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Sealing Damp Basements and Floors against Moisture and Molds

Customers’ Feedback and Tips

Problem: High Humidity, Musty Smell, Dehumidifier Products Used: RadonSeal Concrete Sealer

“Just wanted to send a quick note on how impressed I was with the RadonSeal product.  We bought a new home that had the basement already finished.  Unfortunately, the relative humidity in the basement rooms would constantly hover between low 60% to high 70%.  The rooms acquired a definite “musty smell” especially when they had been closed up.  We bought a heavy duty dehumidifier that would handle 70 pints per day, and the poor machine worked endlessly to hold the humidity level to 50%. After finding your website, (one of the most useful websites I have come across), I reluctantly decided to pull up the carpet and purchase your RadonSeal Standard for the concrete floors. Wow what a difference!!!! – – –  Since applying the RadonSeal on any exposed poured concrete wall that wasn’t finished and the entire concrete floor, the relative humidity is holding at 44 to 46% without the use of the dehumidifier!  I’m sold! I’ll be sure to recommend your product to anyone that has a similar problem. By the way, thanks for your patience in answering my other questions when I called back about sealing large cracks, sealing around the area between the wall/floor, etc.  Your customer service is as good as your product and that’s saying a lot! Thanks again” – Jim M., GA


Problem: Crumbling Basement Walls, Mildew, Basement Smell Products Used: RadonSeal Concrete Sealer

“As for the “amazing results” on our 100 year old basement walls … before RadonSeal, our walls were literally crumbling, the basement smelled terrible and there was mildew everywhere. We stripped the paint off the walls in the main room, sprayed on the RadonSeal Plus and have had no crumbling or water related problems for over 3 years. We just ordered another pail of the RadonSeal Plus to finish 3 smaller rooms in the basement before we sell the home. Based on our experience in the main room of our basement, we know sealing up the remaining walls with RadonSeal will help us sell our home because the basement will look and smell better.” – Cathleen B., ME


Problem: Moisture, Mildew, Dehumidifier Products Used: RadonSeal Concrete Sealer

“Living near the ocean has caused major moisture and mildew problems in my basement. With my dehumidifier going full time I was still having a problem. After some research I decided to give Radon Seal a try. This was the best decision I’ve made in some time. After purchasing ten gallons, following your prep rules to the letter and applying two coats, the change was amazing. Within two days I was noticing a change. After two weeks my humidity index was reading a constant 35 to 40 percent. Thanks for offering such an excellent product.” – Jim H., RI



Problem: Damp Concrete, Musty Smell, Molds Products Used: RadonSeal Concrete Sealer

“My basement is poured concrete from 1910. The walls are 14″. The basement had very high humidity, with damp spots on the walls and floor, and was always musty and moldy. My wife complained regularly about the smell in our house that was coming from the basement.
We excavated, put in weeping tile, insulated, and waterproofed from the outside, but the musty smell and mold was still there along with damp spots on the walls, and floor. This cost us $10,000. I ordered 2 pails of Radon Seal Plus, and applied them. I am completely impressed with it’s performance. The basement is very dry now. The musty mold smells are gone, and I am finally going to finish the basement. Thank you RadonSeal!” – D.D., Grand Portage, MN


Problem: Damp Basement Products Used: RadonSeal Concrete Sealer

Incredible Results
“Amazing product, I wondered how it would perform as it isn’t widely known/advertised. The product was applied as directed and made an immediate impact in my damp basement. Couldn’t be happier – and more dry!” – Jason in Baltimore, Trustpilot review


Problem: Dampness, Mold and Mildew, Radon Products Used: RadonSeal Concrete Sealer

“I am finishing my basement and had great concerns about damp basement air, mold and mildew, and of course radon. Particularly, since we have a newborn in the house. When I received RadonSeal, I was skeptical of its effectiveness like any customer would be. I found it quick and easy to apply. Before I knew it, I was done with two applications. I was concerned about fumes because of my newborn, but there really weren’t any. My radon is now very low and the basement feels dry. I did have a water spillage on the floor recently and noticed the water did not penetrate or absorb, it just stayed there until I wiped it off. I do not have to worry about damp basement anymore thanks to RadonSeal! P.S. I will now recommend RadonSeal to all my friends and neighbors”. – Mark W., MA


