof of Park Abbey Church. Images produced by Group B. @ArchDoc 2021.

Two different scanners were used for this technique: FARO X130 and LEICA BLK360. The placement of the scanner should be made in a sequence so that the outcome overlaps and the point cloud has enough data to process. Each scanner produced different outcomes, which were later crossed with the Total Station results to have one space in AutoCAD to draw from.

Figures 26 to 28. Panoramic images made with FARO X130 3D scanner at the roof of Park Abbey Church. @ArchDoc 2021.

It is important to denote that the point cloud is not enough to understand or record the space with the scans made so far. It would be essential to spend more time on-site to gather more information to understand the area thoroughly. METHODOLOGY

PHOTOGRAMMETRY & PHOTOMERGE

Figure 31. Photo of Group B working at photogrammetry. Image produced by Group B. @ArchDoc 2021.

Figure 29. Placement of camera for photogrammetry at the roof of Park Abbey Church. Image produced by Group B. @ArchDoc 2021.

The camera SONY ILCE-7RM4 / FE 24-105mm F4 G OSS was used for photogrammetry. It was indispensable to use flashes since the space was dark and the artificial light was insufficient. For this technique, it is essential to follow a sequence to smooth the outcome when Metashape is processing the data.

Figure 32 to 35. Photogrammetry done with a camera SONY ILCE-7RM4 / FE 24-105mm F4 G OSS. Image produced by Group B. @ArchDoc 2021.

Figure 30. Difference in the obtained results done by photogrammetry (left) and laser scanning (right). Image produced by Group B. @ArchDoc 2021.

METHODOLOGY

Figures 36 and 37. Park Abbey Church roof made with Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021.

BUILDING ARCHEOLOGY METHODOLOGY

Figures 38 to 41. Group B observing the roof space, understanding the space, the details, and the connections. Photos taken by Group B. @ArchDoc 2021

To establish the building chronology of our site, we relied on making direct observations to identify materials, the structure of the building, the techniques used, the assembly method used at the time of the construction. To cross-check our findings or verify them, we used relevant literature and consulted experts, specifically Pieter-Jan de Vos, Professor Krista de Jonge and, Professor Thomas Coomans. It was essential to the process of understanding the building’s roof the time spent looking at the trusses, its materials, and in general, the details that we could see with our eyes that would not show in the scans. These were clues that helped build the timeline. METHODOLOGY

D O C U M E NTATI O N

P LAN

B 4.38

+1.82M LVL

20.79 3.98

4.21

+0.58M LVL

+1.35M LVL

4.05

+0.101M LVL

3.97

+ 1.23M LVL

+0.903M LVL

+1.22M LVL

+ 0.24M LVL

+1.32M LVL

+1.69M LVL

+1.32M LVL

+1.12M LVL

+1.24M LVL

+1.12M LVL

+1.24M LVL

+ 1.10M LVL

+ 1.151M LVL

3.48

7.71

+ 1.65M LVL

+1.75M LVL

+0.66M LVL

+1.23M LVL

+/-00M LVL

+ 1.26M LVL

+ 0.32M LVL

3.3 16.61

Level zero was assumed for the praticalities of the drawing. The Plan was made using Metashape, Recap and AutoCAD. Figure 42. Plan of the roof the choir of the Saint-John-the-Evangelist’s church of Park Abbey. Plan produced by Group B. @ArchDoc 2021.

DOCUMENTATION - PLAN

R E F LE C T E D R O O F P LAN

4.38

4.21

20.79 3.98

B 4.05

3.97

3.48

7.71

3.3

16.61

Level zero was assumed for the praticalities of the drawing. The Reflected Roof Plan was made using Recap and AutoCAD. Figure 43. Reﬂected Roof Plan of the roof the choir of the Saint-John-the-Evangelist’s church of Park Abbey. Plan produced by Group B. @ArchDoc 2021.

DOCUMENTATION - REFLECTED ROOF PLAN

P L A N : M E T H O D O L O G Y & L I M I T A T I O N S

P LAN

REFLECTED ROOF

1. An initial observation with sketches of the plan was made to describe the approach.

1. The reflected ceiling plan has been made using the laser scan output and record photography.

2. Total Station was set up to establish the coordinate syste and obtain the control points. 3. Photogrammetry was carried out for the vaults on the west part of the site. 4. Laser Scan 5.Throughout the week, continuous observations were made to compare and feed the results gained with the technology vs. the real-life situation. 6.

Recap and AutoCAD were used to produce the drawings.

Advantages: Compared to laser scanning, Photogrammetry provides more clarity in detail in terms of understanding the cracks on the surface and for a better texture. Limitations: Space below the catwalk was covered by a significant portion of the vaults making it difficult to access either by a camera, a Total Station, or a Scan. The point cloud resulting from the scan lacked clarity. To resolve this, more detailed scans had to be taken. 15

Advantages: An overall understanding of the roof structure can be gained from the laser scans. Limitations: Even though the scan seems to cover the whole space, there is a lack of clarity regarding the topmost spaces and corners in the output. Due to the insufficient accessibility to these areas and hindrances in the line of sight: “total coverage” was not achieved. In the end, we had to rely on memory and photos; this could be misleading, and while tracing the point cloud is a “fast” way to produce images, we were missing much information.

