How to Repair Your Wooden Stair Stringers

wood stairs
  • 2-4 hours
  • Intermediate
  • 100-200
What You'll Need
Bottle jack
2 x 4 Lumber
Wood shims
3 L Brackets
Wood screws
Construction adhesive
2 deck screws

Wooden stair stringers are the back bone of any stair case. They are the boards placed at the side to support the weight of the risers and the treads. Wooden stair stringers also support our weight as we go up and down the stairs. If the wooden stair stringer breaks for some reason, your stair case will not be safe to use. Many suggest that in home maintenance, the stringers should be inspected to detect any damages early. Wooden stair stringers can easily be repaired by following the step-by-step guide below.

Step 1 – Examining the Stringers

The first step is to examine the stringers so you can see what repairs you need to make. Check the connections on top and bottom to make sure they are tight. A hammer can be used to tighten any joints that may be loose. The loose joints may be reinforced with ¾ wood screws and a 3” L bracket. These brackets help to brace the stair together and help to prevent squeaking and wobbling.

Step 2 – Repairing Loose Steps

If any steps are loose, they can be repaired by placing wood screws and an L bracket between the risers and the tread. A shim can be driven between the stringer’s top and tread’s end. This will tighten them before the L bracket is installed.

Step 3 – Checking the Stringer Board for Damage

Stringer board can possibly have damaging cracks or splits in it. You can repair these by using mending splints and plates. A good indication that the stringer needs to be replaced will be any splits that remain open when there is no load on the stair. Professional advice should be sought before conducting this repair.

Step 4 – Starting the Stringer Repair

Use a 2 X 4 brace on the hydraulic bottle jack’s top to lift the stairs. This will help to remove the weight from the split or cracked stringer. Apply a mending plate (heavy duty) to the stair stringer’s bottom edge. The mending plate needs to be at least 4 inches long. 2” drywall screws can be used to attach to the mending plate. A mending plate which is hammered down can be installed to outside of the wooden stringer. This will span the area that is damaged. Hammer the mending plate flat down to the stringer.

Step 5 – Cutting the Lumber

Cut piece of the 2 X 4 lumber to 48” to be used as splint. Construction adhesive can be applied on the 2 X 4 face. Using C clamps, clamp the 2 X 4 to the stair stringer. Treated deck screws can be used to now attach splint to the area which is damaged. To reinforce the repair, install a cripple (2 X 4) under the step which is affected below the damaged area. The jack can now be let down slowly. Check mended stringer to make sure it stays in place once a load is placed on top of it.