RadonSeal Deep-Penetrating Concrete Sealer

RadonSeal® has been the most trusted and widely-used concrete sealer for both construction and residential waterproofing projects for the past 17 years. It is a chemically reactive, internal sealer for poured concrete, concrete blocks, mortar, and other cementitious materials.

RadonSeal penetrates deep into concrete (up to 6" depending on porosity), reacts, expands inside the pores, and cures as a hard silicate mineral. Once cured it will seal your concrete permanently against the transmission of water vapor, water seepage, efflorescence, and formulated strong enough against radon gas.

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Unlike common surface sealers (membrane coatings) and waterproofing paints sold in big box stores, RadonSeal will never peel or wear away. It cannot be pushed out regardless of hydrostatic pressure! The internal seal becomes integral to the concrete itself – so there is never a need to reaplly the product again! Think of applying RadonSeal like injecting more cement into your concrete.

RadonSeal is a concrete sealer for damp basements

Choose Between RadonSeal Standard or RadonSeal Plus

STANDARD – Use RadonSeal® Standard for sealing poured concrete (walls and floor) less than 20 years old. Use on outdoor concrete less than 2 years old.

PLUS – Use RadonSeal® Plus (higher mineral content) for sealing older, more porous concrete, such as poured concrete older than 20 years, concrete blocks, cinder blocks, or poured outdoor concrete more than 2 years old. See coverage below.

Before purchasing, please take the time to review the RadonSeal Detailed Instruction & Sealing Various Cementitious Materials

Order Today

For secure and encrypted online processing of your order, click Order Online or simply phone us to place your order. All major credit cards accepted, or order with your PayPal account. RadonSeal is also available through Amazon and eBay. Canadians can purchase through ECO Building Resource, Ontario tel. 905-841-3535.

The only concrete sealer backed up by a Lifetime Money-Back Guarantee

RadonSeal® Standard & RadonSeal® Plus Concrete Sealer
RadonSeal pail Item Size Price Shipping  
RadonSeal® Standard 5-gals. $149
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2.5-gals. $89 $12 Order Now button
RadonSeal® Plus 5-gals. $169
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2.5-gals. $99 $12 Order Now button

Shipping: RadonSeal is not sold in stores. RadonSeal is shipped directly from the factory to your door (via UPS). Orders received by 3 pm ET are normally shipped the same day and UPS Ground delivers within 2 to 5 working days in the lower 48 states. For expedited shipping or shipping to other states (AK, HI) please inquire first by e-mail or telephone. Unopened pails in salable condition are returnable. Please review our Commercial Terms

Commercial Applicators: Available in 55-gallon drums at volume discounts or 24 and 36 pail shipping pallets. Please call or email us at Commercial Inquiries.

Reduce Moisture Transmission, Efflorescence, Dusting, and Radon

Your Damp Basement Solution! – RadonSeal is the heaviest available silicate-based sealer, which penetrates deeper, carries more active minerals, and seals tighter than any other concrete sealer. The penetration does not depend on gravity – it is also used on walls and ceilings (pulled in by capillary action). In case of basement walls, it is normally applied to interior walls to seal against water seepage, water vapor, and radon gas from the ground. However, if there is an opportunity to apply it to the outside, it has the added advantage of preserving the exterior of the concrete and extending the life of waterproofing coating.

Use Before Painting or Installing Flooring – RadonSeal protects concrete against wicking water, efflorescence, and the "alakli attack" so it is commonly used by flooring contractors as a concrete primer. RadonSeal is recommended for sealing concrete before applying paints, adhesives, epoxy floor coatings, concrete overlays, surface levelers, membrane "wet-look" coatings, and moisture sensitive flooring. It does not form a film on the surface so it will not change the appearance or friction of the concrete.

For more info on how RadonSeal works, the “alkali attack," efflorescence, how to protect concrete, paints, and flooring against deterioration, visit Sealing Concrete with RadonSeal

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

  • Concrete Waterproofing - Prevents water seepage into basements, protects 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.
  • Radon Mitigation - Seals concrete against the infiltration of radon gas.
  • Mold Remediation – Prevents the growth of basement mold, mildew, and algae.
  • Reduces Cracking – Bonds and strengthens concrete, prevents rusting and expansion of rebar.
  • Concrete Hardener - Hardens the surface "flint-hard", basically eliminates dusting.
  • Neutralizes Alkalis - Ideal for fish ponds, kennels, and stables.
  • Deep-Cleans – Purges contaminants, minor oil spills, efflorescence, animal urine, and minerals.