DOCUMENTATION

Figure 45 to 50. Images produced using AutoCAD. These show the difference in detail obtained using photogrammetry and laser scanning. Images produced by Group B. @ArchDoc 2021.

PHOTOGRAMMETRY RESULTS

LASER SCAN RESULTS

DOCUMENTATION

Figure 51. Photo collage made using Photoshop showing the vaults from downstairs. The cracks on the vaults and the monitoring system can be seen along the image. Image produced by Group B. @ArchDoc 2021.

Figure 52. Detail of the photogrammetry done on the vaults. Image produced by Group B. @ArchDoc 2021.

DOCUMENTATION

O B S E R VATI O N S

Figure 53. Photo taken for photogrammetry. The concrete ring beam can be seen at the top of the wall. Image produced by Group B. @ArchDoc 2021.

1. There are two distinct styles of vaults in the area documented. The vaults above the choir are much smaller and different in shape and size from those above the nave, indicating the different construction periods. 2. The vaulting height also varies when comparing the vaults above the choir, which is much lower in elevation than the nave. 3. Due to previous instability problems of the church, cracks can be observed on the surface of the vaults. The system used for monitoring stability in the church is no longer in use since interventions have been carried out to consolidate the structure.

Figure 54. Photo taken for photogrammetry where the cracks on the vault can be seen. Image produced by Group B. @ArchDoc 2021.

4. The restoration made somewhere in the 20th century consolidated the brick walls and made a ring concrete beam around them. This intervention significantly changed the way the structure of the building works. There should be a record of the original situation before the intervention. Otherwise, there has been a significant loss of heritage value to the site; these records might be kept in the Park Abbey’s archives (archive research needed).

DOCUMENTATION

D O C U M E NTATI O N

S E C T I O N A - A’ / E A S T - W E S T

Level zero was assumed for the praticalities of the drawing. The section was made using Recap and AutoCAD Figure 55. Longitudinal section, A-A’ (East-West). Image produced by Group B. @ArchDoc 2021.

DOCUMENTATION - SECTION A-A’

S E C T I O N B - B’ / N O R T H - S O U T H

Level zero was assumed for the praticalities of the drawing. The section was made using Recap and AutoCAD Figure 56. Transversal section, B-B’ (North-South). Image produced by Group B. @ArchDoc 2021.

DOCUMENTATION - SECTION B-B’

S E C T I O N S & D E T A I L S : M E T H O D O L O G Y & L I M I T A T I O N S

Figure 57. Working drawing for the Longitudinal section, A-A’ (East-West). The point cloud obtained by laser scanning was retraced in AutoCAD. Image produced by Group B. @ArchDoc 2021

S E C T I O N A-A’ 1. A sketch was prepared on-site of the longitudinal section (E-W Section looking North). 2. Laser Scans made with the Faro Scan were used to draft this section. (The turret and the last bay of the roof over the nave have not been considered. The scans did not provide sufficient detail, although on-site observation of this area was done for historical analysis.) 3. Recap and AutoCAD were used to produce the drawings.

Advantages: An overall understanding of the roof structure can be gained from the laser scans. Limitations: The interference of ambient light and shadows decreases the clarity of the scan and even though the scan seems to cover the whole space, there is a lack of clarity regarding the topmost spaces and corners in the output. Due to the lack of accessibility to these areas and hindrances in the line of sight: “total coverage” was not achieved. In the end, we had to rely on memory and photos; this could be misleading, and while tracing the point cloud is a fast way to produce images, we were missing much information.

Figure 58 to 63. Working drawings for Transversal section, B-B’ (North-South). The wireframe drawing was placed along the scans obtained by FARO X130 and Leica BLK360. The point clouds obtained by laser scanning were retraced in AutoCAD. Image produced by Group B. @ArchDoc 2021

S E CTI O N B - B ’ & D ETAI LS 1. Initial observations of the roof structure were carried out and, sketches were made of the truss Nº3 plus various details. 2. Hand measurements were taken of accessible details of the roof structure. 3. An elevation model of a single truss (Truss No. 3) was made directly using the Total Station and an on-site computer to draw on real-time , which gave an overall idea of the structure. a. S E C T I O N B - B ’ i. Used the scans made with the Faro x130 scan to overlap information. ii. Hand measurements were added to specific places. iii. Recap and AutoCAD were used to produce the drawing. b. D E T A I L S i. With more detailed observation, joinery details of the truss were sketched out based on guidance from our facilitator, Pieter Jan. ii. The joineries of inaccessible areas were made by looking at reference photographs taken on site. iii. Sketchup and Photoshop were used to produce the drawings.

