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A Report on

Woodchester Mansion Submitted by

Priyanka Talreja Towards the degree of Master of Science in the Conservation of Historic Buildings At the University of Bath, Department of Architecture and Civil Engineering. Session 2013-14


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Contents

Title

page no.

List of illustrations.......................................................................................................................3 1. Introduction to Woodchester Mansion 1.1. Background History..............................................................................................................4 1.2. Architectural Features..........................................................................................................4 1.3. South East Corner Room: A Description...............................................................................5 2. Analysis of Structural Aspects of the South East Corner Room With Respect to– A: Structural Form B: Structural Behaviour C: Causes of Structural Damage D: Remedial Action 2.1. Floor vaults...........................................................................................................................6 2.2. Walls.....................................................................................................................................8 2.3. Buttresses............................................................................................................................11 2.4. Arches..................................................................................................................................12 2.5. Roof......................................................................................................................................13 2.6. Other Features.....................................................................................................................15 Bibliography................................................................................................................................16


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List of Illustrations Serial No.

Title Of The Image/Sketch

Reference/ Source of illustration

Fig. 1: (Pg.5)

Level 1 Plan: SE Corner Room

Author

Fig. 2: (Pg.5)

South Side Facades: SE Corner Room

Author

Fig. 3: (Pg.5)

East Side Facades: SE Corner Room

Author

Fig. 4: (Pg.6)

Drawing Room ‘Lierne’ rib vaulting

Author

Fig. 5: (Pg.7)

SE corner room floor-vaults

Author

Fig. 6: (Pg.7)

Slots on Stone vaults

Author

Fig. 7: (Pg.7)

Load Path Diagram

Author

Fig. 8: (Pg.9)

North Side rubble and brick masonry wall

Author

Fig. 9: (Pg.9)

East Side rubble masonry wall

Author

Fig. 10: (Pg.10)

West Side brick wall with corbels visible

Author

Fig. 11: (Pg.10)

Author

Fig. 13: (Pg.10)

Spalling of stones on the buttress as well as window jamb wall due to damp penetration and/or wind erosion West Gable wall with salt deposits observed on the facade. Assortment of masonry materials and styles

Fig. 14: (Pg.11)

Buttresses on south side wall in view

Author

Fig. 15: (Pg.11)

Load balance: Roof-Arch-Buttress

Author

Fig. 16: (Pg.12)

Wall separated from relieving arch on the west wall

Author

Fig. 17: (Pg.12)

Floor Beam Arched Brackets

Author

Fig. 18: (Pg.13)

Author

Fig. 19: (Pg.14)

Underside of the timber roof, showing torching of the slates. Roof Structure of SE corner room

Fig. 20: (Pg.14)

Rain water outlet between the gable walls

Author

Fig. 21: (Pg.15)

South face window with ashlar stone jamb.

Author

Fig. 12: (Pg.10)

Author Author

Author


4 | 16 Case Study Report: Woodchester Mansion, Gloucestershire (National Trust) Field Visit (October 9, 2013)

1. Introduction to Woodchester Mansion 1.1 Background History: Situated in an isolated valley near Stroud in Gloucestershire, Woodchester mansion is a Listed Grade 1 Georgian courtyard house built in stone. It was commissioned by the Roman Catholic convert and philanthropist William Leigh, and designed by Benjamin Bucknall, the young local architect, to be a unique example of 19th Century Gothic revival style of architecture.1 Woodchester Mansion was built between 1857 and 1871 when it was abandoned, a completed masonry shell. It has remained largely undisturbed since.2 Through its unfinished design and interiors, one gets an idea of the grand lives of the Leigh family about 150 years ago.

