Take the quick way to the top with a simple lesson in basic stair construction.
Building nice staircases takes patience and skill. But it’s worth the effort: beautiful stairs help make a home special. But, before you break out the tape measure and circular saw, remember that quality pre-built stairs are available from specialty stair building shops. With dimensions in-hand and an eye on your budget, custom orders for anything from a simple straight run to an elaborate curved staircase are possible. Check your yellow pages under “Millwork” or “Stairs” for local resources.
Stairs are made up of treads (the part you step on), risers (the part your toe bumps), and stringers (the structure that holds the treads and risers up). For safety, codes regulate tread depths and riser heights, and they also require steps to be uniform—uneven steps can trip people up. Rail dimensions and headroom are also determined by building codes. Rules can vary locally, so be sure to check with your local building department. When building your own stairs, set aside plenty of time. Make careful measurements and calculations, mark with a sharp pencil, and cut with a sharp blade, and you’ll find the results satisfying.
Calculating rise and run
Since all risers must be equal, you have to evenly divide up the total height of the stairs to determine your riser height. Most houses have a floor-to-floor height of about nine feet. The floor-to-floor height encompasses both the height of the ceiling, and the structure that the supports the floor above. Eight-foot high walls, plus floor framing ten or twelve inches deep is typical. In most cases, that translates to 15 risers at about 7 to 8 inches for each riser. Be sure to allow for finish floor thicknesses: Oak strip flooring, for instance, can throw your measurements off by three quarters of an inch.
9-foot ceilings: 15 stairs
Higher ceilings require more floor space for comfortable stairs. In this example, the floor-to-floor height measures 118 inches (108-inch ceiling height plus 9-1/4-inch framing and a 3/4-inch subfloor).
8-foot ceilings: 13 stairs
Take headroom into consideration when planning stairs. In this example, the floor-to-floor height measures 106 inches (96-inch ceiling height plus 9-1/4-inch framing and a 3/4-inch subfloor).
At the top of the stairs, you step up onto the second floor; so you’ll have one less tread than you have risers. Standard treads you can buy at the lumberyard are about 11-1/2-inches wide. At that width, you’d need almost fourteen feet of open floor space for a typical staircase in a home with eight-foot ceilings. If you trim the treads back to 10 inches, you’ll save just over a foot of total length. Generous stairs are more comfortable and safer, though, so try to plan for plenty of space for stairs.
To avoid accidents, the height of each stair must be equal. The first riser rests on the subfloor; to accommodate the height of the finished floor, the first step on the stringer is trimmed by 1/4-inch to compensate for the difference in finish floor (3/4-inch) and tread (1-inch) thicknesses.
You’ll need two or three pieces of 2×10 lumber for your stair stringers, depending on the width of the treads. (Codes usually require stairs over 30-inches wide to be supported by three stringers.) Use a two-foot framing square to mark the steps on the board, using the narrow “tongue” of the square to mark the unit rise and the broad “body” or “blade” to mark the unit run. Allow for the thickness of the riser stock when you mark for the tread cuts. Also, when you measure for the riser on the first (bottom) step, don’t forget to lower it to compensate for the thickness of the tread (and raise it to allow for the thickness of the finish floor). Test-fit your first stringer for accuracy, then use it as a pattern for marking the rest. Mark and cut carefully: a sixteenth of an inch can be measured in squeaks in stair building.
Careful fastening can keep your stairs from squeaking. Apply a bead of construction adhesive where treads and risers touch the stringers, and use square-drive finish screws to fasten pieces together. As the lumber shrinks and swells with changes in indoor humidity, the screws and glue will hold everything tight.
Text by Ted Cushman
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