Advantages: Live drawing using the Total Station and AutoCAD proved the easiest and most accurate way to understand the point cloud added later to the final drawing file. On-site observations proved to be quite advantageous while making the model, for they provided a clear understanding of various joineries of the structure. Limitations: The process of using a Total Station and live drawing with AutoCAD is slow, so if the time on site is reduced, it is not the best technology to implement. On the afternoon of the last day of ArchDOC, there was access to different data made with a LeicaBLK360 in the apse. This information was useful to understand the thickness of the vaults. However, there was no time to observe the building or take photos, so tracing the point cloud became an impossible challenge. Many of the joineries of the upper parts of the truss, due to lack of accessibility, could not be measured and were completed using photographs. 22

SCHEMATIC STRUCTURE OF THE ROOF ABOVE THE CHOIR S C H E MATI C STR U CTU R E O F TH E R O O F AB O V E TH E C H O I R RIDGE TILE RIDGE BOARD

COMMON RAFTERS

BATTENS

SLATE ROOF TILES

ROOF GUTTER

ASHLAR PIECE

TRUSS

WALL PLATE Figure 64. Schematic structure of the roof above the choir. Truss Nº3 was used for modeling on SketchUp. Image edited on Photoshop. Produced by Group B. @ArchDoc 2021

DOCUMENTATION - DETAILS

R O O F TR U S S PARTS PARTS OF THE ROOF TRUS

RIDGE PIECE CENTRAL POST

COLLAR TIE BRACE

WINDBRACE

DETAIL 2

PURLIN COLLAR TIE BRACE PURLIN

WINDBRACE DETAIL 1 PRINCIPLE RAFTER TIE BEAM Figure 65. Roof truss parts. Truss Nº3 was used for modeling on SketchUp. Image edited on Photoshop. Produced by Group B. @ArchDoc 2021 DOCUMENTATION

EXPLODED JOINERY DETAILS OF THE TRUSS E X PLO D E D J O I N E RY D ETAI L O F A MODEL TRUSS

MORTISE

PEGS

JOINERY DETAIL OF THE BRACE AND THE COLLAR BEAM

TENON

EXPLODED VIEW OF DETAIL 1

Figure 66. Exploded joinery detail of a model truss. Truss Nº3 was used for modeling on SketchUp. Image edited on Photoshop. Produced by Group B. @ArchDoc 2021

DOCUMENTATION

EXPLODED VIEW OF DETAIL 2

O B S E R VATI O N S HOIST WHEEL In the wooden beams horizontally placed wooden beams at the apse, in front of the small door that faces east, we found rectangular shapes in the wood. We attribute these to the hoist wheel, or (treadwheel) crane, that would have been positioned here to bring up the large pieces of timber.

Figure 67. Location on the plan of the hoist wheel marks on the beams. Image produced by Group B. @ArchDoc 2021

Figure 68. Detail of Pieter Bruegel the Elder’s painting the (great) Tower of Babel (1563) showing a treadwheel crane. Image taken from the Journal of Art in Society webpage.

Figure 69. Photograph of the traces of the hoist wheel. Image created by Group B during ArchDOC 2021.

AXE AND SAW MARKS The purlins, collars, principal rafters, and braces all display visible axe and saw marks. These marks illustrate what kind of tools were used. Figures 11 and 12 show marks that indicate the beams were sawed with a pit saw. Figure 13 shows an illustration of how a pit saw worked. Another technique used on the beams on our site is timber hewing, traces of which you can see in Figure 14. Timber hewing served to convert a trunk from its rounded form into the timber with flat surfaces using an axe.

Figure 70. Photograph of saw marks, showing pit saw technique. Image taken by Hannah Mathew @Archdoc 2021.

Figure 71. Photograph of saw marks, texture, showing pit saw technique. Image taken by Hannah Mathew @Archdoc 2021.

Figure 72. Illustration of a pit saw. Engraving from a 1790’s Book on Trade published in London. Image taken from Lost Art Press (Burke, 2014).

Figure 73. Photograph of collar showing traces of timber hewing. Image taken by Chris Ouiment @ArchDoc 2021.

DOCUMENTATION - OBSERVATIONS

CROSS We observed this cross, almost like graffiti, on one of the braces supporting truss nr. 2, and recognized the shape of a Jerusalem cross. Our hypothesis, therefore, became that it could be a painted consecration cross, but we could not find much material to substantiate this. After consulting Professor Coomans it became clear it is in fact highly unlikely this is a consecration cross. Professor Coomans explained that usually, the 12 consecration crosses are at the main gate of the church, on the columns of the nave and on the inner walls of the church. A church consecration, by which a building becomes the house of God, is a codified ritual carried out by a bishop and it is a very solemn event with procession, singing choirs, incense, and so on. All these things are impossible to imagine taking place in a roof structure. Professor Coomans added that the most credible hypothesis is that this cross has been painted on a beam to protect the roof from lightning (before the invention of lightning rods). It was common to paint crosses on walls of farms, for example, to protect the building (from a storm, evil, etc).

Figure 74. Location on the plan of the cross found on one of the trusses. Image produced by Group B. @ArchDoc 2021

Figure 75 and 76. Photographs of the cross graffiti. Images taken by Marjolein Schut @ArchDoc 2021 DOCUMENTATION

ASSAMBLY MARKS Carpenters’ assembly marks are often found in historical timber structures, they represent numerals and were used to indicate the position of each timber in a given roof structure. The numbering is usually similar to Roman numerals, but with a slight change to indicate Left and Right positioning. In the roof above the choir, each truss has visible assembly marks on the eastern facing side of the beams, counted from truss 1 at apse to truss 5 before southern transept/crossing.

