How to Waterproof Wood for a Boat

If you own a boat or are in the process of restoring a wooden boat, the final and most important stage is ensuring the boat is waterproof and protected from the elements. Most wooden boats need extra levels of care to ensure that they are not damaged by water, humidity, and are protected from harmful UV rays from the sun.

Typically, wooden boats are made with plywood, usually of high-quality marine-grade plywood, or durable hardwood that is resilient to absorbing moisture. However, even the most durable varieties of wood require proper care and waterproof sealant to keep the wood in the best condition possible. This will make your boat last longer and leak-free!

What Waterproof Sealant Should You Use For Wood On A Boat?

There are many types of wood sealants available, and as any experienced boat owner will confirm, you’ll need to choose a sealant that is suited to the marine environment. You’ll also need to consider the construction type of your boat and if your wooden boat has any exposed end grain, which will require special treatment to ensure it’s properly waterproofed.

How to Waterproof Wood for a Boat

Look for a specialized sealant product made for the marine environment and it should protect from the following conditions:

  • Waterproof - Waterproofing for the marine environment, including salt or freshwater. This will prevent rot in the wood and keep your boat from absorbing water throughout the lifecycle of the boat.
  • UV ray protection - Much like sunscreen for your skin, you’ll want a sealant that provides high levels of protection from UV rays. This will also prevent your wooden boat from discoloration and maintain the brilliance in the color of the wood and the gloss of the sealant.
  • Humidity - Your boat will likely spend a considerable amount of time around water, and the water in the air is also a consideration when the boat is dry-docked. Maintaining the sealant on your boat protects year-round and ensures there is no rot, mold, or decay.
  • End Grain Sealant - Depending on the construction of your wooden boat, you may also need to spend time preparing and sealing any exposed sections of end grain. This is particularly important if your wooden boat is made from plywood as it prevents delamination.
How to Waterproof Wood for a Boat

How To Prepare The Wood On Your Boat For Waterproofing

Preparing your boat for waterproofing will depend on the condition of the boat and if it’s made with new wood (green lumbar) or wood being restored. If your boat is new, you’ll be able to sand and prepare the wood for a sealant with minimum effort, and you should use a sealant on the new wood to waterproof and varnish it completely.

If you are restoring your boat, you’ll need to spend more time preparing the wooden surface for sealing, which may involve removing old paint or sealant from all wooden surfaces. 

These are the three principal steps to preparing your wooden boat for waterproofing:

step 1

Preparation Of The Wooden Surfaces

Remove all old sealants or paint and expose the wood using various grades of sandpaper. To save some time, use a 125mm orbital sander and Danielll sanding pads to get the job done. Start first with coarse grade sandpaper (60-120 grit should do it) and then use finer grade sandpaper of around 200 grit to smooth the entire surface of the wood, including the joints and edges.

Danielll Sanding Discs

Danielll Sanding Discs


  • Pre-punched with 8 holes for uniform dust extraction
  • Special stearate coating is designed to prevent clogging and loading
  • Hook and loop sandpaper backing make easy for installation and removal, simplify your work

If you have any small cracks or open joints, use a marine-grade flexible clear caulk such as Boat Life Lifeseal Sealant Tube, in a clear color to seal the cracks. The caulk should be flexible and non-shrinking and specifically designed for use above and below the waterline. Once applied, allow for adequate time to dry before moving onto the next step.

Boat Life Lifeseal Sealant Tube

Boat Life Lifeseal Sealant Tube


  • Designed specifically for fiberglass boats
  • A fast-curing (24 hours) polyurethane/silicone adhesive sealant
  • Permanently flexible, non shrinking. Outstanding adhesion to fiberglass, glass, plastic and wood
step 2

Prepare End Grain

Prepare any exposed end grain and give it a good sanding using the finer grit paper. Be careful not to aggravate the end grain using coarse grit paper as it will be harder to seal. Apply an end grain sealant to the areas required and allow for it to thoroughly dry. Most products take around 10 hours to cure and dry completely.

step 3

Apply The Waterproof Sealant

The final step is to apply a good quality marine-grade sealant. Whether you’re applying a sealant for the first time on the wood, or if you’re applying it to a restored wooden boat, we recommend using TotalBoat Glean Marine Spar Varnish, which is available in a gloss or a satin polyurethane finish that’s specially designed for wooden boats. 

