How to waterproof a plywood porch floor

Written by sal marco
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How to waterproof a plywood porch floor
A porch offer a relaxing environment. (Jupiterimages/Comstock/Getty Images)

Front, back or wraparound porches adorn many homes. Some homeowners enjoy sitting outside on their porches and enjoying their neighbourhood while others use the porch as a means to exit or enter the house. Protecting the porch decking is an important maintenance step. Plywood porch decking encounters water from rain, snow or sleet. Water damages wood causing it to swell, warp and twist. The porous nature of wood allows water to enter and the interior layers and cause rot. Rotted plywood porch decking is a hazard. Protecting the decking from water damage extends the life of the floor.

Skill level:
Moderately Easy

Things you need

  • Hammer
  • Paint scraper or floor scraper
  • Shop vacuum
  • Belt sander or rotary sander
  • 100-grit sandpaper
  • Wood deck cleaner
  • Stiff broom
  • Hose
  • Paint tray
  • Waterproofing stain or clear waterproofing
  • Long-handle paint roller or paint sprayer

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  1. 1

    Inspect the plywood floor for popping nails and hammer the nails back in the plywood.

  2. 2

    Remove the existing finish with a paint scraper or floor scraper. Take off as much of the finish by hand as possible. Vacuum up the debris with a shop vacuum.

  3. 3

    Load a belt sander or rotary sander with 100-grit sandpaper and lightly sand the surface of the plywood. Use a shop vacuum to clean up the dust from sanding.

  4. 4

    Clean the plywood surface with an exterior wood deck cleaner and scrub with a stiff broom. Clean off mould, mildew, grease and dirt. Rinse the deck cleaner off the plywood with a hose. Let the plywood dry completely, usually a minimum of 48 hours.

  5. 5

    Pour waterproofing stain or clear coat into a paint tray or paint sprayer. Choose a waterproofing stain or clear coat depending on your preference. Waterproofing stain will change the colour of the porch floor. Clear coat waterproofing will allow you to see the plywood flooring.

  6. 6

    Dip a long-handle paint roller into the waterproofing material and begin rolling it onto the plywood surface. If you are using a paint sprayer, set the pressure on a low setting, begin sweeping the sprayer nozzle back and forth across the porch floor. Whichever application method you choose begin in the furthest corner and work toward the stairs or porch exit. Continue either method until you cover the entire floor with waterproofing material. Weathered wood is highly porous; apply the weatherproofing stain or clear coat generously.

Tips and warnings

  • Reapply weatherproofing material every year.
  • Wear a dust mask, eye protection and gloves when sanding and waterproofing a porch.

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