Thompson’s Water Seal is a popular deck sealer and waterproofer that has been around for decades. It provides decent water protection for exterior wood surfaces like decks, fences, and outdoor furniture. However, there are several deck sealers on the market today that outperform Thompson’s Water Seal.
Pros of Thompson’s Water Seal
Here are some of the benefits of using Thompson’s Water Seal:
- Inexpensive – It costs less than most other deck sealers.
- Readily available – You can find it at most hardware stores and home centers.
- Water-repellent – It contains solvents that cause water to bead up and run off the wood surface.
- Blocks UV rays – The sealant offers some UV protection to prevent fading and graying of the wood.
- Easy to apply – It goes on easily with a brush or sprayer.
While Thompson’s Water Seal does provide decent short-term water protection for horizontal exterior wood surfaces, it has some significant drawbacks compared to newer deck sealers.
Cons of Thompson’s Water Seal
Here are the main downsides of using Thompson’s Water Seal:
- Requires frequent reapplication – It only lasts 1-2 years before needing to recoat.
- Not durable – The waterproofing tends to break down after exposure to weather, foot traffic, etc.
- Prone to peeling – The sealant can peel and flake off the wood over time.
- Declining water repellency – The beading effect diminishes as the sealant wears away.
- No mildew protection – It doesn’t contain fungicides or algaecides to prevent mildew growth.
- Can trap moisture – May not allow interior moisture to escape, leading to rot.
- Odorous fumes – It has a very strong odor during application.
These limitations mean Thompson’s Water Seal requires reapplication every year or two to maintain its water-repelling effectiveness. There are better options available today.
What to Look for in a Deck Sealer
When choosing an exterior wood sealer, here are some key features to look for:
- Advanced polymers – Look for acrylic, silicone, epoxy, or polyurethane formulations instead of cheaper asphalt emulsions.
- Deep penetration – Sealers that soak into the wood last longer than surface coats.
- Long-lasting – Advanced sealers can protect for 3-5 years or more before needing to reapply.
- Fade resistance – UV absorbers prevent graying and color loss.
- Mildew inhibitors – Algaecides and fungicides prevent mold, mildew and algae growth.
- Low VOC – Environmentally-friendly, low odor sealers are safer to use.
- Easy to apply – Spray-on application is fastest for large decks.
Modern deck sealers that check all of these boxes will provide much longer-lasting protection compared to Thompson’s Water Seal.
The 5 Best Deck Sealers
Based on performance, durability, and overall value, here are 5 of the best deck sealers:
1. DEFY Extreme Wood Stain
DEFY Extreme is a top-rated synthetic resin sealer that provides excellent 5-year waterproofing for decks. It contains acrylic polymers, epoxy resins, and UV blockers for long-lasting protection. The zinc nano-particles provide extra water repellency so rainwater beads up and rolls off the deck. It’s also loaded with mold inhibitors.
2. TWP 1500 Series
TWP 1500 is a high-performing acrylic/silicone sealer blended with weatherproofing resins. It blocks 95% of UV rays to prevent graying and fading. The sealer penetrates deep into the wood grain for long-lasting water resistance. It lasts 3-5 years between recoating.
3. Ready Seal 512 Exterior Wood Stain
Ready Seal is an oil-based, penetrating sealer that nourishes wood while providing a natural-looking, semi-transparent finish. It goes on easily with a sprayer and gives outstanding UV and water protection for up to 5 years before needing to recoat.
4. SEAL-ONCE Marine Wood Sealer
This water-based sealer is formulated for boat decks but works extremely well for outdoor decks too. The 100% acrylic polymers provide excellent UV blockage, waterproofing, and longevity. It protects the wood grain while allowing the texture to show through.
5. DeckWise Ipe Oil Hardwood Sealer
For hardwoods like ipe and tigerwood, DeckWise Ipe Oil is an excellent choice. This penetrating oil finish brings out the natural grain patterns in dense exotic woods. It blocks moisture and provides long-term UV protection with minimal reapplication needed.
How to Apply Deck Sealer
When using a quality deck sealer, proper preparation and application are key to getting long-lasting results:
- Clean the deck – Use a deck cleaning solution and a pressure washer to remove dirt, mildew stains, old sealant, etc. Let the deck dry completely.
- Make repairs – Fix any cracked boards, loose nails/screws, splinters, etc. Replace any rotten boards.
- Remove furniture – Clear everything off the deck to allow complete, unobstructed application.
- Follow instructions – Read the product label and understand necessary safety precautions.
- Apply sealer – Use a brush for seams and edges and a roller or sprayer for open areas.
- Allow to dry – Let the sealer cure fully before allowing foot traffic back on the deck.
- Coat evenly – Maintain a wet edge and coat all surfaces for uniform coverage.
- Clean up – Properly dispose of all brushes, rags, and containers with leftover sealer.
Applying with the right preparation leads to maximum performance from the sealer.
Sealing Pressure-Treated Decking
With pressure-treated lumber, it’s very important to:
- Let it dry out – Give the wood several good dry weeks before sealing.
- Clean thoroughly – Use a deck cleaner and brightener to remove any anti-stain preservatives.
- Start with 1-2 coats – The first coats soak into untreated wood and prep it for better protection.
Sealing too soon can cause adhesion problems if the wood retains any moisture or chemicals. Proper prep leads to greater longevity from the sealer.
How Long Does Deck Sealer Last?
Typical longevity for quality deck sealers is:
| Deck Sealer Type | Lifespan Before Reapplication |
|---|---|
| Asphalt Emulsions (Thompson’s Water Seal) | 1-2 years |
| Acrylics | 2-4 years |
| Silicones | 3-5 years |
| Epoxies | 4-6 years |
| Polyurethanes | 5-7 years |
| Oils | 1-3 years |
Higher-end acrylic, silicone, epoxy, and polyurethane deck sealers provide the greatest longevity, lasting up to 5 times longer than Thompson’s Water Seal before needing to recoat.
Recoating vs. Stripping Decks
When it’s time to refresh the deck’s waterproofing, you have two options:
- Recoating – Apply a new coat of sealer directly over the existing finish.
- Stripping – Remove the old sealer before applying a new coat.
Recoating is quicker, easier, and less hassle. But stripping off the old sealer allows the new coat to bond tightly to bare wood for maximum durability.
Plan to recoat more frequently, as often as every 2-3 years. Or strip the deck less often, such as every 5-7 years before sealing.
Conclusion
If you want superior waterproofing for your wood deck, it’s best to look beyond Thompson’s Water Seal. Advanced decking sealers based on acrylic, silicone, epoxy, and polyurethane polymers offer much longer protection against water damage, UV rays, and mold growth.
Careful prep work and following the manufacturer’s application instructions will provide the greatest performance and longevity from modern sealers. Your investment will pay off for years to come in the form of a beautiful, protected deck surface.
