![]() Timbers are an exactly match and positioned and typically require specialized tagging/marking systems to track their future assembly. The process requires laying entire frame assembles (ie bents or wall sections) in a shop or yard. Exact dimensions as well as localized characteristics are transferred (copied or scribed) onto each other. Here’s a great description from New Heritage Woodworking:Įach timber is custom mated to its adjoining timber and vice-versa. Think of Scribe Rule as truly custom fitting timbers to each other by literally mapping the shapes onto adjoining pieces. No math, no reading of measurements at all. There is an amazing history there, of which I only know a tiny fraction, but imagine carpenters in older times, building entire cathedrals without referring to any measurements, or any tape measures, and using only a pair of dividers and a plumb bob to do all of the layout. Everything can be laid out with a carpenter’s square, which amazingly, is not what they would use on the other side of the ocean… Brilliant, huh? This is the most commonly used system in the US to this day. Get it? Every timber, no matter that it may be off from its “true” dimensions (rarely will you get an actual 8×8, unless you pay a lot of money, maybe), has an invisible, perfect timber contained within it. All joinery is cut to this inner timber, which usually shares two adjacent square faces with the outer irregular timber. For example, a 7×7 post may actually measure 7 1/4″ by 6 3/4″ it would be laid out as if it were a perfect 6 1/2″ by 6 1/2″. ![]() It’s based on the idea that within every irregular, rough sawn (or hewn) timber there lies a slightly smaller perfect timber (see drawing). The term “Square Rule” was coined by Edward Shaw in his 1830′s book Civil Architecture to describe this traditional system which began in the U.S. I like this description of Square Rule from the Heartwood School: Compare this situation to what people were familiar with back in Europe, where builders had to learn how to adapt to using crooked trees and irregular timbers, because many of the biggest and straightest timbers were already long gone. Tom Cundiff says that with the “discovery” of abundant big, straight timbers in colonial America, carpenters were able to work with some of the finest available wood available anywhere in the world. Square rule is an American method of layout. They are two singular approaches to achieving the same basic effect - making two different pieces of wood relate to each other, and join in a logical way. They are Square Rule and Scribe Rule layout. ![]() However, I can say a few things about the two systems we employed when building our timber frame. Reading about it, and having someone describe it to me makes my brain slowly turn off. Personally, I’m in the camp of really needing to see and do layout to actually understand it. I don’t feel fully qualified, and besides, you can find some pretty good documentation elsewhere. ![]() I’m going to be very honest here - I will not be making any in-depth attempt to describe timber frame joinery layout here on this blog as part of my documentation for building our timber frame and straw bale house. Understanding layout - the most important part of timber framing
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