Thompson’s WaterSeal Wood Protector Review for Any Wood

Ian Mutuli
Updated on
Ian Mutuli

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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You are not alone if you have a deck that needs urgent treatment. The cold, wet seasons like winter take a toll on your deck as it is outdoors, so it will be no stranger to mildew and other forms of deterioration. If you are looking for the best treatment, here is a detailed Thompson's Waterseal Wood Protector Review to narrow your list down.

What is a Wood Sealer?

A water sealer is a formula or protective coating that protects your outdoor surfaces from harsh elements like algae, mildew, water, stains, and UV damage. Left unprotected, your structures like fences, decks, and more would rot with time, becoming very unsafe to use.

Thus, you will need a good sealer to maintain the integrity and beauty of your surfaces. Ideally, it needs to maintain the natural color of your wood, prevent UV damage, repel water and stains, and prevent fungi like mold and algae from growing.

Thompson’s Waterseal Wood Protector

THOMPSONS WATERSEAL 21802 VOC Wood Protector,...
  • Item Weight: 9.65 lb
  • Country of Origin: China
  • Brand name: Thompson's Water Seal
  • Item Dimensions: 4.1"L x 6.6"W x 11.0"H

The Thompson's WaterSeal is known for superior waterproofing abilities, maintaining the color of your deck, and giving your deck or fence a fresh, clean look. However, it can be disappointing if you need sun protection, and truthfully, the application process can also take a toll on you.

Read on to learn the main features you expect to get from this Thompson's Waterseal, such as ease of application, performance as a waterproofer, UV graying protection, stain and mildew prevention, and durability.

1. Ease of application

This sealer is easy to apply, but this depends on the quality and state of your wooden surface. However, these are some general directions to follow before applying.

  • Only use on wooden surfaces
  • Apply during warmer seasons; 50°F during application followed by 48 hours with the same temperature and no rain
  • Apply on porous wood; you can perform a splash test to see if water beads form on the surface. If they do, your surface does not require treating
  • Do not apply on stained surfaces
  • Do not use as a paint additive; you will need to sand previous paint before applying
  • Store in a cool, dry place; avoid freezing
  • Apply a thin layer

With these manufacturer recommendations out of the way, you will need to get down to applying your water seal. If your deck needs preparation before treating, you will need to scrape, brush, pressure-wash, and dry all impurities such as leaves, mildew, algae, paint, stains, oil, dirt, and more. In short, your surface needs to be smooth and clean before you can apply.

The application process is easy as you will only need to shake the bottle well before applying a light layer all over the surface. You will also need to shake or mix the contents occasionally as you apply. Additionally, you can use a brush, roller, paint pad, or sprayer for application.

After you apply, give the surface at least 48 hours to dry, but this also depends on the temperature and lack of rain. When it dries, you can apply your paint after 30 days.

2. Appearance after application

This Thompson's Waterseal does not alter the appearance of your surface, so your deck will look clean and new after the initial application.

3. Waterproofing

One of the best qualities of the Thompson's Waterseal is the ability to repel water. After application, a splash test leaves water beads on the surface that do not get absorbed. Hence, your deck will be safe from water damage for the rainy season and winter.

4. Durability

According to the manufacturer, how long the Thompson's Waterseal lasts depends on the environment.

You can perform a splash test every year to see how well the waterproofing is holding up. Generally, the treatment lasts up to two or three years, after which environmental elements such as snow, rain, and sun damage will have started to affect performance.

Additionally, the state of your deck before applying this coating affects how well the Thompson's Waterseal will perform. For example, a deck that had mildew or algae is likely to darken the coat.

5. UV Protection

While the company states that this Thompsons Waterseal offers UV protection, the performance is quite dismal, and you might notice some UV graying a few months after application. This poor performance is arguably the biggest reason you could find not to use the Thompson's Waterseal.

6. Mildew, algae, mold prevention

You want a coating that can keep fungi away from your deck and other surfaces for a long time. The Thompson's Waterseal resists mildew, algae, and mold for a few years, after which you will need to reapply it.

