Things You'll Need
Home Depot risers are sold either finished or unfinished and in a variety of measurements, usable as is on Home Depot precut stair stringers. If your staircase is narrower than the premade risers are long, though, you can cut them to fit the size of staircase that you're building. The risers are cut squarely -- with 90-degree angles at each corner -- meaning you can resize them using the factory-straight edges and angles for two of your own riser sides and angles, lessening the time required for ripping the size of risers you need.
Measure the width of the staircase from the outer edges of the stair stringers running up both sides of the stairway, using with a tape measure. Next, measure the rise of the step, from the base of the step along the stringer to the top of the step area of the stringer, flush with the base at the next level. Measure each step individually before cutting each stringer to fit.
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Mark the measurements you took in Step 1 on a Home Depot riser. Use one edge of the riser as the bottom edge of your measurement and one side of the riser as a side for your measurement to limit your cuts to only two. Mark the top cutting line along the length of the riser, placing a carpenter's square against the riser side to create a straight guideline to make your mark with a pencil. Mark the width of the step onto the riser in the same way, placing the carpenter's square onto the base of the stair to guide you in making a line across the shorter width of the riser with the pencil.
Place the riser onto a table saw platform with a marked line aligned with the saw blade. Cut the riser along the line, then realign the riser with the second marked line and cut it again, finishing the riser.
Place the riser vertically across the stringers. The top of the riser should fit flush with the top of the step so you can place the stair tread over the riser. Nail the riser into place against the stringers on both sides using finish nails and a hammer. Place a nail through each riser corner into the stringer, with an additional nail in the center, between the corners.
Continue by following Steps 1 through 4 for each riser on the staircase.
If the floor along the bottom of the staircase is uneven, create a cardboard template for the bottom riser and scribe the floor edge onto the riser using a compass and pencil. Run the point of the compass along the floor with the pencil against the cardboard held against the stringers to translate all floor irregularities onto the cardboard.
Wear safety goggles and a particle mask when cutting to avoid getting wood particles in your eyes or lungs.