Cut one, test one
Lay out the first stringer, drop it in place, and check the top and bottom steps against the finished floor before cutting the rest. Remember to drop the bottom step by the tread thickness so the first riser isn't taller than the others.
- • Use 2×12 stock — a cut 2×10 leaves too little throat depth.
- • Space stringers 16 in on center for 5/4 treads, 12 in for thinner.
- • Account for finished flooring on both levels in total rise.
FAQ
How do I calculate stair stringers?
Divide total rise by your target riser height and round to a whole number of steps, then divide total rise by that count for the exact riser. Multiply treads by tread depth for total run, and the stringer length is the hypotenuse of rise and run.
What is the maximum stair riser height?
The IRC allows a maximum 7.75 inch riser and requires a minimum 10 inch tread for residential stairs. Local codes can be stricter.
How many stringers do I need?
Three for a standard 36 in wide staircase. Add one for every additional 16 inches of width, or use closer spacing for thin treads.
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