Stair Building

[peterjcb]

I have to construct a simple staircase for my new garage loft that has a total rise of 127" and a run of 160". I figured that I'll be using a riser of 7 15/16" and a run of 10".
That works out perfectly and I understand that much... but how do I go about figuring the angle of the cuts on my stringer without a CAD program? I have long forgotten my old geometry equations :oops:

I have actually nailed some OSB on the wall and traced out the treads and risers, it seems that I could theoretically try to measure the angle from my drawing on the wall. Is this an acceptable way to do stairs?

Also, would a riser of 7 15/16" be a generally acceptable height?

[roger g]

It's been a long time since I did this but I think this is the way I used to do it. I used to take the distance from FINISHED floor to FINISHED floor and divide it by seven and one half inches (or whatever you want) and the answer for you is 16.94 which is almost 17 risers. 17 risers times 7.5 equals 127.5 inches which is one half inch more than you have. Divide that half inch by 17 risers and you get .o3 of an inch. Deduct that .03 from 7.5 and you get 7.47 of an inch. Therefor your 17 risers are 7.47 of an inch each. 17 times 7.47 equals 126.99.
Sometimes I used to go on my basement floor and markout a complete set of stairs with al the nosing and everything just to see if it all worked out. Don't forget to take into consideration any thick covering on the treads.
I don't remember any formula, just simple math and drawing on the basement or garage floor. Get a welders marking pencil. It's like soapstone.

Roger

[roger g]

I forgot. I think 7 15/16 is a little high. We used to try to have risers at 7.5 and treads about 8.5. I can't remember about the nosing and open stairs and other things.

Roger

[Rich]

Typically for a stair going to a basement you can go a little steeper but I don't usually. A rough check for stairs is the tread plus riser is 17.5" theres another one that's 2 times the riser plus the tread equals something - forgotten it. What will typically govern is your local building codes.
Do you have a framing square?

[peterjcb]

I just checked the rise on my house steps and it's 8" rise...so there's no problem there.
Rich, I have a framing square and I bought those two little brass stops that they sell for the framing square when marking the cuts on the stringer board.
My question was really how to figure out the angle of the cut on the stringer board.

[Rich]

You don't need to know any angles... set the stops on the framing square at your rise and run and lay it across the top edge of the stringer (I assume a 2x12 stringer) with the point of the square pointing towards the bottom of the stringer. Mark it and move it up to the next one. The top cut will be the same as the vertical side of the square.
Where you may run into issues is the top and bottom cuts where you'll need to account for the tread material you are going to use. You will also need to account for the finish flooring material.

[Rich]

Oh I found that formula I couldn't remember.
2 times the riser plus the tread is roughly equal to 26 (exterior use 25 for interior use). (7 15/16*2)+X=26
15 7/8-26=-X
So tread length would be 10 1/8" (good figuring on your part). :)

[roger g]

Another problem that happens with stairs is that where the risers are too steep. It's hard to explain at 5:30am but some stairs in design, looks right but when you actually make them they end up being easy to go UP stairs but dangerous to go DOWN stairs. The overhang of one step really interferes with using the tread of the lower tread. Even though the math works out, the use is terrible and dangerous.
Rich was very right in that local code practices prevail.

Roger

[Rich]

Here is an image that shows how the framing square should be and what the dimensions are for your stair.
Stair Layout (http://www.construction-resource.com/images/projects/stairlayout.jpg)