Wood Sealers - Everything You Need To Know

Wood Sealer


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 so you can protect your wood from the elements long-term.


What Is A Wood Sealer?


There are a wide variety of wood products on the market today, which can cause a bit of confusion amongst homeowners. Wood paint, wood stain, wood oil, wood sealer or wood waterproofer are all terms you will commonly see when shopping for exterior wood products. The reality is, wood is a highly porous material meaning it has a tendency to rot and is largely vulnerable to the elements if left untreated. This means that it is important to apply a treatment to the wood in order to provide it with the necessary properties to keep it protected. 


You may be wondering at this point, what is the difference between the various products for exterior wood? The main difference between the various products that are deisgned for wood are appearance, level of weather protection & durability. While some wood products are designed to change the appearance of wood, some treatments are to improve the performance of the wood. The main types of wood treatments that are primarily designed for appearance purposes are:


  • Wood paint - this is an opaque, coloured paint that completely covers the grain of the wood, offering a strong burst of colour to the wood
  • Wood stain - this is designed to maintain the grain of the wood while providing it with added colour
  • Wood oil - provides full character and enhances the natural beauty of the wood while providing adding a hard, durable finish to the surface of the wood


This is where we come to waterproofing products for wood. Waterproofing treatments are designed to maintain the look of bare, natural wood while preventing rotting and weathering. This is crucial as untreated wood is highly porous, meaning it will absorb large amounts of water. When the wood gets saturated over a period of time, the moisture causes the wood to discolour and will encourage the growth of lichens and moss. Over time, the moisture will also cause the wood to rot and decay as the water breaks down the timber. For this reason, protecting exterior wood from weathering is crucial in order to keep it looking attractive and protecting it from damage.


Waterproofing products such as wood sealers and wood waterproofers protect exterior wood by providing it with water repellent protection that repels water from the wood. This prevents any water ingress on the wood and ensures that lifespan of the wood is extended.


Having said this, not all waterproofing products are designed in the same way. With any waterproof surface, it is crucial that it is highly breathable. While water must be prevented from entering the surface, if the treatment is not breathable, any moisture inside the surface will become trapped. Eventually, the moisture will build-up inside the material until it causes the waterproofing treatment to fail. A wood 'sealer' like many sealing products generally has low breathability, as it creates a film on the surface of the wood. This film can completely prevent moisture from travelling through the surface, keeping moisture out but also trapping moisture in. Due to the film that is created, this moisture eventually causes the film to burst, leaving the wood unprotected once again. The film that is created by sealers also provides the added risk of the film peeling, flaking or bursting when exposed to weathering. 


Due to this, any waterproofing product you apply to exterior wood must be highly breathable. This means that it does not impact the ability for water vapour to pass through the surface, ensuring moisture does not get trapped in the timber. For a wood waterproofing product to be considered highly breathable, it must have an SD value of below 1. The lower the SD value, the more breathable the waterproofing treatment is and the better it can protect exterior wood long-term. Highly breathable wood waterproofing products generally do not form a film on the surface of wood. These wood waterproofers insteadb absorb deep into the wood, providing the wood with water repellent properties, rather than creating a water repellent film on the surface. This means that there is no film to peel, blister or become weathered, ensuring long-term durability in all weather conditions.


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.



Damp exterior wall


At Emperor Paint, we developed our super hydrophobic technology for a range of surfaces, including exterior masonry & exterior wood. Emperor Exterior Wood Waterproofer is a clear water repellent treatment for wood that does not alter the appearance of wood in any way once applied. It achieves this by penetrating into the timber instead of creating a film on the surface. This maintains the natural beauty of the wood while preventing any discolouration or damage caused by constant exposure to weathering. 


In independent testing conducted by UKAS accredited laboratory Lucideon, Emperor Exterior Wood Waterproofer when subjected to 25 year accelerated weathering was found to have no change in performance or appearance after the 25 year period. This means it will keep exterior wood waterproof for a minimum of 25 years without failing. This far exceeds the lifespan of many wood treatments which range from anywhere from 1 year to 10 years. For this reason we offer a 10 year manufacturers guarantee, ensuring its performance in any weather conditions for a minimum of 10 years.


Whether you are looking to protect your fencing, shed, cladding, garden furniture or any other bare exterior wood, applying Emperor Exterior Wood Waterproofer is the best way to keep timber looking clean, dry & pristine. The difference between wood that has been treated and wood that has been left untreated is immense. The image below is what happened when once fence panel was treated with Emperor Masonry Paint and the other fence panels were left untreated. The level of moisture that exterior wood can absorb can not only cause damage but will cause the wood to change colour during wet conditions. This discolouration can be prevented by applying a super hydrophobic treatment to the wood.