1.2 Architectural Features: ‘The principle of Gothic architecture is infinity made imaginable.’ Samuel Taylor Coleridge Bucknall was inspired by the French architect Eugene Violett-le-Duc, who believed that construction, must always be apparent, there is nothing to hide.3 Woodchester mansion, the highest expression of a pure style, not matched by any other British domestic architecture of the period4, consisted of 16 rooms including the dining, library, drawing, billiards room and a chapel. The rooms have stone vaulted ceilings decorated with ornate stone ribs with fan shaped springing. Typical features of the Gothic style visible in Woodchester mansion include  pointed arches  vaults  gables and bay windows  steeply pitched roofs  turrets, gargoyles  decorative corbels  pinnacles, grouped chimneys  quatrefoil and cloverleaf windows  stained glass,  patterned floor tiles, and polychrome brickwork. 5 Woodchester Mansion, if completed, would have been the finest building in the Gothic revival style. 1

Verney, D. (1970) Goom, J.C. [Online] 3 Verney, D. (1970) 4 Russiello, J. (2006) 5 Woodchester Mansion Trust, site 2


5 | 16 1.3 South East Corner Room: A Description The area of interest for structural analysis in this essay is the South East Corner Room of the Woodchester Mansion, located right above the Drawing Room on the ground Floor. This room has external walls on two sides and sits on top of the lierne vault of the drawing room. The materials used in the roomare local limestone, bricks from within the estate manufacturer and Cotswold stone roof tiles. The gable ends have pinnacles or decoratively carved grotesques and quatrefoil air ventilators on thema trademark of Benjamin Bucknall’s work.6 Corbels supporting the stone gutters and gargoyles throwing rainwater from the building are carved decoratively.

Fig.1: Level 1 Plan: SE Corner Room

Fig.2: South Side Facades: SE Corner Room

Fig.3: East Side Facades: SE Corner Room 6

Verney, D. (1970)


6 | 16 2. Structural Aspects of the South East Corner Room. The elements of the South East corner room have been analysed for their behaviour from the bottom to the top as follows:

1.1 Floor Vaults: Structural Form: The floor of this room is not a flat surface like other rooms but consists of vaults from the Drawing Room below. The Drawing Room ‘lierne’ rib vaulting with stone infill has been illustrated below (Fig 4). The ribs fan out across the ceiling from the capitals and a carved ceiling boss is fitted where the ribs intersect.7 The reverse ends of these ribs and ceiling bosses form a part of the SE corner room floor.8 (Fig.5) Thin slots for lifting the bosses are visible on the upper side of the lierne vault, so they could be lifted up with a device called ‘Lewis.’ 9 (Fig.6) Structural Behaviour: The design of vaulted ceilings in the mansion is typical Gothic in stylewith the mass of the building being carried on arched stone ribs of the vaults supported on columns. The ceiling boss is placed where ribs meet and it locks the ribs, distributing loads evenly.10 Cause of Structural Damage: If there is major cracking on the walls above (due to various reasons elaborated in section ‘walls’), it will cause the floor vaults to crack owing to the load transfer path.11 (Fig.7) Remedial Action: To avoid the floor vaults to crack, tie bars have been used on the upper storey load bearing stone arches so as to add tensile forces and distribute loads evenly.12

Fig.4: Drawing Room ‘lierne’ rib vaulting

7

Woodchester Mansion Trust, site (Drawing Room) Goom, J.C.(2008) 9 Woodchester Mansion Trust, site 10 Woodchester Mansion Trust, site 11 Goom, J.C.(2008) 12 Goom, J.C.(2008) 8


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Fig.5: SE corner room floor-vaults