TIMBER RAFT PEG HOLES Felled timber was transported across Europe by rivers, using timber rafts. The logs making up a timber raft, thousands at a time, were kept together with crossbeams, which would be fastened to the logs by wedging twigs or pegs into a hole in the log, sometimes with rope. These wedges (with the piece of rope, or pieces of willow twig) would soak up water and swell, making the connection virtually rock-solid. These timber raft peg holes (houtvlotverbindingen or vlotgat in Dutch) are often still visible in timber structures.

Figure 77. Location on the plan of the assabley marks on the trusses. Image produced by Group B. @ArchDoc 2021

Figure 79. Photograph showing the Timber Raft Peg Holes. Image taken by Komal Nandrekar @ArchDoc 2021

Figure 78. Photographs of the assembly marks on the rafters. Images taken by Group B @ArchDoc 2021

Figure 80. Location on the plan of the Timber Raft Peg Hole. Image produced by Group B. @ArchDoc 2021 DOCUMENTATION

BUILDING ARCHEOLOGY

This chronology is based on the building archeology method discussed in the chapter of Methodology on page 12. The roof structure above the choir and the apse of Saint-John-the-Evangelist’s church is topped with a ridge piece (ridge purlin), with purlins running parallel to the ridge. This type of ‘purlin roof’ (gordingenkap, in Dutch) structure appears in the historical Low Countries 1 from around 1550 onwards (Dirk van Eenhoge V. D., 2018). Before this time, timber roofs in the Low Countries were constructed as what is called a “common rafter roof” (sporenkap, in Dutch). In a “common rafter roof,” the rafters run perpendicular to the ridge’s top of the walls, 1

It is important to keep in mind that the area we refer to today as Flanders had a very different territorial organization in medieval times. For example, during a large part of the Middle Ages Leuven (and Park Abbey) were part of the Duchy of Brabant, state of the Holy Roman Empire, while the County of Flanders, to the west of the Duchy of Brabant, was part of the kingdom of France.

CHRONOLOGY OF THE CONSTRUCTION

with the roof plates on the trusses. This is a notably different construction style from what we see in the roof above the choir & the apse, where we have loose rafters nailed to the ridge purlin. Figures 81, 82, and 83 below show two roof structures examples and illustrate the visible differences in style. Based on this typology, we can be reasonably sure the roof of the “Saint John the Evangelist Church of Park Abbey in Heverlee” was built after 1550. We have few written sources or documented research about the construction history of Park Abbey, and many of the reports covering the archeological documentation of the site use two main publications as the basis of most references on the architectural history of the abbey: Raymond M. Lemaire’s inventory from 1971 “Bouwen door de eeuwen heen. Inventaris van het cultuurbezit in Vlaanderen. Architectuur, Deel 1. Provincie Brabant, arrondissement Leuven.” (Lemaire, 1971) and the tourism publication from Stefan van Lani from 1999, “De Norbertijnenabdij van Park”. (Lani, 1999). What is of note for our survey of the

Figure 81 and 82 provide an example of a common rafter roof (sporenkap), showing the roof construction of above the choir of the Dominican church of Leuven from the 13th century. Figure 81. Drawing of the common rafter roof (sporenkap) above the choir of the Dominican Church in Leuven by R.M. Lemaire (1942). Image taken from ‘De oudste dakconstructie in de Leuvense binnenstad: bouwhistorisch onderzoek in de predikherenkerk (prov. Vlaams-Brabant)’CITATION Tho04 \l 1043

Figure 82. Photograph taken from the lower part of the common rafter roof (sporenkap) construction above the choir, created by Oswald Pauwels (2001). Image taken from ‘De oudste dakconstructie in de Leuvense binnenstad: bouwhistorisch onderzoek in de predikherenkerk (prov. Vlaams-Brabant)’CITATION Tho04 \l 1043 (Coomans, 2006).

Figure 83 provides an example of a roof structure with a ridge purlin, which is similar to what we found on our site, the roof above the choir and the apse of Saint-John-the-Evangelist’s church, Park Abbey. Figure 83. Photograph of the roof structure with ridge purlin in the O.L.V. Church (Church of Our Lady) in Bruges, 2nd half of the 16th century. Image created by O. Pauwels, taken from the report of Agentschap Onroerend Erfgoed. (Dirk van Eenhoge V. D., 2018)

BUILDING ARCHEOLOGY

roof structure above the choir and the apse of Saint-John-the-Evangelist’s church is that both publications mention that what used to be a straight closure of the choir was reconstructed at the beginning of the 17th century into the rounded apse we see today. Van Lani added specifically that under Abbot Jan Druys, the choir was extended with one bay in 1628. Still, unfortunately, there is no direct reference to the source of where specifically this information comes from. The bibliography clarifies that much of Van Lani’s publication is based on his research in the Park Abbey’s archives. We think it would be interesting to carry out further research in the Park Abbey archives to shed more light on the building history of the church. Moreover, in Figure 84, one can see there is indeed a difference in material between the apse and the last bay before the apse and the choir of the church that comes before.

