How to Seal Your Boat Deck in 6 Simple Steps

Sealing your boat deck is necessary to protect it against damage caused by saltwater, air, and the sun. However, if you’re a first-time boater, knowing how to seal a boat deck might not be something you’re familiar with. 

In this blog post, you’ll learn how to seal a boat deck in six simple tips. Stay tuned for everything you need to know about the sealing process, boat sealants, and our expert tips. 

How to Seal a Boat Deck

If you aren’t sure how to seal a boat deck, follow these six steps: 

1. Prepare the Deck

Preparing the marine plywood or substrate is the first step to sealing a boat deck. Remove any loose parts, and make sure the substrate is clean, dry, and free of any previously applied products. For optimal results, sandblast the steel, aluminum, or fiberglass. And if sandblasting isn’t an option, try rubbing it with coarse sandpaper. 

Read Next: Boat Cleaning Basics

2. Prime the Deck

Next, prime any joints, seams, cracks, holes, and rough areas with a coat of PermaFlex or marine sealant. 

3. Patch Any Cracks

After priming the deck, patch and profile any joints, seams, cracks, holes, and rough areas with a mixture of a liquid rubber base and a thickening activator. Wall and floor junctions will require about a one-inch bead of the mixture, and cracks require about ¾ of an inch of the mixture. The liquid rubber base can smooth or level any horizontal surfaces if necessary. 

4. Broadcast the Granules

Apply another coat of PermaFlex or marine sealant. Then, while it’s still wet, broadcast the rubber texture granules onto it. Once the product cures, the texture granules will have bonded in place, and any excess ones can be removed. 

5. Apply Liquid Rubber Base

The next step is to apply one coat of liquid rubber base on the granules. Generally, the amount of liquid rubber base you’ll need depends on the amount of texture on the floor. (The more liquid rubber base you apply, the less textured the finished floor will be.) Wait for the liquid rubber base to cure enough to walk on, then proceed to the next step. 

6. Apply Topcoat

Last but not least, apply a topcoat to the deck. We recommend using another coat of PermaFlex or the marine sealant of your choice. 

Sealing a Boat Deck

Types of Boat Deck Sealants

So, what type of boat deck sealant should you use? There are three types of chemicals used in marine sealants: silicones, polysulfides, and polyurethanes. 


Polyurethane is more of an adhesive than a sealant, which makes it ideal for permanent bonding. It’s useful for hull/deck joints and bonding through hull fittings. However, it isn’t compatible with most plastic materials. 

We recommend using polyurethane to join materials that never need to be separated. 


Because silicone is easy to apply and highly chemical resistant, it’s the best material for isolating dissimilar metals. Although the adhesion isn’t as strong as other boat sealants, it is compatible with plastics. However, note that silicone leaves a residue that’s hard to remove. 

We recommend using silicone to insulate non-similar metals and bed plastic. 


Because polysulfide is made of synthetic rubber, it’s the most versatile sealant. It comes in one and two-part application methods, and the latter is popular for caulking teak decks and bedding wooden parts (like rub rails and cockpit coamings). One-part polysulfides are easy to use and durable, yet they take a bit longer to cure. And while both types bond well to most surfaces, they shouldn’t be used on plastic deck fittings, frames, or acrylic or polycarbonate windshields. 

We recommend using polysulfide for almost everything you wouldn’t use polyurethane or silicone for.  

Tips for Sealing Boat Decks

Ready to give it a go? Here are our expert tips for sealing your boat deck: 

Preparation is key: For your boat deck sealant to work, the surface must be clean, dry, and free of old sealant and debris. Many surfaces must be cleaned with acetone and thoroughly dried before the sealant process can begin.  
More is better: Depending on the manufacturer’s instructions, using liberal amounts of sealant is often required. This is especially important when joining hardware to decks. 
Work in a well-ventilated area: Ensure that all sealants, tools, and cleaning materials are readily available throughout the process.  
Stock up on mineral spirits, acetone, and kerosene: These are the best way to remove excess, spilled, or misapplied sealants. 
Seal regularly: You should reapply sealant at least every three years (but sooner is preferred).  

The Bottom Line

As industry experts, the Discover Boating team is here for all your boating needs. Check our boating blog for maintenance guides, boating lifestyle tips, and more!