Exterior wood sealed


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.




    • 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)




Like any decorating project, the first step is the prepare the surface ready to be treated. Ensuring the surface is sound and clean is crucial if you want beautiful, long-term results. When it comes to exterior wood, it is rarely ready to treat straight away.


Before you do anything else you must clean the exterior wood. Any dirt, debris or organic growth will be visible once the treatment is applied as it is completely invisible. The cleaning required will depend on the extent of the dirt. On decking & other areas that can become quite dirty, you can use a power washer to give the timber a good thorough clean. In some cases, hot soapy water and a soft brush is enough to remove dirt from the surface of the wood. In other cases, you may wish to sand down wood that has been signficantly discoloured and where cleaning alone is not sufficent. This can be done using a 180-grit sandpaper, which will help remove the top layer from the wood.


Once any large dirt and debris is removed from the wood, you must apply a fungicidal cleaner to any wood that is not new timber. This is because organic fungal growth such as moss and lichens can discolour the wood. Once you apply the waterproofing treatment, organic growth is significantly reduced so you want to ensure that the wood is free from any organic growth to start with. A fungicidal cleaner such as Emperor Exterior Cleaner kills any fungal growth, ensuring that it does not continue to grow after the timber is treated. Simply apply the fungicidal cleaner to the wood by brush, roller or pump-sprayer and leave it to dry for two hours. After this period, not only will the discolouration be removed, but any deep ingrained dirt is dislodged and can be easily cleaned away. While many fungicidal cleaners refer to themselves as masonry cleaners, these can also be used on wood.


Once the wood is clean, it is time to check whether it is all sound. Any rotting and decaying wood will not only leave you with a less than perfect finish but will also compromise the waterproofing of the timber. Remove any areas of wood that are rotting and fill these using an exterior wood filler. Many fillers come in different shades to help you best match up the shade of the wood to the filler you are adding, to create a seamless bridge between the wood and the filler. 




Emperor Exterior Wood Waterproofer can be applied using a low-pressure pump, brush or roller. It is a thin, watery solution that is very easy to apply. Simply apply the treatment to the clean, bare wood at a coverage of 5m2 per litre. As an invisible treatment, it can be more difficult to see where you have applied to treatment as the quick drying formulation will only look slightly darker for a small period of time. Due to this, ensure you start at an easily identifiable area and work your way round the area systematically. This is a one-coat application treatment, so once you have applied the treatment you can simply leave this to dry for 1 hour at 20°C. At lower temperatures it can take slightly longer for the product to dry. Once dry, you will be left with completely water repellent exterior wood that is protected from weathering for at least 25 years. 


Sealing wood


Frequently Asked Questions




As Emperor Exterior Wood Waterproofer works below the surface of the timber in the same way a moisturiser would, it does not change the appearance of exterior wood in any way, which can be the case with a wood sealer. Many wood sealers form a film that creates a sheen on the surface of the wood, changing its appearance. The only way Emperor Exterior Wood Waterproofer changes the appearance of bare, natural wood is by preventing discolouration, green growth & decay, by keeping the wood dry and protected from the elements.




All waterproofing products have different lifespans depending on their durability. This durability is often linked with their breathability, otherwise known as the ability for water vapour to travel through the coating. The lower the breathability of a wood sealer or waterproofer, the more chance that it will fail as water will begin to build-up in the material, eventually causing the treatment to fail. A wood sealer that refers to itself as 'breathable' is likely to have a lifespan of 1-10 years, as it is not highly breathable, meaning eventually it will fail when moisture gets behind the film it creates. Emperor Exterior Wood Waterproofer is not only highly breathable but it also does not create a film, so there is no film to peel, flake or burst. Water will not become trapped in the surface or underneath a film, meaning it can perform long-term without failing. Independent tests showed that after 25 years of heavy weathering, the treatment still performed on exterior wood as effectively as when it was first applied. Due to this, it will exceed this 25 year period and protect exterior wood for decades.




Sometimes the best way to tackle of a problem is to address it before it happens. The best way to deal with weathered wood is to protect it before it is weathered, as this is going to save you time and money in the long run. If you are installing new exterior wood, whether it is fencing, cladding, decking or furniture, applying a waterproofing treatment as early as possible will ensure you extend its lifespan for as long as possible before it has a chance to weather. Having said this, once wood is already weathered, giving it a bit of TLC and applying a waterproofing treatment can be an effective way to help get a number of extra years out of it without having 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. Contact them today by emailing info@emperorpaint.co.uk or calling them on 0161 509 9009. Alternatively, shop our range of exterior waterproofing treatments today and get free delivery on all orders .