Whether or not the choir was extended with one bay in 1628 would be valuable to know because we believe that the timber roof structure from the apse to the crossing was done in one single building phase. We arrived at this conclusion because we observed no signs that the choir had been adjusted since its construction, so there might have never been a reason for the roof structure to be renewed. Additionally, the assembly marks on trusses provide a valuable indication that the roof was constructed in one single building phase: the marks were chiseled in an east-west direction, counting from truss one at the apse to truss five, before the crossing/southern transept, as illustrated with Figure 85 below. We know that the assembly marks on the other side of the transept/crossing, above the nave, were carved west-east, numbering 1 to 5 again, also stopping before the crossing.

At the time of our survey, we had no access to the outside of the church around the apse, so we could not view the exterior ourselves. Like the image of Figure 84, additional drone footage gave us an impression of the outside view. However, at first glance, there seems no reason to believe the choir was altered on another occasion other than the extension of 1628 (this information still needs to be verified with data from the archives).

Figure 85. Photograph showing a close-up of the assembly marks on one of the trusses in the Sint-John-the-Evangelist Church. Image created by Group B during ArchDOC 2021.

Figure 84 Drone image from the roof above the choir and apse of Saint-John-the-Evangelist’s church (with the South Transept visible in front). Image taken during ArchDOC 2021.

Figure 86. Plan of the choir of the Saint-John-The-Evangelist Church, with the location of the assembly marks indicated. Image created by Group B during ArchDOC 2021.

BUILDING ARCHEOLOGY

Figure 87. Photograph with a view of the church from the cloisters, looking at the Southern Transept from the west. Photo taken in 1987, author unknown. Image taken from the Beeldbank Agentschap Onroerend Erfgoed Vlaanderen.

Figure 88. Photograph with a view of the church, looking at the southern transept from the east. Photo taken in 1987, author unkown. Image taken from the Beeldbank Agentschap Onroerend Erfgoed Vlaanderen

BUILDING ARCHEOLOGY

In these three images, the difference in the pitch of the roof above the nave and above the choir can be seen. Figures 87 & 88 clearly show the point where the church roof meets the top of the south transept. In Figure 89, it can be seen the point where the two tops of the roof meet, on the spot where the north transept used to be (demolished in 1729). The clear difference between the two sides of the roof, above the nave and above the choir, further points to the fact that they were constructed at different times. To summarize our findings with regards to the building chronology of the church roof above the choir, based on the typology of the structure (the purlin roof), we would place the construction sometime after 1550, making this our “terminus post quem” (the time after which the roof must have been constructed). Our written source claims that the church choir was extended with one bay in 1628, and our timber roof structure does indeed also span this part of the building. Based on the assembly marks, we can see that the roof was built in one single phase, which would subsequently imply that the roof was constructed in 1628 or after that date. This conclusion poses an interesting hypothesis for further (archival) research on the building history of the church to verify the date of the extension of the choir in the written sources of the abbey. Finally, we had observed alterations in the roof construction at the crossing, which we can place in 1729 when the north transept was demolished: there is a different truss in place that no longer corresponds with the ones included in our survey. So, 1729 would be our “terminus ante quem” (the date before which the roof must have been constructed).

Figure 89. Photograph of the church roof looking from east to west. Photo taken by Sofia Marin for ArchDOC 2021.

BUILDING ARCHEOLOGY

Figure 90. The roof of the Church of Park Abbey made with Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021.

Figure 92. Photo for photogrammetry done with a camera SONY ILCE-7RM4 / FE 24-105mm F4 G OSS. Image produced by Group B. @ArchDoc 2021.

Figure 91. Joinery detail of the brace and the collar beam. Detail made on SketchUp and Photoshop. Image produced by Group B. @ArchDoc 2021.

Figure 93. Photo collage made using Photoshop showing the vaults from downstairs. The cracks on the vaults and the monitoring system can be seen along the image. Image produced by Group B. @ArchDoc 2021.

SITE SIGNIFICANCE

CONSERVATION STATE

We believe the site’s significance, and then we mean specifically the roof structure, lies with the craftsmanship of the construction, the building methodology that one can still read from the materials, and the traces left on by the assembly methods. The roof structure is a valuable site for preserving such layers of construction from centuries ago and presents a source for future research.

The site is conserved well in a good state, with maintenance works conducted in the second half of the 20th century. The wooden trusses and tie beams are original and in good condition. Some of the rafters were replaced, and the brick wall was consolidated by adding a concrete ring beam to tie the newly stabilized structure.

SIGNIFICANCE

The vaults have some visible cracks and, we know that the structural stability of the church was monitored for a while since the reference points are still in place. However, we understand the actual monitoring is not being done anymore. Based on the cracks in the vault we observed, we would recommend reinstating the regular monitoring to implement the preventative measure in a timely fashion. /

CONSERVATION

FINAL REMARKS

ArchDOC 2021 offered us a bonafide crash course in architectural heritage documentation principles, methods, and tools. Thanks to the excellent guidance from our facilitators Christian Ouimet and Pieter-Jan de Vos and - if we may say so ourselves - excellent teamwork in our group, we managed not to get too overwhelmed and set out our course of action from the start. The great strength of the ArchDOC workshop is, of course, the hands-on experience. Being able to use the equipment and software we have had lectures about and learning their strengths and limitations by working through the recording process yourself. Last but not least, to be on-site to look and even feel your way around the subject matter.

