Sealing Basement Floors

Basement floors can be a problem to live with and to finish if you have moisture problems. There are several ways of dealing with the moisture, including filling cracked basement floors, sealing the basement floors, using a dehumidifier and/or sump pump, and laying moisture barriers for basement floors — prior to installing your flooring choice.


Sealing basement floors is very important. Although most people may think that it is unnecessary because there is carpet or other flooring covering it, sealing your concrete or cement basement floors can prevent mold and mildew from developing and can help your flooring to last longer. Basement floors are especially susceptible to moisture because they are underground and the concrete is directly touching the dirt. Unsealed concrete will act like a sponge and wick water into the basement, and this can cause various problems in your home, including mold, mildew.


A large percentage of homes may have a water problem in their basement and the inhabitants may not even realize it! Mold, algae, and mildew growth can cause health problems for all the members of your family and can even cause death if a person is exposed to it for a long period of time. This is why it is of utmost importance to seal your basement floors to make sure that this will not be a factor in your home.

How does water enter your basement? There are a few different ways. Cracked basement floors are one of the ways that water can get into your basement. Water can be moved into your basement through your concrete floors if they are not sealed. Humidity could also cause a moisture problem in your basement. The first thing to do is to make sure that as much water as possible is moved away from your home via French drains, gutters, grading, filling cracks, and drains. Dehumidifiers and sump pumps can be invaluable in some areas to further keep moisture at bay. Then you will be ready to learn how to seal basement floors and walls to keep your basement moisture, mildew, mold, and algae free.

Seal your basement floors and walls to keep water from the ground soaking into the concrete. There are many different options for sealing basement floors. Read the instructions on the sealant that you choose to make sure that you know how to seal your basement floor and to ensure that it will work just as it is designed to. Applying the sealant as directed will help your floors to be dry and mold, mildew, and algae free for years.

Sealing your basement floors will also help your flooring to last a long time. This way you will be able to put down any flooring that you choose without having to worry about it being damaged by moisture or water. There are also moisture barriers for basement floors that are available for use in addition to sealing the basement floors. Using both methods will allow you to have peace of mind in putting down your new flooring.

If you are having moisture problems in your basement, you will want to take up the existing flooring to try to determine where the moisture is coming into your basement. If you have more than hairline cracks, then you will want to mix up some mortar to fill the cracks. Make sure that all cracks are filled before you seal the floor. If there are not any cracks, then moisture may be coming from the ground underneath your flooring. Applying a sealant will definitely help if this is the case.

Sealing basement floors is a way to take care of your health by preventing mold, mildew, and algae and will help your flooring that you lay down over your concrete to last much longer. Keep the moisture and water away from your basement by sealing your concrete basement floors to help your health and your flooring budget!

77 thoughts on “Sealing Basement Floors

  1. basement floor has been lightly painted years ago. Inspector when we moved in said it had water underneath. We have used a dehumifier and get lots of water. We put in heat. How can we seal the floor?

  2. If you are getting that much water from the air, and the concrete is showing evidence of water, you may need to do more than seal the floor. You may need to look into a sump pump or French drain to remove water from the area.
    Once you have the water problem fixed you can seal the floor using any number of available products.

  3. I have a new concrete patio. it is a fully covered patio that should not get wet. it is about 15×26 in size.
    The problem that I am having is that I am finding myeslf going out onto this patio with my socks on to bbq and find my socks soaking wet…. I kept thinking “how can this be, it’s covered!”
    Is it possible that this slap is wicking up water throug it from underneath? How do I put a stop this? thank you

  4. You didn’t mention what the weather was when your socks were getting soaking wet. Yes, concrete can absorb ground water and get damp, or even wet. But even covered patios can get wet when it rains, if there is any wind (I speak from experience).
    Options I see you have include:
    * retrofitting a French Drain around the edge of the patio — expensive
    * install a “flooring” on top of the concrete that will keep you away from the damp concrete but will let the moisture evaporate so it won’t cause mold — the flooring could be a lattice, raised teak, or some outdoor-proof wood
    * lay Raven Industries vapor barrier on the concrete and install brick or stone for a new floor look
    * don’t wear your socks outside — either take them off or put shoes on ;~> Just kidding; you really want to use the patio any time and with any footwear.
    Let us know what you did.

  5. I have a concrete basement floor that had been tiled, the tiles were glued down. We’re removing the tiles and planning on installing carpet. I was thinking of sealing the concrete first. I have already cleaned the floor with heavy-duty cleaner, but the glue is still there. My question is, can I apply a sealer over the glue, or do I have to somehow figure out how to remove the glue before sealing the floor?

  6. My thought is that sealing the glue just adheres it one more time/way to the concrete. That doesn’t seem like such a big deal to me. The reaction I have though is that your carpet is going to be lumpy. Does that matter to you?
    And why are you sealing the concrete — is it for moisture proofing the space?

