From DIYinfo.org
[edit] Setting Out Stairs
How to set out a stair. In the sketch below, look at the red triangles. It is plain to see that if you can mark those out accurately on your stringers, everything else is just detail.
I take the total rise and the total going and calculate the total angle distance. I divide the total angle distance by the number of risers. I use this measurement to set out the stair strings. The short red lines on the sketch. Then I add in the vertical and horizontal lines from them, using my steel square set up with guides (see sketch below) .
Here are a couple of stair triangles. I check them to see that they comply with the BCA table that defines the various allowable ratios. To see it again go back to the Stair Building intro page.
I used a cheap students calculator to do most of my calculations.
When I had my size, say 331, I punch into my calculator a series of 331 and hitting + and getting 662, 993, and so on. Very accurate. Set the tape at one end and just tick them off. Doing it this way any individual pencil mark might be a touch out, but the overall length is still spot on. I still use this method for running any series of numbers.
I don't use the actual steel square method. That is using the square with guides on it, as in the sketch, with the rise and the go set on the square, and then moving along from one mark to the other. In a stair with say 17 steps it is easy to creep 20mm and you wouldn't know it.
I use the square or a template as a tool to get the horizontal and vertical lines, but the datums for those lines are the series of 331 : 662 : 993: ...........that I pencilled in earlier from my calculator work.
If you don't have a steel square handy or are using it for something else, it is easy to make a one off template out of a bit of scrap Masonite and a couple of battens. Here's one made with an offset for a particular stair.
I still use the steel square, but I try to set it up to two risers and two treads, that lets me pencil in the longer marks. The square set up is easy, it is just two lengths of 50x25 (2x1)tek screwed to each other over the square, clamp it first and set the angle perfect, then screw the battens together close to the steel.
[edit] If In Doubt, Draw It Out
It is quite easy once you have the correct rise and go worked out, to start marking out your strings. I very rarely do. I almost always draw part of the stair out full size on a bit of ply, MDF. or something similar. A couple of saw horses and a sheet of ply.
I am not talking about a big deal here, only three treads or rises, that's all I need. I pencil in the rise times three on a square end of the sheet, and the go time three on the edge of the sheet and join the points to give me an exact stair angle to set my squares and bevels to.
I mark out the layout at the top, It could be double timber joists, it could be concrete or I might have to fit inside the flanges of a steel beam. I draw it out, correct, full size, down to the thickness of the floor covering (if any).
I do the bottom the same and gradually draw the lot. Most times it is very simple, and once it is laid out, it is clear which bits of the strings I have to cut off to fit snug here and there.
I don't physically use it as pattern, more as full scale drawing of the important parts, the top and the bottom of the stair. In many cases I don't need to refer too it much at all after doing the sketch, the actual fact of drawing it out reminds me of something I could otherwise have missed.
I'll repeat that because for me this works all the time. The actual fact of sketching it out, considering the top layout, and the layout at the foot fixes the details in my mind far more that a brief check of the drawings and then going straight ahead with the marking and cutting.
[edit] Author
Bill Bradley
More DIY and home improvement pages on my website. Bill's site
