How to Fix a Soft Floor in a Boat

Fiberglass is a composite material made of an epoxy resin sandwiched between layers of cloth or mat made of woven glass fibers. When age or the wear and tear of boating breaks the fibers or the resin, a soft spot can develop in your boat's floor, or deck. The only treatment for a soft spot in the deck is to cut it out and replace it, using a process similar to building a sandwich.

Things You'll Need

  • Plastic mallet
  • China marker
  • Reciprocating saw
  • Grinder
  • 80-grit sandpaper
  • Epoxy
  • Cardboard
  • Duct tape
  • 1 1/2-ounce fiberglass mat
  • 6-ounce fiberglass cloth
  • 320-grit sandpaper
  • Sanding block
  • Automotive paste wax
  • Electric buffer
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Instructions

    • 1

      Tap on the deck around the soft spot with a plastic mallet, to find out how large the soft spot is. A sharp, resounding thunk indicates a good deck, but a dull thud means under-deck damage. Draw a square around the soft spot with a China marker.

    • 2

      Cut the soft spot out of the deck with a reciprocating saw. Bevel the sides of the hole, using a grinder and 80-grit sandpaper, to a 45-degree angle. Mix the epoxy's resin and hardener according to the instructions provided with the epoxy.

    • 3

      Go below deck and tape a piece of cardboard over the hole, using duct tape, to secure the cardboard. Return to the deck and apply a layer of epoxy to the cardboard. Cut a piece of 1 1/2-ounce fiberglass mat that's slightly larger than the bottom of the hole. Press the fiberglass mat into the epoxy.

    • 4

      Cut a larger piece of 6-ounce fiberglass cloth. Apply apply more epoxy to the fiberglass mat and press the cloth into the epoxy. Repeat twice more. Wait until the epoxy cures, then repeat the application of fiberglass and epoxy until both are at the deck level.

    • 5

      Apply a final layer of epoxy and allow it to cure. Sand it down to the level of the deck with 320-grit sandpaper, wrapped around a sanding block. Apply automotive paste wax to the repair. Allow the wax to dry and buff with an electric buffer.