  7. Thank you for your reply. I don’t think the carpet will be lumpy because the glue is pretty thin, and we are putting down a high end pad. I want to seal the floor because I noticed a very slight musty odor that I believe is coming from the floor. It is barely detectable. I did a moisture test (with saran wrap and tape) and no condensation appeared, so I don’t think I have a serious moisture problem. I just want to be sure the floor is sealed so we don’t develop problems with the carpet in the future. So do you think it is ok to go ahead an apply the sealant over the glue? Is there a brand you recommend?

  8. Glad to hear you’re putting quality padding down. That will help the life of the carpet.
    That musty odor is indeed telling you something about the humidity in the basement. In addition to sealing the floor you may want a de-humidifier so you don’t have poor air quality or mold.
    Why don’t you visit my article on vapor barrier paint to see if you get ideas for your floor sealing. And yes, I think it’ll be fine. At least I don’t see any reason to not seal over the glue with what I know today.

  9. I am going to be putting a ceramic tile floor in our basement in front or our french doors. The rest of the floor will be carpeted. Do I need to put something under the tile or can it go directly on the cement? Also, if I do this now (upstate NY~cold) will it adhere properly?

  10. You don’t need to put anything like vapor barrier, if that’s what you are asking about. And if the basement is heated the floor temperature should be fine, though the ground is cold so the curing period may be a bit longer.
    If you want to insulate the floor before tiling and carpeting there are several ways to do that. You can read about them on this site. It’s a good idea, in my opinion, to insulate the floor to keep you and your feet warm when using the space.

  11. we have a store room in our basement and we noticed some moisture problems in that room so we sealed the floor with radon loc. We then laid tile and grouted the floor. In a few areas the grout isn’t drying, does this tell me that we still have a moisture problem. Note after we sealed the floor with two of their sealers we let the floor dry out for about a month before we tiled.

  12. I agree with your assessment that you seem to still have a moisture problem. The question is where the moisture source is coming from.
    I trust you followed the directions of the two products for the two different coats you applied. Did you conduct another moisture test before you laid the tile?
    Is water/moisture coming in from the side, like an adjacent space through the basement wall? Is there a drip from above?
    Have you tried putting a space heater in there to raise the temperature of the room to help the grout dry? What about a dehumidifier to help too?

  13. I recently noticed that a musty smell in my basement (formerly garage) and when barefoot, the carpet feels damp. The house is a 40-year old split level w/ a heat pump, so of course it’s always cooler down there. I plan to get a dehumidifier in a couple of days and was thinking about pulling up the carpet and using a sealer, then underlayment on the concrete floor to help w/ the moisture. Am I on the right track or would that be overkill? Thanks.

  14. When it comes to harboring mold, which your basement is or will be doing soon, you can’t be too careful. In addition to removing the carpet and padding, you need to find the water source. You could have a rising water table or it could be as simple as a leaking water heater.
    Read my articles on Moisture Proofing floors to help guide you in your basement reflooring. You don’t want to have water issues contribute to health issues, much less construction issues.

  15. I live in a condo that is on the first floor built over a concrete slab. A few years ago, I installed Pergo flooring in the kitchen, and within 6 months it began “lifting”. I now want to replace my carpeting in the living and dining areas, and replace the kitchen flooring. If I seal the concrete, will this solve my moisture problem? I also just purchased a dehumidifier as well? I would appreciate any advice!

  16. I’m gathering you glued your Pergo down instead of floating it. You want to check for efflorescence which looks like a white powder on the concrete; that indicates you have moisture coming through the concrete which is bringing salts up to the surface. Sealing the floor will probably take care of that problem.
    Another approach is to lay Raven Industry’s moisture barrier film (see all related articles) and float your Pergo, maybe with an underlayment of cork to help insulate the floor.
    Good luck.

  17. A few years ago we put an underlayment down in our basement and put vinyl, peel and stick tiles down. Today we pulled up the tiles and the underlayment and underneath we found a damp area. This is the only spot in the basement where we found this problem and we are unsure of how to proceed. Can we take care of this problem ourselves or do we need to call in a pro??

  18. I just bought a house with the basement unfinished. Its been 3 months with a few showers and I have noticed no problems. We just had a heavy storm drop a good ammount of rain in a short period, this time the moisture did come into the basement. The basement wall is block with a concrete covering about 1″ thick, the floor is concrete, depth unknown, with tile on top. The water appears to have either A)filtered in through the block and flowed behind the concrete covering down to the floor or B) came up through the floor … though I am leaning towards A since the moisture only appears on the flow towards the outside wall … the grade where the largest ammount of water came in is fine on the outside with working gutters and extensions. I have only a week away from getting carpet installed and have to be out of my current residence at the end of may so have very little time to address this issue as I thought I didn’t have one since other storms procuded no moisture … the storm left a small shallow pool of standing water in two areas and other areas where moisture came in but looks like it dried or it moved and pooled to the two spots … My question do you think since this only appears to happen with heavy storms and the ammount of water really isn’t alot is a dehumidier enough to deal with the moisture in the short term until I can address the larger problem since time is really a factor for me? I thought about sealing the base of the concrete covering that meets the floor but am concerened that that may just direct the water elsewhere that I may not be able to readily detect. Any other solutions you could recommend?

