In this video, Ask This Old House general contractor Tom Silva shows how to permanently patch a decaying porch post.

Project details

Skill

Cost

Estimated Time

Steps for repairing a porch post:

  • Unscrew and remove the handrail attached to the rotted porch post.
  • Temporarily support the porch roof on either side of the rotted post with a hydraulic jack and a long 2x4 post.
  • Use a reciprocating saw to cut the top of the post free from the overhead beam.
  • Remove the rotted post and lay it across two sawhorses.
  • Cut away the rotted section from the bottom end of the post using a circular saw.
  • Cut a new post section from a rough-sawn cedar 6x6.
  • Mark and cut a half-lap scarf joint into the new post section using a circular saw and reciprocating saw.
  • Set the new post section on top of the old post and trace the half-lap scarf joint onto the old post.
  • Cut a mating scarf joint into the old post.
  • Sand the joint smooth with a random-orbit sander, then fine-tune the joint with a hammer and chisel.
  • Apply several beads of construction adhesive to the scarf joint cut into the post.
  • Evenly spread the adhesive over the entire joint with a flexible-blade putty knife.
  • Fasten the new post to the old post with four 5-inch-long structural screws. Use an impact driver to drive the screwheads about ¼ inch below the surface.
  • Use a power plane to trim the new post section flush with the old post.
  • Fill all screw holes and cracks with exterior-grade wood putty.
  • Once the putty dries, sand the post smooth.
  • Coat all bare wood surfaces with exterior-grade spray primer.
  • Screw the base plate to the bottom of the post.
  • Stand the repaired post back in place on the porch, then release the hydraulic jacks and remove the temporary 2x4 posts.
  • Secure the top and bottom of the post with screws, then apply a paint top coat to the post.
  • Reattach the handrail to the post.

Tools

Tools & Materials

  • Cordless impact driver
  • Bottle jack
  • Reciprocating saw
  • Circular saw
  • Layout square
  • Random orbit sander
  • Hammer
  • Caulk gun
  • Putty knife
  • Power planer
  • Sash paint brush - 3-inch
  • Wood chisel