Fig.6: Slots on Stone vaults Fig.7


8 | 16 1.2 Walls: The walls in this room continue from the drawing room upwards and extend up through two storeys until they come in contact the underside of the roof rafters. Structural Form: A mixture of brick and uncoursed rubble masonry has been used to construct the North side wall adjacent to the interior corridor. (Fig 8) The East and the South side walls are peripheral, and hence built entirely of coursed ashlar on the outer face. Good Jurassic building limestone acquired from 25 quarries in the estate has been used for this. It has a rubble infill and uncoursed rubble stone masonry on the inner side. (Fig 9) The infill walls and mullions are thin. On the exterior facade string courses on the walls are slightly darker because of the higher shell content.(Goom, J. 2013) Ashlar stone with very thin mortar joints has been used for door and window surrounds.13 The internal Western wall is made of brick and has carved stone corbels for supporting the ceiling and the second floor beams. 14 This wall is thinner than the other three walls. (Fig 10) Holes in the wall, ‘put log’, for scaffolding are visible. Structural Behaviour: Masonry is generally relatively strong in compression 15and Woodchester mansion has survived only because of its solid construction of massive stone walls. 16The load of the brickwork has been supported by two relieving arches over the vault as seen (Fig 9).17 The wall in between buttresses on the south front is not a load bearing wall. (Goom, J. 2013) Cause of Structural Damage: Since the walls have all been built in a traditional fashion without any iron cramps or timber lintels they have survived remarkably well. (Goom, J. 2013) Forces or stresses are not alone in causing dimensional changes to materials; all materials expand and contract with changes in temperature and moisture content.18 Damp penetration due to persistent roof leakage has affected some parts of the stone work causing them to decay.19 Wherever the wall has become saturated, the stonework has deteriorated- not only through frost action but, where significantly loaded, by compression resulting in disintegration of the stones. (Fig 11) 20 Spalling of brickwork in the interior may be due to natural weathering or due to absorption of moisture. 21 The drying effect of wind around projecting elements such as cornices has drawn moisture and salts to the surface of the wall as seen on the West facade22 (Fig 12) Cracking in zig zag form has been observed on the interior side of the east wall. (Fig 9) Brickwork when laid in lime mortar has the capacity to accommodate major movements. The foundation of

13

Forsyth, M. (2008) Goom, J.C.(2008) 15 Beckmann, P.(1995) 16 Hart-Davis, D. (1989) 17 Goom, J.C.(2008) 18 Beckmann, P.(1995) 19 Goom, J.C.(2008) 20 Goom, J.C.(2008) 21 Forsyth, M. (2008) 22 Forsyth, M. (2008) 14


9 | 16 Woodchester Mansion is stacked on solid bedrock23. Differential settlement is inevitable and redistribution of loads is signalled by cracking.24 As pointed out by Clive, cracking has been observed on the interior but not on the exterior side of the same wall. This may be due to varying stresses along the thickness of the wall due to eccentric loading25 ‘or’ presence of an air cavity wide enough to break the capillary action of the water that has penetrated on the interior wall. Green staining is apparent on the stone walls at the eastern end; this does largely appear to be dry. Remedial Action: Repairs on masonry must always be flexible and reversible; so hydraulic lime, rather than concrete for pointing works should be the choice. (Clive, 2013) In case of spalling of stones, ‘like for like’ repairs is a preferred option by using natural stone with the same dressing (Goom, J. 2013) Renewal in ashlar stone work should always use suitable new stone and lime based mortar must be used that is softer than the stone.26 Surface deposits which are harmful to the stone must be removed in frost free weather with nebulous spray water cleaning, without damaging the structure of the stone. Where failure appears to be associated to ground movement, archaeological and geological investigation is required. Then, repointing, replacing whole or just the decayed face can be done.27 Cracks can be treated by ‘stitching’-short lengths of masonry taken out and new stones bridging the gap are mortared in. Minor cracks can be repaired through careful pointing which restores its full section by retaining the weak bedding mortar.28

Fig.8: North Side Wall 23

Verney, D. (1970) Forsyth, M. (2008) 25 Beckmann, P.(1995) 26 Forsyth, M. (2008) 27 Forsyth, M. (2008) 28 Beckmann, P.(1995)p 89 24

Fig.9: East Side Wall


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Fig. 10 : West Side Wall with Corbels visible

Fig. 11: Spalling of stones on the buttress as well as window jamb wall due to damp penetration and/or wind erosion.

Fig. 12: West Gable wall with salt deposits observed on the facade.

Fig. 13: Assortment of masonry materials and styles.


11 | 16 1.3 Buttress: Structural Form: Buttresses on the Southern facade are distinctive features on the exterior of Woodchester mansion. They are set close to the windows and each buttress corresponds with a springing point of an arch on the interior of the building. (Goom, J.C. 2013) (Fig 14.) Structural Behaviour: Buttressing is required to counterbalance the lateral thrust of the arch on the stonework.29 ‘The weight of the building pushes the arch outwards and is balanced by external buttresses pushing inwards.’30 (Fig 15.) Elements like springer stones, brackets, corbels are vulnerable and would fall over if not for buttressing. (Clive, 2013) Cause of Structural Damage: The apparent structural defect is the leakage of gutters that has caused overloading of the buttresses, resulting in compression and hence vertical cracks.

