Vapor Barrier Paint

You want to install hardwood flooring in your basement but hear you can’t do that because of moisture problems so often found in basements. A vapor barrier can be the solution to that dilemma. And vapor barrier paint is one alternative for basement moisture problems.

Vapor barrier paint is yet another weapon in a homeowner’s arsenal to fight against damage caused by water vapor. Vapor barrier paint is made by many paint manufacturers in different grades, as we will see. There may be reasons you can’t or won’t use traditional vapor barriers for your floors before installing wood or carpets in your basement. That’s one cases when vapor barrier paint is great.

It is important to understand how water vapor acts in order to understand the uses of water vapor barrier paint. In a process called convection, warm air always moves toward colder air. Thus, during cold months, the warm air in your house is constantly seeking to escape outdoors. Warm air also expands, putting more space between its molecules compared to cold air. Expansion allows warm air to hold more water vapor. When this warm air encounters the cooler surfaces of your home, such as exterior walls, it cools down and contracts, squeezing out water that collects on the cool surfaces.

Underslab and in-wall water vapor barriers are designed to keep water out of your home. They defend against groundwater seepage, rainfall, and floods. But having water form inside of your home is also bad. It is here that water barrier paint plays a role in protecting your home’s interior surfaces.

Water vapor barrier paint is often applied to drywall walls and ceilings in attics, where warm air tends to rise. Without water vapor barrier paint, the warm air would release its water inside of the walls and ceilings, where the water would saturate the insulation and framing. This water damage can render insulation useless and cause rot in structural members.

Not every household paint or enamel is an effective water vapor barrier, though. In order to qualify as water vapor barrier paint, a product must attain a Perm rating less than 1.0 under the ASTM D1653 Test Method for Water Permeability of Organic Coating Films. The lower the Perm number, the less water vapor the barrier paint allows to pass during a given amount of time at a given temperature and humidity. When shopping for water vapor barrier paint, ask for it by name and check the Perm rating which should be on the can.

Water vapor barrier paint is often sold as a primer, to be applied under a final coat of a different paint. The primer is generally sold in white. It can be colored to some extent without degrading its water vapor barrier properties. Usually, the can’s label will tell you how many ounces of pigment can be added to a gallon of water vapor barrier primer. The instructions will also state the maximum surface coverage of a gallon, and whether one coat or two are recommended.

Water vapor barrier paint is also used directly on concrete floors. Products such as Aquapel, made by L & M Construction Chemicals of Omaha, Nebraska, penetrate porous concrete and chemically bond with it to seal out water vapor.

Water vapor barrier paint is not a substitute for other water vapor barriers when they can be installed. In some cases, such as cinder block construction, it is impossible to install conventional water vapor barrier sheeting behind exterior walls. In these cases, a high-grade (low Perm) water vapor barrier paint is essential.

Older homes in need of water vapor barriers are also good candidates for water vapor barrier paint. It would be a bad idea to try to pull back the insulation in an old home’s ceiling and try to install plastic behind it. It makes much more sense to paint the ceiling with a good water vapor barrier paint.

Water vapor barrier paint complements other forms of water vapor barriers and can be a valuable tool in insulating older homes.



23 thoughts on “Vapor Barrier Paint

  1. hi, i am interested in putting down traffic master’s allure vinyl planks in a new basement.
    i live next door now and that basement is dry.
    i am installing a dehimidifier just in case.
    i understand the planks have a tape edge and they free float (no glue necessary). my question is re: proofing the basement floor. i would like to do so but do not want to spend for their basement proof. it was recommended that any proof will do. Might you recommend a close comparison to Traffic master’s basement proof at a more reasonable homedepot $??? thank you

  2. Hi. I am interested in installing an inexpensive wood floor in my small basement apartment. The floor is tiled in linoleum and is too cold and hard. It doesn’t have a moisture problem, but it’s just uncomfortable. I would like to raise the wood flooring just a bit, so that it has some “life” to it, a little more spring than the concrete directly. My question is, am I crazy? Can this be done easily? I imagine just laying down some intermittent supports (maybe 1×1’s?) crosswise to the floorboards, without nailing them down. Please advise me!

  3. There are two things you can do to improve the feeling of your floor. You could lay a cork underlayment before installing the wood flooring. The cork will add some insulation so the wood floor won’t be quite as cold or hard — and it adds a touch of bounce to the flooring.
    You can also check out some flooring systems designed for basements and concrete floors. I have several articles on moisture proofing your flooring on the site.

  4. We have an old house with a concrete slab that apparently has either no water barrier layer or one that has been breeched, as we now have a small amount of rising damp. Would installing this kind of paint on the flooring be useful or might we be better off putting a damp-proof plastic on the concrete and pouring new floors over it?
    I’m also concerned about the breathability of the house with internal sealants like this. What’s your opinion on that?
    Thanks!

  5. Hi Sabrina,
    What is your definition of “rising damp”? Do you mean mean that moisture is somehow literally rising up and making the concrete feel damp, or do you actually have a small amount of water seeping in?
    I’m not sure if you’re implying that your house is tight and you doesn’t want
    to poison the air, or if you just recognize the issues of what some finishes will do to the air quality. If you choose low VOC finishes air quality won’t be damaged, or at least not much.
    Have you looked over the articles on on moisture proofing yet? They might help you decide what you’d like to do. I can help more if I know exactly what extent of a moisture problem you have.

