Basic Deck Stairs

Measure the overall height your stairs need to cover and the width you want them. Divide the overall height by about 7 and drop the decimal — that whole number is how many steps (rises) you need. Divide the overall height by that number of rises to get the exact height of each step.

Then decide your tread depth. If it doesn't matter exactly where the stairs land, two 2x6 boards side by side gives about an 11" tread with a little nosing — an easy, comfortable default. If your stairs must land at a specific spot, divide your total available run by the number of treads instead.

Set your speed square (or rafter square) to your calculated rise and run measurements. Line the square up with the edge of the stringer board and trace the rise/run notch. This first stringer is your template for every following one, so take the time to get it right.

Slide the square down the board, lining it up with your previous mark and the board's edge, and trace the next notch. Repeat for every step, then cut both stringers with a circular saw for the straight runs and a hand saw to finish each inside corner cleanly.

Screw the ledger/back board to the tops of both stringers, then attach that assembly to your landing or deck framing, checking it's level and that both stringers are plumb and evenly spaced for your stair width.

Starting at the bottom, screw down the first tread's two boards to the stringer notches, using a pencil laid on its side as a quick, repeatable gap spacer between the boards. Work your way up, checking each tread stays level, and screw every tread down securely.