RadonSeal Deep-Penetrating Concrete Sealers

RadonSeal® Deep-Penetrating Concrete Sealer has been the leading concrete sealer for commercial and residential projects since the late 1990's. It is a reactive, internal sealer, for poured concrete, concrete blocks, mortar, and other cementitious materials. Unlike most concrete sealers sold in stores, it is not a surface sealer.

RadonSeal penetrates deep into concrete (up to 4"), chemically reacts, expands inside the pores and cures as a silicate mineral (read "The Chemistry Behind RadonSeal" below). it's like injecting more cement into the concrete! It makes concrete stronger and denser, and hardens its surface. Once cured, your concrete will be sealed permanently against water seepage, efflorescence, water vapor, and even radon gas. Radon is the most potent carcinogen in your home.

Use radonseal to waterproof a damp basement

RadonSeal does not change the appearance or slip-resistance of the concrete. Unlike common sealers (coatings) and waterproofing paints sold in big box stores, it will never peel, delaminate, or wear away. It cannot be pushed out from inside the pores by negative-side pressure regardless of hydrostatic pressure! The seal becomes integral to the concrete itself – no re-application is ever needed.

  • Concrete Waterproofing - Prevents water seepage, protects outdoor concrete against freeze-thaw and road salts.
  • Efflorescence - Reacts with alkalis and stops or reduces the unsightly "white powder."
  • Vapor Transmission – Reduces humidity by restricting water vapor inflow. You may not need your dehumidifier.
  • Radon Mitigation - Restricts the infiltration of radon gas.
  • Mold Remediation – Reduces the growth of mold and mildew, eliminates musty odors in basements.
  • Reduces Cracking – Bonds and strengthens concrete, prevents the rusting and expansion of rebar.
  • Concrete Hardener - Hardens the surface "flint-hard", greatly reduces dusting.
  • Neutralizes Alkalis - Ideal for fish ponds, kennels, and stables.
  • Deep-Cleans – Purges contaminants, minor oil spills, old efflorescence, and animal urine from inside concrete slabs.

The Only Concrete Sealer Backed by a Lifetime Money-Back Guarantee!

Eco-Friendly – RadonSeal® is a user- and environment-friendly waterborne sealer formulated for an easy and safe application. No solvents, zero VOCs, no fumes or noxious odors.

Most Recent Reviews Online

Which RadonSeal is Best for My Concrete?

RADONSEAL STANDARD – For indoor poured concrete such as basement floors and walls, foundation slabs, and garage floors less than 20 years old. Also use on outdoor concrete (driveways, sidewalks, walls, rooftops, decks) less than 2 years old. It penetrates the best into tighter concrete.

RADONSEAL PLUS – Use RadonSeal® Plus on older and more porous concrete, such as concrete blocks, cinder blocks, poured indoor concrete over 20 years old or poured outdoor concrete more than 2 years old. It carries more minerals for larger pores in concrete.

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For secure and encrypted online processing of your order, click the ORDER NOW button or phone us to place your order. All major credit cards are accepted or order with your PayPal or Amazon account. RadonSeal® is available online through Amazon, eBay, Home Depot, and Sears.

RadonSeal® Standard and Plus Concrete Sealers
RadonSeal pail Item Size Price Shipping  
RadonSeal® Standard 5-gal.   $159
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2.5-gal. $89 $12
RadonSeal® Plus 5-gal.   $179
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2.5-gal. $99 $12

SHIPPING - RadonSeal® is not sold in "brick and mortar" stores. Shipped in 5-gallon pails (half-filled for 2.5 gallons) directly from the factory via UPS® or FedEx® Ground. Orders received by 1 pm ET on a workday are normally shipped the same day and delivered within 1–5 working days to the lower 48 states. EXTRA SHIPPING COSTS - for expedited shipping or for shipping to Canada, Alaska, or Hawaii, please inquire first by email or phone before placing your order.

