RadonSeal - Your First Choice for Sealing Concrete

radonseal waterproofs damp concrete

Q: "I have dampness not a radon problem in my basement, can I still use RadonSeal?" A: Absolutely! Sealing against tiny atoms of soil gas is much harder than sealing against water. RadonSeal can retard both water vapor and soil gas intrusion."

Water molecules are held back inside the capillaries of concrete by the surface tension of liquid water. Until the pores become wet, it takes a lot of pressure, and time, to push through a "blob" of water. Meanwhile, gases ooze easily through the pores. RadonSeal® Penetrating Concrete Sealer was developed to provide a much tighter seal, in order to keep out not only liquid water, but even gases like radon.

  • Do-It-Once-And-Forget-It – Once cured, RadonSeal becomes an integral part of the concrete so there is no need to ever re-apply the product again.
  • Your First Choice Among Penetrating Sealers – RadonSeal penetrates deeper and seals tighter – penetrates up to 4" into concrete and seals not only against water but also against water vapor and even radon gas.
  • Your First Step Before Painting Concrete – RadonSeal leaves the concrete surface paintable. RadonSeal will protect paint and concrete stains against moisture and alkali. Thus, increasing the service life of the paint.
  • Your First Step Before Installing Moisture Sensitive Flooring – RadonSeal protects adhesives, flooring, carpeting, tiles, and concrete levelers against moisture, efflorescence, and “alkali attack.”

RadonSeal Deep-Penetrating Concrete Sealer Does More!

  • Waterproofs concrete and concrete blocks against water from both sides against high hydrostatic pressure.
  • Reduces infiltration of water vapor.
  • Reduces infiltration of radon gas.
  • Neutralizes alkali and lime, protects concrete, stops or reduces efflorescence.
  • Densifies and strengthens concrete, hardens its surface.
  • Reduces concrete cracking.
  • Makes concrete suitable for painting, adhesives, and patching.
  • Waterborne, no chemical solvents, zero VOCs, non-hazardous.
  • Easy and safe spray-on application.
  • Permanent, no re-application is ever required.

Customers' reviews and tips on Waterproofing wet basements, Sealing damp basements, and Sealing basements against radon.

Protect Your Family Against Radon

Radon gas is the most potent carcinogen in your home. It kills over 21,000 people in the U.S. every year. The health risk is proportional to the radon level in your home. Women are more susceptible than men and children are the most at risk. More on Lung Cancer Risks from Radon

Radon gas gets in through the concrete and openings in basements, crawlspace, or foundation slab. Read on How Radon Gas Sneaks into Homes

RadonSeal concrete sealers and crack repair kits provide an affordable radon mitigation method for homeowners.

The Concrete Sealer That's Permanent

When concrete cures by the hydration of Portland cement (reaction with water), it produces "free lime" (calcium hydroxide) as a by-product. RadonSeal® chemically reacts with the free lime and forms a gel, which forcefully expands into capillaries (pores) and hardens as an insoluble silicate mineral (calcium silicate hydrate C-S-H). This is the same mineral produced by the hydration of cement, which bonds the concrete and gives it strength. RadonSeal products become a natural part of the concrete matrix - silicates are the primary binders of concrete.

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Silicate minerals are hard and chemically stable like, for example, quartz and granite. Similarly to newly poured concrete, the curing process takes time and RadonSeal will reach its full strength in 60 to 90 days. RadonSeal provides a permanent internal bond for the life of the concrete, which cannot deteriorate physically or chemically.

RadonSeal Binds Concrete Into a Solid Dense Mass – Concrete sealed with RadonSeal has a lower permeability, a higher compressive and flexural strength (up to 45%), resulting in a harder surface (almost flint-hard) therefore basically eliminating concrete dusting.

Allows Concrete to "Breathe" – RadonSeal does not trap moisture but allows the concrete to "breathe" and dry out. RadonSeal does not seal every single microscopic pore inside concrete.

RadonSeal can help waterproof more porous concrete and concrete blocks when paints, coatings, and other types of chemical sealers often will fail. Review How To Waterproof Concrete Blocks & How to Waterproof Cinder Blocks.

RadonSeal Protects Your Concrete Against Efflorescence

The Cancer of Concrete – The concrete's interior remains much more alkaline than its surface (about 400 times!) and moisture migration carries the alkalis to the surface. Lime and alkali attack even the concrete itself, slowly "eating away" the concrete from within. In regions with highly alkaline soils (e.g. Nevada), alkali carried by water from the soil can even "eat away" inches of a concrete slab.

