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Water is concrete’s biggest enemy. It carries salts and chlorides into the slab, where they corrode reinforcing steel and cause spalling and cracking, and in basements it feeds mold, mildew and musty odors. A good waterproofing sealer greatly reduces how much water concrete absorbs. Be wary of any product that promises to waterproof concrete permanently, though: no sealer can guarantee that.
Penetrating Sealers vs. Surface Coatings
Many “waterproofing” products are elastomeric, latex or acrylic coatings that sit on top of the concrete like a raincoat. They help at first, but water can get behind them from below or through cracks, and the film eventually bubbles, peels or flakes.
Penetrating sealers, including silanes, siloxanes, silane/siloxane blends and silicates, soak into the pores and react inside the concrete. They block liquid water while still letting the slab breathe, so there’s no film to peel. For lasting water protection, a penetrating sealer is the better choice. Learn more in best penetrating concrete sealers.
Our Pick: Lithi-Tek 9500
Our favorite concrete waterproofer is the Lithi-Tek 9500, an invisible penetrating sealer that densifies concrete and makes it water repellent.
- Water beading: rain beads up and rolls off treated surfaces instead of soaking in.
- Less moss and algae: helps limit growth in damp, shaded areas.
- No change in look or traction: it leaves no film, so the surface isn’t slick.
- Long life: because it works inside the concrete, it only wears away if the concrete surface wears away.
Coverage and cost
The 9500 is a concentrate: one gallon covers about 1,000 sq. ft. per coat, and two coats are recommended, so plan on about 500 sq. ft. per gallon. That’s roughly $0.10 per square foot per application, far less than the cost of replacing concrete.
Where to buy
Available direct from the manufacturer, on Amazon, at Home Depot and at Lowe’s.
How to Get the Best Results
- Clean the surface and let it dry completely. See how to clean concrete before sealing.
- Apply in dry weather, within the temperature range on the label.
- Apply two coats as directed rather than one heavy coat. See how to apply concrete sealer.
- Check your concrete each season for efflorescence, cracks or discoloration.
Waterproofing a Basement?
Basements have their own challenges, including hydrostatic pressure and moisture coming up through the slab. See best concrete sealer for basement waterproofing and basement waterproofing explained.