  19. Hi Shannon,
    It’s really up to you/your budget if you want to call a pro in directly. Chances are you could seal your floor yourself and that would take care of the problem……then again, it might not if the moisture is coming from elswhere and somehow traveling to the area you found the water. My guess? Since you didn’t mention any water trails, it’s probably happened just the way you’re figuring.
    Another thing to consider, if you do hire a pro vs. doing it yourself, at least the pro is supposed to have the experience to figure out what’s going on and how to fix it properly which takes a lot of the guesswork out of the equation.
    Good luck!

  20. Hi Josh,
    Yes, I think I would go with a dehumidifer for the interim until you can really figure out for sure where the water is coming in and why. After all, there’s really no point in trying to solve the water problem until you know what the problem is! ;o) Granted, it may take some time to figure out, depending on how long it will be until it leaks again and if you can actually observe where the water is coming in at……..until then it’s a guessing game.
    Good luck and hope you can eventually figure out where the problem lies.

  21. part of my basement which is carpeted with industrial grade carpet was soaked when the tubing from the humidifier on the furnace was blocked while we were away in the late spring. Last week I had the carpet taken up when because i thought it smelled. Underneath was so much glue and a black tarry substance neither of which we are able to remove completely. I want to put new carpeting down but should i seal the floor first? I have a dehumidifier and no moisture issues but I don’t know if i should just put a good carpet pad and carpeting down or seal it first.

  22. Hi Grace,
    So long as you are positive that you don’t have moisture issues, then you’re ok. BUT, keep in mind that concrete basements do draw moisture thru the concrete from the ground, which is a major reason why carpets become smelly and the basement air feels ‘damp’. Ideally, you should scrape or use solvents to remove the glue and black goo and then seal the concrete, but that’s entirely up to you, it depends on what you can live with yourself. I do think you’ll notice quite a difference if you seal it.
    If you use chemicals to remove the glue & goo, try to find something that has low/no VOC – that’s the fumes that are bad for your health and fumes don’t normally disperse as well in basements because there isn’t usually as many windows/doors to open for the fumes to dissapate.

  23. My basement was musty and I removed the carpet many years ago but left the basement floor as is with glue stuck to the cement floor since we had stopped using the basement. Now we are ready to put a floor on it but I still see these very tiny four-legged creatures in the basement.
    They are as big as a grain of salt. I believe they fed on the wallpaper that was also on the gypsum board walls but was also removed a few years ago. Before I go ahead and put new flooring I am worried that once the job is done that these tiny creatures will resurface. We have seen these creatures only in the basement and they are white or off-white in color.
    At the same time I have noticed that some of my books have the same type of creatures but they are brilliant white in color and I looked them up on the internet and I believe they are called book lice which apparently like humid environments and feed on glue or adhesives. With all this said and done, I decided to look into my basement walls and they are covered with fiberglass pink throughout and in addition, a layer of tar only halfway up the height of the
    foundation walls.
    These walls have 60% humidity in them. I was also told that this basement was excavated two feet lower than the normal range of excavation that is done, and it was done to provide a higher ceiling apparently.
    There is also a sump-pump pit that gathers lots of water and works very regularly to remove it. I was advised to remove the existing walls and insulation and that I should put a new soya-based liquid foam that will seal all pores in the concrete foundation walls and will remove about 70% of the humidity in the basement. Supposedly this product is not dangerous for the health and environment and will break the thermal bridge that creates an environment for mould on foundation walls.
    Once I go ahead and do all this, I am still worried that my basement floor will release humidity enough to provide a home for these creatures. So I did a saran wrap test in the last 24 hours and it seems like the floor does not release humidity but I know that in future this can change.
    Keep in mind that during the last two summers I have been running a dehumidifier on my first floor and I empty it out everyday. I do not run it in the basement for fear that if there is humidity or hidden mould that it can be rethrown back into the air once it comes out of the dehumidifier. We are planning to put wood flooring but I am worried that if I put a polyethylene vapor barrier, that over the years water will build up and be trapped between the cement floor and the plastic cover and again provide a home for these creatures to feast.
    My other option is to put a subflor or dri-core floating system directly above the cement floor, however, I am worried that the air gap between the concrete slab and the subflor will allow air to create similar humid conditions if water builds up in this air space enough to provide a home for these creatures to proliferate.However the manufacturer claims that any water build up will flow freely through the raised plastic dimpled pattern towards the basement drain due to the air gap providing air flow. Another option would be to put styrofoam directly onto the concrete floor and then build a wooden floor on top of this but again, I do not know if the concrete slab once and if it releases humidity over time , if these creatures can form and live between the styrofoam and the concrete slab.
    The glue on the cement floor from the carpet that had no underlayment is hard to remove and even if most of it comes out, my worry is that small glue partilces will remain and will provide organic material for these creatures to feed on. So my question is multi-tiered:
    1)if most of the glue does not come out instead of wasting time removing it, being that the urethane application on the walls will remove a good chunk of the humidity, do I still have to seal the cement floor or can I just place the dri-core subflor floating system directly onto the cement floor?
    2)If the glue comes out fully, do I just place the dri-core subflor floating system directly onto the cement slab?
    3)Under either instances (1) or (2), do I have to still put a sealant or tar in order to block humidity from coming out of the cement slab and creating moisture conditions that these creatures will be able to feed on?
    4)Can the sealant or tar, if applied on the whole basement floor, release toxic chemicals over the years that will harm our health?
    5)We are thinking of putting bamboo floors due to their health benefits, do you think they can warp?
    6) Is hardwood bamboo better than engineered bamboo, which do you recommend given the state of our basement?
    7) If none of my ideas are correct to remedy the situation, do you have a better strategy so that we can start using our basement without worrying that we will be seeing these transparent-like tiny creatures all over our basement and stuff?
    The contractor is coming in a few days to start ripping the walls, are you able to provide me with some answers ASAP, it would be deeply appreciated. Thank you for your time and I am glad I found your website because I have spoken to many people and I get many confusing and contradicting pieces of advice?

