There are a few different methods for laying out the joinery in a timber frame — scribe rule, square rule, mill rule etc
This post will take a deeper look at some Square Rule based framing.
Back in the fall of 2009 we worked on a frame which will be the workshop of an NBSS student using the Square Rule method. The project was carried out at Brookwood Farm in Canton MA which provided a great backdrop for our work along with the location of a later Scribe Rule project — restoring the old English style 2 bay barn that was discovered on the property.
Rather than custom scribing each joint in the frame — which is labor and time intensive, square rule framing allows you to effectively make some parts of the frame interchangeable (Think Model T Assembly Line) — so braces, joists are all cut to the same size to start. This method of framing came from the USA and was in part an answer to the need to speed up production as America rapidly expanded westward. Effectively you are using a square to find/define the virtual ‘perfect’ smaller timber inside the potentially rough stick you are working on — thus where the joinery is cut you are cutting back the side opposite your reference faces to square up that smaller perfect timber. This way you have nice clean and consistent mating surfaces. In the joint below you can see this on the top of the timber where it goes from clean cut joint to the rougher edge as the timber came from the mill.
This system allowed craftsmen (and women) to cut joints on the ground or in separate locations and then put them together for the first time at the time of raising. For those new to the trade that can seem daunting — but with practice and the old adage of ‘Measure Twice, Cut Once’ its not as scary as it might seem.
Below is a slideshow outlining the process of building a timber framed workshop/barn