The complexity of the site was challenging but not impossible to overcome. The different layers of history and construction could get confusing quickly because there was not a great diversity of building materials. But it was a valuable lesson in the importance of determining the goal of your survey and aiming your research from the start of the recording on day one. In terms of access, the site also brought along its particular complexity; for example, when we wrote down our deliverables at the start of the week, we included the transept and bell tower. However, we quickly realized it would be impossible to record that area as it was used as the workstation for the groups and their instructors: see Figure 94 to illustrate this. Furthermore, we had to let go of adding the bell tower to the survey as there was not enough time to complete all recordings on site.

Aside from the gazillion small things we learned along the way: leveling a total station is more complex than you would think, medieval carpenters had clever marking systems you can still read today, white surfaces are not photogrammetry-friendly among many, the most important lesson we will take from this week is that there is not one all-encompassing method or tool that will give you a complete representation of the subject you are documenting. To get the most accurate and complete recording, you will need to combine methods and choose which one suits the area you wish to record best after careful observation. This brings us to the other main take-away of this workshop: the importance of direct observation is hard to overstate. Not just to take in important details that give you more information on the building process (like the assembly marks or the timber raft peg holes), but it happened more than once that we would be looking at the results from laser-scanning or a photogrammetry image on the computer and, noticed there was information missing that we had seen with our bare eyes, or that a result was unclear and we would have to go back to the location to see what the assembly looked like. With technology advancing as fast as it is, it can be easy to get lost in the newest laser scanning tools and point clouds and the amazingly accurate and realistic results they provide. But at the end of the day (or at the end of an ArchDOC week), there is no technology so advanced (yet) to substitute physically being on the site and using your own two eyes. We learned the importance of keeping in the back of your mind that technology is just the tool to document what you have observed in reality and always strive to corroborate the data with your observations. Figure 94.Photograph of the situation in the transept during ArchDOC week in october 2021. Image produced by Sofia Marin.

FINAL REMARKS

WHO WE ARE

Figure 95. Group B in the roof of Park Abbey Church. October 28th, 2021

Marjolein

Sofía

Hannah

Komal

Pieter-Jan

TEAM - WHO WE ARE

Christian

STUDENTS Marjolein Shut - History & Conflict Studies Sofía Marín - Architect Hannah Mathew - Architect Komal Nandrekar - Architect FACILITATORS Pieter-Jan de Vos - Building historian Christian Ouimet - Conservation technologist Figure 96. Group B in front of Park Abbey. October 28th, 2021 @Mario Santana.