  24. OK, answers to questions………
    1.) I think it would be a good idea to put a vapor barrier on your cement floor – after all, it can only help, right?
    2.) Yes. However, (copied and pasted from DriCore‘s FAQ portion of the site:
    The DRIcore moisture management system allows any seepage or moisture to channel freely under the DRICore subfloor panels to keep floors both warm and dry.
    NOTE: DRIcore is not a replacement for a good foundation nor a solution for home drainage maintenance, flooding, or continued water leakage. Any leaks or excessive moisture should be attended to prior to any flooring installations.
    3.) I would think so, if nothing else than to help cut off the little critter’s food supply.
    4.) Yes & No. If you prefer the “No” answer, be sure to buy a sealer that has Low or No VOC’s. It won’t be a problem to find these brands – most manufacturers are jumping on the environmentally friendly bandwagon. Don’t use tar.
    5.) Any kind of wood flooring can warp – especially in a humid environment. This is part of the reason why you need to acclimate your flooring materials before you ever lay them. So long as the subfloor is even, then ideally your flooring should be too.
    (again, copied & pasted from their website) DRIcore panels may be required to acclimatize for longer periods depending on the humidity and temperature of the room where the installation is to take place. The recommended humidity and temperature to be maintained for a below grade installation is 30-50% relative humidity and 21° C (70°F).
    Allow panels to stand for at least 48 hours by stacking or laying them out on the floor with the plastic cleated surface down. During seasonal periods of high humidity conditions such as June, July or August, it is recommended to acclimatize DRIcore panels simultaneously with the finished wood flooring to be installed for about 2 weeks to allow for the balancing of the moisture contents of both products. Check with the finished flooring manufacturer for their recommended temperature and humidity guidelines.
    6.) I would think that engineered bamboo would be a better choice, mainly because it would most likely expand & contract better with the humidity and temperature changes.
    Sounds like you’re on the right track with your thinking, need to address the critters if possible. I’ve read that fresh air & sunlight helps to control their numbers aside from chemicals of course.
    Good luck with your project!

  25. We are in the process of purchasing a house. The basement of the house has a mixture of 9×9 tile and painted floor. The house was built in 1959 and the basement tile is from that period. We found a white fluffy pouder like deposit coming from under the paint and also from under the tiles.
    What is this? Is it harmfull? How would you remove it, and/or prevent it from reocurring? Is this a deal breaker?
    Any comments would be appreciated.

  26. Hello in Wisconsin!
    I’d insist that samples be taken of this powder and that it be tested for asbestos. It’s probably efflorescence, but it would be smart to be sure. This could indeed be a very real and scary problem considering the dust. If it is asbestos, then it has obviously deteriorated so badly that really, only a professional should remove and dispose of it. Yes, it’s costly, but remember, it can be deadly.
    I don’t know how you’re planning on financing this home, but if it would be a mortgage, many times the seller will have to pay to have it fixed because the bank will insist on it as part of the deal. Obviously, if it’s asbestos, then the Realtor and seller would still have to disclose this even if you decide not to buy this home. Face it, they’ll have a tough time selling it as-is if this is asbestos.
    I’m not quite up the federal laws, but I wouldn’t be surprised if it were even illegal. Businesses, schools, etc. have been shut down when asbestos is found and cannot reopen until it’s been cleaned up and inspected and given the green light to reopen. Asbestos particles become airborne and float everywhere, which is what makes it so hazardous to your health. I seriously doubt the seller would be allowed to sell it if somebody blew the whistle about the asbestos.
    Again, that’s if it’s asbestos, which I’d be almost willing to bet it is. Get it checked out ASAP.

