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Traditional Fabrication Techniques

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Traditional Fabrication Techniques

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    1. Traditional Fabrication Techniques Bath University 7th September 2006 Charley Brentnall Carpenter Oak and Woodland 15 minutes on the use of traditional timber jointing and framing techniques in the production of contemporary buildings and structures. Covering: Selection and specification of materials Jointing techniques Workshop practice Details and Tolerances Modern frame types in usage/case studies. 15 minutes on the use of traditional timber jointing and framing techniques in the production of contemporary buildings and structures. Covering: Selection and specification of materials Jointing techniques Workshop practice Details and Tolerances Modern frame types in usage/case studies.

    2. The frame drawings The fabrication usually flows from the design or drawing process.The fabrication usually flows from the design or drawing process.

    3. The frame drawings Here’s a frame detail for Camery building at Wells Cathedral that we are working on at present. Purcell Millar TritonHere’s a frame detail for Camery building at Wells Cathedral that we are working on at present. Purcell Millar Triton

    4. Detailing … and the associated detailing that will integrate the frame into the rest of the envelope.… and the associated detailing that will integrate the frame into the rest of the envelope.

    5. Taking Off Cutting Lists Cutting lists are usually developed along with an estimate. This might be early in the project to confirm a cost plan. Later the cut list will be sent to a mill. We don’t often go to tender these days preferring to negotiate fixed rates with two maybe three mills and be assured of their quality and service. Cutting lists are usually developed along with an estimate. This might be early in the project to confirm a cost plan. Later the cut list will be sent to a mill. We don’t often go to tender these days preferring to negotiate fixed rates with two maybe three mills and be assured of their quality and service.

    6. Specifications and Standards The current BS for oak is well known to be deficient in its flexibility. COWCo’s standard green oak grade takes from both BS 5268 and the old CP112. It’s far from ideal but does the job. The new grade being developed by TRADA will be a welcome solution to this situation. For other timber species the BS can be used. The current BS for oak is well known to be deficient in its flexibility. COWCo’s standard green oak grade takes from both BS 5268 and the old CP112. It’s far from ideal but does the job. The new grade being developed by TRADA will be a welcome solution to this situation. For other timber species the BS can be used.

    7. Grading Timber in the Yard Once the timber has been specified it is cut to a grade by the sawmill, coded to the cutting list and delivered to the yard. Here it’s checked off and re-graded by the team leader and allocated to a final position in the frame. The Grading rules just dumb the best down to the lowest denominator. Ultimately it’s the individual carpenters who uses their skill to position “defects” in places of low stress. You can see that good legs are a pre-requisite for a framer.Once the timber has been specified it is cut to a grade by the sawmill, coded to the cutting list and delivered to the yard. Here it’s checked off and re-graded by the team leader and allocated to a final position in the frame. The Grading rules just dumb the best down to the lowest denominator. Ultimately it’s the individual carpenters who uses their skill to position “defects” in places of low stress. You can see that good legs are a pre-requisite for a framer.

    8. Setting Out/Lofting Dimensions are often set out on the workshop floor creating a full scale drawing using snapped chalk or ink lines. The techniques of then applying these dimensions to the timber to give tolerances of around 2 - 5mm were “rediscovered”, or recovered, in the mid-8o’s from the Compagnion in France. They had been used by carpenters in this country from the early Mediaeval period into the 19th C.Dimensions are often set out on the workshop floor creating a full scale drawing using snapped chalk or ink lines. The techniques of then applying these dimensions to the timber to give tolerances of around 2 - 5mm were “rediscovered”, or recovered, in the mid-8o’s from the Compagnion in France. They had been used by carpenters in this country from the early Mediaeval period into the 19th C.

