At first glance, the Johnny Square 7” speed square from Johnson Level is almost identical to my other two 7” aluminum squares. The long side of the triangle – the hypotenuse – now crosses your project at your desired angle. Make sure to cut on the waste” side of the line so the rafter size will be as accurate as possible. The square 10 defines a number of apertures or slots configured to enable the user to make a number of markings for carrying out a number of operations as will be explained.
As desired, the user of the square 10 may then mark a second line coincident with the first line and also parallel to the edge of the workpiece by moving the marking instrument to the scribe guide notch 38 directly opposite the scribe guide notch 38 used for marking the first line. This cut is called the plumb cut since it is plumb or vertical when the rafter is installed.
Many of the newer combination squares have the level mounted within a protractor which you can adjust to measure any angle. Just wipe off the square with a damp cloth to remove any debris and it will be ready to use for years to come. French Compagnon Roof Framing Kernel Angles and Framing Square Usage to geometrically draw out a bastard hip using a framing square.
I began cutting triangle shapes from scraps of plywood to mimic where the clamps would be placed on the square. After the rafter length is set and cut, make another cut 3/4 inch from plumb to allow for two-inch ridge board for where rafters meet. The square 10 includes a face side 20 and an opposing bottom side 22. The face and bottom sides 20 and 22 may include a number of markings for use in carrying out operations using the square 10 as will be described herein. The picture above shows the first rafter lengths in green which is from the ridge to the wall plate.
The traditional steel square’s rafter table ( patented April 23,1901 ) is limited in that it does not have tables that allow for work with unequal pitched roofs. On the back of a framing square along the inner edge of the tongue (the shorter arm) inches are divided into 10ths (green arrow). So in that instance, I work out roughly what the overhang will be at each end of the roof and make sure the rafter tails are long enough to allow for that when setting out the rafter lengths.
The long, diagonal edge of the square (which is actually a triangle, as you may have noticed by now), has markings from 0-90º in one-degree increments, to allow you to easily find and mark any angle. The result on my Construction Master calculator is 2 ft. 11 5/8 in. Next, I press the Run key, instructing the calculator to use that dimension as the ‘run,’ which is the first element of the right triangle I am working with.
Stanley’s similar tool is called a Quick Square and Irwin’s is simply called the Rafter Square. The scribe guide notches are typically defined by a number of teeth formed in a slot formed in the body of the rafter angle square that extends parallel to the ruler side of the body. Draw a line from the pivot point directly along the straight edge of the speed square.
Measuring Pitches – Part of the speed square’s role as a protractor, and its original mission as a tool, is in quickly finding common (and uncommon) rafter angles for the pitches on roofs. The user then rotates the square 10 about the pivot point 54 until the desired angle along the hypotenuse side 16 is aligned with an opposite edge of the workpiece. To mark the birdsmouth angle place the pivot point of the square where the birdsmouth mark meets the edge of the board.
My current framing square, made by Empire Level, is made of light blue aluminum. Accordingly, a rafter angle square including aligned scribe guide notches on opposing sides of the scribe guide notch is desirable. We will look at two of those scales in a bit, but first I want to point out some key features that allow the square to work as it does. It is well worth the effort to rough out the wall system to be square and level so the roof framing is simple. When considering the purchase of a new square, go for quality, those $12 ones just will not cut the mustard under normal everyday use.
My old black steel framing square was easy to read in various llighting conditions, was very resistant to gouges from my rock knife when I used the square to make cuts in drywall or to make cuts in lumber as one might do to avoid chipping up wood when cross-cutting with a power saw. Only a level roof, or a 0 pitch will require a 45° angle side cut (cheek cut) for hip and jack rafters.
Measuring – Along one of the right-angled edges of the square is a conventional English ruler which is either 7″ or 12″ (depending on the model of speed square). This line, which is perpendicular to the material edge that the speed square lip is hooked onto, is a 90-degree angle. I then slide the square along the bottom edge until the 8 in. mark on the body intersects the parallel plumb line I drew earlier; you’ll see that the line I trace will be exactly 4 in. long.
