My basement had multiple cracks (no comments about my builder's skills). This product stopped leaks completely. Now I can install drywall. I bought the crack repair kit on Amazon, but I needed more co... See more
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A reasonable and helpful company. They answered questions, and assisted finding right product. The product isn't cheap, not expensive either, but works as it should. They provide plenty of documenta... See more
The customer service over the phone was amazing. The gentleman I talked to walked me through all the products I had questions on for 45min. He did not try to upsale me and even talked me out of one of... See more
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Fantastic product and support. Especially happy with Mike, who patiently answered my questions on multiple occasions and helped me find the right product for my project. The concrete sealant for my... See more
Company details
Written by the company
It happens to thousands of homeowners each year – the sale of their home falls through because of high radon in their basement. They have to hustle to get a radon mitigation system installed and hope that the buyer will not walk away. But for many years after, they may wonder about the long-term effects of the radioactive gas on their children. Since radon gas seeps into basements from the ground, the US Environment Protection Agency had tested the obvious solutions back in the 1980's – caulking all cracks and sealing the concrete with various coatings but the improvements were not significant or lasting. Thus, the fan-based system which draws soil gases from underneath basement slabs became the standard. There had to be a better way! Novion Inc. was founded in 1987 to pursue innovative high-tech solutions. Penetrating concrete sealers, already well-proven for waterproofing concrete on major projects, seal concrete internally and permanently. Perhaps, they could be improved to penetrate deeper and seal even tighter to keep out the single-atom radon gas. After extensive research and testing, the first concrete sealer specifically developed to reduce radon infiltration through concrete was ready for the big debut – RadonSeal® Deep-Penetrating Concrete Sealer. Novion Inc. was incorporated in Connecticut and RadonSeal was made available directly to homeowners and contractors on radonseal.com website. Subsequently, we have continued to add unique innovative products, not available in stores, for basements, indoor or outdoor concrete, bricks, pavers, and masonry. Going beyond radon remediation, we provide durable and cost-effective solutions for waterproofing basements, sealing concrete slabs against vapor, and mold remediation. Our products also protect and beautify indoor or outdoor concrete, pavers, and masonry. Our mission is to supply cutting-edge, professional-grade, and environment-friendly products, superior to those sold in stores. Our customer support offers technical expertise and objective guidance on the best solutions for customers' needs. Whether you are a homeowner, contractor, or building owner, we will provide the top-quality products and service to solve or prevent problems with your basement, parking lot, pool deck, brick or masonry walls. It can be just a matter of time before your basement or outdoor concrete starts giving you problems. Act now and give us a call. We are here to help!
Written by the company
Contact info
494 Bridgeport Ave, Ste 101336, 06484-4748, Shelton, United States
- 203 225-0366
- admin@radonseal.com
- radonseal.com
4.6
Excellent
2K reviews
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This company invites their customers to review, whether positive or negative
Replied to 36% of negative reviews
Typically replies within 24 hours
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Radon seal DIY crack repair kit is…
Radon seal DIY crack repair kit is worth the money. I have used it many times over the last four years and each time it has seal stopped the foundation water leaks dead in it’s tracks. Also this company has great customer service. If you have questions you can call them and they’re happy to help guide you through. I highly recommend this product and company.
22 December 2025
I ordered lastiseal
I ordered lastiseal. Transaction was seamless. Delivery straightforward and timely. Online instructional PDFS were a big help as were the detailed explanation regarding exactly how the sealant works and what to expect in terms of appearance and performance.
22 December 2025
Products fine, shipping was the problem
Was hoping to have this issue fixed this week but after multiple “operational delays” by FedEx the package didnt show up until Friday night after business hours. Package was out for delivery 3 days before it finally arrived. Making me look like an a**hole telling my customer “its being delivered today and I should be able to finish up tomorrow… “ only to get package delayed messages when I get home.
1 December 2025
The kit had more included than I could…
The kit had more included than I could imagine. Instructions were clear and all worked as described!
15 October 2025
Great Product, Great Delivery
My basement had multiple cracks (no comments about my builder's skills). This product stopped leaks completely. Now I can install drywall. I bought the crack repair kit on Amazon, but I needed more compound. I ordered it directly from the RadonSeal website on Sunday, and it arrived on Tuesday. This seller does care about customers.
17 November 2025
Purchased the CrackWeld 2 pk
Purchased the CrackWeld 2 pk. floor repair kit and absolutely LOVED this product. Arrived in a few days, the instructions were easy to follow and the product was a lot easier to work with than expected. Dries quick & harder than concrete! It's a bit expensive, but worth the money.
11 November 2025
Phone Order - Rep Advice
ordering by phone was quick and the rep was able to answer my questions to make sure I was ordering the right sealant
13 November 2025
..........
3 November 2025
A reasonable and helpful company
A reasonable and helpful company. They answered questions, and assisted finding right product. The product isn't cheap, not expensive either, but works as it should. They provide plenty of documentation, but experience is crucial. Good company and I will work with them again as needed. Highly recommend products and service.
7 November 2025
One cartridge had leaked in bag and…
One cartridge had leaked in bag and only got 1/2 contents usable, did not fill 3.5 crack with all four tubes, has to order more, pricey
27 October 2025
Fast delivery of (5-gal) concrete…
Fast delivery of (5-gal) concrete penetrating sealer. Good consultation from Patrick at RadonSeal.
29 October 2025
I had some questions
I had some questions, he answered them without a problem. He was courteous and polite. He explained the different and economic ways to order your product. Thank him for us.
29 October 2025
White Spots Remained.
I used the product on my patio per the instructions. After the product dried it left white patches and looked terrible. I contacted the manufacturer and they suggested using an Etcher to remove the effervescence. The Etcher and scrubbing with a broom did not work. The radonseal was expensive and doesn't look good. It required extra expense, time and work. The result is not satisfactory and I would not recommend the product.
26 October 2025
Unprompted review
Reply from RadonSeal
Good Afternoon,
We are truly sorry to hear about your experience!
The purging of efflorescence is not a common occurrence, but it can happen on certain concrete. As we note in our documentation, RadonSeal can “clean” the concrete by drawing out efflorescence and salts from within.
This purging process is actually beneficial, especially for customers planning to apply epoxy, coatings, stains, or paint afterward. Pulling sub-efflorescence and impurities to the surface, it helps prevent them from becoming trapped beneath paint, epoxy, and future coatings, where they could later cause damage.
In the majority of cases, if the residue is efflorescence, it should dissolve easily with a concrete etcher.
A few possible factors could also contribute to what you’re seeing; for example, if the concrete had been sealed previously, or if it’s new concrete that was treated with a curing agent. Either situation can affect deep absorption and can create a buildup of the sealer on the surface.
Any penetrating sealer can cause mild discoloration if the surface does not absorb the product evenly. This is why we always recommend spot testing before treating the entire surface. Concrete varies greatly, so testing ensures compatibility and helps confirm proper absorption before full application.
That said, we would like to continue to help you get this resolved. Please contact us between 9-5 pm EST or email us at admin@radonseal.com
We truly appreciate your understanding and cooperation.
Product Info: https://www.radonseal.com/product/radonseal-standard-concrete-sealer/
FAQ (PDF): https://www.radonseal.com/wp-content/uploads/2024/03/RadonSeal-FAQ.pdf
Kind Regards,
-----------------
Patrick
Product Tech
RadonSeal
The rep I worked with went out of their…
The rep I worked with went out of their way to ensure that my product arrived in time for application in our new build schedule.
14 October 2025
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