CANADIAN ORDERS - We ship to Canada but Ontario residents can purchase RadonSeal from ECO Building Resource in Aurora, Ontario (905)-841-3535.

RETURNS - Unopened pails in salable condition are returnable. Please review our Commercial Terms.

CONTRACTORS or ARCHITECTS - RadonSeal® is available at volume discounts in 55-gallon drums or in 24- and 36-pail shipping pallets. Please call or email us at Commercial Inquiries. See LEED certification below.


The approximate coverage rates below take into account the number of recommended applications.

Coverage rate varies depending on the porosity and composition of the concrete. Concrete with larger pores or more alkalis will consume more sealer. Cinder blocks are very porous and have the lowest coverage per pail.

  • POURED CONCRETE – 1,000 sq. ft./5-gal. pail in 2 applications,
  • HEAVYWEIGHT CONCRETE BLOCKS – 500 sq. ft./5-gal. pail in 3 applications,
  • CINDER BLOCKS – 400 sq. ft./5-gal. pail in 4 applications.

For example, a typical basement (floor 800-1,000 sq. ft., 8-ft. poured concrete walls) would need TWO 5-gallon pails to cover both the floor and foundation walls. A typical basement with concrete block walls will need TWO 5-gallon pails of RadonSeal Plus for the walls and ONE pail of RadonSeal Standard or Plus for the floor.

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Product Uses

RadonSeal Concrete Sealer is most often applied to waterproof basement floors and walls but is effective for sealing and strengthening a wide range of cementitious materials indoors or outdoors. RadonSeal may not work well on fiber reinforced concrete with additives, thin concrete floors (<2"). Please review RadonSeal Uses, Limitations, and Application

  • POURED CONCRETENew or old, basement walls and floors, building facades, fish/koi ponds, retaining walls, seawalls.
  • CONCRETE SLABS – Warehouse floors, garage slabs, carports, driveways, sidewalks, curbs, parking lots, patios.
  • CONCRETE BLOCKS, CINDER BLOCKS Foundation walls, retaining walls, building walls.
  • MORTAR – Mortar between blocks, porous mortar in older stone foundations.
  • LIMESTONE – Walls, floors, building blocks, facades, interior or exterior.
  • STUCCO – Porous stucco applied over concrete.

EXCEPTIONS: RadonSeal cannot seal lightweight blocks/CMUs or split-face blocks or haydite blocks (due to low cement content), stamped concrete (hard surface and release agents), acid-stained concrete (alkalis already neutralized), "popcorn" blocks (extremely large pores).

COMMON RESIDENTIAL USE: Basement floors, basement walls, garage floors, driveways, sidewalk, patios, koi ponds.

COMMON COMMERCIAL USE: Parking garages, building facades, concrete rooftops, concrete decking, sidewalks, industrial floors, concrete structures, warehouse floors, storage tanks, cooling towers, water treatment plants, bridges.

RadonSeal concrete sealer is ideal for koi ponds and fish ponds, kennel floors, and stables because in addition to waterproofing and preserving the concrete, it also neutralizes alkalis and surfaces caustic to animals.

There are many challenging situations for sealing concrete.
Read up User Reviews Waterproofing Concrete, Wet Basements, Roofs, and Koi Ponds

If you are not sure about choosing the correct sealer, visit our Sealers Guide.


CONDITIONS: The concrete must be dry inside. After a heavy rain, let outdoor concrete dry for at least 2 days. Avoid heavy rain for 24 hours after the application. Air and surface temperatures must be above freezing during the application and for three days after. Mask or remove glass, aluminum, metals, tiles, and plants.

SURFACE PREPARATION: To apply RadonSeal, the concrete surface must be bare and porous – paint, old sealers, adhesives, oil, efflorescence, grease, etc., must be removed prior to application. Vacuum excessive dust, dirt, or loose particles. Allow concrete to dry for 3 days after power washing. If the concrete is polished or troweled very hard, you have to make the surface porous by acid etching or grinding.

