Does Thompson's WaterSeal actually work?

Thompson's Clear WaterSeal provides basic waterproofing that beads water for 1-2 years but has no UV protection and no mildewcide. Wood will gray quickly. Their Penetrating Timber Oil is significantly better providing color UV protection and waterproofing for 3-4 years. For best performance choose the Timber Oil not the clear waterproofer. Better alternatives at similar prices include Ready Seal and DEFY Extreme. How long does Thompson's WaterSeal last?

How often do I need to reapply Thompson's WaterSeal?

The clear waterproofer lasts 1-2 years on horizontal surfaces like decks. The Penetrating Timber Oil lasts 3-4 years on vertical surfaces and 2-3 years on horizontal. The solid waterproofing stain lasts 3-5 years on vertical surfaces. Reapply when water no longer beads on the surface. Higher-performing products like TWP last 3-5 years and Ready Seal lasts 2-3 years at similar or slightly higher cost. Can I apply Thompson's WaterSeal over old stain?

Do I need to strip before applying Thompson's WaterSeal?

Yes Thompson's requires bare wood for proper penetration. It does not adhere well over other products. Clean the wood thoroughly strip any existing stain or sealer and let the wood dry completely before application. Applying over old finish will cause poor adhesion peeling and reduced protection. For the clear waterproofer apply one coat only as a second coat can cause white hazy film. What is better than Thompson's WaterSeal?

What are the best alternatives to Thompson's WaterSeal?

Ready Seal at $40-50 per gallon provides color UV protection waterproofing and mildew resistance with no back-brushing required. TWP at $45-60 is the professional standard lasting 3-5 years. DEFY Extreme at $30-40 is water-based with synthetic resin that outperforms Thompson's in testing. If staying with Thompson's choose the Penetrating Timber Oil over the clear waterproofer for significantly better performance.

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Finishing

Thompson's WaterSeal Guide: Products, Application, Drying Time & Alternatives Compared

Lumberama Editorial Team, Deck Sealing & Waterproofing Experts Oct 26, 2024 11 min read

Thompson's WaterSeal Overview

Thompson's WaterSeal is the most recognized name in wood waterproofing, found in every major hardware store. The brand offers several product lines at accessible price points ($18-30/gallon), making it the default choice for many homeowners tackling their first deck or fence sealing project. However, it's important to understand what Thompson's does well, where it falls short, and when a different product would serve you better.

Product Line

Thompson's WaterSeal Clear Multi-Surface Waterproofer: the original product. A clear water repellent that provides waterproofing with minimal UV protection and no color. It beads water effectively for 1-2 years on horizontal surfaces. Best for: pressure-treated wood where you want waterproofing without changing the color. Not recommended for: cedar, redwood, or any wood where UV graying is a concern (no UV protection means the wood will gray rapidly).

Thompson's WaterSeal Penetrating Timber Oil: an oil-based penetrating stain with UV protection and waterproofing. Available in several wood-tone colors. This is Thompson's best-performing product, significantly better than the clear waterproofer. Apply in a single heavy coat, and it provides 3-4 years of protection on vertical surfaces. Price: $25-35/gallon.

Thompson's WaterSeal Waterproofing Stain: available in semi-transparent and solid formulations, both water-based. Provides color, UV protection, and waterproofing. The solid version lasts longer (3-5 years on vertical) but can peel. The semi-transparent version lasts 2-3 years and fades gracefully. Price: $28-35/gallon.

Application

Surface must be clean, dry, and free of any previous sealer or stain. Thompson's does not adhere well over other products and requires bare wood for proper penetration. For the Clear Waterproofer: apply with a pump sprayer, brush, or roller. Apply one coat only (applying a second coat before the first has fully absorbed can cause a white, hazy film). Let excess absorb for 10-15 minutes, then wipe any puddles. For the Penetrating Timber Oil: apply one heavy coat with a brush or stain pad, working the product into the wood grain. Don't over-apply or allow puddling. Drying time: 24-48 hours for light foot traffic, full cure in 30 days.

Limitations and Alternatives

Thompson's Clear Waterproofer has significant limitations: no UV protection (wood grays quickly), no mildewcide in the base formula, and relatively short protection life (1-2 years on horizontal surfaces). For the same price or slightly more, several products outperform it significantly. Ready Seal ($40-50/gallon) provides color, UV protection, waterproofing, and mildew resistance in a single no-back-brushing oil-based formula that lasts 2-3 years. TWP ($45-60/gallon) is the professional standard with 3-5 year protection. DEFY Extreme ($30-40/gallon) is a water-based option with synthetic resin technology that outperforms Thompson's in independent testing. For homeowners on a strict budget, Thompson's Penetrating Timber Oil (not the clear waterproofer) offers the best value in the Thompson's lineup.