Problem: Moisture Spots Basement Floor, Garage, Condensation Products Used: RadonSeal Concrete Sealer

“My house is 59 years old. I have lived in it 19 years. It always has had moisture spots show up on the basement floor as well as the garage floor. This year in North Carolina it rained the majority of days in the last 2 months, so the problem got worse. I Googled in hopes of finding a solution, when I found Radon Seal Plus. Being the skeptic I am, I usually want to be shown before I pay, but I couldn’t argue with a guaranteed product. I purchased the 5 gallon pail, prepared the surface according the the well-written instructions; and to my delight it covered both the 1000 sq. basement, plus double-car garage floor with 2 coats. By that night I already could “feel” the difference in just how dry the air was in both places where I applied it; because the dampness was no longer coming through the concrete. After checking the next day….and ever since, the floors stay very dry. My garage no longer has condensation problems either. This product proved itself to be ‘tried and true’. I am a female, and if I can easily use it with great results, so can anyone else. Thank you Radon Seal Plus, you made me a happy home camper. With appreciation” – Susan K., NC


Problem: Damp Basement, Remodeling Products Used: RadonSeal Concrete Sealer

“My basement was basically a big open concrete slab floor and block wall room. There had been a bit of minor water damage/seepage but no apparent major flooding. I did a little research on the Net and found a product called RadonSeal (www. ). It’s a liquid sealer that is sprayed on concrete that soaks into the block and dries to form a plastic-like barrier. I bought 2 5-gal buckets and sprayed the hell out of my basement before I started any remodeling. I could immediately feel a difference in the dampness in the air. Within a day or so, the dehumidifier I have was extracting less than 1/4 of the moisture it had before. I put 3-4 coats on the block walls and 3-4 coats on the slab floor. It works like a charm.” – Pat McD., OH


Problem: Damp Basement, Musty Odor, Allergic Children Products Used: RadonSeal Concrete Sealer

“I have always had a musty and damp basement and having two very allergic young children to mold and mildew this worried me. In NJ we have had tremendous rainfall this past season and I knew I had to do something quick. I applied your Radon seal on the cinder block as directed and have not had any dampness in the basement anymore. I cannot thank you enough for having a product that says what it does. Your service was excellent and very patient in answering all my concrete questions before helping me place my order.” – Ken L., Edison, NJ


Problem: Dampness, Musty Odor, Cracks Products Used: RadonSeal Concrete Sealer & Diy Foundation Repair Kit

“Want to let you know that the Radonseal penetrating sealer you sold me has done a great job! The basement is noticeably less damp, the musty smell is nearly gone, and the leaking hairline floor slab cracks are no longer wet. I also used your crack injection sealer and it completely stopped rainwater leakage from the crack in my 10 inch thick poured basement wall. I really commend your attempt to keep your products user friendly while developing materials that tackle so many difficult concrete challenges. Rarely have I found such an instructive and insightful website. I have already recommended your products to several other friends based on the immediate successes I have had.” – Hugh B., NY


Problem: Nasty Pungent Odor Products Used: RadonSeal Concrete Sealer

“I purchased RadonSeal to prevent moisture build-up in my finished basement, but I ended up with a very pleasant surprise. Last year, we purchased a 28 year house in rapid decline and went about restoring it.  We found & repaired several issues with the foundation, but a nasty smell remained. As it was a daylight basement, we opened the windows and “aired out” the basement every chance we could, but the smell remained, even 6 months later. Even so, we still planned to finish the basement. Not giving it much thought, I bought RadonSeal as prevention for Radon and to prevent moisture buildup between the foundation and finished walls. However, the next day we went downstairs and like magic – that mildew smell for months?? GONE!! Completely and totally gone!! We had contractors and family all helping during the restoration – everyone knew about the ‘bad smell’ in the basement to the point of questioning why we wanted to finish it. NO ONE could believe the immediate change. I am happy to say, the basement has been finished for almost 1 year now and we have had no problems with moisture, radon, or that nasty, musty smell.  I was so happy I am buying more to use in my newly built garage as a floor primer before I put down the epoxy covering. I am very happy – and would be a reference to anyone considering using it! Thank YOU!” – R.W., Olathe, KS