How To Remove Efflorescence Safely

Radon Seal pailRadonSeal can applied with a low-pressure sprayer like the hand-pump "garden sprayer," a paint roller (3/4" nap), or with a brush. Adjust nozzle on pump sprayer to a fan pattern. Shake or roll the pail before use. Pull out the pouring spout and fill the pump sprayer.

1. Dampen the Concrete - use the sprayer or a mop and a bucket to dampen the concrete surface with water (it breaks surface tension).

2. Apply RadonSeal in a Continuous Glistening Film – avoid puddles, do not over-apply. Spread out any puddles with a roller.

3. Apply the Next Application - after about 30 minutes of spraying, return to the beginning of the section while still damp and apply a second coat. Concrete blocks require 3 back-to-back applications and cinder blocks 4 applications.

The sealer should absorb within about 10 minutes (the surface still looks damp but there is no glistening film). If the concrete is unusually porous or alkaline, it will absorb very fast, letting you know that it needs more sealer – spray on another application.

4. Wash the Concrete Floor - Two to three hours after the final application, rinse the surface with water and scrub with a stiff-bristle brush or push broom, shop vac and let dry. Washing the concrete will remove any unabsorbed sealer which would leave glassy or whitish areas. It will also ensure that the surface will remain porous for painting, coating, adhesives, and surface levelers. If needed, sweep off any efflorescence or contaminants purged by RadonSeal in a couple days.

Protect Your Family Against Radon

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

Radon gas kills over 21,000 people in the U.S. every year. After smoking, it is the second leading cause of lung cancer deaths in the U.S. "Radon in homes causes more deaths than fires, drownings and airplane crashes combined." (EPA) More on Lung Cancer Risks from Radon

The health risks are proportional to the radon level in your home. There is no "safe" radon level. 70 percent of radon-attributed deaths are caused by homes with radon below 4 pCi/L, which is the US EPA's "Action Level." The health risk is proportional to the radon level in your home.

Always reduce radon to a practical minimum! RadonSeal provides an effective radon mitigation method. In comparison to fan-based mitigation, it saves on the initial cost and operating costs year after year.

RadonSeal is the strongest sealer in the market place – it seals concrete not just against water and vapor, but also against the single-atom radon gas. It was specifically developed for that purpose in 1990's. Most homeowners reduce their radon level well below 2 pCi/L. RadonSeal performance is backed up by a lifetime guarantee to the homeowners.

Radon Reduction Guarantee: RadonSeal® Penetrating Concrete Sealer must be applied to all basement walls and the floor, or to the entire slab-on-grade foundation slab. RadonSeal will reduce and/or keep the indoor radon level below the Action Limit of 4 pCi/L. However, you must also seal or caulk all cracks, joints, protrusions, and any openings in the basement walls or slab. The guarantee does not apply to basements with stone foundations, protruding rocks, dirt floor, attached crawlspace, or radon carried in by water from a private well. If your radon level exceeds 20 pCi/L, you must phone us first for consultation. Let RadonSeal cure for at least 30 days before testing.

Read up User Reviews Sealing Basements against Radon Gas

Reduce Humidity, Efflorescence, Dusting, and Radon

Your Damp Basement Solution! – RadonSeal is the strongest silicate-based sealer because it penetrates deeper, carries more active minerals, and seals tighter than other concrete sealers. Its penetration does not depend on gravity because it penetrates by capillary action – also used on walls and ceilings. In case of basement walls, it is usually applied on the inside to seal against water seepage, water vapor, and radon gas from the ground. However, if there is an opportunity to apply it also to the outside, it has the added advantage of preserving the exterior surface of the concrete and extending the life of any waterproofing coating by protecting it against saponification caused by alkalis from the concrete.