Fig. 14 : Buttresses on the South in view

(Goom, J.C. 2013) Stone decay has been observed on the side of a buttress as a result of overflowing31 (Fig 11.) This has also affected the wall adjacent to it and damage on the window jamb is a possibility. Remedial Action: In the 1980’s temporary fixing of the buttresses was carried out, but it needs to be redone. (Clive, 2013) The sloping joints on the top of the buttress must be weatherproofed and the distressed stones must be replaced sensitively.

29

Woodchester Mansion Trust, site 30 Woodchester Mansion Trust, site 31 Goom, J.C.(2008)

Fig. 15


12 | 16 1.4 Arches: Structural Form: Arches are a characteristic feature of Gothic Revival Architecture and create wide, high spaces. There are two types of load bearing arches seen in the South East corner room: The principal structural arch built of stone and the relieving arch built into the brick and rubble walls. The relieving arch stones on the east side wall show ridges so as to provide key to the plaster for completion.32 Structural Behaviour: The timber roof load from the principal arch is transmitted to the vertical column on North side and the buttresses on the south side of the Mansion. 33 Arches carry vertical loads by developing stresses that follow their shape along curved paths.34 As per John Goom, the presence of fireplaces on the north side interior wall shows the need for relieving arches to spread the load evenly. Relieving arches on the south side Fig. 16: Wall separated from help to create large arched openings for windows. Windows without relieving arch on the mullions are built into the relieving arch thus eliminating the need for west wall a lintel. Since stone masonry is not good in tension, hence lots of relieving arches have been constructed as per Clive. Cause of Structural Damage: A fairly common cause of cracking in arches is differential settlement of the supports. No foundation will carry any load without settlement.35 Hence, the joints open on the intrados. (Fig 16.) On the second floor level, fractures are visible on the arris of the supporting arch, probably from the time when the centering was taken down.36 Discolouration on the stone arch brackets is because of bat droppings rather than water penetration. (Fig 17.) Remedial Action: Repointing and grouting masonry arches can, if applied to maximum depth greatly strengthen an arch.37 The arris fractures have been repaired but not pared in.38Low pressure cleaning must be done to clear the discolouration.

32

Woodchester Mansion Trust, site Woodchester Mansion Trust, site 34 Beckmann, P.(1995) 35 Beckmann, P.(1995) 36 Goom, J.C.(2008) 37 Feilden, B. (1994) 38 Goom, J.C.(2008) 33

Fig. 17: Floor Beam Arched Brackets


13 | 16 1.5 Roof: From a visual inspection, it is evident that the roof on the South East corner is a typical timber structure with purlins and battens topped with Cotswold slate tiles. The underside of the slates have been torched, i.e., plastered to make it weatherproof.39 (Fig 18.) Structural Behaviour: The South East corner roof is a timber structure supported on a stone arch. Cause of Structural Damage: Water penetration is the major cause of decay, Bucknall had taken efforts to keep stone gutters and water pipes clear.40 At the junction of the stone wall and the timber batten, decay has been observed. The coping stones themselves are generally a much stronger stone but in some instances these also are decaying.41 Regular leaks result in decay of stonework beneath the copings. Surface decay in the valley timber observed. On the exterior front, the old Cotswold stone slates are all beginning to show signs of lamination.Wind and weather erosion has resulted in slippage of slates near the ridge.42 The house lies close to the wooded hill side and its gutters are prone to jam in the autumn. While the mansion was abandoned, trapped rainwater soaked in to the walls. In winter, the expansion of freezing water shattered the stone43. There are a number of carved finials on gables all of which are showing significant signs of weathering.

Fig. 18: Underside of the timber roof, showing torching of the slates. 39

Goom, J.C.(2008) Hart-Davis, D. (1989) 41 Goom, J.C.(2008) 42 Goom, J.C.(2008) 43 Woodchester Mansion Trust, site (priests door) 40


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Fig. 19: Roof Structure of SE corner Room

Remedial Action: Timbers in the valleys beneath any roofs are vulnerable to decay and incorporating lead soakers in all valleys may act as extra protection. For cleaning off the surface decay/frassiness of the valley timber, vacuum pressure or gentle bristle washing or sandblasting to remove any historic surface can be carried out.44 To avoid slippage, the ridge tiles must be patched and made water tight like other areas.45 Instead of using wooden pegs to secure stone slates, dry heartwood must be used as it absorbs moisture from the air and is less prone to rot or attack by wood-boring beetles.46 Correct detailed lead cover flashings can protect the cornice stone and help promote water run-off evenly47.