Problem: Musty Smell, Mildew, Vinyl Tiles Products Used: RadonSeal Concrete Sealer

“Several years ago, I applied your Radonseal to a portion of my basement to create a pantry area for food, clothing and valuables. While my basement had never leaked, the constant flow of moisture vapor through the floor caused that well known musty/concrete smell and mildew to form on anything stored for long. After letting RadonSeal set for a few weeks, I covered the floor with linoleum tile using standard mastic. I’m happy to report that after over 8 years, the pantry has been dry clean with no musty smell or mildew on anything stored there. The tiles have stayed absolutely flat and secure and bone dry. As a guy who is very skeptical of product claims, I’ve verified it works, and works very well. Thanks for making a great product, and one that gives the added (and even more important) benefit of blocking dangerous radon gas.” – Chris H., NH


Problem: Damp Foundation, Spalling, Musty Odor, Painted Products Used: RadonSeal Concrete Sealer

“I used RadonSeal Plus to waterproof small areas of my poured concrete foundation that were damp, spalling and causing a musty odor in the basement. The house was built in 1933 and the walls were originally painted with calcimine then CalciCoater. There are bare spots where the moisture has lifted the paint. I poured RadonSeal into a bucket and used a paintbrush to cover the bare areas with excellent results. There is no sign of spalling or moisture and the odor is gone. I found RadonSeal easy to use and I was pleased that it was non-toxic and environmentally safe. Thank you for such a fine product.” – Susan D., MA


Problem: Dampness, Moldy Smell in Carpeted Media Room Products Used: RadonSeal Concrete Sealer

“I have a 30 yr old contemporary house with a poured concrete foundation and basement floor. One corner of the basement contains a finished study/media room with a carpet and pad directly on the concrete floor. The room always had a strong smell of mold and dampness. My wife would not watch TV or listen to the stereo in this room! I found RadonSeal via a web search and was impressed by the content and completeness of the web site. The user comments seemed to be genuine, unlike some other sites I have encountered. Deciding that the product seemed to be worth a try, I placed an order for Radon Seal Plus. I then removed the old carpet and pad from the room and discarded them. After scraping and grinding off most of the old carpet adhesive, I applied the Radon Seal Plus and then, had a new carpet and pad installed. After 8 months, including a lot of wet summer weather, there is no evidence of any damp or moldy smell in this room – this product really does work as advertised!” – Mark S., MA


Problem: Damp Spots, Musty Smell, Dehumidifier Products Used: RadonSeal Concrete Sealer

“I sealed my entire basement. I am very impressed! Radonseal has done a wonderful job on the moisture problem. I have a dehumidifier and it doesn’t even run any more. Before radonseal the basement smelled damp and had water spots. Now it doesn’t smell musty or have any water at all. It is nice and dry! Thanks so much for Radonseal!” – Sincerely, Karmen K., MI


Problem: Moisture, Basement Smells Products Used: RadonSeal Concrete Sealer

“Hello – Thank you for making this product available. Our basement smells clean and fresh now, after all the scrubbing and applying coats of Radonseal, and the surface seems harder and truly SEALED. We are using Radonseal to seal out moisture (not radon) which is our big problem in the northwest. The rainy season is just beginning here so I’ll let you know now it works as the winter goes on. P.S. Building codes should require this type of treatment on all new concrete and blocks, if prevention of problems was considered important.”