Read up User Reviews Sealing Damp Basements and Floors against Moisture, Molds, Musty Odors

Use Before Painting or Installing Flooring – RadonSeal® leaves the surface paintable. It is recommended for sealing concrete before applying paints, adhesives, epoxy or urethane coatings, "wet-look" sealers, concrete overlays, surface levelers, or moisture-sensitive flooring. RadonSeal prevents wicking water, water vapor, and efflorescence from pushing off or cracking paints and coatings. As it purges minerals from inside the capillaries, it opens up the pores and is often used by flooring contractors as a primer.

For more info on how RadonSeal® works, efflorescence, the “alkali attack," how to protect concrete, paints, and flooring against deterioration, visit RadonSeal - Your First Choice for Sealing Concrete

Use as a Concrete Densifier – RadonSeal will make concrete denser and stronger (up to 40% in flexural strength). It makes concrete surfaces resistant to abrasion. Use on concrete to reduce concrete dusting, concrete crumbling, and overall wear.

The Chemistry Behind RadonSeal®

The history of penetrating silicate concrete sealers dates back to Germany in World War II, when they were used to strengthen quickly poured, thin military runways. After the war, the Army Corps of Engineers started using the sealers for the preservation of concrete dams and bridges. As the technology evolved, the use of silicate concrete sealers expanded from preserving structural concrete to waterproofing outdoor and indoor concrete. Somewhat diluted, they are also used as "surface hardeners."

During the last couple of decades, penetrating silicate concrete sealers have become widely used in the US and abroad, be it at Disney World or Sydney Opera House. Many architects specify them for major buildings. The sealers have been successfully used on thousands of major concrete structures and buildings.

How Does RadonSeal Work? When concrete cures, it produces "free lime" as a by-product of hydration. RadonSeal reacts with the free lime and alkalis inside concrete and expands inside the capillaries. It forms a silicate mineral – it's like injecting Portland cement into the concrete. Simply, it results in a higher grade of concrete that is denser, stronger, and tighter.

RadonSeal waterproofs concrete internally but usually it does not make its surface "bead" water, it does not make it slippery when wet, and leaves it paintable. It will absorb individual water drops (it “wets”) but larger puddles will remain, because the concrete is waterproof.

RadonSeal - Your First Step When Moving

The RadonSeal spray-on application makes it easy for a do-it-yourself home repair or home improvement project.

Selling Your Home
Before putting the house on the market, seal all the concrete in your basement with RadonSeal® to avoid any last-minute glitches at closing! Buyers are wary of fresh paint. Stop moisture problems and musty odors. Play it safe and reduce radon to a minimum – radon levels fluctuate widely and a bad short-term radon test could scuttle the closing.
Buying A Home
If there is a radon or moisture problem, negotiate a discount for conventional radon mitigation or waterproofing. Then, do it yourself with RadonSeal and save! In any case, protect your family's health by reducing dampness and radon to a practical minimum.
Newly Built Homes
Now is the best time to preserve the concrete and prevent future moisture or radon problems. In a finished basement, the floor-to-wall joints are unreachable. Sealing the basement is particularly important in today's energy-efficient homes, which draw not-so-fresh air from the ground through the porous concrete.

Architects, Builders, and Contractors Using RadonSeal

RadonSeal prevents or solves problems with moisture, molds, and radon in residential, institutional or commercial buildings like schools, apartments, hospitals, and hotels. It preserves commercial and industrial concrete assets indoors and outdoors – warehouses, factory floors and walls, cooling towers, water treatment plants, and bridges.

It also protects parking areas, garages, and factory floors against oil spills and most chemicals. Info for builders and contractors on RadonSeal Commercial Applications.

RadonSeal reduces costs and warranty callbacks, improves results, adds value, and increases customer satisfaction for a variety of contractors:

• Waterproofing Contractors

• Radon Mitigation Contractors

• Building Contractors

• Basement Remodeling Contractors

• Flooring Contractors

• Architects

• Painting Contractors

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.