Back to Blog

Waterproofing for Wood: A Guide

Timber Knowledge Tips & Guides
01 January 0001 min read

Wood is a versatile and beautiful material used for countless applications, from furniture to decking. However, as a natural material, it is susceptible to water damage and decay if left untreated and exposed to the elements. 


As a result, waterproofing wood is an essential step for wood projects, especially those outdoors. 

Why Waterproof Wood?

Waterproofing wood is essential for preserving its integrity, appearance, and lifespan, particularly for pieces exposed to the elements or in damp environments. Wood is a porous material, and when it absorbs water, it can swell, warp, and become prone to fungal growth, all of which compromise its structural stability. 


Waterproofing creates a barrier on the wood’s surface, preventing moisture penetration and protecting against damage. This not only maintains the wood's aesthetic appeal by preventing discoloration and the growth of mould and mildew, but also ensures its strength and durability over time. 


Investing in waterproofing will help extend the life of wooden structures, from outdoor decking to bathroom cabinetry, saving money on potential repairs or replacements down the line.


When to Waterproof Wood

Treating timber is recommended in the following situations:

  • Outdoor wood projects like decks, fences, pergolas, and sheds

  • Wood exposed to moisture, such as boat parts, docks, and bathrooms

  • Furniture and floors prone to spills, like tables and kitchen floors

  • Wood in direct ground contact, for example, posts and stakes 

  • Any untreated, bare wood at risk of water damage

It’s best to seal wood before assembly or installation for maximum protection. However, previously untreated wood can still be waterproofed through thorough surface preparation and application.


Types of Waterproofing Wood Treatments

Various commercial products for waterproofing wood are available, usually falling under three main categories:

1. Wood Sealers

Sealers for wood create a protective film on the surface while allowing the natural grain and texture to show. Common types of sealers include:

  • Oil wood sealants: These include oils like tung or linseed. They penetrate deep into the wood and provide water resistance and mild protection but require frequent reapplication. 

  • Varnishes and lacquers: These products form a hard, durable, water-resistant coating that provides excellent protection. However, they are prone to cracking over time and don’t allow the wood to breathe. 

  • Waxes: Waxes saturate the wood while allowing it to breathe and offer moderate water resistance, but need frequent renewing. 

  • Shellacs: These are made from resin secretions of the lac beetle dissolved in alcohol. Shellacs are easy to apply but not very water-resistant.

2. Paints and Stains

Waterproofing wood can also be achieved using:

  • Oil-based paints: While these paints provide a protective finish, waterproof painted wood is prone to chipping and cracking with time. 

  • Water-repellent stains: These stains offer protection along with colour and allow the grain to show. However, they are less effective than wood waterproofing paints or varnishes. 

  • Waterproofing wood stains: These are speciality stains containing wax, oil, or resin to repel water and offer good protection.

3. Epoxies and Polyurethanes

These synthetic resins create a plastic-like finish and offer excellent adhesion and water resistance. They can be used as clear coatings over wood, fillers to seal cracks and holes, and fibreglass-reinforced epoxies to waterproof window frames and boat hulls.


Step-by-Step Guide to Waterproofing Wood

Follow these key steps for foolproof wood waterproofing:

Step 1- Clean and Prepare the Wood

Remove existing finishes with chemical strippers or sanders, smoothing out rough areas, eliminating any cracks, holes or defects with fillers, and allowing them to dry completely. 


When waterproofing painted wood, clean the surface and sand the painted wood lightly. Then, apply a clear waterproofing sealant suitable for outdoor use to allow the original paint colour to show through.

Step 2 - Select a Waterproofing Product

Select an appropriate waterproofing product like oil, varnish, or paint, carefully considering the wood type, use, desired finish, exposure levels, and maintenance requirements. 

Step 3 - Apply a First Coat 

Apply a first coat per the product's instructions, allowing proper drying/curing time before adding more coats. Lightly sand between coats for maximum adhesion, wiping away sanding dust.

Step 4 - Apply More Coats

Build up 3-5 thin, even coats for best results, permitting proper drying time between coats. Apply along the wood grain, maintaining a wet edge when brushing to prevent lap marks. Extend the finish over all edges and ends, applying extra coats on end grains, which tend to absorb more product.

Step 5 - Allow the Coat to Dry

Allow the final coat to dry fully, as advised by the product guidelines. Check for any missed spots and apply more of the product as required. Clean brushes and equipment with the appropriate solvent when done.


Finally, inspect and reapply the finish periodically for continued protection.


Specialised Waterproofing Techniques

Beyond basic surface applications, more heavy-duty waterproofing options exist for demanding situations:

  • When treating wood for boat hulls or decks, epoxy coatings and fibreglass lamination help resist constant water exposure. 

  • Flexible sealants like elastomeric caulk and sealants prevent moisture entry on moving joints.

  • Pressure-treating lumber with water-repellent preservatives protects posts, stakes, and framing from ground moisture. 

  • Marine varnishes are needed for weatherproofing wood. They contain UV inhibitors and can withstand the sun, water, and temperature changes.


Maintaining Waterproofed Wood

Maintaining waterproofed wood involves regular cleaning and periodic reapplication of the waterproofing sealant. Start by cleaning the wood surface with a mild soap and warm water to remove dirt, grime, and mildew. Use a soft brush to gently scrub the surface, taking care not to damage the wood. Rinse thoroughly and allow the wood to dry completely.


Check periodically for any cracks or damage to the waterproofing sealant, and reapply the sealant as needed according to the manufacturer's directions. How often you need to reapply the waterproofing sealant depends on the product used and the exposure of the wood to weather elements. Generally, it's recommended to reapply the sealant every 1-3 years. 


Regular maintenance will help preserve the waterproofing properties of the wood and prolong its lifespan.


Get Waterproofing Today with Woodshop Direct

Waterproofing your wood is a crucial step in ensuring the longevity and durability of your wooden structures, particularly those exposed to the elements. It not only protects the wood from moisture damage but also enhances its natural beauty, making it a worthwhile investment for any woodwork project.


At Woodshop Direct, we understand the importance of quality wood and wood finishing products. We offer a wide range of hardwoods cut to size, along with a selection of high-quality wood finishing products, including oils, waxes, lacquers, and stains. Our products are designed to provide superior protection and finish, ensuring your wood projects stand the test of time. 


Our friendly team is also on hand to provide expert advice on waterproofing products and techniques.