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In this video, This Old House general contractor Tom Silva shores up an old deck with new supports.

Steps for replacing a deck post

  1. Install temporary 2x4 posts beneath the outer deck beam.
  2. Cut free any diagonal bracing with a reciprocating saw.
  3. Pry out the nails securing the existing vertical posts to the deck frame. Pull out the old deck posts and discard.
  4. Set a metal post base on top of the concrete pier, then drill a ½-inch-diameter x 3-inch-deep hole down into the pier with a hammer-drill and carbide-tipped masonry bit.
  5. If there's a metal pin or rod protruding from the top of the concrete pier, cut it flush with a reciprocating saw.
  6. Secure the metal post base to the concrete pier with an expansion anchor. Tighten the anchor with an impact wrench.
  7. Cut a new post to fit between the post base and underside of the deck frame. Fasten the post with galvanized hanger nails. Install one post under each corner of the deck.
  8. Use metal hangers to attach existing lattice panels or rails to the new posts.
  9. Stretch a tight chalk line between the two corner posts. Position the line 16 inches down from the top of the deck beam.
  10. Measure down to the chalk line at a midpoint between the two corner posts. If the midpoint dimension is 16 inches, then you know the beam is straight.
  11. Cut and install a post between the two corner posts. If the beam sags down, cut a post long enough to raise and straighten out the beam.
  12. With the new posts securely fastened in place, remove the temporary 2x4 posts.
  13. Install 2x4 diagonal bracing between the posts and deck beam. Secure each brace with 3-inch decking screws.

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