TEAM - WHO WE ARE

IMAGE INDEX Figure 1. Plan of Leuven, 2015, from the Nationaal Geografisch Instituut. Figure 2. Engraving of L.Vostermans, 1669, image from Studio Roma https://www.studioroma.be/wp-content/ uploads/2018/11/0046_ill-5.jpg, accessed 16 January 2022. Figure 3. Photograph Park Abbey. October 28th, 2021. Photographer: Sofiía Marín. Figure 4. Detail showing Park Abbey on a 1560 map by Jacob van Deventer. Image from Studiebureau Archeologie. Figure 5. Park Abbey on an engraving by Gramaye, 1606. Image from Parcum. Figure 6. Detail from a country map showing Park Abbey, 1665, from Joris en Willem Subil. Image from Studio Roma. Figure 7. Park Abbey on a print by Sanderus, 1726, image from Visit Leuven. Figure 8. Park Abbey on a painting by Van Gobbelschroy, 1836, image from Visit Leuven. Figure 9. Aerial photo of Park Abbey. @Google Earth Figure 10. Section of Park Abbey Church. Taken from “ArchDOC Topics and Groups_2021-2022”. Figure 11. Park Abbey outside church south façade. Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021. Figure 12. Park Abbey outside church north façade. Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021. Figures 13 to 15. Group B surveying the roof of Park Abbey Church. Photograph taken by Pieter-Jan de Vos. October 2021 Figure 16. Chart of the percentages of each technique used to produce the deliverables for the survey of Park Abbey Church. Image produced by Group B. @ArchDoc 2021. Figure 17. Placement of the Total Station at the roof of Park Abbey Church. Image produced by Group B. @ArchDoc 2021. Figure 18. Control points. Image produced by Group B. @ArchDoc 2021. Figure 19. Wireframe drawing made with Total Station and AutoCAD. Image produced by Group B. @ArchDoc 2021. Figures 20 and 21. Photographs showing various control points around the roof of Park Abbey Church. Photos taken by Christian Ouimet. October 2021 Figure 22. Group B at the roof Park Abbey Church. Photo taken by Marjolein Schut, October 2021. Figure 23. Scan of truss Nº3 at the roof of Park Abbey Church. Scan done by Aziliz Vandesande. October 2021. Figures 24 and 25. Placement of the FARO X130 3D scanner at the roof of Park Abbey Church. Images produced by Group B. @ArchDoc 2021. Figures 26 to 28. Panoramic images made with FARO X130 3D scanner at the roof of Park Abbey Church. @ArchDoc 2021. Figure 29. Placement of camera for photogrammetry at the roof of Park Abbey Church. Image produced by Group B. @ ArchDoc 2021. Figure 30. Difference in the obtained results done by photogrammetry (left) and laser scanning (right). Image produced by Group B. @ArchDoc 2021. Figure 31. Photo of Group B working at photogrammetry. Image produced by Group B. @ArchDoc 2021. Figure 32 to 35. Photogrammetry done with a camera SONY ILCE-7RM4 / FE 24-105mm F4 G OSS. Image produced by Group B. @ArchDoc 2021. Figures 36 and 37. Park Abbey Church roof made with Photoshop Photomerge. Image produced by Group B. @ArchDoc 2021. Figures 38 to 41. Group B observing the roof space, understanding the space, the details, and the connections. Photos taken by Group B. @ArchDoc 2021 Figure 42. Plan of the roof the choir of the Saint-John-the-Evangelist’s church of Park Abbey. Plan produced by Group B. @ArchDoc 2021. Figure 43. Reflected Roof Plan of the roof the choir of the Saint-John-the-Evangelist’s church of Park Abbey. Plan produced by Group B. @ArchDoc 2021. Figure 45 to 50. Images produced using AutoCAD. These show the difference in detail obtained using photogrammetry and laser scanning. Images produced by Group B. @ArchDoc 2021. Figure 51. Photo collage made using Photoshop showing the vaults from downstairs. The cracks on the vaults and the monitoring system can be seen along the image. Image produced by Group B. @ArchDoc 2021. Figure 52. Detail of the photogrammetry done on the vaults. Image produced by Group B. @ArchDoc 2021. Figure 53. Photo taken for photogrammetry. The concrete ring beam can be seen at the top of the wall. Image produced by Group B. @ArchDoc 2021. Figure 54. Photo taken for photogrammetry where the cracks on the vault can be seen. Image produced by Group B. @ArchDoc 2021. Figure 55. Longitudinal section, A-A’ (East-West). Image produced by Group B. @ArchDoc 2021. Figure 56. Transversal section, B-B’ (North-South). Image produced by Group B. @ArchDoc 2021. Figure 57. Working drawing for the Longitudinal section, A-A’ (East-West). The point cloud obtained by laser scanning was retraced in AutoCAD. Image produced by Group B. @ArchDoc 2021 Figure 58 to 63. Working drawings for Transversal section, B-B’ (North-South). The wireframe drawing was placed along the scans obtained by FARO X130 and Leica BLK360. The point clouds obtained by laser scanning were retraced in