  27. Thank you for your post. I am assuming your concern about asbestos will be because of the tiles? I did some research and I think the pouder substance is “efflorescence” and it is caused by moisture from the basement floor. Assuming that the asbestos issue is resolved, is there a way of preventing the moisture from penetrating the basement again? will a sump pump work, sealing the basement floor?? We will talk with our agent today and see what are our next steps. Thank you.

  28. Hello again,
    Just for the sake of health concerns, I sure hope you’re right and it’s ‘just’ efflorescence. I’m sure you know that efflorescence is caused from moisture seeping up through the basement floor. The only way to keep it from happening is to address the moisture problem itself. I’m presuming the floor is concrete, right? Problem is that efflorescence damages the concrete (and it’s integrity). Hopefully, it’s not damaged to the point where you’d need to jackhammer the concrete and and pour a new basement – which is a very extreme scenario.
    Does the basement flood? Just wondering since you were inquiring as to whether a sump pump would help. If it floods, then yes, a sump pump would help to remove the water faster, but it still doesn’t address the moisture itself. You may need to have a professional come in and see if they can figure it out and advise you what to do.
    Do you have any idea where the moisture is coming from? I know that can be a really tough question considering you don’t live in the house.
    There are quite a few different ways to address moisture issues, but it’s going to depend on the source(s) of the moisture. There’s dri-core systems, vapor barrier paint, plastic sheeting, fixing cracks in the floor, etc………
    Sometimes, problems can be addressed by simply having a few feet of gravel around the house (which can be landscaped to look nicer) can take care of water coming in the basement, but it just depends.
    Do you plan on having an inspector check out the house? That’s usually a requirement for obtaining a loan and if you have a good inspector, often times they’ll have a good idea of what a moisture problem stems from.
    Wish I could be of more help, but without knowing the source of the moisture, it’s next to impossible to tell you how to remedy the problem.

  29. Hello again, I appreciate your answers from August 10 concerning my basement and I was thinking of trying a different strategy. I would like to apply a product called Demilec Airmetic Soya that is a urethane supposedly all-natural onto the basement floor and completely cover the glue stuck to the basememt floor slab. Once the urethane is applied then I would let it dry and then apply 2 inches of sandcoat (sand and cement)directly over the urethane. Then I would install ceramic tile on top. 1) Do you think that this procedure would alleviate any humidity from forming on the basement floor tile? 2) Do you think that the tile will keep warm with or without heating the basement?
    As for the basement walls they currently have tar on them from the basement floor up to the level of the land outside, then they have fiberglass pink , and then they have a paper barrier that has an aluminum coated siding and then there is the drywall. Now I had the walls tested with a humidity meter reading and they seem to have anywhere from 60-90% humidity in some places. I opened the wall in two areas and when I removed the fiberglass pink it was dry, and the wall is not wet at all. Under these conditions what shall I do: 1) Should I leave it as is and just buy a dehumidifier and run it everyday to remove the excess humidity? or 2) Shall I rip open the walls and start from scratch and apply urethane on all the perimeter walls and omit the need to run a dehumidifier all the time? Do you have any recommendation other than my two options? Keep in mind that the book lice like to feed on glue, wallpaper and thrive in hot humid conditions. Thank you for answering before and I hope you do not mind answering me again on this new strategy.

  30. Your flooring suggestion sounds ok so long as the urethane is recommended for use as a vapor/moisture barrier. I think your floor will be cool to the touch without in-floor heat, it is underground, and it’s just always going to be cool.
    I’m hesitant to advise you further on your walls, this is a flooring site afterall. In other words, my knowledge doesn’t extend to walls. As far as the humidity in the drywall, remember, you’re going to be blocking a lot of that humidity when you do your floor. It might be worth it to do the floor, use a humidifier for a few days or so and test the walls again. It very well could be that the humidity in the walls is residual from the humidity in the air via the cement floor. It sounds like the walls were taken care of so that moisture couldn’t seep through them.

  31. Hello again, I appreciate your answer from August 21, with respect to the basement I found a glue remover that will supposedly remove all the glue from the basement floor, It is called the Glue Buster from Surf-Pro products. Once this is done, my cement slab shall be cleaned with methyl hydrate and then it should be okay and free from glue residue that those little critters feed on. However,1) before I install the Dri-core, shall I seal the cement slab with a sealer, an epoxy water-based paint, an epoxy glue or shall I leave it bare.2)By sealing it, do I trap the humidity in the cement slab which can create potential cement deterioration in the future. 3)Does the slab have to breathe.4) If you do recommend sealing it, which product is the least toxic and does not off-gas, the sealer, the epoxy paint, the epoxy glue. 5)there are a few little cracks in the cement, shall I just use a cement contact to seal them or shall I use a sealer. 6)My main concern is the health of my family and I do not want anything that I put to be toxic and release fumes after many years into our home, what do you recommend!

