How to Put Styrofoam Under a Boathouse

Look underneath any marine dock or boathouse that doesn't include floating cement walkways (yes, cement can float), and you likely will find blocks of styrofoam. Easily fabricated and cut to size, styrofoam blocks provide long-lasting, buoyant material that doesn't break down when exposed to water. As a result, the product gets used quite often for flotation. However, attaching these blocks to the bottom of the dock or boathouse frame can take a bit of work. If you don't mind getting wet, the job can be tackled with a few basic tools and patience.

Things You'll Need

  • Building permits
  • Multiple blocks of styrofoam billets
  • Cutting tools
  • Water-proof adhesive
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Instructions

    • 1

      Talk to your local jurisdictional building authority to make sure you're allowed to install styrofoam under your boathouse. Some areas may have environmental concerns with certain products.

    • 2

      Plan how many styrofoam billets you will need to augment existing water buoyancy or to support your boathouse. Cut the blocks to size to fit the areas you need to support.

    • 3

      Apply a strong, waterproof adhesive to the top of the block. Cover the block billet sufficiently so the glue seals the foam and the bottom of the dock or boathouse structure.

    • 4

      Place the block in the water. Position yourself in the water to pull the block under the dock. Push it up and against the bottom of the boathouse structure or dock. Press firmly until the adhesive has stuck firmly.

    • 5

      Continue the process until the boathouse or dock is supported as designed in your plan.