Over time, even sturdy balusters in a staircase handrail can sustain damage that will render them unsteady and unsafe to use. You will need to decide whether to replace just the damaged balusters or the entire set. Follow these instructions to replace stair rail balusters.
Step 1 - Measure the Height of Existing Balusters
Use the tape measure to check the height of the existing balusters. Get a replacement that is 1 or 2-inches longer. You can trim it to the exact height required.
Step 2 - Examine All the Balusters for Weakness or Damage
Check the rest of the balusters near the broken one for weakness and damage if they have had to assume an extra load for some time. If several are damaged or weakened, prepare to replace all the balusters.\
Step 3 - Obtain New Balusters
If your baluster is a standard style, purchase as many new balusters as you need for replacements. If it is a unique type, remove an intact baluster carefully and take it to a carpenter who is experienced at wood turning and shaping to get new balusters made.
Step 4 - Replace 1 Baluster
Remove the baluster, either by striking it with a rubber mallet to split it, or by twisting it gently to release it from the glue at the base and top. Use a claw hammer or needle nose pliers to extract the thin nails holding the baluster to the base and top rail.
Step 5 - Prepare the Stair Rail Base for the New Baluster
Clean and sand the bottom baluster hole, removing any debris or splintered wood that may prevent the baluster from setting properly into the hole. Sand the edge of the hole with coarse sandpaper (80-grit) and then fine sandpaper (220 to 400-grit) to remove adhesives and finishes such as paint or wood stain.
Step 6 - Measure the Bannister for Correct Fit
Use the bevel gauge to determine the proper angle of the stair handrail. Measure the height of the area that will hold the baluster. Check with a plumb line whether the balusters closest to the replacement are vertical and plumb with the handrail. If not, adjust the replacement so it is at the same angle as its neighbors.
Step 7 - Prepare and Install the Baluster
Cut and shape the baluster to the correct length and diameter to fit the stair rail. Paint or stain the baluster then let it dry overnight. Put wood glue on both the base and the top of the baluster. Insert the baluster tenon into the base first, then align the top with the handrail. Nail it into place with the finishing nails. Fill the nail holes with wood putty as needed.
Step 8 - Replace All Balusters
If you need to replace all the balusters, carefully remove the top handrail of the staircase and extract all the balusters. Refinish the bannister holes and insert new balusters. Reattach the top handrail.