Wood Sealers – Everything You Need To Know

When it comes to treating and protecting wood, it can be difficult to know exactly what product to use with a seemingly endless number of wood paints, stains, oils, sealers and waterproofers on the market.

That’s why our team of experts have put together this handy guide that contains everything you need to know regarding exterior wood sealers and treatments.

In this guide we will cover:

• What a wood sealer is
• The problems sealing wood can cause
• What other solutions are available
• How to waterproof exterior wood

What Is A Wood Sealer?

Wood itself is highly porous and vulnerable to moisture, rot and weathering, so applying a protective treatment is often key to keep wood in good condition.

Protective products come in different forms, with traditional wood sealers being one of the most common options. Their purpose is to reduce how much rainwater the timber absorbs and help protect it from weathering and decay over time.

Not all waterproofing products work the same

Keeping water out is only half the job when protecting exterior wood. Timber also needs to release any moisture already inside it.

Many traditional wood sealers do exactly what the name suggests, they seal the surface of the wood. While this helps block water initially, it can also seal the natural pores of the timber and trap moisture underneath. Over time, this can lead to peeling, blistering, rot and the wood becoming more prone to damage than before the sealer was applied.

Highly breathable waterproofers do not form a surface film. Instead, they absorb deep into the wood, bonding within the fibres to provide long-term water repellence without peeling or blistering.

Super Hydrophobic Technology

To overcome the problems caused by traditional sealers, newer waterproofing treatments were developed using super hydrophobic nano-technology.

A super hydrophobic surface completely repels water as the water is more attracted to itself than the treated surface.

In short, the water forms ‘beads’ on the surface and eventually falls off before it can absorb into the material.

When used in breathable wood treatments, this nano-technology lines the pores of the timber rather than sealing them shut. This helps keep water out while still allowing moisture vapour to escape naturally.

The result is a completely water repellent, highly breathable surface that keeps exterior surfaces dry and free from weathering.

Learn more: What does super hydrophobic mean?

This technology is used in products like Emperor Wood Waterproofer, which absorbs into the wood itself rather than forming a surface film. This helps reduce water absorption while still allowing the timber to breathe naturally, without changing its appearance.

Independent testing by the UKAS-accredited Lucideon laboratory found that after 25 years of accelerated weathering, it showed no loss of performance or change in appearance. This makes it one of the longest-lasting waterproofing products available for exterior wood.

By preventing water absorption, the treatment reduces discolouration, stops moss and algae growth and protects wood from decay.

How To Waterproof Exterior Wood

Wondering how to waterproof exterior wood? The process of applying any coating or treatment to wood is one that contains a number of steps, as wood is rarely ready to be treated straight away.

Ensuring it is clean and suitably prepared is crucial for achieving beautiful results that stand the test of time.

YOU WILL NEED:

• • Emperor Wood Waterproofer
  • Paint brush, roller or pump-sprayer
  • Dust sheet
  • 180 grit sandpaper (may be required)
  • Masking tape
  • Exterior wood filler and filling knife (may be required)

1. Preparation

Proper preparation is essential for long-lasting results. Exterior wood is almost never ready to treat straight away, so start by giving it a thorough clean.

Remove dirt, debris and any organic growth. For heavily used areas like decking, a power washer works well.

For lighter dirt, hot soapy water and a soft brush are usually enough. If the wood is badly discoloured, lightly sand it with 180-grit sandpaper to refresh the surface.

For any wood that isn’t brand new, apply a fungicidal cleaner to eliminate moss, algae or lichens that can stain the timber.

Cleaners like Emperor Exterior Cleaner attack organic growth to ensure it can’t grow on the wood once treated. Apply with a brush, roller or pump sprayer and leave it to dry for around two hours before moving on.

Once the timber is clean, inspect it to make sure it’s sound. Any rotten or decaying areas will affect both the finish and the long-term waterproofing.

Cut out any damaged sections and repair them with an exterior wood filler. Most fillers come in different shades, allowing you to match the colour of the timber for a seamless, professional-looking repair.

2. Applying the wood treatment

Emperor Exterior Wood Waterproofer can be applied with a brush, roller or low-pressure sprayer.

As the treatment is invisible and dries quickly, start in a clear, easy-to-track area and work methodically so nothing is missed. Only one coat is needed.

Allow it to dry for around 1 hour at 20°C (longer in cooler conditions). Once dry, the wood becomes fully water-repellent and protected from weathering for up to 25 years.

Read more: How to apply wood waterproofer 

What finish does it leave?

Emperor Exterior Wood Waterproofer works below the surface, so it doesn’t alter the look or create a sheen like some wood sealers do. It simply keeps the wood dry, helping prevent discolouration, green growth and decay while maintaining its natural appearance.

What is the lifespan of wood sealers?

Lifespan varies by product and breathability. Lower breathability sealers often fail sooner as moisture gets trapped behind the film. Breathable options tend to last 1–10 years. Emperor Exterior Wood Waterproofer is highly breathable and film-free, so it won’t peel or flake. Independent tests showed it was still performing after 25 years, meaning it can protect wood for decades.

Should I seal wood when it is new or already weathered?

It’s always best to protect wood before it weathers, as this extends its lifespan and reduces long-term maintenance. If the wood is already weathered, treating it can still refresh it and help you get more years out of it without needing to replace it.

We hope we have answered any questions you may have had regarding wood sealers and how to waterproof your exterior wood.

If you have any other questions, feel free to get in touch with our team of experts who are on hand to help. You can chat to them by emailing [email protected] or calling them on 01254 936121.

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This article was written by the Emperor Technical Team, a group of experts with an average of over 25 years experience in the building industry. They work daily with homeowners, tradespeople and specification professionals to deliver practical, expert guidance that promotes long-term results, supports wall health and helps create homes that are prepared for the future.