Fig. 20: Rain water outlet between gable walls 44

Forsyth, M. (2008) Goom, J.C.(2008) 46 Forsyth, M. (2008) 47 Forsyth, M. (2008) 45


15 | 16 1.6 Other Features: Windows: The south face of the mansion is heavily glazed. All windows have an inner and outer arch with a recess between to take a curtain rail. The window openings are metal casements damaged by rusting ironworks.48 Strong westerly wind gust is a cause for concern for shattering of glass.49 (Fig 11.) Broken panes of Historic glass must be restored with ‘crown glass’ as it radiates a wonderfully warm, soft and worn quality to old buildings. 50 Interior elements: Blocks of ashlar around doors are not finished identically on either side-this functional appearance is characteristic of Gothic Revival Architecture. Lintels, shelves, door surrounds and fireplaces are all made up of stone and hence damage of these elements due to rotting and leakage is minimized. However, the limestone used for interiors is porous, and lead lining was not used-this has created a lot of problems and caused decay.

(Goom, J.C. 2013)

Fig. 21 South face window with ashlar stone jamb.

‘’All architecture proceeds from structure, and the first condition at which to aim is to make the outward form accord with that structure.” Viollet-le-Duc . As a stunning success of the Victorian Gothic Revival abandoned in mid-construction but with much of its spectacular detail complete, the Woodchester Mansion is exceptional in the heritage world as a window on construction methods that link directly to our medieval Gothic heritage. 51All the structural elements in this Grade 1 building have a story to tell and as much as possible, the interventions must allow letting it all flow.

48

The Mansion. [Online]. Beckmann, P.(1995) 50 Forsyth, M. (2008) 51 The Mansion. [Online]. 49


16 | 16 Bibliography

Woodchester Mansion Site Visit. 1. Goom, J.C, 2013: Architect John Goom, pers. comm., 9th October 2013. 2. Clive, 2013: Civil Engineer Clive, pers. comm., 9th October 2013. 3. Woodchester Mansion Trust, Poster/Plaque within individual rooms. Books 1. Beckmann, Poul, 1995. Structural Aspects of Building Conservation. Mc-Grow Hill Book Company 2. Feilden, Bernard, 1994. Conservation of Historic Buildings. 4th ed. Butterworth. 3. Forsyth, Michael, 2008. Materials and Skills for Historic Building Conservation. Blackwell Publishing, 4. Quiney, Anthony, 1989. Period Houses, a guide to authentic architectural features. London: George Phillip. ISBN 0-540-01173-8. 5. RMH Lawrence, 2003. A Study of the stone used to construct Woodchester Mansion, A Construction, Materials and Skills essay, pp. 162-165. 6. Verney, David, 1970. Gloucestershire Vol.1: The Cotswolds.1st ed. Penguin Books.p. 487, pp. 488. Journal Article 1. Hart-Davis, D., 1989. Unfinished masterpiece. Country Life, 183(22), pp. 162-165. 2. Goom, J.C., 2008. Woodchester Mansion: Condition Report 2008. Woodchester Mansion Trust. 3. 2008. 'Your mansion, my stage', AV Magazine, p. 52, Business Source Complete, EBSCOhost (Viewed 17 October 2013). Internet references: 1. 2. 3.

The Mansion. [Online]. Available from: http://www.woodchestermansion.org.uk/History.aspx [Accessed October 8, 2013] Goom, J.C. Woodchester Mansion. [Online]. Available from: http://www.johncgoom.co.uk/woodchester.html [Accessed December 4, 2013] Russiello, James, 2006. 061018. Nympsfield, Woodchester Mansion Original Plans! [Online]. Available from: http://bathdailyphoto.wordpress.com/2006/10/17/061018nympsfield-woodchestermansion-original-plans/ [Accessed December 4, 2013]

UoB 3 Structural Conservation A  

Woodchester Mansion, Bath: A case study