    9. Laying Out Frames are cut 2 dimensionally in the workshop or framing yard. Principal members sit at the intersect of two frames or planes. They are fitted first into one frame then taken away and cut into another… …and finally assembled 3 dimensionally on site. This demands a joint cutting technique that ignores the dimensional inaccuracy of sawn green timbers. Different carpenters approach this in different ways: In the states Square Rule is commonly used In this country some variant on Plumb and Levelling Frames are cut 2 dimensionally in the workshop or framing yard. Principal members sit at the intersect of two frames or planes. They are fitted first into one frame then taken away and cut into another… …and finally assembled 3 dimensionally on site. This demands a joint cutting technique that ignores the dimensional inaccuracy of sawn green timbers. Different carpenters approach this in different ways: In the states Square Rule is commonly used In this country some variant on Plumb and Levelling

    10. Laying Out With sawn timber the section cannot be assumed to be square. A theoretical plane is set out upon the timber using a spirit level. The timber itself is levelled using wedges. (See the right hand end of the upper beam - two wedges - one pink). With sawn timber the section cannot be assumed to be square. A theoretical plane is set out upon the timber using a spirit level. The timber itself is levelled using wedges. (See the right hand end of the upper beam - two wedges - one pink).

    11. Plumb and level scribing And a plumb bob is used to set out the joint and scribe timber to timber. We use ones shaped like a hollow doughnut within which there are cross hairs which can be used to sight datum off the floor.And a plumb bob is used to set out the joint and scribe timber to timber. We use ones shaped like a hollow doughnut within which there are cross hairs which can be used to sight datum off the floor.

    12. Pre-assembly A truss A frame has been assembled. Then it’s braces is laid on to be scribed to the collar. The black centre line snapped on the back of principle rafter allows any bow to be ignored. In the back ground the other truss has its braces fitted and the arris will be run off with planes. A truss A frame has been assembled. Then it’s braces is laid on to be scribed to the collar. The black centre line snapped on the back of principle rafter allows any bow to be ignored. In the back ground the other truss has its braces fitted and the arris will be run off with planes.

    13. Numbering Up Once assembled the frames are coded up with chisel cut numbers. Disassembled and stacked ready to go to site.Once assembled the frames are coded up with chisel cut numbers. Disassembled and stacked ready to go to site.

    14. Traditional pegged joints We also code the ends for easy identification in stacks. The Mortice and Tenon is the main joint in timber framing. It is most efficient in compression. Unlike joinery or Japanese carpentry, which relies on an interference fit for stability, European framing generally uses bracing. The joints are cut to joint a tolerance of 1.5 mm. Tenons are usually 35mm by 100mm deep. The 19mm or 25mm peg holes are spaced close to the shoulder to allow a minimum relish on the tenon. Edge distance. We also code the ends for easy identification in stacks. The Mortice and Tenon is the main joint in timber framing. It is most efficient in compression. Unlike joinery or Japanese carpentry, which relies on an interference fit for stability, European framing generally uses bracing. The joints are cut to joint a tolerance of 1.5 mm. Tenons are usually 35mm by 100mm deep. The 19mm or 25mm peg holes are spaced close to the shoulder to allow a minimum relish on the tenon. Edge distance.

    15. Off set pegging/Face The shoulders are pulled tight by cleft tapered oak pegs. This is achieved by off-setting the holes in the two parts of a joint. The joints are set out from and Faced from one side. Mortice wall to mortice usually being 35mm – 35mm or 1 ˝” – 1 ˝”. This minimises the effects of green timber shrinkage. In this floor beam joint the pegs have been sited low down to avoid the beam being hung up on it’s pegs. The shoulders are pulled tight by cleft tapered oak pegs. This is achieved by off-setting the holes in the two parts of a joint. The joints are set out from and Faced from one side. Mortice wall to mortice usually being 35mm – 35mm or 1 ˝” – 1 ˝”. This minimises the effects of green timber shrinkage. In this floor beam joint the pegs have been sited low down to avoid the beam being hung up on it’s pegs.

