I get asked this question a lot, how many stair stringers do I use when building a set of stairs? These questions are actually easy to answer and with a little bit of common sense and the ability to read a tape measure effectively, I should be able to give you a clear explanation that will provide you with the answers that you are looking for.
It’s common in the construction industry for roof rafters and floor joist to be 16 inches on center and we can also use this measurement while building a new set of stairs and figuring out how many stringers we actually need to use.
If you have a stairway that’s 48 inches wide and you divide your 16 inch on center measurement into 48 inches, you will find that you need to use for stair stringers. If you’re stairway is between 30 and 36 inches you will need three stair stringers.
How many stair stringers you actually need will also be determined by the thickness of your stair treads. If you’re going to use a 4 x 12 stair tread, there’s a good chance that you would only need one stair stringer at each end of the stairs, if you’re stairway is less than 40 inches wide.
If you’re going to use 2 x 12 stair treads, you could space your stringers 24 inches on center. The thickness of the stair tread will affect the amount of stair stringers you actually need, but you can’t go wrong with the original 16 inch on center measurement, unless you’re going to be using stair treads that are less than 1 inch thick.
Always check with a building professional first, before building your stairway to verify the amount of stair stringers you will actually need. This article is only meant to give someone a general idea but cannot be used in every situation effectively.