Olympic Waterguard vs. Thompson’s WaterSeal

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In this article, we compare two clear protective decking coats: Olympic Waterguard and Thompson WaterSeal. After reviewing the features of these two products, we’ll discuss the similarities and differences between them. Then, we’ll reveal the major differentiating factor, and advise you on when to use Olympic Waterguard, when to use Thompson WaterSeal, and which is better. 

What Is Olympic Waterguard?

Olympic is a company that makes wood stains, with a specific concentration in exterior stains used to protect wooden decks. 

Waterguard is the marketing name given to one of their most popular products. It is a clear, film-forming finish that repels water. The manufacturer claims that it includes UV blocking protection from sunlight, but it is not clear how effective this is, since they also advertise that wood protected with Waterguard will still show weathering and fading as it ages. 

Wet deck

A look at the ingredients in Olympic Waterguard shows that it contains paraffin, linseed oil, an unspecified resin, and various solvents, as well as one ingredient considered to be a trade secret. 

Olympic Waterguard touts it’s ‘satisfaction guaranteed’ warranty. However, like most deck stain warranties, it is almost impossible to invoke. If the inspector sent by the manufacturer determines that the surface wasn’t properly prepared or that there was ‘too much footfall’ on the deck, you’re unlikely to get any benefit from Olympic’s satisfaction guarantee. 

For what it’s worth, Olympic recommends that the area be prepared through thoroughly removing all traces of previous finishes or sealers, followed by cleaning with an Olympic-brand cleanser.

Consumer Reports graded exterior decking stains and clear sealants on a scale of zero to 100. Of the 28 products tested, Olympic Waterguard performed the worst, earning an overall rating of only five points. It was also given a ‘poor’ rating for appearance after one year of weathering. 

This suggests that decks covered in Olympic Waterguard may need to be reapplied every year. 

Olympic Stain 56500-04 Maximum Waterproofing...
  • Enhanced waterproofing protection to help make sure your wood is protected from cracking due to...
  • 1 Quart
  • delivers enhanced waterproofing and sunblock UV defense
  • Item Package Weight: 2.59 pounds

Olympic Waterguard Application 

Olympic Waterguard is a one-coat product. You should test the sealer on an inconspicuous area before committing to sealing the entire deck. This product is best used to seal pressure treated wood decks.

Backbrushing, or working the finish into the wood via multiple passes of a brush or roller, is recommended by the manufacturer to achieve appropriate penetration. 

Olympic Waterguard can be applied at temperatures as low as 35 degrees Fahrenheit, although the recommended temperature range for application is between 50 and 90 degrees Fahrenheit. Brushes and rollers can be cleaned using water and dish soap.

One gallon of Olympic Waterguard should be enough to cover between 250 and 350 square feet of decking. Highly porous woods such as cedar, ash, and chestnut and open-grain woods such as elm and oak will absorb more Waterguard than less porous or closed-grain woods like cherry, rosewood, maple, birch, or yellow poplar

What Is Thompson’s WaterSeal?

Edward Addision Thompson was a polymer chemist. In the 1920’s, he developed a product that provided some protection from weathering when applied to concrete, and it was widely used in the construction industry. 

It wasn’t until 1982 that they expanded to clear decking sealants. WaterSeal was the name given to what has developed into a wide range of products. Their product line includes cleansers, ‘penetrating timber oil’ and exterior stain, along with rattle-can products labeled for ‘small projects’. 

Thompson’s describes many of their products as ‘oil-based’, but there is no indication of what oil is used. The main ingredients appear to be denatured alcohol and paraffin. The company claims that their product penetrates the wood to form a waterproof barrier, which could indicate the presence of a drying oil such as linseed oil or tung oil, but these ingredients are not mentioned. 

House deck

The WaterSeal line includes clear and semi-transparent products as well as tinted stain/sealer combinations. 

In the same Consumer Reports test referenced above, Thompson’s clear coat WaterSeal earned a ‘Poor’ rating for appearance after one year, despite the marketing team’s promise that it lasts for four years. It earned an overall score of 12 out of 100. Thompson’s does not offer a warranty.  

