square rule design

I occasionally see workshops advertized for
square rule design. Can you give me a rough idea what is meant by square rule design?
Thank you.
Richard

Richard,

Square rule "layout" is what you are actually refering to.

Basically, timber frame layout is the process of locating and drawing out the joinery on each piece of timber in the frame. Historically this has been done by laying out each section of the frame full scale, leveling them up, and transferring (or scribing) the size and shape of each piece from one timber to the other, at the locations of the joinery, in order to assure the accuracy of the assembly. This system of layout is known as "scribe" or "scribe rule" layout, and has been in use for over 1000 years. In fact it is still common practice in most areas of the world, other than the United States.

Square rule layout is a system that appears to have developed in this country shortly after the American revolution. It simplifies the process of layout, by allowing the layout of each piece of timber indivdully. This is accomplished by "sizing" each timber at the location of the joint. In other words wood is removed from the timber at the joint to create a given size or dimension. This is referred to as "housing" the timber and helps easily identify the two systems of layout.

The advantage of square rule layout is primarily that you only need to handle one timber at a time. It also lends itself to standardization of common members, like braces, and works well is smaller "production" shop settings. One disadvantage is that it doesn't work as well with curved timbers, or timbers with rounded edges.

I believe a third sytem of layout developed roughly 100 years after square rule. I call it "mill rule" layout. In mill rule the assumtion is made thad the sawmill sized the timber correctly when it was cut. In fact, mills of the late nineteenth century could easily saw very accurately sized timers. Mill rule layout is done by cutting the joinery directly into the face of the timber at the joint, with no need for a housing. This greatly reduces layout and machining time. In fact mill rule is common practice in many modern American timber frame shops.

Which system of layout is best is the kind of question these forums are made of. Both scribe and square rule timber framing have a beauty and elegance that some would say is lost in mill rule framing. But that's another topic.

Rudy R Christian

Rudy,

Thank you for the explanation. Would you happen to know of any books on the three methods of layout you outlined.
Richard