This article explains how to make quick use of a framing square and its imprinted data to get some basic roof measurement data like roof pitch or slope, rafter lengths, and end cuts, stair stringer cuts, lengths of braces and other construction measurements. We can reverse the usual use of a framing square (finding the rafter length) to figure out the roof dimensions (or slope). Make sure that the gusset does not extend above the top edges of the rafter and then nail the gusset to the rafters using 6d nails. Each rafter only spans half the width of the building, and they start at the face of the ridge beam.
When building cabinets, boxes, or other furniture pieces, hold the speed square against the wood to measure angles before cutting or attaching pieces of wood. Using one end of the shed floor that is the same width as the rafter assemblies, make a line on the exact center of the floor. Well, first off, the post would be a mile long to explain most of the uses for the square and second most people can’t get used to the idea of using the run / rise for a roof instead of degrees. Over time the ratio over 12″ (1 foot) was more commonly used as it was easy to reference on the framing square.
Our sketch above illustrates the concepts of run (horizontal distance) and rise (vertical distance) along the length of a rafter. The user may also position the marking instrument in the opposing scribe guide notch of the second edge and slidably move the square along the edge of the workpiece to mark a second line in a second direction opposite the first direction but still parallel with the edge of the workpiece and coincident with the first line. Modern carpenters have used steel squares and more recently aluminum framing squares for decades.
By firmly holding the fence against the edge of a board, you can use the other right-angle or 45° angle edge as a fence for your hand or circular saw. Just to keep it simple I will use the same building dimension in all three examples. Instead of just marking the angle, a thicker plastic square can serve as a shoe for a circular saw to ride along. Hold the pivot point against the board and move the square until your desired angle lines up with the edge of the board.
Merriam-Webster defines a square as: a four-sided shape that is made up of four straight sides that are the same length and that has four right angles. As a carpenter and builder the Johnson Speed Square or Johnny Square is the first square I reach for and I end up using it for 99 percent of my squaring lines, square cutting and line and angle marking applications. But today, carpenters use large 4-foot by 8-foot sheets of plywood or oriented-strand board to rapidly cover the roof rafters or trusses.
As long as I can remember I’ve always owned and carried a Johnson Speed Square in my tool belt. I found I did prefer the burgundy aluminum version with the white markings easier to read, but this was OK. I would like it to have the cut notch rather than the smooth corner for marking. Our photo below shows the unit-5 octagon scale on an Empire Level framing square. This number gives the length of the hip or valley rafter per seventeen units of run.
So a 20 foot wide building with a 40 degree pitch = 40 d ridge angle and 50 d seat angle (wall plate) just square off the 50 d to get the bird mouth ( 1/3 depth of rafter). Whether you’re building houses or just need to get the right cut for your flower boxes, this square offers the a perfect solution with exact measurements and quality construction. As mentioned previously, making 45 or 90-degree cuts with a speed square can be even easier. The values on the calculator that we use for common roof framing are: Pitch, Rise, Run, and Diagonal.
The fence element 18 includes a pair of flanges 40 and 42 configured to enable the user to arrange the square 10 relative to the workpiece. Another feature I really like, which is also found on some other brands, is the pivot point notched out of the 90º corner of the square. A ready reckoner is pretty much a ‘rafter calculator’ – a book full of rafter lengths tables. Use with the French Rabattement de Surface method (folding) or the German Flachenklappung method.Basiswissen Schiften or Charpente Les Traces.
When a rafter that was not an even increment, I had to go back to the calculator to determine the last few inches. If you look closely at the tongue on the back side of the framing square you will see two small numbers stacked one on top of the other with a larger single number just to the right of this smaller set of numbers. There are many other ways the speed square can be used, but I will focus on these two in this tutorial.