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Sikagard-400 Enviroseal is a water-based, 40% silane penetrating sealer for concrete. It’s built for bridge decks, parking garages and other reinforced concrete that faces water, freeze-thaw and deicing salts. You may know it as MasterProtect H 400 or, before that, Enviroseal 40. It’s the same 40% silane sealer under Sika’s name. It’s one of the better-documented penetrating sealers you can buy. It’s sold mainly through contractor and construction-supply channels, not big-box stores, and it won’t fix cracks or change how the concrete looks.
| Type | Penetrating water repellent (no film) |
| Chemistry | Water-based alkylalkoxysilane, 40% active content |
| Finish | Milky white in the pail, dries clear; no change in appearance |
| Coverage | 100–200 sq ft/gal on concrete and brick, depending on porosity |
| Coats | Apply to saturation (no fixed coat count) |
| Dry/recoat | Dry in about 4 hours at 70°F and 50% RH; may stay slippery for several hours |
| Cure | Allow 5–7 days for full reaction before judging a test area |
| Best for | Driveways, garage slabs, parking decks, bridge decks, ramps, precast and cast-in-place concrete above grade |
| Not for | Cracked or unsound concrete, below-grade waterproofing, a wet-look finish |
| New concrete | After it reaches about 80% of design strength, typically 14–28 days |
Watch: Sikagard-400 Enviroseal in 60 seconds
What It Is / How It Works
About the name: The product began as Enviroseal 40. It was later sold as MasterProtect H 400 under Master Builders Solutions, the construction chemicals brand formerly owned by BASF. Sika acquired that business, and Sika's U.S. data sheet now calls it Sikagard-400 Enviroseal, "formerly MProtect H 400." Some Sika documents also list it as Sikagard H 400. Sika's Master Builders site labels it "Sikagard-400 Enviroseal (formerly known as MasterProtect H 400)." Whichever name is on the pail, it's the same water-based 40% silane penetrating sealer. It's sold by Sika, not by a separate company called "Sikagard."
Silane molecules are small enough to soak into concrete pores. Once inside, they react with the moisture and minerals there to form a water-repellent lining in the capillaries, without a coating on the surface. Water and chloride-laden slush bead off, while water vapor inside the slab can still escape. Sika lists a penetration depth of 0.24 in (6.1 mm). It also lists an 87% chloride reduction and an 85% reduction in water weight gain in NCHRP 244 Series II cube tests, a 99% chloride reduction in the Series IV southern-climate test, and a 0 rating (no scaling) after 100 freeze-thaw cycles with deicing salt (ASTM C672). It's approved as Alberta DOT Type 1b.
Where It Works Best (and where it doesn't)
It's a strong choice for exterior concrete that faces salt and freeze-thaw. Think driveways, sidewalks, garage aprons, parking decks, ramps, barrier walls and precast panels. It's rated for traffic-bearing surfaces and works on horizontal and vertical surfaces, indoors or out, above grade.
It won't stop water coming through cracks, failed caulking, bad flashing or structural defects, and Sika says so plainly. It also isn't a basement waterproofer against hydrostatic pressure, and it won't add color, sheen or stain resistance against oil. In California's South Coast AQMD, its use is limited to specific project types under Rule 1113. If you're shopping retail options in the same category, see our best silane-siloxane concrete sealers.
Pros
- High 40% active silane content
- Published DOT-style test data for chloride, water absorption and salt scaling
- Invisible finish that stays breathable and doesn't wear off like a film
- Rated for traffic-bearing surfaces
- Wide application range of 40–110°F
- Water-based; tools clean up with hot soapy water
Cons
- Hard to find in big-box stores; usually sold in 5-gallon pails and drums through contractor suppliers
- Name changes (Enviroseal 40, MasterProtect H 400, MProtect H 400, Sikagard H 400) can confuse shoppers
- Won't bridge cracks or fix defects; repairs come first
- Can leave a slippery surface for several hours
- Coverage varies a lot with porosity, so a test area is needed
- Usage restrictions in Southern California's South Coast AQMD
How to Apply It
- Wait for cure. New concrete should reach about 80% of design strength first, typically 14–28 days.
- Repair and caulk first. Fix cracks and defects. Let joint sealants cure 6–12 hours, or until they skin over, before sealing.
- Clean. Remove sand, dust, dirt, oil, grease, chemical films and old coatings. Power washing, sandblasting or shotblasting may be needed. A dry surface penetrates best, a slightly damp one is acceptable, but there should be no standing water.
- Check the weather. Surface, air and material should be between 40°F and 110°F. Don't apply if temperatures will drop below 40°F, or rain is forecast, within 12 hours.
- Test a 5 x 5 ft area. Give it 5–7 days to react fully before you judge coverage and beading.
- Apply to saturation. Stir before and during use, and don't dilute. Use a low-pressure, non-atomizing sprayer. On flat surfaces you can pour it and spread it with a squeegee or broom. Plan on 100–200 sq ft per gallon.
- Keep traffic off until it's dry. That's about 4 hours at 70°F and 50% RH, longer when it's cool or humid.
How It Compares
Eagle Natural Seal is a widely available water-based silane/siloxane blend at about 200 sq ft per gallon. It's easier to buy and suits homeowner driveways and patios. Eagle doesn't publish an active-solids percentage or DOT test data for it, though.
Other 40% silane sealers from commercial brands target the same bridge-deck and parking-garage work. When you compare them, look for actives percentage, penetration depth and NCHRP 244 or ASTM C672 results, not just the marketing claims.
Film-forming acrylics add sheen and color enhancement, but they wear off and can trap moisture. For the different sealer types, see our best concrete sealers for 2026.
FAQ
Is Sikagard-400 Enviroseal the same as MasterProtect H 400?
Yes. Sika labels it "Sikagard-400 Enviroseal (formerly known as MasterProtect H 400)," and the older Master Builders data sheet lists Enviroseal 40 as its earlier name. The specs carried over, including 40% silane and 100–200 sq ft per gallon.
Will it change the look of my concrete?
Sika says it dries clear and doesn't alter the surface appearance. Test a small area if appearance matters.
Can you put it over an existing sealer?
Not over a coating. Sika says to remove coatings and chemical films so the silane can soak into bare concrete.
What's the VOC content?
The current Sika data sheet doesn't state it. The earlier MasterProtect H 400 data sheet listed less than 350 g/L, excluding water and exempt solvents. Use is restricted in the South Coast AQMD, so check the current SDS and your local rules.
Verdict
Sikagard-400 Enviroseal, formerly MasterProtect H 400 and Enviroseal 40, is a serious, well-tested 40% silane sealer. If you can buy it through a contractor supplier, it's an excellent choice for exterior concrete exposed to salt and freeze-thaw. The drawbacks are practical: limited retail availability, confusing names, the need to test for coverage and nothing to offer if your concrete is cracked. Current details are on Sika's product page. Our rating: 4.4/5
How we reviewed this product: this is a research-based review built from the manufacturer's technical data sheet and current retail listings. We have not run our own hands-on tests of this product. Details were checked in October 2026; always follow the current label.