TotalBoat Gleam Marine Spar Varnish

TotalBoat Gleam Marine Spar Varnish


  • Apply up to 3 coats in 1 day—without tedious sanding between coats
  • Gleam 2.0 Gloss has exceptional depth and clarity
  • Gleam 2.0 Satin highlights the wood grain and prevents sun damage

TotalBoat Glean is a classic marine-grade varnish and contains premium tung oil and phenolic resins for a transparent amber finish on all types of interior and exterior wood. It is self-leveling and has a fast drying time, allowing for recoats in 1 hour when applied in temperatures of around 72°F.

How To Apply A Waterproof Sealant To Your Boat

If you have a smaller boat, you can do this using a soft bristle brush and a soft cloth. If you’re sealing a larger wooden boat, you may want to consider using a roller or a spray gun to apply the sealant.

Applying Sealant To Smaller Boats

Use a soft-bristle polyester brush to apply the sealant such as the Wooster range of brushes.

Wooster Brush

Wooster Brush


  • Excellent for all interior or exterior stains, sealers and wood toners
  • White China bristle/sable polyester blend, square trim
  • Nickel-plated steel ferrule

We would recommend using two brushes to apply the sealant, one larger brush around 4 inches to apply an even coat to larger areas, and a smaller brush (1 inch) for any hard-to-reach crevices on the boat.

To prevent brush strokes when the sealant dries, you will also want to apply a small quantity of thinner to the TotalBoat varnish and give it a good mix. To keep it consistent between products, use the TotalBoat Special Brushing Thinner 100 for brushing and rolling. 

TotalBoat Special Brushing Thinner 100

TotalBoat Special Brushing Thinner 100


  • Improves solvent-based paint and primer flow when applying by brush or roller
  • Slower drying properties extends working time in warm weather
  • Brushing thinner can be also used for cleaning painting tools and equipment

As TotalBoat Gleam Marine Spar Varnish is self-leveling, you’ll be able to apply even coats every time using a gradual brushing motion over the wooded areas. Allow the appropriate time for the sealant to dry between coats, and apply a maximum of 3 coats of sealant per day. Most sealants will recommend between 4 and 6 coats of sealant to completely waterproof and seal your wooden boat.

After use, be sure to clean the brushes thoroughly and allow them to dry.

Applying Sealant To Larger Boats

If you are sealing wood on a larger boat, you may want to consider using a roller and tray or a spray gun to apply the sealant to your boat. If you’re using a roller, you’ll want to use a high-density foam roller or a short pile roller.

Kupoo Foam Paint Roller

Kupoo Foam Paint Roller


  • High-density foam mini paint roller apply a lint-free,ensures no fibre loss and achieves and ultra-smooth finish
  • Steel Piant roller frame with chrome plating provides durability with reduced chance for rust,can use with most 6 inch Mini roller covers
  • The Paint Roller Tray contains a large amount of paint,Designed to Fit Most 4" & 6” Paint Rollers

Take your time when using any roller and make sure you apply even pressure on the roller each stroke. If you encounter small bubbles, slow down and apply the sealant gradually to prevent bubbles from forming on the sealed wooden surface.

If you’re using a spray gun, ensure you apply the waterproofing sealant with even strokes, and be sure to use the spray gun in a ventilated area with the appropriate protective equipment. Once finished, be sure to clean the spray gun immediately after use to prevent clogging of the nozzle.

Keep Your Boat Waterproof

Whichever products you choose to use, always make sure you read the instructions and follow them carefully. If you waterproof the wood on your boat correctly, it will last longer and look better. If you provide your boat with extra care now, you will thank yourself in the future.