There are two types of layout methods for timber framing; square rule and scribe rule. Scribe rule involves full-scale layout and mating each piece together before marking and cutting, a laborious process but useful for irregular timbers. Square rule assumes a perfectly square timber exists inside every timber, and if we take measurements off of this perfect square, we can cut all of our joinery and then assemble it later and it will fit. No test fitting needed… or very little. We’ll be covering square rule layout in this article.
The first thing you should do is take your plans and match each timber in your plans to a physical timber in your stack. Disassemble your stack and layout all your timbers so you can examine each timber individually.
Next, inspect each timber. Rotate the timber 360 degrees. Look for knots or other defects that you might want to avoid. Sight down the timber and look for which way it’s crowning. The crown side is the side at the top of the hill. You need to mark the crown side. You need a crayon or carpenters pencil. Don’t mark the end of the timber, it’ll likely get sawn off later. Mark the middle of the timber with an “X” to signify the crown side. The crown side will face up in the frame and most likely be covered by flooring. If your timber is straight and doesn’t have a crown, pick the least attractive side to face up and mark it as the crown side. When selecting timbers for various parts of the frame, keep in mind the position of the joinery on each piece. You want to avoid selecting timbers with knots at joint locations. You also want to select your best looking timbers for parts of the frame that may be visible once the frame is finished.
Next you need to mark the reference side. This is the side of the timber that will be on the outside of the frame. For parts in the middle, not on the outside of the building, a direction of one of the bents is specified. For example, if you had a 4 bent barn with bent 1 at the North end and bent 4 at the South end, you might specify that bents 1, 2, 3 would be layed out from the North while bent 4 be layed out from the South. Take a crayon and mark a small “V” on the reference face, pointing in the direction of the crown (you should have this marked already).
Use a buider’s crayon to mark the part number so it can be matched to the plan. Each part (timber) should have it’s own number that corresponds to that part number in the plan. In the old days, parts would be labeled with roman numerals or symbols. They cut roman numbals into the timbers because curved numbers took longer. Since we have markers, just use regular numbers. Mark the timber on a side that won’t show (exterior of house, flooring, roofing).
Square off your timber to the overall length. Keep in mind your overall length may/may not include tenons, so make sure to include those before cutting the timber to length.
Setting up the Timber
Make sure the timber you’re about to mark and cut is on a solid work surface. Something you can pound on that will transfer the force of your mallet blows to the ground (a bouncy cush will force you to work way harder).
If you have a bunch of one kind of part to make (rafters, joists, girts, etc.) Line them up and cut them all at once, you’ll save a lot of time doing batches instead of doing one at a time.
Measuring and Marking
Before you hook your tape measure on the end of the beam and start pulling the tape, read the following paragraph about measuring. First, not all tape measures are the same. If your crew is using multiple tape measures measuring long timbers, you may be in for a surprise. Compare the tape measures beforehand to ensure they’re the same. Or buy a new tape measure for everyone on the crew of the same brand, prior to starting work on that project. Second, don’t hook the metal end of the tape onto the end of the beam. It’s just enough wiggle for us to be off by a wiggle. Get a little quick clamp and clamp the tape onto the beam, starting at 10″. I use 10″ because it’s easy for me to add and subtract to my tape measure reading. If my plan calls for an overall length of 156″, I’ll clamp my tape so the beam starts at 10″ and measure 166″ and mark it with a knife.
Let’s talk about marking. Although we’re dealing with large rough looking timbers, everything we do must be very precise in order to get a good fit. When you mark a timber, you’re want
Layout the Joinery
Most timbers aren’t the perfect width (they’re probably not perfectly square either). If you The square rule method assumes you can cut a perfectly square end to the timber (90 degrees angles and all sides same length) into an imperfect timber. We do this by downsizing the timber to a common measurement.
For example, if the plans call for 8″x8″ timbers, and your timbers measure between 7 3/4″ and 8 1/4″ you would downsize to your joints to 7 1/2″, the next largest 1/2″ increment all the timbers have in common. This is a good reason to mill your timbers at 8 1/2″ or so. Keep in mind that your timbers will shrink when they dry.
Imagine if you hand hewed the timbers! It’s far from perfectly straight and square, but anywhere a joint is made, it’s downsized to it’s perfect number. In the picture to the left, the barn beam is sometimes as thick as 9″, sometimes as thin as 8 1/4″, but at the joints, it’s downsized to exactly 8″. The joints fit perfectly.
To be continued…