Stair Construction   How Hard Is It To Build Stairs

When I first started my career in carpentry, building a set of stairs seemed like a complicated and daunting task. We're not talking finished oak, curved or spiral staircases. I'm talking about your normal carpet covered straight run staircases or porch and deck staircases.

My first stair building experience sort of took the mystery out of it all. I didn't have to do much figuring because it was a deck replacement job. All I did was save the old stringers from the demo of the old deck. In doing so it all started to make sense to me. How the stairs were attached, the width of the treads, and how high each step was became less of a secret to me.

Anyone with the courage to take on this job needs only patience, basic math, a framing square and the ability to stand back and look at the big picture.

The first thing I look at is how high it is to the top of the landing or deck the stairs will be rising to. A comfortable step is in the 7 to 8 inch range. With this in mind I divide the height to the landing by seven. If the height to the landing is 70" then it will take 10 rises to get to the top of the landing. I used 70" to simplify this example. Ninety-nine times out of a hundred it will be 7" and some odd fraction. For instance if the height was 73 1/2", the rise would be 7 1/2".

When building stairs there is always one less tread than there is risers. In this case with 10 risers, that means there are 9 treads. When cutting my stringers, I like to make the cuts for my treads 10" long. At this dimension I can use a 2x12 for treads without ripping them to a narrower width. This gives me a nosing or overhang of 1 1/4". It also makes it easier to figure out how much room the stairs will require. In this case 9 treads X 10" = 90". The total run of the stairs is 90".

An example of how easy this works are stairs that go from the 1st floor to the 2nd floor of a house with an eight foot ceiling. This takes 14 risers at 7 and 5/8 inches (I've cut so many of these it is forever imbedded in my mind). This means there are 13 treads. Thirteen times ten is 130". I always made my stairwell opening 120". This lets 10" of the stringer (a full tread) sit on the deck or concrete floor. It also leaves plenty of headroom for the stairs below if there is a basement. The same well opening above (120") also gives you enough headroom.

This can seem like an overwhelming project. Like any other project, if you take the time and patience and a little thought you can acquire the ability.

 Laying Out Stringers

You won't need anything other than an ordinary carpenter's square and pencil to apply the rise and run figures you've arrived at to the stock for your stringers, but before you do, you'll have to get some wood worthy of the challenge. Construction-grade spruce or pine 2 x 12s are the usual stock used for making staircase stringers, though you can probably get away with 2 x 10s for shorter staircases involving only a few steps. The crucial thing is that the wood be sound, relatively clear and have no large knots. By the time you cut notches out for the stairs, there will be quite a bit less wood in a stringer than when you started, so be sure that what's there is good. Two stringers are okay for utility stairs up to 32 wide, but I'd go with three stringers for anything wider. A good rule-of-thumb is one stringer for no more than a 32 stair width.

The second illustration shows you how to hold your carpenter's square over the stringer stock to mark the outline of each stair. Notice how the 7 1/2-inch point along the left side of the square is lined up with the edge of the lumber while the 10 1/2-inch spot on the right side of the square lines up with the same edge. These are, of course, the rise and run figures we calculated earlier. Applying them to the stringer stock in this way, using the carpenter's square, automatically creates the correct angle and orientation we need. I don't even know the angle (in degrees) of the resulting stairs, and I don't have to. The square takes care of everything.



Remember how we settled on seven steps for our example? The actual stringers we'll create for a job like this will only have six stairs, because the seventh stair, the top one, is actually formed by the upper surface of the deck itself. Also note that the bottom-most step is actually closer to the bottom of the stringer than the rise figure. This reduction in height must match the thickness of the stair tread you'll be adding later, usually 1 1/2 inches.

Cutting, Fitting and Installing Stringers

Cutting stair stringers is a job that requires precisely-stopped cuts through thick stock. I like to use a combination of handheld circular saw (to do the bulk of the work), and a jigsaw or sharp handsaw to finish the last bit of the two cuts that intersect to form the inside corner where one part of a stair meets another. Using a circular saw for the whole job will result in overlapping cuts that will weaken the stringer significantly. Lay out and cut a single stringer and test-fit it against the deck. If it checks out, use it as a tracing pattern for the other stringers you'll need.

The first illustration shows an excellent way to support the stair stringers where they're joined to the deck and where they rest on the ground. A notch cut in the bottom edge of each stringer accommodates a 2 x 4 ledger face-nailed to the edge of the deck. The top of the stringers are also nailed to this ledger and to the deck with spikes driven in through pre-drilled holes in the stringer.


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