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 is 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 wooder sealer is
• Super hydrophobic technology
• How to waterproof exterior wood

What Is A Wood Sealer?

Exterior wood products can be confusing because there are so many options like wood paint, wood stain, wood oil, wood sealer, and wood waterproofer. Wood itself is highly porous and vulnerable to moisture, rot and weathering, so applying a protective treatment is essential to keep wood in good condition.

The difference between wood treatments

Most exterior wood products fall into two categories:
1. Appearance-focused products
2. Protection-focused products

Appearance-focused treatments

These mainly change or enhance how the wood looks:

• Wood paint – opaque colour that covers the grain completely.

• Wood stain – adds colour while keeping the grain visible.

• Wood oil – enhances the natural look and grain, adding richness and a durable finish.

Waterproofing products for wood

Waterproofing treatments are designed to keep the natural look of bare wood while preventing rot and weathering. As wood absorbs large amounts of water, untreated wood can:

• Discolour

• Develop moss and lichens

• Begin to rot and decay over time

Waterproofers and wood sealers repel water to reduce moisture absorption and extend the lifespan of the wood.

Not all waterproofing products work the same

A key requirement for any waterproofing treatment is high breathability. While the coating must repel rainwater, it must also allow water vapour inside the wood to escape. If it can’t breathe, moisture becomes trapped under the coating and eventually causes failure.

Why some wood sealers fail

Many traditional sealers create a film on the wood surface. This film:

• Has low breathability

• Traps moisture inside

• Eventually peels, flakes or bursts

• Breaks down under weathering

Once the film fails, the wood becomes unprotected again.

Why breathability matters (SD value)

A high-performance wood waterproofer must be highly breathable, meaning it allows vapour to pass through freely. Breathability is measured using SD value:

• SD value under 1 = highly breathable

• Lower SD = better breathability and longer-lasting protection

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

Super hydrophobic technology refers to a highly advanced form of waterproofing treatment that utilises the latest nano-technology. A super hydrophobic surface is ultra water-repellent, often known as the ‘lotus effect’, named after the lotus leaf that this feature. This 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 applied to waterproofing products, super hydrophobic nano-technology lines the pours of building materials but does not seal these pores. This means that while water is too large to pass through the pores, water vapour (as a gas) can pass through these pores, meaning the breathability of the material is not impacted. The result is a completely water repellent, highly breathable surface that keeps exterior surfaces dry & free from weathering.

Learn more: Super hydrophobic 

At Emperor Paint, we created advanced super hydrophobic technology designed to protect exterior surfaces, including wood and masonry. Emperor Exterior Wood Waterproofer is a clear, invisible treatment that penetrates deep into the wood rather than forming a surface film. This keeps the natural look of the wood while stopping moisture from being absorbed.

Proven 25-Year Performance

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

• Guaranteed waterproof protection for a minimum of 25 years

• Backed by a 10 year manufacturer’s guarantee

• Outperforms traditional wood treatments that typically last 1–10 years

Ideal for Any Exterior Wood

Emperor Exterior Wood Waterproofer can be used on:

• Fencing

• Sheds

• Cladding

• Garden furniture

• Any untreated exterior timber

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

Why Waterproofing Matters

Untreated exterior wood absorbs large amounts of moisture, causing:

• Colour changes and dark patches

• Rot and long-term structural damage

• Increased weathering and faster deterioration

A super hydrophobic treatment prevents this by keeping water out while allowing the wood to breathe.

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

Clean the surface:
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.

Treat organic growth:
For any wood that isn’t brand new, apply a fungicidal cleaner to eliminate moss, algae or lichens that can stain the timber. Products like Emperor Exterior Cleaner dissolve organic growth and loosen deep-set dirt. Apply with a brush, roller or pump sprayer and leave it to dry for around two hours before moving on.

Once the wood is clean and free from growth, it’s ready for waterproofing treatment.

Check the Condition of the Wood

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. It’s a thin, easy-to-use solution—simply coat clean, bare wood at 5m² per litre.

Because 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.

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

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