How to Install Prefabricated Interior Wood Stairs

Measuring and Ordering

• 1

  Take a tape measure and extend it from the top of the landing straight down to the floor. This gives you the total rise of staircase.

• 2

  Measure from the first riser at the bottom of the stairs to the point on the floor directly below the landing. This measurement gives you the total run.

• 3

  Measure the width of the opening from wall to wall.

• 4

  Order your prefabricated stairs from the manufacturer. Tell them your stairway is between two walls and that you need a handrail. Give them the rise, run and width measurements.

Stair Installation

• 5

  Have helpers assist you in carrying the stair assembly to the installation site. Set the assembly on the floor and drill two 1/8-inch holes in the top riser about 10 inches apart.

• 6

  Find the location of the wall studs with a stud finder. Nail 4-inch long blocks of the thickness of a drywall panel to the studs at the top and bottom of each wall.

• 7

  Move the stairs into position with the top riser level with the top of the landing header. Nail two 2-by-4 blocks into the floor at the bottom of the assembly to hold it steady.

• 8

  Place shims, thin pieces of scrap wood, behind the pilot holes of the top riser, if needed to fill any gap. Check the treads for level. Fasten the riser to the header with 3 1/2-inch finishing nails driven into the pilot holes.

• 9

  Check each tread for level again.

• 10

  Nail the side boards, or housed stringer, to the shims at the top studs. Use 3 1/2-inch nails. Check treads for level one last time

• 11

  Nail the side boards to the shims at the bottom of the stairs.

Handrail Installation

• 12

  Install the handrail to one side of the wall after the drywall has been applied to the framing.

• 13

  Find the wall studs with a stud finder. Place a vertical length of tape to mark the studs.

• 14

  Take a 4-foot spirit level and stand it up against the wall at the top tread. Ensure that one end of the level rests on the nose of the tread. Make a vertical line and a horizontal line at the 36-inch mark.

• 15

  Repeat the process at the bottom step.

• 16

  Have a helper assist you in holding the rail along the 36-inch-high marks at the top and bottom of the stairs. Make marks on the wall at each stud location on the underside of the railing.

• 17

  Take a bracket and center it under the mark closest to the top of the stairs. Mark the screw holes. Repeat for the stud closest to the stair bottom.

• 18

  Use a finish nail to determine the center of the studs at the top and bottom. Mark the center point of the stud.

• 19

  Take a bracket and center it under the stud mark closest to the top of the stairs. Mark the screw holes. Repeat for the stud closest to the stair bottom.

• 20

  Drill pilot holes at the screw holes. Screw the bracket to the wall. Repeat for the stud at the bottom.

• 21

  Place the handrail into position. Have a helper hold it steady as you drill pilot holes for the screws and screw the fasteners to the handrail. Repeat at the other end. Install any additional brackets.