Whether a stair stringer is open or closed influences the look it imparts. A closed stringer is created with either cleats holding the step tread in place or possibly recessed cuts that encompass the tread. The result is a step where you cannot see where the tread begins or ends. In contrast, an open stringer is cut to outline the tread in a distinct zigzag pattern and the tread ends are exposed. Builders typically install closed stringers against a wall and open along a free expanse. However, they are interchangeable, and converting your closed stringer to open will create an informal, open or country look.
Removing Closed Stringer Stairs
Remove the floor covering from the stairs. Use a utility knife to cut through carpeting or linoleum, then pull and tear as necessary. If the stairs are wood, this is not necessary.
Access the area beneath your stairs. Cut an opening in between studs to gain entrance, scoring the drywall or paneling with a utility knife. Take care to avoid cutting electrical wire; scoring the surface lightly and pushing on the cut-out portion is the safest way to gain entry.
Look at the stair construction to determine the best method of attack. Individual stair techniques vary widely. Determine if a mortise or cleat holds the treads and risers in place. Check for triangular-shaped blocks connecting the tread and risers and nails through the butt joint where the treads and risers meet. Builders also commonly face nail the treads and risers to a middle stringer, if present, since it is open-cut to support the steps.
Remove the wedges that hold mortised treads and risers in place. Work from beneath the stairs, digging out the wedges with a chisel and hammer. If cleats were used, pry those away with a crowbar.
Pry away any triangular blocks spanning the tread and riser connection, underneath the stairs. Pull any other visible nails, such as those driven through the butt joint formed by the tread and riser.
Move to the front of the staircase. Working from the top down, pry up on each tread with a hammer and crowbar to loosen any face nails. Pull the nails with a nail puller when you can get a grip. Repeat with the step riser before continuing with the next step lower. Cleated closed stringers may allow the tread and riser to break free if other nailing is removed; mortised stringers will continue to hold the board ends securely.
Return to the rear of the staircase and knock mortised treads loose, pushing them forward. Pull or pry risers down to release. Alternatively, cut through the middle of each tread to release the boards.
Detach the stair stringers from the top floor landing, unbolting the joist hangers, and repeat at the bottom of the stringers, against the subfloor. Lower any stringers that come free at this point. Pry the outer stringers and skirts away from walls, which may be nailed in place, taking care to avoid damaging the wall sheathing.
Building Open Stringer Stairs
Find the distance between the subfloor at the bottom of the stairs and the surface of the top floor. Divide the result, which is the total stairs rise, by 7 inches to determine the number of steps.
Divide the total stairs rise by the step count to find the individual step rise, or step height. The ideal is 7 inches.
Choose the step run, or the step depth, using the rule of thumb that one rise plus one run should equal between 17 and 18 inches. The ideal step run is 11 inches. Multiply by the step count previously found to obtain the total stair run, which is the length the stairs extend in a horizontal plane.
Square the total stairs rise. Square the total stairs run. Add the results and find the square root to calculate the stringer length, which is in inches. Cut 2-by-12-inch boards, one for each stringer removed from the old stairs, to length plus a few extra inches to allow room for error; you will remove excess board length later.
Attach stair gauges, small screw-on guides, to a carpenter's square. Align one with the rise measurement and the other with the run. Alternatively, create a jig by clamping a straightedge in place with the same measurements. Lay the square, now forming the precise step outline, on the stringer with the gauges or straightedge running along the stringer edge and the triangular portion resting on the board.
Trace around the square to create the first step guide marks. Slide the square down, aligning with the end of the first step, and repeat. Continue until all steps are outlined.
Cut the stringer along the zigzagging guide marks, using a circular saw until near the inner corner, where the run meets the rise. Switch to a handsaw to ensure accuracy; cuts weaken the stringer substantially, so avoid unnecessary cuts.
Measure from the first step down to the thickness of the tread desired -- typically 1 inch. Mark on either side of the stringer and connect with a straightedge. Repeat at the stringer top, extending a square line across the stringer rise plus 1 inch. Make the job easier by using the previous stringers to scribe the end angles exactly.
Cut the ends of the stringer. Hold it in place and check the accuracy. Use the first stringer as a template for additional stringers.
Hang the stairs, following the previous methods of attachment. Secure the top with joist hangers, bolt the bottom in place against the subfloor, then cut treads and risers for each step. Allow up to 1 inch tread overhang past the stringers, on the side. Spread glue and set the tread or riser, as applicable, in place. Reinforce with finishing nails. Work from the bottom up for easiest installation.
Secure the rear of the steps, underneath the stairs, as desired. Reinstall triangular blocks or nail through the butt edge formed by the tread and riser. Nail through the stringer into the wall as previously attached. Finish with trim, including step nosing.