Water carries the dissolved alkali to the surface and evaporates, leavingefflorescence behind (“white powder”), also referred to as the cancer of concrete. Efflorescence in basements, or on a slab, is a telltale sign of capillary water seepage. This leaching enlarges the pores in concrete and doubles the permeability of older concrete, speeding up deterioration.

RadonSeal helps solve the efflorescence problem by neutralizing the alkalis inside the concrete and by stopping water migration to the surface.

Strengthen Outdoor Concrete against Spalling

Concrete is not a rock! Just like wood, concrete breathes and it ages. Concrete also deteriorates in the presence of moisture, only slower, and needs a sealer just like wood does. RadonSeal keeps out moisture and harmful chemicals. The freeze-thaw cycle, road salts, deicers, and chemicals disintegrate outdoor concrete by pitting, spalling, rebar corrosion, and cracking. Unlike other sealers, RadonSeal waterproofs driveways and outdoor concrete not only against surface water but also against water coming up from below through the gravel bed.

One of the most common problems is the damage resulting from the corrosion of steel embedded in concrete. Rust expands the steel and the internal pressure causes cracking and spalling.

Chlorine ions from road salts or in marine environments greatly speed up the disintegration of concrete.

RadonSeal® protects the concrete as well as embedded steel. It seals the concrete against water migration and de-icing salts, and makes it resistant to most chemicals. In addition, it encapsulates embedded steel, shielding it against chlorides and corrosion. And similarly, it protects the wire mesh under stucco.

Sealing bricks or pavers? Do you want your concrete to "bead" water? Use LastiSeal Brick & Masonry Sealer

Protect Concrete Paints Against the "Alkali Attack"

All concretes contain "free lime" (calcium hydroxide), the by-product of the hydration of cement. The presence of moisture in concrete then creates a destructive alkaline solution, which attacks all paints, coatings, and adhesives on its surface by reacting with fatty acids ("saponification"). "Alkali attack" destroys waterproofing coating on foundations.

Newly poured concrete is very caustic with a pH value of 11 - 12 (the pH of flesh-eating lime is 12). Although the alkalinity of the surface gradually drops as the "free lime" reacts with atmospheric carbon dioxide (carbonation), it takes months or years to fall below the pH level of 9 required by many flooring and paint manufacturers under their warranty conditions.

RadonSeal neutralizes alkalis deep inside concrete and prevents the migration of water to its surface, which protects paints, adhesives, and floor coverings.

Use RadonSeal Before Painting Concrete

Save Money – Painting concrete without sealing it first is a waste of money! The paint or surface sealer will soon peel because of the “alkali attack,” efflorescence, or just the pressure of water vapor. Some people may decide to re-paint but the paint is not designed for a double layer, it traps more water vapor and it all just speeds up the peeling. The right procedure is to remove the old paint first but it is a hard job and the new paint will peel sooner because the concrete got older and more porous.

Cleans Concrete – RadonSeal passes through the pores in the surface, leaving them open. As it reacts and expands deep inside the pores, RadonSeal® purges contaminants, dirt, oil spills, and loose minerals for several days. It can be easily brushed off. As it purges minerals from the concrete, RadonSeal opens up the pores which improves paint adhesion.

RadonSeal neutralizes alkalis inside the concrete and seals it against moisture migration and efflorescence. This protects and greatly extends the life of paints, surface sealers, and waterproofing coatings (about three-fold).

Waterproof Your Concrete Before Installing Flooring or Carpeting

Covering a concrete floor inevitably traps water and vapor that is pushing up through the concrete, particularly when using impermeable plastic sheets, linoleum, VCT tiles, or dense carpet backing. The moisture gradually builds up and may eventually cause molds, mildew, and musty odors. 

The moisture with dissolved alkalis attacks adhesives and even carpeting and plastic tiles. This may cause “plasticizer breakdown,” which releases noxious fumes into indoor air and permeates the concrete, which either has to be replaced or sealed with RadonSeal and Ion-Bond Armor.

RadonSeal neutralizes alkalis and prevents moisture from bringing up more alkalis from the concrete. Before covering a concrete floor, use RadonSeal to reduce the alkalinity (pH value) of the surface and to seal against capillary water seepage and vapor transmission.

Concrete Repairs and Patching Concrete

RadonSeal also bonds and strengthens already deteriorated or seeping concrete. Before resurfacing or patching concrete, remove any loose, cracked, or soft concrete and seal the old concrete or mortar with RadonSeal. This will protect the "cold joint" with the new concrete against alkalis and vapor pressure. Let cure for at least 5 days, brush off any purged minerals, and patch or resurface.

How RadonSeal Can Help with LEED Certification

RadonSeal’s state-of-the-art concrete and masonry sealers can earn your project valuable credits towards LEED certification.