Most of time, if you build a deck or a porch on your house, you’re going to need some stairs to get on and off of it. You might have a ground level deck in which case you won’t need stairs, but if you’re reading this, I’m going to assume you do.
You’ve got the deck framed and you may or may not have installed the decking. You can install stairs on your deck before or after you install the decking. If you don’t have the decking installed yet, you will need to know the thickness of your decking in order to calculate your rise accurately. Most decking comes in an actual 1″ thickness, so I’m going to use that in this article, but be sure to double check yours before you start doing math.
When I’m using a 5/4″ x 6″ decking (which is actually 1″ x 5 1/2″), I make my stair run 10 1/2″. This works out to have the two deck boards with a 1/4″ gap between them and about a 3/4″ nosing. The rise is going to depend on the height of your deck. If the height of your deck is 70″, that would work out to be 10 steps with a 7″ rise. Stair codes say you can’t have your rise be more that 7 3/4″ and I try to keep it above 6″ just because I think a shorter rise make for an uncomfortable step. The other thing to keep in mind is that you want to keep all of your rises consistent. Code says that your stair rise cannot differ more than 3/8″. When stairs are different heights they become tripping hazards. So you want to measure the height of your deck from the spot the stairs will sit on the ground (preferably a concrete pad) to the top of the finished decking. If your decking isn’t installed yet, you can measure to the top of the framing and then add the thickness of the decking. In my case, I would measure 69″ and then add 1″ to get a total of 70″.
One thing that most people don’t think about when framing stairs is to account for the thickness of the decking. Most people with measure to the top of the framing, divide that number up and then cut all the stairs evenly. The problem with this is that, once you install the decking, your first step will be an inch taller than the rest. So, you need to measure to the top of the decking, divide that number evenly and then take the width of the decking off the bottom. Then you install the stringer 7″ down from the top of the framing, not the top of the decking.
This makes my very first step 6″ and the rest 7″. Once I add decking to all the steps and the deck, all the rises will be 7″.
Don’t be afraid to draw out your stair layout on a piece of cardboard first. This way you can do the math and double check your measurements before you start marking up the lumber. Another thing to consider is to get a set of stair buttons. These are little pieces of metal that you clamp onto the framing square at the desired measurements for your rise and run and you won’t have to line up every mark you’re going to make.