How to Install Stairs in a House

Load the stairs into the house upon delivery, keeping all packing material intact. This task requires several people, because the prefabricated stairs are heavy, especially if constructed of hardwood or steel.

Lift the stairs into position so that the top edge of the top riser is level with the floor on the upper level.

Add shims between the back of the top riser and the header board on the upper floor as needed to ensure that the two pieces fit tightly together. The header board is the outer floor joist of the upper-level floor.

Stagger a level over the top stair and the upper-level floor so it extends from the floor onto the top edge of the stair riser. Check that the top riser is level with the floor. Check the side of the staircase for plumb and adjust with shims as needed.

Drive four 16d nails, spaced evenly apart, through the riser of the top stair and into the header board of the upper-level floor.

Screw the staircase to the studs of the adjoining walls with 3-inch wood screws. Add shims as needed to fill any gaps between the stair stringers and studs. Drive the screws in at an angle through the stud, shim and stringer.

Remove any protective packing material, usually cardboard, and finish the stairs with paint or stain. Stairs can be ordered with finish already applied, so all that's needed is to remove the protective material.

Install your choice of balusters and handrails to the sides of the stairs. Depending on the type of balusters chosen, they may set into a hole, mount to the side of the stringer or mount to the top of the steps. If one side of the stairs is set against a wall, you need to install a handrail to the wall when the wall is finished, and balusters and railing to the open side of the stairs.