  32. Hello again! So glad you found some products to remove the food source of those little fiends!
    You can use any of the products you mentioned for sealing the cement, just make sure that the product you use will seal fine cracks along with the cement. Most manufacturers are very concious of consumer’s wants & needs and have responded by developing products that are low or no VOC (volitale organic compounds – the fumes & off-gassing that you’re worried about). Manufacturer’s are getting ‘greener’ all the time! You shouldn’t have a problem finding a product to meet your needs, there are lots of them. ;o) If you go to Lowe’s, Home Depot, or something similar, just tell them that you need a moisture or vapor sealer for a basement floor that has a few fine cracks and that you want something that’s low or no VOC, they’ll fix you right up.
    It’s very possible that this will take care of your moisture issues you won’t even need the DriLoc flooring system. I don’t know if you saw it, but I have an article on DriLoc here.

  33. We have a 2 year old ranch with un unfinished basement. We are getting so much dust in the house, upstairs and down. I was wondering if we sealed the basement floor if that would help. I am thinking about having the duct work cleaned out too (I think the contractors swept stuff into the floor vents when the ..ahem….cleaned up)I also have 2 good size cracks running across the basement floor. What should I use to take care of those?
    Thanks for your help.

  34. Hi Rick,
    I don’t think that sealing the basement floor is going to help with the dust issue. I really think you’re hitting the nail on the head with the idea of having the ducts cleaned out.
    There are products that can be found at your local hardware store to fill in the cracks in the basement floor. What kind of warranty did your new home have from the builder? You certainly shouldn’t have cracks across the basement floor after so short a time.

  35. I have a water problem in my basement. I have a french drain and have a sump pump in the basement but water still gets into my basement. I have tried Dry Loc water sealant but water still comes into the basement. What I want to do is coat the entire cement floor and quarter way up the cement walls with roofing tar. When the tar is set I will then cover the floor with ceramic tiles. Will this keep out the water?? Is it worth a try or am I creating more problems??? thanks-

  36. Hi Brian, I wouldn’t use roofing tar, it releases harmful vapors into the air that you certainly wouldn’t want in your home. You need to determine where the moisture is coming from first before you can figure out what actions to take to remedy the problem. There are brush-on products that can be used to seal the floor and walls but I cannot tell you whether it’d be recommended without knowing more about where the water is getting in at. I would suggest that you click on the “Moisture Proofing” link on the right hand side – there you can read more about different options that you may have for a remedy to your problem if you know it’s source.

  37. Thanks for your response. I’ve tried two different types of brush on products and neither one worked. The water (1 inch sometimes more) comes in after heavy rains so its a matter of hyrdostatic pressure. The water comes up through the cement floor (there are no cracks) and also at the seam where the cement wall and floor meet. The house is only 5 years old. I had one contractor guarantee a water proofing system where he would install a drainage pipe in a trench INSIDE the perimeiter of the basement – for ten thousand dollars!
    I am looking for a more reasonable solution. Hope you can suggest a solution. thanks

  38. Hi Brian,
    There’s so many thoughts passing through my brain about your situation and the thought that keeps coming back is that the real
    issue needs to be resolved — keep the water from coming in, or
    at least confine it to one space.
    My old basement had a sump pit with a sump pump. That kept the
    water confined so the rest of the basement was dry and only
    the pit was wet. The pump took care of it.
    It’s also possible that your French drain needs to be repaired or improved. Is the daylight opening
    below the drain? Is it plugged? Did the foundation get water
    sealed properly? Lots of questions here – and that’s outside the “The Flooring Lady” realm as it’s more to do with construction type issues rather than flooring.
    Some type of a stay dry floor-system would be fine, IMHO, if your floors only got
    damp rather than wet. Mold is a concern and still would be even if your floors only got damp.
    Yeah, you really, really need to figure out something to keep the floors from getting wet in the first place, and this does indeed usually require a pretty big expense for something as major of a problem as you seem to have.

  39. we have a 98 year old house that has a cement basement. it was made from river sediment, we are told, and the cement has small as well as pebble-sized particles. my question is, do we need to do something special to seal this type of concrete or will a good sealant fill in the many bumps and divets caused by the inclusion of larger rocks?

  40. Hi Kathy,
    I doubt a typical sealer will fill in the “many bumps and divets”, but you shouldn’t have any problems sealing it. You might want to consider a clear epoxy coating though, which will do a better job of filling in, or even a thin layer of concrete and then sealing that.

  41. Hi Kathy,
    We will be listing our house for sale next month. We have an unfinished basement and are talking currently to a company to reseal an old crack in a wall, which has leaked some water. Our realtor suggests that we seal the basement floors and walls, so it looks clean and assures the new owners. Will sealing take care of possible mold as well? Without adding a lot of expense, what type of products/services would you recommend?