Problem: Damp Basement Walls, Musty Odor Products Used: RadonSeal Concrete Sealer

“Just wanted to let you know that the Radonseal product solved my basement dampness problem better than I expected. Our new home in Pike County, PA doesn’t have gutters installed yet and all the rain of the past few weeks left large puddles all around the foundation. Before I applied Radonseal the basement walls were very damp. You could actually feel and smell the dampness. A few weeks after I applied the two coats of Radonseal I noticed that not only had the dampness on the walls disappeared, but the musty odor was gone. I have a few gallons left over and plan to apply it to the inside of the garage too. This is a great product!” – Frank D., VT


Problem: Prep for Finishing a Basement Products Used: RadonSeal Concrete Sealer

“My wife and I decided to finish our basement and we wanted to seal it first. After much research, I chose your RadonSeal Plus. My contractor is glad I did. He will be recommending this product to all his future clients! It’s easy to apply and has no odor. It’s safe! We have a small child, another one on the way, and pets. The product’s qualities were very important to us. It’s user friendly, environmentally safe, seals out water and gases, prevents mold, and has a 20 year guarantee! You certainly cannot ask for more in a product and we are extremely happy with it.” – Frank H., CT


Problem: High Humidity in House, Finishing Basement Products Used: RadonSeal Concrete Sealer

“It has been several months now since I used the RadonSeal Plus in my basement and I can’t even begin to tell you how happy I am with the results! At first, it started as a project to just keep the humidity down in my house, but after I have experienced such great results, I am finishing out my basement the way I always wanted it. I owe it all to the team at RadonSeal. Thanks again, I will be sure to recommend your sealer to all my friends.” – Eric S., IL


Problem: Moisture, Crumbling Concrete Walls Products Used: RadonSeal Concrete Sealer

“I just wanted to send an email to thank you for your wonderful product and service. I had a huge problem with moisture and crumbling walls in my 100 year old poured concrete basement. I purchased the radon seal plus, applied it to my walls and have had no moisture or crumbling since the application (and it has been raining for days here!!) Your staff was VERY helpful and responsive to all of my questions and I really appreciate that. Thanks again!” – Bethany B., IN


Problem: High Humidity, Concrete Dusting Products Used: RadonSeal Concrete Sealer

“Application went easily and the coverage was just as advertised – covered an approximate 1,500 square foot, year old basement floor at two coats with less than 8 gallons. Purchased Radonseal to hopefully reduce basement humidity as well as eliminate dusting. Living in wetlands the basement has required a dehumidifier operating year round – basement humidity without de-humidification was close to 70%. Since applying the sealer humidity has dropped greatly and the dehumidifier runs much less. Basement floor even looks better, more ‘finished’ looking – and no dust. Purchased more to do the basement walls (hoping to lower humidity even more) and the garage floor (dust). Good product, fast delivery.” – Tom H., CT


Problem: Damp Garage, Radon Products Used: RadonSeal Concrete Sealer

“RadonSeal is Awesome!
Applied RadonSeal Plus per instructions to my garage concrete floor and concrete block walls. Radon levels cut to less than half and improving as time goes on, just like it says in the instructions. Moisture levels and humidity in my garage have been greatly reduced. Thank you RadonSeal!” – Ryan, Trustpilot review


Problem: Damp Basement Products Used: RadonSeal Concrete Sealer

“I’m writing this to let you know that I’m pleased with Radon seal that you advised. Your customer service was very helpful and knowledgeable, a great assistance in choosing the product for my damp basement that I needed. I’m a former building contactor and having been referenced by other contractors to your product. I had some concrete work done earlier this year and had some concerns and your service staff gave me the advice that I was looking for I must have called three or four times and each time gave me a knowledgeable answer to my concerns. I feel your product not only addressed all concerns, it is as advertised. I wish you continued success, as I’m ordering another of your products today” – Paul C., Omaha Nebr. 

