• In this video, This Old House general contractor Tom Silva shows how to save a wood deck from a catastrophic collapse.

    1. Temporarily brace the deck against the house with a series of 2x4 stakes and 2x6 diagonal braces.
    2. If necessary, raise the deck to its original height by installing several temporary 2x6 support posts beneath the deck. Tap the posts into place with a sledgehammer.
    3. Drill a ½-inch-diameter screw-shank clearance hole through the ledger board, but not into the sill plate. Position the hole 3 inches down from the upper edge of the ledger and at a slight upward angle.
    4. Place a ½-inch x 10-inch galvanized lag screw with washer into the hole, then use an impact wrench to drive the screw into the sill plate. Repeat to install one lag screw in each joist bay.
    5. If there's a gap between the ledger board and house foundation, cut filler pieces from pressure-treated wood to fit snugly into the space.
    6. Use a hammer drill fitted with a ½-inch-diameter masonry bit to bore a hole through the ledger and into the foundation.
    7. Insert a ½-inch x 10-inch masonry wedge anchor into the hole and then use a hammer to tap the anchor into the hole.
    8. Tighten the hex nut on the wedge anchor with the impact wrench. Continue to install masonry anchors, spacing them 36 to 48 inches apart.
    9. If the existing joist hangers are undersized or badly corroded, reinforce each one with an engineered-lumber joist hanger.
    10. Slip the engineered-lumber joist hanger over the existing hanger and secure it with galvanized hanger nails.
    11. Remove the temporary support posts and braces.
    • Difficulty: Moderate
      Requires mid-level carpentry skills
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      Tools List

      • sledge hammer
      • circular saw
        Circular saw
      • drill
      • impact wrench
        Impact wrench
      • hammer drill
        Hammer drill with ½-inch-diameter masonry bit

      Shopping List

      2x4s and 2x6s½-inch x 10-inch galvanized lag screws with washers

      ½-inch x 10-inch masonry wedge anchors

      Pressure-treated 2x4

      Engineered-lumber joist hangers