  42. Hi Sue,
    So long as the floors and walls are sealed well to prevent moisture, then yes, it should take care of the possibility of mold growing as well. Sealing floors has been covered many, many times on this site, I recommend that you look at the links on the right-hand side of the page and click on “moisture proofing” to see what kind of method(s) would suit your situation best.

  43. Hi – I am going to finish my basment. It has a concrete slab floor in good shape. A few times a year after a really, really hard rain, there is one small spot in and near a corner that appears damp, goes away after a couple of hours. Doesn’t happen anywhere else. No standing water. No cracks. I am going to carpet the floor. What should I put down prior to carpeting in terms of sealant or vapor barrier?
    Also, the walls are cinder block and were painted white about 40 years ago. They don’t get moist or damp so should I leave them as is or paint over them with Drylock paint? Thanks for your help.

  44. Hi Barry,
    Look on the far right of this page and click on the link for “Moisture Proofing” – you’ll find lots of info there to read up on. As far as your walls, if they don’t get damp then I don’t think it’s going to matter if you use drylock paint or not – it would fall under the category of “what do you want?”.

  45. Hi There,
    I’ve got a 170 year old house and have two issues in the basement. The first is the simple fact the concrete floor was poured about 40 years ago by the man who rennovated the house. They are not level and when wet have pooled areas. Even bigger (because I’m working on sealing the basement better) is the fact the ceiling is low (about 6 feet). Is it possible to grind down a concrete floor and gain a few inches, or it that completely nuts? The other issue I have is actually overhead. I’ve got wire and insulation (which are dusty and seem to grow cobwebs) and I’m looking for some kind of fabric with vapor barrier qualities to staple up there and cover it all up. Have you got any suggestions for these two oddball issues?
    Thanks you much, Ken

  46. Hi Ken,
    This is a flooring site, so I don’t feel that I can help with the ceiling issue, though I’d think just some sort of breathable plastic barrier would work.
    While the idea if grinding down the cement floor might sound crazy, it’d be worth a shot if that’s what YOU want to try to do. You might still need to put a thin skin of concrete on it afterwards, but should help give you a little head space.

  47. Hi Brain,
    We had the same problem you are experiencing in your basement. Water was seeping through the floor and where the wall meets the floor. They suggested that we have new drain tiles installed in the basement for $10.000. We decided not go this route.
    We called the Rotor Roeter. They cleaned out our drain tiles and their equipment was able to clean out some small tree roots as well. This was last Spring and have had a perfect dry basement and the sump pump runs all the time again. Don’t wait to long since your basement walls may begin to bow due to the high water pressure. We now are also running clean water through the drain tiles which helps to keep clay and silt to a minimum. It is in particular important that you do this step during the summer months since clay becomes hard and acts as a stopper. Hope this info helps.

  48. what is the best sealant to use for an existing moisture problem in concrete flooring (15 lbs of moisture) – we have a vinyl floor product called Konetco from Canada and it is bubbling in some area due to the moisture in concrete release the glue

  49. Hi Bobbi,
    At this point, there isn’t much you can do until you’re ready for new flooring. The flooring would have to be removed and then the moisture problems dealt with. There’s more on the site about different methods/products for dealing with moisture proofing.


  51. Hi Sheri,
    Go to the top of the page and all the way to the right – click on the link for “Full Archives” – you’ll find info there that can help you. There are also epoxy paints – that way you can do this in one step. ;~)

  52. Had warer come in on existing painted basement floor, paint has bubbled in places and a fine dust or mold is growing, have tried cleaning with bleach but some mold returned, what can I do? Will I have to scrape all paint off and re seal? Home is 40 years old but we use our basement a lot.

  53. Hi Barby,
    Hopefully you won’t have to resort to that, but you really do need to address *how* the water got into the basement. I’m guessing that you probably do need to strip the paint and reseal. Read right above your post too.

  54. Hi Amber,
    I can’t really say that there is a *best* sealer for basement floors because it depends on what method you choose to seal with as well as what kind of a moisture problem you have. Check out the Moisture Proofing section to find out what sort of options are available.

  55. We have water sipping through the sub-floor tile in our storage closet. We have had a plumber replace the storm drain line in the basement, we have detached the down spout and it drains into the yard. After attempting to solve the problem there is still water in our basement. We believe that the water is due to water sipping through concrete that is not level with our drive, which causes the water to stand at low points and sip back into the house. What do you suggest?

  56. Hi Roz, The first thing you need to do is to get a foundation specialist in to try and determine where the moisture is getting in. You might need to have a sump pump installed below the concrete floor and the foundation specialist would know about.

  57. Hi there, I live in a 2 year old semi-detached home. My carpet in the basement that came with the new home has been wet (damp) since we moved in. I was told by the builder when i complained that this was normal for a new home. I tried pursuing it and put a gadget that tracks humidity in the room. Although the air was somewhere between 55 and 76% humidity the carpet is always very damp. Is it possible that there is a problem with my foundation or that my builder did not put down a vapour barrier? I haven’t lifted up the carpet yet to see what’s under it. I do believe, however, that mold has set in. It has a musty smell.