As the waterproofing wears off, you will notice that it becomes easier for the wood to get moist, thus enabling the growth of these fungi.

7. Price

The Thompson's Waterseal comes at a very affordable price and in different size bottles. You can buy this model with a 1.2-gallon capacity, while you can also find it in several packs suitable for different deck sizes.

8. Coverage

As seen above, the Thompson's WaterSeal comes in different capacities for your deck size. Thus, it is best to discuss the best surfaces to treat to get the ideal coverage. According to the manufacturer, you can use the Waterseal on;

  1. Exterior wooden structures
  2. Fences
  3. Decks
  4. Wooden furniture

The type of wood you want to treat will not affect performance, and you can expect to get good coverage of 200-400 sq. ft per gallon. In addition, you will only need to apply one thin layer of the coating so it can dry faster.


  • Affordable.
  • Easy to apply on smooth, clean, surfaces.
  • Excellent water repelling.
  • Best for decks and outdoor furniture.
  • Resists mildew, mold, algae, and more contamination.
  • Cures fast when it is 50°F hot.
  • Won't stain your deck or wooden surfaces.
  • Durable.
  • Offers excellent coverage.


  • Not enough UV damage prevention.
  • Many online customer reviews state it can peel off during or after winter.
  • You will have to sand your surfaces again before reapplying.


While it is not the best for offering UV protection, the Thompson's Waterseal Wood Protector is your best bet for keeping your outdoor wooden furniture in good condition for many years. As a clear sealer, it will not stain your fixtures; it will only improve the appearance, highlighting the natural tone better.

The sealer is also affordable and easy to apply when your deck is well maintained. It will help you keep mildew, algae, mold, water, and dirt away. Additionally, it makes it easier to clean the deck area or wipe your outdoor furniture when you feel the need to.

Frequently Asked Questions (FAQs) About Thompson’s WaterSeal Wood Protector

a) When should I apply it?

You need to apply this water seal to your deck often to protect against moisture that would otherwise invite mold, algae, and rotting. While the durability of this Thompsons product depends on the state of your deck when applying, it can last anywhere between a few months to over two years before you need to repeat the application.

b) Where should I apply it?

You can apply this waterproofer on all wooden surfaces, including furniture, deck, floors, fences, and more.

c) How long does it take to cure?

Drying time depends on the weather and temperature when you apply. According to the manufacturer, it is best to apply when the weather is sunny and temperatures not lower than 50°F.

Thus, you can apply this sealer at any time in autumn. In addition, give it at least 24 to 48 hours to dry after application. After the sealer is all absorbed by the wood, you can then wait another 30 days to paint or finish with any stain of choice.

d) Is the Thompsons Waterseal Wood protector water or oil-based?

This product is water-based, but it comes with film-forming properties to prevent water damage once absorbed by the surface.

e) Is Thompson’s Waterseal toxic?

The product is VOC-compliant and is non-toxic to humans, animals, and plants. However, it does come with a strong odor that you could find uncomfortable to live with. For this reason, it is best used outdoors where there is enough air circulation to eliminate the smell.

f) Is it good with water damage prevention?

Yes, this Waterseal comes with film-forming properties that repel water and moisture to prolong your furniture and deck's lifespan. You will notice water beading immediately after the surface cures.

g) Do Thompson’s sealers offer enough UV protection?

Most customer reviews report not getting enough sun protection, with UV greying common for all treated surfaces exposed to direct sunlight.

h) Can I apply the sealer together with a stain?

No, you will only need to apply the sealer first, and then you can finish off with the best stain. Mixing the two will interfere with the healing process, and the film-forming properties of the Waterseal will not be effective.

i) How often do I need to Apply the Thompson’s Waterseal?

You will need to reapply this sealer for all your outdoor structures once every two years for best results. However, this relies heavily on the weather and the condition of your deck before and after applying the seal.

Ian Mutuli

About the author

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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