Problem: Damp Basement Wall, Flower Box Products Used: RadonSeal Concrete Sealer

“My clients had received a bid to tear out the entire wall, dig out the flower box (which had been retaining the most of the water from the daily watering), then apply a backer board over the outside wall and use some “Yellow Jacket” product… To say the least they gave me a call, I went over to assess the area. There were no serious molding issues, but it wouldn’t be long. So I took on the job, cleared out the planter box against the outside wall, wire brushed it, scrubbed it, let it dry for two days then applied several coats over the course of a few days. Before I put the dirt back, I drenched the wall. The results … seeing was believing! Save them a ton of money!!!! God Bless” – Scott, WI


Surface: Slab-on-Grade, Harwood Floors, Seepage Products Used: LastiSeal Brick & Masonry Sealer

“We had engineered hardwood floors laid over our entire house, except kitchen and bathrooms when we moved into this house 1 year and a half ago. Last summer I noticed some water bubbling through the floors. When my husband started pulling the floor up we saw the floor had molded from underneath…. Don’t go with a product from Lowe’s – LastiSeal Masonry & Brick Sealer by RadonSeal is the best concrete and masonry sealer there is PEROID – it penetrates very deep and closes up all the concrete’s capillaries. My parents had a concrete problem and I did tons of research as to the sealer that would work the best and I found LastiSeal and can’t say enough positive things about it. It can’t be found in stores, but there is tons of information about it on website.”
– forum on
engineered flooring


Problem: Efflorescence, Musty Smell, Laminate Flooring Products Used: RadonSeal Concrete Sealer

“We would like to thank you for your great product and service. We planned to finish our basement with laminate floors. But we heard a lot of stories about the problems of laminate flooring “peaking” due to excessive moisture in the basement. Although our basement is only two years old, the “white powder” could be seen on some walls, and it always smelled musty when we went to basement. Before finishing it, we applied RadonSeal Plus to the entire basement. Now it has been two months, there is no more “white powder” coming out from walls and there is no more concrete smell. Thanks!” – Cheryl X., IL


Problem: Condensation in Crawlspace, Mold on Joists Products Used: RadonSeal, LastiSeal, BioZap

“Thank you so much for such  quality products. My crawlspace wasn’t encapsulated & moisture barrier not applied 100%. Some the ductwork had condensation and mold was noted on the floor joists. After much research, I decided to use your products. The RadonSeal Plus was suggested for my cinderblock foundation areas, Lastiseal for the brick areas & BioZap for the mold removal and future prevention. The application process for the RasonSeal and Lastiseal almost sounded too good to be true (using a garden sprayer) but I was pleasantly surprised. The BioZap is also working well to remove the mold and I am spraying the areas for prevention of further mold. Doing most of this work ourselves has paid for the products. We hope sealing the foundation with your products and doing the other things will eliminate the need for a dehumidifier, which my husband did not want. I have already been recommending your products to others.” – Sylvia B., NC


Problem: Crumbling Mortar Joints, Musty Odor, Efflorescence Products Used: RadonSeal Concrete Sealer

“RadonSeal works really nice. My mortar joints have gone from crumbling to solid, my floor has gone from damp to dry, the musty odor is gone, and piles of minerals have been exorcised from the walls and floor. I’m going to use it also on the exterior of my foundation to seal it up nice and tight. Excellent product!” – Paul D., Manitoba


Problem: Condensation on Concrete Floor Products Used: RadonSeal Concrete Sealer

“I have applied the radon sealer couple years ago. The floor in my shop used to get wet from condensation every spring. It has worked GREAT! I have a dry floor year round – thank you.” – Rick R., Grand Rapids, MN


Problem: Sweating Garage Floor, Moldy Walls Products Used: RadonSeal Concrete Sealer

“I have lived in my present home for 10 years. For some reason my garage floor recently started to sweat. I found out about Radon Seal on the internet and ordered a 5 gallon pail. In Arkansas the humidity is always very high and I was having a moisture problem in my garage. The walls were starting to show signs of mold and the floor was very wet on certain days. After I used Radon Seal (about 2 months ago) I have had “no” problem with moisture. I have cleaned the walls for mold and repainted my garage. It looks just like it did when the house was new.
Your product works great and I am so glad! Thank you.” – Robert A., AR


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