  58. Hi Tara, Damp carpet in a new home is NOT normal. It is entirely possible that your contractor did not put down a moisture barrier. If one was not installed, then I would see what recourse you have with the contractor.

    Otherwise, it sounds like the carpet will be need to be removed and you might consider having a foundation expert come in and assess if there are any foundation problems.

  59. I just took up old linoleum in the basement to put down tile and water’s dampening the floor. It’s uniform throughout, making me think it’s being wicked up by unsealed concrete due to the high water table. I’ve waited 3 months and the rainy season never seems to end here. Can I just seal the floor while it’s damp or do I need to find a way to dry it?

  60. Hi, Can you tell me if sealing our basement with a moisture barrier sealant will also prevent radon gas from seeping through the concrete floor?

  61. I have a concrete floor. There was mold when I pulled the carpet. I am wanting to put laminate flooring back down. If I put down heavy plastic before I install the laminate will that keep possible mold from leaching through into my laminate. Thank you.

  62. Clyde,
    You will want to find out what is causing the mold before sealing or installing new flooring. I would contact a professional in your area to assess the moisture level and the best way to provide a subfloor.

  63. I know someone who is having problems concerning their concrete basement floor. It seems that when they paint the floor with concrete paint, it will eventually bubble and produce a white fiborous substance. What may be causing this reacction and what can be done to solve the problem?

  64. Steve,
    It sound like the fibrous substance could be efflorescence which is caused from moisture seeping up through the basement floor. The only way to keep it from happening is to address the moisture problem itself.
    Efflorescence damages the concrete (and it’s integrity). Hopefully, it’s not damaged to the point where you’d need to jackhammer the concrete and and pour a new basement – which is a very extreme scenario.
    You may need to have a professional come in and see if they can figure it out and advise your friends what to do!

  65. We have a daylight basement in Roswell, Ga. When we have excessive rain, there are a couple of areas that water enters into the basement thru the joint of the wall and floor. It used to be worse but I have worked to better drain those areas outside to keep water away from the house. This has vastly reduced occurrences, but when we get deluges…water does get in. We have carpet installed right now, but with this last rain we had to pull it back in some areas and discard some of the padding and then dry the carpet out. This is the third time in 6 years we have had to do this. We want to fix the issue this time. Although, we do get it all dried out when this occurs, we never really get rid of the musty smell. I want to know if there is some way I can seal the wall-floor joint inside because I do not think that I will be able to completely drain the water outside from one area …it will find a way in during heavy downpours. I am not talking a lot of water, I would say we get about 2-3 gallons each time, with most of it being soaked up by the carpet and pad. I would appreciate some advice here…thanks

  66. Michael,
    I would suggest that you contact a local contractor to assess the problem and offer a solution. It sounds as if you may have bigger water issues than have been addressed in the past.
    The musty smell is from the dampness, mold and mildew, this should improve as the basement is dried and cleaned.

  67. I was reading your comments…and the one that said..” sound like the fibrous substance could be efflorescence which is caused from moisture seeping up through the basement floor. The only way to keep it from happening is to address the moisture problem itself. ” what about using the product called radonseal which claims to seal your cement so that moisture cant get through it?

  68. We just bought our house not too long ago. We have noticed that this house has a musty smell throughout and can’t figure out where the smell is coming from. Sometimes that smell gets stronger. Can it be a result of dampness? How can we tell if we have a mold problem? Someone told us that there is water coming up the basement floor, which is covered by tiles, and that this is something that can’t be fixed. Can this be true? We don’t know what kind of professional can help with this. Any insight you can provide will be greatly appresicated.

  69. Julie,
    This can definitely be the result of dampness. There are other things to look at besides the basement (although it is a possibility). There could be a drain leaking, a water pipe leaking, roof damage letting in moisture, many different things.
    If there is water coming up the basement, it should be able to be redone and sealed correctly.
    If you cannot find the source yourself, I would suggest contacting a general home inspector and letting them know of the problem, they may be able to assist you.

  70. Robin,
    Sealer will bubble from air getting underneath it as it dries.
    If the bubbles are bad they may crack open and need to be resealed. If they are small, they may dry correctly.
    I would keep an eye on them and make sure that they do dissolve during the drying process.

  71. Bought a house about a year ago that had some dampness issues in the basement that we have controlled with a dehumidifier. Yesterday i noticed water on the otherside of the basement seeping from a crack in the floor that leads from the drain from the upstairs basement. The water is coming from the 1st half of the crack only and flows into another floor drain. The crack extends about 15ft from the drain and Ys out another 3ft each side. Do you think it could be solved by mortaring up the crack & sealing it or do you think the problem is greater than that?

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