How to Build Deck Stairs

Question

I just built a new backyard wood deck, which turned out rather well. I am however having difficulty making up deck stairs. My total rise from the ground to the top of the deck board is 20.5". I imagine I will need three stair risers of 6 27/32 inches. I will be using 5/4" x 6" deck boards for the stair treads and the backs will be open. The two boards for my stair tread will turn out to be 11". I guess they should overhang a bit. I would like my deck stairs to be 48" across.

Answer

Remember that for 3 stair risers there are 2 stair treads. A carpenter never makes a set of deck stairs with the same number of stair treads as stair risers. If he did, the top stair tread would be flush with the upper floor or backyard wood deck. Always place that first step down one stair riser from the floor or deck surface.

I would make the stair run 10 3/4" to give about a 1/2" overhang with about 1/4" gap between the boards. You've got the stair rise correctly figured as 6 27/32". I would recommend that you use pressure treated wood for the deck stair stringers, supports and pads. Also for 48" wide deck stairs, 3 stair stringers are required. Be sure to compact the dirt well under the pads.

Dave