Waterproof Decks

Fluid Floors provides a superior waterproof deck coating in the greater Seattle area. Through decades of experience we have developed unique techniques to create a durable waterproof surface that is as beautiful as it is functional. On this page you will learn the benefits of a waterproof or urethane deck coating. The process involved to create one. The products we use and why we like them.

Benefits and Features

A Slip Resistant Surface

is pretty significant here in the northwest. EPDM Rubber granules
are broadcast into the base coat to create a non-skid surface.

Eliminates Moisture

Urethane adheres tenaciously to the plywood or concrete
decking, creating a good bond to seal it from water intrusion.

Easy Maintenance

No more stripping and staining every 2 years. A simple pressure
washing will clean and brighten your deck. Learn more about deck maintenance here.

Dry, Usable Space Underneath

A great solution for more storage, RV parking , or covered
patio space.

Directs Water Away

from your home and foundation. Sloping the deck away from the
home protects your building from water intrusion.

Protection Against

mold and mildew. Industrial strength coatings are troweled on for
thickness to keep the decking material dry. Mold and mildew can’t survive without

Surface Prep

A urethane coating adheres well to plywood, concrete, metal, and older coatings when the surface is properly prepared.

New Construction

  • We recommend 3/4” PC buff plywood (plugged, cross banded, fir faced) from Plywood
    Supply installed over joists. Or 1/2” plywood may be used over existing materials. Overall
    thickness needs to be a minimum of 3/4”.
  • Plywood should be tongue and groove.
  • Install with good side up.
  • Slope at 1/4” per foot away from the building.
  • Install fascia first with plywood running over top of fascia.
  • Fasten with non-corroding screws every 4” along butt joints, 12” OC over intermediate
  • Plywood must be kept dry. We can’t stress this enough. It has to be completely dry for
    proper adhesion of the coating.

Door Pans

We always use metal door pans that we have fabricated to ensure quality. It is important to
install a door pan even on decks that will be covered. A threshold without a door pan is
susceptible to water intrusion through weather and cleaning.


All metals used are 26 ga. for quality.

  • Flashing is installed where any horizontal surface meets a vertical surface.
  • If posts are present, they will be flashed.
  • Scuppers and drains, if used, will be installed at this stage.
  • All metals are galvanized or painted metal and stapled every 2”.


We grind all seams smooth and flashing for adhesion. Then all seams are taped and sealed
using our own special technique to create a flawlessly smooth and watertight seam.

Existing Decks

  • Decks are cleaned using a pressure washer. for more information on this step see our blog,
    How to maintain your urethane deck.
  • It is then allowed to dry completely
  • Decks are then primed with an epoxy water base primer for a strong bond. This step is not
    usually needed on new plywood surfaces.
  • Top coat is then applied.

Base Coat and Top Coat

Tufflex Standard Outdoor RBC base coat is troweled on to achieve the thickness (3.175 mils) needed for good waterproofing. This is a single component, liquid-applied, water-catalyzed, urethane-polyuria, elastomeric base membrane. For more information about this product please visit our urethane coating page.

Why We Like Tufflex

  • Excellent adhesion
  • Non-gassing, which means no bubbling
  • Fast curing


While the base coat is curing, rubber granules are broadcast into it which creates a non-skid surface. This is necessary since a finished surface without it will become slippery when wet. The base coat then cures for 24-72 hours, depending on weather and temperatures. It is safe to walk on after this time. The deck is now considered to be waterproof. Top coat can be applied anytime after this point.

Optimally, all siding and exterior painting should be complete before the top coat is applied. Top coat has a one week cure time before placing heavy objects on the surface.

Ready To Get Started?

Monroe, WA 98272
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