AutoCAD. Image produced by Group B. @ArchDoc 2021 Figure 64. Schematic structure of the roof above the choir. Truss Nº3 was used for modeling on SketchUp. Image edited on Photoshop. Produced by Group B. @ArchDoc 2021 Figure 65. Roof truss parts. Truss Nº3 was used for modeling on SketchUp. Image edited on Photoshop. Produced by Group B. @ArchDoc 2021 Figure 66. Exploded joinery detail of a model truss. Truss Nº3 was used for modeling on SketchUp. Image edited on Photoshop. Produced by Group B. @ArchDoc 2021 Figure 67. Location on the plan of the hoist wheel marks on the beams. Image produced by Group B. @ArchDoc 2021 Figure 68. Detail of Pieter Bruegel the Elder’s painting the (great) Tower of Babel (1563) showing a treadwheel crane. Image taken from the Journal of Art in Society webpage. Figure 69. Photograph of the traces of the hoist wheel. Image created by Group B during ArchDOC 2021. Figure 70. Photograph of saw marks, showing pit saw technique. Image taken by Hannah Mathew @Archdoc 2021. Figure 71. Photograph of saw marks, texture, showing pit saw technique. Image taken by Hannah Mathew @Archdoc 2021. Figure 72. Illustration of a pit saw. Engraving from a 1790’s Book on Trade published in London. Image taken from Lost Art Press (Burke, 2014). Figure 73. Photograph of collar showing traces of timber hewing. Image taken by Chris Ouiment @ArchDoc 2021. Figure 74. Location on the plan of the cross found on one of the trusses. Image produced by Group B. @ArchDoc 2021 Figures 75 and 76. Photographs of the cross graffiti. Images taken by Marjolein Schut @ArchDoc 2021 Figure 77. Location on the plan of the assembly marks on the trusses. Image produced by Group B. @ArchDoc 2021 Figure 78. Photographs of the assembly marks on the rafters. Images taken by Group B @ArchDoc 2021 Figure 79. Photograph showing the Timber Raft Peg Holes. Image taken by Komal Nandrekar @ArchDoc 2021 Figure 80. Location on the plan of the Timber Raft Peg Hole. Image produced by Group B. @ArchDoc 2021 Figure 81. Drawing of the common rafter roof (sporenkap) above the choir of the Dominican Church in Leuven by R.M. Lemaire (1942). Image taken from ‘De oudste dakconstructie in de Leuvense binnenstad: bouwhistorisch onderzoek in de predikherenkerk (prov. Vlaams-Brabant)’CITATION Tho04 \l 1043 Figure 82. Photograph taken from the lower part of the common rafter roof (sporenkap) construction above the choir, created by Oswald Pauwels (2001). Image taken from ‘De oudste dakconstructie in de Leuvense binnenstad: bouwhistorisch onderzoek in de predikherenkerk (prov. Vlaams-Brabant)’CITATION Tho04 \l 1043 (Coomans, 2006). Figure 83. Photograph of the roof structure with ridge purlin in the O.L.V. Church (Church of Our Lady) in Bruges, 2nd half of the 16th century. Image created by O. Pauwels, taken from the report of Agentschap Onroerend Erfgoed. (Dirk van Eenhoge V. D., 2018) Figure 84 Drone image from the roof above the choir and apse of Saint-John-the-Evangelist’s church (with the South Transept visible in front). Image taken during ArchDOC 2021. Figure 85. Photograph showing a close-up of the assembly marks on one of the trusses in the Sint-John-the-Evangelist Church. Image created by Group B during ArchDOC 2021. Figure 86. Plan of the choir of the Saint-John-The-Evangelist Church, with the location of the assembly marks indicated. Image created by Group B during ArchDOC 2021. Figure 87. Photograph with a view of the church from the cloisters, looking at the Southern Transept from the west. Photo taken in 1987, author unknown. Image taken from the Beeldbank Agentschap Onroerend Erfgoed Vlaanderen. Figure 88. Photograph with a view of the church, looking at the southern transept from the east. Photo taken in 1987, author unkown. Image taken from the Beeldbank Agentschap Onroerend Erfgoed Vlaanderen Figure 89. Photograph of the church roof looking from east to west. Photo taken by Sofia Marin for ArchDOC 2021. Figure 90. The roof of the Church of Park Abbey made with Photoshop Photomerge. Image produced by Group B. @ ArchDoc 2021. Figure 91. Joinery detail of the brace and the collar beam. Detail made on SketchUp and Photoshop. Image produced by Group B. @ArchDoc 2021. Figure 92. Photo for photogrammetry done with a camera SONY ILCE-7RM4 / FE 24-105mm F4 G OSS. Image produced by Group B. @ArchDoc 2021. Figure 93. Photo collage made using Photoshop showing the vaults from downstairs. The cracks on the vaults and the monitoring system can be seen along the image. Image produced by Group B. @ArchDoc 2021. Figure 94. Photograph of the situation in the transept during ArchDOC week in October 2021. Image produced by Sofia Marin. Figure 95. Group B in the roof of Park Abbey Church. October 28th, 2021 Figures 96. Group B in front of Park Abbey. October 28th, 2021 @Mario Santana.

IMAGE INDEX

BIBLIOGRAPHY

PUBLICATIONS

WEBSITES

Eenhoge, Dirk van, Debonne, Vincent & Haneca, Kristof, ‘Middeleeuwse dakkappen in Brugge en ommeland. Een catalogus.’ Onderzoeksrapport Agentschap onroerend erfgoed (2018) pp. 1 – 136.

Visit Leuven, Abdij van Park https://www.visitleuven.be/en/parkabbey, accessed October 2021.

Haslinghuis, E.J., Janse, H., ‘Bouwkudige Termen. Verklarend woordenboek van de westerse architectuur- en bouwhistorie’ (2013). Hemert, R. van, ‘Houtconstructies. Balklagen, gebinten en kapconstructies’ (2013). Janse, H., ‘Bouwtechniek in Nederland 2. Houten Kappen in Nederland 1000 – 1940’ (1989).

Vlaanderen, Onroerend Erfgoed, Beeldbank, Norbertijnenabdij van Park https://beeldbank.onroerenderfgoed.be/images?erfgoedobject=https%3A%2F%2Fid. erfgoed.net%2Ferfgoedobjecten%2F42566&page=4 , accessed November 2021. Historic Graffiti: Teacher’s Notes’ The Norfolk Medieval Graffiti Survey (2017), pp. 1-23, p. 19. http://www.medieval-graffiti.co.uk/teachers%20handbook.pdf

Lemaire, Raymond M., ‘Bouwen door de eeuwen heen. Inventaris van het cultuurbezit in Vlaanderen. Architectuur, Deel 1. Provincie Brabant, arrondissement Leuven.’ (1971). Smeets, Maarten, Ginst, Vanessa Vander, ‘Archeo-rapport 117. Het archeologisch onderzoek in de Sint-Jan-Evangelistkerk te Heverlee’ Studiebureau Archeologie (2013) pp. 1 – 68. Vynckier, Geert, Detloff, Andre & Laecke, Johan van, ‘Registratie van een toevalsvondst in de abdij van Park te Heverlee – Leuven (Provincie Vlaams-Brabant)’ Onderzoeksrapport Agentschap onroerend erfgoed (2016) pp. 1 – 23.

BIBLIOGRAPHY