After the oak frame drawings have been approved by the structural engineer and signed off by Peter the client, a cutting list is compiled itemising the dimensions of every component of the frame — width, depth and length. This is sent to the mill in Normandy in the North of France and will be cut and delivered in three weeks.
An allowance of 100mm is added to be safe. All of the braces for this frame are curved and therefore have to be cut from bent stems or branches to maintain their strength. It’s a great way to use wonky grown timbers that might otherwise be wasted. There will be over 80 in total along with a number of heavier curved members — the sling braces and collars that make up some of the trusses. Jowl posts too will need a curve cut at the top where they join the tie beam.
There are basically two grades of timber — QPA and QP1. QPA is the higher grade and has a very strict criteria of straight grain, knot size and sap allowance, and is selected for the parts of the frame which are doing the most work such as the floor beams, wallplates, purlins, ridge, principal rafters and so on. Some of the vertical timbers that are in compression can be QP1 quality. The mill that we use in France is extremely experienced at cutting for oak frames, and likes to see a copy of the oak frame drawings so that they can tailor the milling to suit the frame.
Last week’s blog may have foolishly commented on the smooth running of the project thus far… Pride before a fall and all that! The recent trouble at Calais and operation ‘Stack’ delayed the arrival of the oak by a full three weeks. At one point it felt like we would be better off planting our own acorns and waiting for the results.
After we’d pulled all our hair out and stamped our feet the oak finally arrived. Now the work really begins.
Next week: Rob looks at timber framing in the workshop
About the author:
Rob Dawson built a stunning oak frame home in 2009 for less than £100,000. He is now the owner and founder of Castle Ring Oak Frame.