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. RadonSeal chemically reacts with the free lime inside concrete and expands inside the capillaries. It forms a silicate mineral – the same mineral produced by the hydration of cement paste, which bonds, strengthens, and seals the concrete. Sealing with RadonSeal is like injecting portland cement into the pores in concrete. Simply, it results in a higher grade of concrete that is denser, stronger, and tighter.


Coverage depends greatly on the porosity and composition of the concrete. Concrete with larger pores or more alkalis consume more sealer. Cinder blocks are very porous and have the lowest coverage. On average, a typical basement (floor 800-1,000 sq. ft./poured foundation) would require TWO (2) 5-gal. pails to seal both the basement floor and foundation walls.

  • POURED WALLS – 2 applications will cover 1,000 sq. ft. (per 5-gal.)
  • CONCRETE FLOOR – 2 applications will cover 1,000 sq. ft. (per 5-gal.)
  • CONCRETE BLOCKS – 3 applications will cover 500 sq. ft. (per 5-gal.)
  • CINDER BLOCKS – 4 applications will cover 400 sq. ft. (per 5-gal.)


ECO-FRIENDLY – RadonSeal® is a user- and environment-friendly waterborne sealer formulated for an easy and safe application. Non-hazardous, ZERO VOCs with no fumes or noxious odors.

CONDITIONS – The concrete should be dry. After a heavy rain, let the concrete dry for 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 glass, aluminum, metals, tiles, and plants.

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

How To Safely Remove Efflorescence

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

1. Dampen The Concrete - use your sprayer, roller, or mop to dampen the concrete with water (breaks surface tension).

2. Apply RadonSeal In A Continuous Film – avoid puddles, do not overapply.

3. Apply A Second Application - 30 minutes later, while still damp, return to the beginning section and apply a second coat (concrete blocks require 3 applications).

The sprayed on film of RadonSeal should absorb within about 10 minutes (the surface still looks damp but there is no more gloss). If the concrete is unusually porous or alkaline, it will absorb very fast, letting you know that it badly needs more sealer – spray on another application. RadonSeal will not change the appearance or the profile of the concrete. It does not leave a surface film or color on the surface.

If you intend to paint the concrete floor, apply adhesive, epoxy, patching compounds, or surface levelers we advise you wash the concrete 2 hours after applying RadonSeal. Washing the concrete will ensure removal of any possible residue of the sealer.

4. Wash The Concrete Floor - Two hours after the final application, rinse the surface with water and lightly scrub with a push broom, shop vac or let dry.

RadonSeal will not change the appearance or the profile of the concrete. RadonSeal waterproofs concrete internally (2-4" inside) but does not make the surface water-repellent. The surface does not bead water and does not become slippery when wet. It will absorb water drops (it “wets”) but larger puddles will remain, because the concrete is waterproof.

Product Use

RadonSeal is not advised for use on fiber reinforced concrete, thin concrete floors (<2"), lightweight CMU's, splitface blocks, or "popcorn" blocks. It is most commonly applied to waterproof basements, foundation walls and floors, but also effective for sealing a wide range of cementicious materials (indoor or outdoor).

  • CONCRETE BLOCKSfoundation walls, retaining walls
  • CINDER BLOCKS outdoor or indoor
  • CONCRETE FLOORS – make dry damp concrete floors, sweating concrete
  • MORTAR – seal porous mortar in older stone foundations
  • LIMESTONE – building blocks, facades
  • STUCCO – applied over concrete

COMMON RESIDENTIAL USE: basement floors, basement walls, garage floors, retaining walls, driveways, pools, walkways, koi ponds.

COMMON COMMERCIAL USE: parking garage, concrete facade, sidewalks, industrial flooring, concrete structures, warehouse floors, cooling towers, water treatment plants, bridges.

Basement Health - Your First Step When Moving

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

Selling Your Home
Before putting the house on the market, RadonSeal all the concrete in your basement 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 can 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! 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. Sealing the concrete foundations 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 on RadonSeal Commercial Applications. Info for Builders and Contractors

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