Wood is one of the most common building materials — especially outdoors, used in countless applications from furniture to decks and more.

However, wood’s natural porosity makes it susceptible to water damage, which can lead to rotting, warping, and other structural issues over time. Waterproofing wood is essential to extend its lifespan and protect your surfaces.

In this blog post, we’ll explore everything to do with waterproofing wood. We’ll also talk about MDF or Medium-Density Fibreboard, which is a wood-based product commonly used in furniture and joinery.

Signs Your Wood Needs Waterproofing

Wood’s porous nature allows moisture to penetrate, resulting in potential problems like rot, mould, warping, and cracking. Even well-treated wood can become vulnerable over time. Look for these signs to determine if your wood needs waterproofing:

• Water stains or discolouration
• Mould or mildew growth
• Swelling, warping, or cracking
• Faded or peeling finishes
• Raised grain or rough texture
• Persistent damp smell in wooden furniture or structures

Proper waterproofing ensures that wood remains both durable and visually appealing, even in challenging conditions. By protecting against water damage, you can enhance the lifespan of wooden structures.

MDF vs. Wood: Can You Waterproof MDF?

MDF (Medium-Density Fiberboard) is a man-made product created from wood fibers, wax, and resin — compressed into a dense, uniform sheet used mostly for furniture and joinery. Liquid waterproofing can be used on MDF! It’s commonly applied on MDF joinery before being resurfaced with another material (such as tiles or microcement).

Types of Waterproofing Products for Wood

Wood is usually waterproofed with a liquid formula; but there are several types of formulas on the market, with different benefits depending on the intended use and exposure. Here are the most common methods:

Varnishes and Polyurethane Coatings

These coatings create a glossy or matte protective layer on the surface. Polyurethane works better on wooden surfaces that are indoors, while varnish is best suited for softer woods.

Use for indoor furniture, countertops, and cabinetry. They’re not recommended for outdoor areas.

Epoxy Resin

Epoxy forms a hard, waterproof barrier when applied to wood. It’s commonly used for wooden boats and marine applications, countertops, and outdoor furniture. It’s not recommended for areas exposed to the sun, as it’s not UV- or heat- resistant.

Oil-Based Finishes

Natural oils like linseed or tung oil penetrate deep into the wood to enhance its water resistance — but they aren’t fully waterproof. They’re ideal for retaining the wood’s natural look and feel, so often used to touch-up interior wooden furniture and decorative items.

Wax and Waterproofing Sprays

Wax or specialised sprays can provide temporary water resistance and are easy to apply. These are typically used for quick fixes or minor waterproofing needs, but not for a long-term waterproofing project.

Liquid Membrane Waterproofing

Liquid waterproofing systems are applied at first like paint, but then dry to create a seamless and durable yet flexible barrier on wood surfaces. SEMCO Liquid Membrane™ is made from a hybrid elastomer blend with UV-resistance, exceptional elongation*, anti-fracture protection, and waterproofing capabilities all in one — making it an easy choice compared to other products. It’s a particularly capable solution if you’re waterproofing decks or balconies made from wood. Note that it's a semi-clear finish.

*Elongation means it can stretch as the wood moves underneath, which happens naturally according to temperature.

How to Waterproof Wood

Here are the general steps for waterproofing wood using a our liquid membrane:

Step 1: Preparation

• Sand the wood to a smooth finish, removing any old coatings or rough spots.
• Sweep off all debris or dirt. As wood often absorbs water, avoid pressure washing wood prior to the application.

Step 2: Masking

• Use painter’s tape to mask off areas that you don’t want to coat.

Step 3: Application

• Apply the first coat of liquid sealer using a 12mm nap roller.
• Once you can walk on the surface and not get any residue on your shoe, or cannot leave a fingerprint impression, it is ready to re-coat.
• Apply another thin coat of SEMCO Liquid Membrane™ in an alternate direction over the first coat of SEMCO Liquid Membrane™.

Step 4: Drying

• Let topcoat dry to the touch, approximately 1–2 hours at 21 °C and 50% RH.
• When last coat has dried to the touch, inspect final surface for pinholes, voids, thin spots or other defects.

Notes

• Avoid application in direct sun light in the afternoon or temperatures of over 30°C as it might cause the product to dry too fast before it can adhere to the substrate.
• To make your new Liquid Membrane surface trafficable, it must be sealed with our SEMCO Titan Shield Gloss sealer.
• It can not be applied to wet substrates or substrates still containing moisture.

Waterproofing wood is a vital step in protecting your investment and preserving the natural beauty of wooden items and structures. Whether it’s an outdoor deck, balcony, or furniture pieces; a good waterproofing product will ensure longevity and resilience against all the elements. A DIY-friendly solution for waterproofing anti-fracture protection in one, SEMCO Liquid Membrane™ is a go-to for waterproofing wood.