A DIY Guide to Waterproofing a Roof Deck

Roof Deck

Roof deck waterproofing is an excellent way to protect your deck material from wearing out, especially if it is wood. When exposed to moisture, wood can absorb a lot of water, swell, and warp over time. It will then degrade and encourage mold or mildew growth.

The most common way to waterproof a roof deck is by applying a sealer to sustain its finish. Thankfully, there are more waterproofing options for decks, including waterproof membranes and rubberized coatings. Some of them are simpler than others but useful.

This guide explores all the tips on how to waterproof a roof deck. You’ll learn about the different waterproofing options for roof decks. Keep reading to learn more.

Waterproofing a Roof Deck: Step-by-Step Guide

If your roof deck is worn out and no longer waterproof, you need to visit this website to get immediate and personalized help. But if you have all the essential waterproofing tools and products, consider applying the waterproof by yourself.

Here is the step-by-step guide on how to waterproof a roof deck.

Step 1: Inspect the Roof Deck

The first thing to do is check for the signs that your roof deck needs waterproofing. If the deck looks faded, worn out, twisted, or rotted, you’ll need to waterproof it. 

You can also do a series of tests to determine the condition of the deck. Place a few drops of water on the deck. If they bead up, know that the deck has protection. But if the water gets absorbed by the wood, know that the old waterproofing layer is worn out.

Alternatively, you can apply tape to the deck surface and press it firmly. Remove it to see if the wood fibers or old stain are trapped. The presence of wood fibers or stains on the tape could signify a moisture problem, calling for waterproofing.

Step 2: Prepare Your Deck for Waterproofing

Regardless of the waterproofing option, you’ll choose, it’s essential to prepare the deck properly for waterproofing. Start by removing every item on the deck, including potted plants and furniture. Cover all the delicate ground plants that are adjacent to the deck.

Clean the entire deck surface by removing all the dirt and grime. Sweep away all the loose debris using a broom and remove the dirt between the cracks using a thin stick.

Check if the deck boards are loose, creaky, or warped, then repair or replace them. Also, hammer in all the popped-up nails to create an even surface. Fill in all the holes and cracks using the recommended filler that suits the deck.

Sand the deck surface, especially if you had treated it with a sealer some time back. Removing the remnants of the previous sealant layer will help to create a clean and smooth surface. It will also boost the effectiveness of the new waterproofing material.

Finally, wash away all the dust, grime, mold, and mildew using a power washer, a deck cleaner, or even both. A deck cleaner will restore the wood’s appearance and remove stains like rust from nails. But since it’s potentially hazardous, use it with caution.

When using the pressure washer, spray water between deck boards to remove the remaining debris. Allow the deck to dry completely before waterproofing it.

Step 3: Waterproof the Deck Surface

Once you’ve prepared and cleaned the deck surface, you need to restore its moisture resistance by waterproofing it. You can use any of these waterproofing methods.

  • Waterproofing sealant
  • Waterproof membranes
  • Rubberized Coatings

Waterproofing Sealant

After the deck surface has dried entirely, apply a thin, even coat of waterproof sealant using a stain brush or a roller with a long handle. The sealant material should be mold- and mildew-resistant and also have UV protection.

Apply the coat onto one or two boards at a time, along the lengths and not the widths. That will help to prevent the lap marks that may make the boards unattractive after applying the sealer. Use a paintbrush to seal the corners, cracks, and board ends.

For safety purposes, remember to put on protective clothing, rubber gloves, and safety goggles to prevent skin irritation. Also, don’t apply sealant in direct sunlight because it will dry very fast before absorbing into the wood, reducing its effectiveness.

Waterproof Membranes

Another excellent waterproofing material is a waterproof vinyl membrane for decks. One benefit of the vinyl membranes is that they help to keep the areas below decks dry. It will allow water to run off only on the edges of the deck rather than the entire surface.

Alternatively, you can install EPDM sheets on the deck to perform the same role. Both materials are helpful in waterproofing elevated decks and rooftop decks, especially if you’ll use the underside for storage. You can cover the membranes with decking tiles.

When installing the decking tiles, the roofing contractor has to elevate them slightly to allow water runoff. Most decking tiles have designs that allow them to snap together like a floating floor without adhesives or nails. That makes the installation process easy. 

Rubberized Coatings

If your deck is made of plywood, consider waterproofing it with rubberized paint. The paint can repel water and also offer some level of safety because it isn’t slippery. Thankfully, you can quickly apply it on the deck like any other paint.

To apply a rubberized coating, stir the paint thoroughly and pours some of it onto your deck. Spread it uniformly with an ordinary paint roller. You may also need to add a primer or apply several coats of rubberized paint for better results.

Step 4: Finish up the Process

Once you’ve applied the waterproofing of your choice, consider staying away from the deck for at least 48 hours (for sealant and rubberized paint) to allow it to dry completely. Return all the furniture, drop cloths, and other items you had removed from the deck.


When you apply roof deck waterproofing onto your deck, you’ll prevent moisture from damaging it. As a result, your roof deck will last longer than expected. The good news is that you now understand the process of waterproofing a roof deck by yourself.


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