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Timberwork Case StudiesMSc. Building Conservation
22 February 2013
Paul Price
Woodwrights
Oak frame carpentry and timber conservatio
n
Topics:1.Recognising historic carpentry
2.Repairs: surveys and methods
3.Case histories
An overview of historic carpentry and timber
repair
Historic timberworkPart of our built heritage – in Ireland: especially
roofs.A valuable record of historic craftwork - timber
conversion and scribe carpentry.
Christchurch Cathedral,
Dublin. 17th C. oakwork
Ilustrations from:McCracken, E. (1971) The Irish Woods Since Tudor Times
Holy Trinity Church, Fethard, Co.
TipperaryMedieval oak roof
frame, discovered 2010
See-sawing (swivel or trestle sawn)
Timber Conservation Aims
Conserve the overall aesthetic form of the structural
frame while repairing the structure.Preserve original timber as much as possible.
Timber surfaces, which preserve marks recording the original timber conversion and framing methods.
Dunsoghley Castle, Co. Dublin.
High quality scribe carpentry;Double collar; Arch-braces with locking tenons; Scribe numbers visible.
Timber Conservation ProcessSurvey: historical value, condition, and
structure.Repairs: minimal, unobtrusive, reversible.
Outlook: maintenance check-listNorway - Loft repair.Timber replacement: New timber selected, cleft and hand hewn to match original decayed element.
Recognising historic carpentry
Conversion: logs into timber
Carpentry: scribing, jointing and raising frames
Oak - tough and durable. Baltic pine –
imported.
Two forms of historic timberwork:
Treewrightingaxe-hewn, boxed
heart,often smaller ‘stuff’,
cottage roofs;
Frame carpentryhewn plus rip-sawn,mortice and tenon,
large range of scantlings,
use of grown “bends”,larger, more durable
buildings.
Hewing: Turning logs into timber.Marking and notching
Hewing
Notching
Juggling
Finishing with broadaxe
Hewing: Finishing- A broadaxe was used to give a flat finish
Close up of hewn
surface
Stop mark
Axe nick marks
Note mutual angle of marks
Pit-sawn surface with
framers’ level mark
Scribing: Timber placed over full scale layout so thatjoints can be scribed to allow accurate fit of irregular timbers
Plumb bob
Referenceline
Scribed shoulder
Scribe carpentry workshop
Numbering: Usually Roman - chiselled or
race-knifed
Recognising historic timberwork
Hewn or pit-sawn surfaces
Carpenters layout marks - scribe lines and references
Mortice and tenon joints
Chiselled numbers at joints
Scribed joints - shoulders scribed to match irregularities
Repairs: surveys and
methods
Surveys
Record DrawingsBasic survey - Schematic timber drawings and
photographs.Full Survey: Archeological level recording.
EstimatingAnnotate basic survey schematics with current
condition and possible repairs
Bishops Palace, Salisbury, Wiltshire, EnglandRoof by Francis Price 1726 Our repairs 1998
Cathedral Church, Cashel
Nave roof 1780Large span 46ft
=14mTransition carpentry
Diagnosing a structural problem.
– Is it really a problem?
Cashel Cathedral Church Roof:
• Queen post roof with king strut
• Ceiling load has deformed roof
Joint separation 100mm+
Cashel: Structural schematic
Original
Current
Movement appears locked but should be monitored
Repair Methods
Repair Methods for Historic Timberwork
•Steelwork: straps, flitch plates, cables, brackets, bolts, screws to secure joints and framing.
•Carpentry: replacement timbers, patch and end repairs.
•Resin: consolidation, packing, patch and end repairs.
Beware the “honest” repair
Making repairs look distinctive from original workis often an excuse for unsightly repairs.
METAL REPAIRS:•Often cheapest and best if hidden or subtle- no disassembly needed.•Reversible and easier. Unsightly if visible and poorly designed.•Use galvanised or stainless steel for repairs.
CARPENTRY REPAIRS•Potentially damaging disassembly required for replacement or end repairs.•Requires high quality repair carpentry for good results.•Decide whether to match conversion methods.•Use oak with oak etc.
End repairs•require careful fitting and assembly•use dry timber where possible.•may have to use green -allow for shrinkage and later tightening
New tenon repair - only possible if frame elements disassembled
Multiple scarf repairs to softwood wall
Rafter notch joint reformed in resin
RESIN REPAIRS:•Good for consolidating valuable decayed timber and for packing out steel repairs.•Bad for large end repairs. Can be very ugly.•Always use resin designed specifically for structural timber work.
Exposed to weather for 600 years
Timber durability:Excellent if kept dry.Good if sheltered.Bad if continually damp.
Leaking weathervane - king post decayed
Case Histories
Barn, Co. Wicklow18th Century
An exceptional and unusual barn frame
Barn in WicklowShipping marks on Baltic Pine on hewn surfaces.Race knifed symbols denoting timber baulk quality and quantity.
Unusual framed cantilevered roof overhang
Bridled scarf with sallied abutments in a 10 cm by 6.5 cm timber !!
Dragon tie hip assembly: Note numbering
Purlins scribed over hip bevel
Curved EndNew tie and reassembly numbers
Historic pine: Left side has been sandblasted.Note serious loss of fragile but intact surface.
Winchester Cathedral, South TransceptDendro date 1313Difficult working conditionsLaminated in-situ repairs
Disassembly: can see inside joints•Soulace brace with locking tenon•Axed tenon faces•Drawbored tenon•Centre lines
Southwick Barn. Hampshire, England
Collapsing barn- uprighted, mostly in-situ steel repairs
Gusset bracket and flitch repairs
Wooton Bassett,Wiltshire, England
Decay of 19th century oak repairs due to impermeable black paint
Repaired frame prior to stripping impermeable paint
Frame and replastered panels then limewashed
House at Laxfield, Suffolkworking with Traditional Oak Carpentry Co
Structural frame repairs - support carefully!
Cill plate decay - due to constant wetting, impermable paint, and cement mortar/render.
Exterior new timber conserving interior -Coach screwed together with resin packing
Installing new cill with new and repaired timber
Frame reassembled with new plinth built up.Exterior frame aesthetic conserved.
Decay treatment
Interior timber entirely saved.
Poor quality of framing timber -hedgerow stuff
Charlton Court Barn, West Sussex, England
Major repairs•Roof stone removed, frame realigned, joints reassembled•Very costly - steel building over, detailed repairs throughout. Use for special buildings.
Dendro-dated to 1404
Patch repair: coach screwed and plugged
End repairs:Tabled stop splay scarf
New aisle sway brace
New timbers where missing•Re-make in new timber on pattern of existing.•Better than unsightly exposed steel. •Can make decision to match existing conversion to similar pieces.
Purlin span decreased using in-line steel angles - no plywood
Completed frame repair •Aesthetic conserved •Structure repaired
Topics:•Recognising historic carpentry
•Repair surveys and methods
•Case histories
An overview of historic carpentry and timber
repair
Thank-you
Paul Pricewoodwrights.ie
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