How to Build Stairs
Stairs are an integral part of multi-level houses and many yards. It might be necessary to build a simple staircase between the floors of a house, down to the basement, up to an attic, or on an outdoor deck.
Building stairs requires careful planning and consideration. Yet the actual construction is fairly straightforward, as long as you follow codes and basic building techniques.
Stair Building Essentials
At its most basic, a staircase consists of horizontal treads that you walk on, vertical risers that separate the treads, and stair stringers that hold the treads and the risers. Other items contribute to the staircase, but those are the three main elements that need to be planned and designed before the building begins.
The stair tread is the step—the part that you walk on. Stair treads should be 10 inches deep or greater. Stair tread width should be at least 31 1/2 inches.
The stair riser is the vertical board that runs from the top of one tread to the bottom of the one above it. A riser closes up the treads for a cleaner look and for improved safety.
Risers can range from 6 1/2 inches to 8 inches high, but generally should be 7 3/4 inches, if possible.
A stair stringer is a long V-notched piece of wood that is positioned diagonally from the top header to the bottom landing. Treads and risers rest on the stringers.
Depending on your need, staircase slopes range from 30 to 50 degrees. At least two stringers are used in every straight staircase run, one on each side. Sometimes, one or two carriage stringers run down the middle.
Stringers are sized and cut to exact specifications to adhere to building codes. You can cut your own stair stringers from two-by-twelve dimensional lumber or purchase pre-cut stringers.
Other Stair Elements
Stair Header and Landing
The upper part of the stairs is attached to a stair header. The stair header is part of the house, deck, or other structure receiving the stairs—technically, not part of the staircase. The header must be strong enough to support the top section of the staircase.
The landing is the ground or floor at the bottom of the staircase. The landing must be level and strong enough to hold the bottom of the staircase.
Skirt boards on the outer side of the stringers provide a clean look and make the stairs safer since they make it more difficult for feet to accidentally slip off.
Hand railing is required for most staircases. If the staircase has more than four risers, you'll need to have railing on at least one side.
Codes and Permitting
Staircase, guard, and railing building code provide specifications while leaving some room for flexibility. Check with your local building permitting office for code that applies to your area and to your project. With few exceptions, obtaining a building permit is required when building stairs to ensure safety and code compliance.
When to Build Stairs
Indoor staircases can be built at any time of year. For outdoor staircases, it's safest to build in dry weather. Any pressure-treated wood that you cut for outdoor stairs must be treated with a copper solution before the wood comes into contact with water.
When installing stair treads, work while standing on the ground as much as possible. When you need to stand on stair treads to work on upper treads, make sure that the treads are already securely attached to the stringers.
Pay particular attention to the point where the top of the stringers attach to the header board. On freestanding stairs, this is the only attachment point, so it needs to be very secure.
What You'll Need
Equipment / Tools
- Bubble level
- Speed Square
- 2 Stair gauges
- Carpenter's square
- Cordless drill
- Circular saw
- Hand saw
- Tape measure
- 4 Two-by-twelves for stringers and skirts
- One-by-eights for stair risers
- Bullnose stair treads
- 3-inch screws
- 2-inch screws
Determine Staircase Slope
Lay the one-by-four on edge from the top of the header (the topmost point of the staircase) down to the ground at an angle. With the Speed Square, estimate a 40-degree angle from the top landing down to the ground and make a mark on the ground.
Rest the one-by-four board horizontally on edge at the stairs' top landing. Rest the bubble level on top of the board. Have an assistant at the top slowly extend the board outward until it passes the mark on the ground. Run the tape measure from the top of the extended board down to the mark on the ground. Be sure to keep the one-by-four level while doing this. The resulting measurement on the tape measure is the stair rise.
Calculate Number of Stair Risers and Treads
Divide the stair rise by 7 to arrive at the number of stair risers your staircase should have.
If the number is whole, leave the number as-is (for example: 70 divided by 7 equals 10). If the number has a remainder, round up or down from the 0.5 point (for example: 72 divided by 7 is 10.28, so round down to 10).
Subtract 1 from the number of stair risers to arrive at the number of stair treads.
Calculate Riser Heights
Divide the total rise height from earlier by the estimated number of risers needed to cover that distance. For example, if the rise height is 72 1/4 inches and the estimated number of risers is 10, the resulting riser height is 7.25 (or 7 1/4) inches: an acceptable riser height.
Lay out Stairs on One Stringer
Attach the stair gauges to the carpenter's square, with the short end of the square representing the tread and the long end representing the riser. Clamp the square along with the gauges onto the two-by-twelve board. Draw an outline of the L-shaped tread and riser combination.
Start at the bottom of the stringer and progressively work upward, unclamping and then re-clamping the gauges. Make sure that you are drawing on the outside of the carpenter's square.
Mark Cut Points on Stringer and Make Cuts
The top of the stringer will have excess wood. Make sure that you mark off 3/4-inch of wood to account for the top riser that will not be installed there (the header replaces this riser). Similarly, mark the bottom of the stringer with the thickness of the tread.
Use the circular saw to make those two cuts on the stringer.
Dry-Fit a Stringer Against Header and Floor
Lay this first stringer snug up against the top header and bottom landing. Check to make sure that both ends fit well and that you have drawn out the treads and risers correctly.
Draw Stringer Outline on Skirt Boards
Lay a stringer on one of the one-by-twelves. Draw the outline of the stringer on the one-by-twelve. Remove stringer template from the one-by-twelve. Repeat for the other side skirt board.
Cut Stair Notches in Stringers
Use the circular saw to notch out the V-shapes from this first stringer. If this first stringer is acceptable, use it as a template for the other stringers.
Cut Skirt Boards
Cut the one-by-twelve to produce a skirt board. Repeat for the other side.
Attach Stringers to Skirt Boards
Use the cordless drill and 2-inch screws to attach the stringers to the skirts. Remember that skirts are on the outsides of the stringers.
Attach Stringer/Skirt Boards to Header or Rim Joist
Temporarily attach a stringer/skirt board to the header (or rim joist, if a deck) with a screw or nail. Go to the back of the header. Permanently attach the stringer/skirt by driving 3-inch screws through the back of the header. Repeat for the other side.
Square the Stairs
At the front of the staircase, run a measuring tape diagonally from the top to the bottom. Repeat diagonally across the other side. If the two numbers match, the staircase is square and true, and you can now attach risers and treads.
Cut and Attach Risers
Cut risers from one-by-eight board to the required width and riser height. For example, if your stairs are 32 inches wide, cut boards to that width. If your risers are 7 1/4 inches high, there would be no need to rip the boards because one-by-eights are exactly 7 1/4 inches. Otherwise, rip the board to the necessary size.
Cut and Attach Stair Treads
Cut a stair tread to the correct width. If the treads are already 10 inches deep, leave as-is and use. Otherwise, rip accordingly so that the stair will be 10 inches deep from the end of the bullnose to where the back of the tread meets the riser.
What You Need to Know About Pressure Treated Wood. American International Forest Products.