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.

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! Once cured, it will seal your concrete permanently against water seepage, efflorescence, moisture, water vapor, and even radon gas.

Use radonseal to waterproof a damp basement

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

Unlike common sealers (coatings) and waterproofing paints sold in big box stores, RadonSeal will never peel, delaminate, or wear away. It cannot be pushed out from inside the pores regardless of hydrostatic pressure! The seal becomes integral to the concrete itself – never needing to reapplied again. RadonSeal makes the concrete denser and stronger.

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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, Sears, and Rakuten.

RadonSeal® Standard and Plus Concrete Sealers
RadonSeal pail Item Size Price Shipping  
RadonSeal® Standard 5-gal.   $149
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2.5-gal. $89 $12 Order Now button
RadonSeal® Plus 5-gal.   $169
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2.5-gal. $99 $12 Order Now button

SHIPPING - RadonSeal is not sold in stores. RadonSeal is shipped directly from the factory to your door (via UPS® or FedEx® Ground). Orders received by 2 pm ET are normally shipped the same day and delivered within 1–5 working days to the lower 48 states. EXPEDITED SHIPPING - In order to expedite shipping or when shipping to other states (AK, HI) please inquire first by email or phone before placing your order. RETURNS - Unopened pails in salable condition are returnable. Please review our Commercial Terms.

CANADIAN ORDERS - RadonSeal® can be purchased through ECO Building Resource, Aurora, ONT (905)-841-3535.

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

Choose RadonSeal Standard or RadonSeal Plus

STANDARD– RadonSeal® Standard is recommended for use on indoor poured concrete (basement floor and walls, foundation slabs) less than 20 years old. Use on outdoor concrete (driveways, walls, sidewalks, rooftops, decks) less than 2 years old.

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


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

Coverage rate varies and depends greatly on the porosity and composition of the concrete. Concrete with larger pores or more alkalis consume more sealer. Cinder blocks are exteremely porous and have the lowest coverage.

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

For example, a typical basement (floor 800-1,000 sq. ft., 8' poured concrete walls) would need TWO (2) 5-gallon pails to cover both the floor and foundation walls. A typical basement with concrete block walls needs THREE pails of RadonSeal.

Product Use

If you are having trouble choosing the correct sealer please visit our Sealer Guide.

RadonSeal 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 take the time to review the RadonSeal Detailed Instruction & Sealing Various Cementitious Materials

  • POURED CONCRETENew or old, basement walls, building facades, fish/koi ponds, retaining walls, seawalls.
  • CONCRETE BLOCKSInside/outside foundation walls.
  • CINDER BLOCKS* Basement walls.
  • CONCRETE SLABS – Basement floors, garage slabs, carports, driveways, commerical sidewalks, curbs, parking lots.
  • MORTAR – Porous mortar in older stone foundations.
  • LIMESTONE – Walls, floors, building blocks, facades, interior, exterior.
  • STUCCO – Porous stucco applied over concrete.

LIMITATIONS - Stone/rock, lightweight CMU's, splitface blocks (low cement content), or "popcorn" blocks (very large pores), stamped concrete, stained concrete.

COMMON RESIDENTIAL USE: Basement floors, basement walls, driveways, patios.

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

Reduce Humidity, Efflorescence, Dusting, and Radon

Your Damp Basement Solution! – RadonSeal is the strongest silicate-based sealer that penetrates deeper, carries more active minerals, and seals tighter than any other concrete sealer. The penetration does not depend on gravity – the sealer is also used on walls and ceilings (penetrates by capillary action). 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 to the outside, it has the added advantage of preserving the exterior of the concrete and extending the life of the waterproofing coating by protecting against saponification.

Use Before Painting or Installing Flooring – RadonSeal protects concrete against wicking water, efflorescence, and the "alkali attack." It is often used by flooring contractors as a concrete primer. RadonSeal is recommended for sealing concrete before applying paints, adhesives, epoxy or urethane coatings, "wet-look" sealers, concrete overlays, surface levelers, and moisture sensitive flooring. It does not form a film and does not change the appearance or surface profile of the concrete. RadonSeal prevents wicking water or water vapor from pushing off or cracking the coating.

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 - Restricts the infiltration of radon gas.
  • Mold Remediation – Prevents the growth of basement mold, mildew, and algae.
  • Reduces Cracking – Bonds and strengthens concrete, prevents the 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, old efflorescence, and animal urine from inside the concrete.

What Are People Saying ...


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 inside. 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, 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 machine-troweled very hard, you have to improve the surface porosity by acid etching or concrete grinding.

How To Safely Remove Efflorescence

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

The sprayed on layer of RadonSeal 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 or let dry. Washing the concrete will ensure removal of any unabsorbed sealer which would leave glassy or whitish areas. And it will ensure that the surface remains porous for painting, coating, adhesives, and surface levelers. If needed, remove any purged efflorescence or contaminants in a couple days.

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 – the same mineral produced by the hydration of cement paste that holds concrete together. 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.

RadonSeal will not change the appearance or the profile of the concrete. RadonSeal waterproofs concrete internally but it does not make the surface water-repellent. The surface will 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.

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

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.