    16. Compatibility with metals Some “purists” tend to forget that Steel has been used with timber framing from year dot. Some timbers eg Oak and Western Red Cedar are fairly acid. It’s best to consider using stainless steel or protection with these.Some “purists” tend to forget that Steel has been used with timber framing from year dot. Some timbers eg Oak and Western Red Cedar are fairly acid. It’s best to consider using stainless steel or protection with these.

    17. Assembly and Erection on Site The exciting bit then begins Frames are delivered to site and re-assembled in either individual pieces or section The exciting bit then begins Frames are delivered to site and re-assembled in either individual pieces or section

    18. Assembly and Erection on Site Whole sections can be craned into place. Then temporarily braced with 4 x 2s or guys. Some fettling of the joints will occur as this is probably the first time that the frame has gone together in 3DWhole sections can be craned into place. Then temporarily braced with 4 x 2s or guys. Some fettling of the joints will occur as this is probably the first time that the frame has gone together in 3D

    19. Assembly and Erection on The frame is pegged up as erection progressesThe frame is pegged up as erection progresses

    20. Moffet House – Andy MacAvoy It’s a quick process. The framers typically leave site after 3 – 5 days. There's then a completed structure ready for the external envelope. It’s a quick process. The framers typically leave site after 3 – 5 days. There's then a completed structure ready for the external envelope.

    21. Coldstone Manor Robert Franklin Architect Cruck framed roof to a swimming pool enclosure in the Cotswolds. Oak performs well in the environment.Cruck framed roof to a swimming pool enclosure in the Cotswolds. Oak performs well in the environment.

    22. Nimmo James Brotherhood Partnership A spere truss form with wedged king post.A spere truss form with wedged king post.

    23. Orchard House Edward Nash Partnership Externally exposed frame with no expressed bracing.Externally exposed frame with no expressed bracing.

    24. Orchard House Edward Nash Partnership with lath rain screen infill Bold areas of glasswith lath rain screen infill Bold areas of glass

    25. Bedales Theatre Feilden Clegg Architects The Olivier Theatre at Bedales School combined traditional framing with balloon and engineered work.The Olivier Theatre at Bedales School combined traditional framing with balloon and engineered work.

    26. Bedales Theatre Feilden Clegg Architects The entrance Foyer was a straight interpretation of an aisled barn form with the arcade narrowed to emphasize the central axis. (Built by the pupils) Where as the Auditorium with wide spans and demanding loads combined old ways with new.The entrance Foyer was a straight interpretation of an aisled barn form with the arcade narrowed to emphasize the central axis. (Built by the pupils) Where as the Auditorium with wide spans and demanding loads combined old ways with new.

    27. David Douglas Pavilion Gaia Architects The David Douglas Pavilion celebrated the discoveries of it’s namesake. Built in home grown Douglas Fir, of which you can get superb quality in this country.The David Douglas Pavilion celebrated the discoveries of it’s namesake. Built in home grown Douglas Fir, of which you can get superb quality in this country.

    28. David Douglas Pavilion Gaia Architects The round wood is scribed to curved plates.The round wood is scribed to curved plates.

    29. Maggie’s Centre, Inverness Page & Park Architects Right out the other end with the Maggie’s Centre Inverness Home grown spruce.Right out the other end with the Maggie’s Centre Inverness Home grown spruce.

    30. Building Machines. Trebuchet & Ballista As well as decks, bridges and other structures We’ve had a plethora of machines to build in recent years TV reconstructions.As well as decks, bridges and other structures We’ve had a plethora of machines to build in recent years TV reconstructions.

    31. Think long term – timber grows on trees in 60 – 120 year rotation. Plant Now! We have a policy of re- planting 10 trees for every one used. Given that it takes a 60 – 120 year rotation for the next harvest These will be used by a generation we’ll never know. We have a policy of re- planting 10 trees for every one used. Given that it takes a 60 – 120 year rotation for the next harvest These will be used by a generation we’ll never know.

    32. Traditional Fabrication Techniques The End

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