The manufacturer’s instructions recommend applying two coats of Thompson’s WaterSeal products, waiting only one hour between coats. 

One gallon of Thompson’s WaterSeal will cover approximately 200 square feet of wooden decking.

Thompsons Waterseal 41851 Gl STN Tran Woodlnd Cedr
  • Color: Woodland Cedar
  • Transparent
  • Wood sealer and stain, all in one
  • Prevents water damage

Olympic Waterguard vs Thompson’s WaterSeal

Now that you understand what these products are, it’s time to compare and contrast them. 


These two products come from different manufacturers, but have many similarities. Both are wood finishes marketed for exterior wood protection, and make unverified claims about their efficacy. They dry quickly and are easy to clean up. 


Both products are wood finishes marketed for their ability to protect exterior wood. 

UV Blocking Capabilities

Both Olympic Waterguard and Thompson’s WaterSeal advertise the inclusion of UV blockers. However, since they do not protect wood from fading and weathering, it’s difficult to verify this claim. 


Olympic Waterguard and Thompson’s WaterSeal also advertise their mold and mildew discouraging properties. However, independent testing does not support these claims. 

Lack of Transparency

Neither product has a clear, transparent list of ingredients. 

Level of Protection

They both make claims about protecting wood, but it is far from clear that they do a better job than simpler alternatives such as tung oil or linseed oil

Dry Time

These products both dry quickly – within about one hour. 

Ease of Clean Up

Olympic Waterguard and Thompson’s WaterSeal products can be cleaned off of brushes or rollers using soap and water. 


These two products differ from each other in several important ways. The number of coats, satisfaction guarantee, color availability, and application time differ significantly between Olympic Waterguard and Thompson’s WaterSeal. 

Deck with water repelling finish

Number of Coats

Olympic Waterguard is a one-coat product. Thompson’s WaterSeal requires two coats. 

Application Time

Because Olympic Waterguard only requires one coat, it takes less time to apply than two-coat formulas like Thompson’s Water Seal. 


Olympic Waterguard comes with a customer satisfaction guarantee. Thompson’s WaterSeal does not. 


Olympic Waterguard is a clear coat. The Thompson’s WaterSeal line of products includes clear sealers, but also covers tinted stains/sealer combinations. 

Major Differentiating Factor

If you are choosing between these two products the major differentiating factor is the time it takes to apply them. Olympic Waterguard only requires one coat. While you only need to wait one hour between the two coats required for Thompson’s WaterSeal, this does significantly increase the time needed to complete the project. 

Keep in mind that you can always opt to paint your deck instead of staining it.

When To Use Olympic Waterguard

It’s hard to find a justifiable reason to choose Olympic Waterguard as a protective coating when there are so many superior options.

If you have a temporary structure that only needs protection from the weather for one year, it could be reasonable to choose Olympic Waterguard as a protective coating. 

When To Use Thompson’s WaterSeal

Thompson’s WaterSeal does not appear to live up to the promises made by the marketing team. While it performs slightly better than Olympic Waterguard, it is still among the worst-performing finishes tested by Consumer Reports.

You might also choose Thompson’s WaterSeal if you live in a very dry environment. 

Which Is Better, Olympic Waterguard or Thompson WaterSeal? 

Thompson WaterSeal clear coat received a score of 12 out of 100 in Consumer Report’s test of 28 clear decking finishes. Olympic Waterguard scored a 5 out of 100. You can expect WaterSeal to perform slightly better than Olympic Waterguard, so it is appropriate to say that WaterSeal is the superior product. 

However, neither of these products is likely to look good after a year, so it would probably be best to choose a different product.

Ellenkate grew up on job sites run by her family’s construction company. She earned her theater degree from The Hartt School, a prestigious performing arts conservatory in Connecticut. Her design and DIY work from her Chicago loft was featured in the Chicago Reader and on Apartment Therapy.