  6. ‘m doing a radical renovation spec. house and built a passive solar room with a 6″ concrete slab floor over 2″ of styrofoam. I failed to put a vapor barrier under the styrofoam, and the inspector wants me to install a vapor barrier before the slate / tile floor. All the existing concrete floors likely have no vapor barrier, but I’m getting nailed on my addition. The Schluter DITRA underlayment has a vapor barrier, but it defeats the very effective heat sink I’ve created in the insulated concrete floor. Is there a paint that will act as a vapor barrier that I can install a slate /tile floor over? FYI The slab is about 10 inches above grade with about 4 inches of compacted gravel as a base. I need to give my engineer some instructions to add to my plans. Got any ideas? Thanks Chris in St. Louis

  7. Could you further explain why you’re being asked to put a vapor barrier down? You might want to read the articles I mentioned in the previous post (the underlined link). I hope some of those ideas help out.

  8. We have a previously installed ceramic floor in our basement that is damp virtually all summer. Also, although our garage has floor drains, there is also seepage through the floor. We can’t pull up the entire 1000 sq ft floor, but we have to get rid of the seepage. We are looking at ways to drain water away from the house, but need a plan to waterproof the ceramic floors.

  9. French drains around your house will go a long way to rid you of your moisture problems. A sump pump may be called for too, if the water table is really as high as it sounds it is.
    The waterproofing your are contemplating (painting the tiles) may keep moisture out of the house, but it won’t keep it out of the tiles. To preserve your flooring you need to first remove the water source and then put a layer down between the concrete and flooring.
    You have a big project ahead of you, but it’s important to do correctly and well so you don’t endanger your health with mold and poor air quality.

  10. I have cinder block walled daylight basement divided into two spaces; one an ex-hair salon with plenty of plumbing for a second kitchen that I want to rent as a effiency apartment, and the other space currently being used for laundry, storage with huge outside window and outside entrance door that later on would like to rent as yet a third rental space. FYI, I will rent my primary upper level as the 1st rental. This house was built in 1962 and the cinder block walls are leaching that white powder residue and while there is no obvious moisture, the walls have the exterior moisture that I suppose is pushing in and causing the residue flaking. What can I use as a barrier to prepare for either paint or wall covering to create these rental spaces?

  11. We are looking at buying a lakefront cottage. Currently the crawlspace has no vapor barriers/protection. The dirt “floor” has small puddles, most likely from water seeping up from the clay ground. There are already rotted floor joists where they “sistered” in new joists next to the rotting ones.
    The local Be-dry people gave us an estimate of over 16k to install a vapor barrier, humidistat, trenches, etc.
    We simply cannot afford this, but we are in love with the rest of the house/property. I was thinking that adding in some fiberglass insulation with foil backing into the floor joists, then adding a layer of plastic (air barrier) on top of the insulation, and sealing it.
    Would vapor barrier painting the sub-floor and joists along with the insulation be an effective and cost-efficient alternative?

  12. Forgot to mention, the house in question is a bank-owned, and they are refusing to pay or do any repairs, so we are asking them to take off the price of some of the major mechanicals.
    Looking through some DIY sites, it looks like the best route (for our money) is to lay down some heavy duty tarp, place a real dehumidifier, use the vapor barrier paint, insulate, then put on the plastic, in that order, as we get money to do so.
    Cost of supplies: $2500
    Cost of doing it professionally: $16600.

  13. Ewww……… I take it you got a written estimate or two to show the bank? That should motivate them to come down some.
    I wouldn’t think that a dehumidifier is necessary, so long as you have a vapor barrier put down – remember too, that it needs to go up the sides some too. That’s usally put down before any insulation as well so that the insulation doesn’t get soggy. If you have ventilation holes, keep them open, it really does need to breathe under there. We do close ours up in the winter though – and have screens over them to keep little critters from having access to under the house.
    Good luck!

  14. We recently purchased a 1950’s house built on a concrete slab. It appears that there was water damage in one of the bedrooms in the past where cork tile floors are stained and buckled and a french drain has been dug outside the windows. The air quality in this room has tested with elevated mold levels so we are removing the tiles, washing with bleach solution and sealing any cracks we find in the concrete. After this we intend to install carpeting to make the room usable until we can afford wood floors in the next few years. Should we apply vapor barrier paint before carpet? Any other suggestions to minimize moisture issues?

  15. Yes, a vapor barrier would be in order, glad French drains have been added! I’d suggest something other than carpeting in a basement – they always attract moisture in the air (humidity) and wind up smelling musty – not to mention the health concerns that go along with this.
    I’d suggest a laminate floor until you can save up for a wood floor. Either Lowe’s or Home Depot has a 50% clearance going on right now (sorry, I forget which!), so this might even be more economical than carpeting anyway. Good luck!

  16. I like The Flooring Lady’s suggestion of laminate flooring. I also think linoleum would be a good choice, and maybe even cheaper. Engineered flooring could also be nice, like bamboo or other beautiful would that appeals to you.
    If you have major water problems there read the articles in the moisture proofing section of this site. I just read several articles and find them valuable for helping in your situation.

  17. Dear Flooring Lady,
    Thank you for your great wisdom on so many topics; you have really helped us to narrow things down and weigh the options…So, my question is this: We are putting in engineered 5″ plank floors with a top layer of Chestnut wood in our bathroom and kitchen. We are two fairly careful adults, so we will wipe up, but recognize the inherent danger of moisture in these locations. From our research, it seems that the people who have done this and who remain happy with their choice have taken extra steps to seal the floors. What do you recommend in this regard, and how many layers should we put on? Thanks very much…

  18. I am considering finishing my poured cncrete basement walls. I have been advised to glue hard foam to the walls and build a wall frame in front of this insulation and then drywall the frame.
    I am contemplating leaving a gap at the floor and elevating the foam insulation and the frame wall about 2 inches off the floor with cncrete bricks.
    What is your assessment of this approach? Where would the vapor barrier paint be applied.
    What suggestions do you have for changes in this approach?

  19. Jim, I’m going to address your questions backwards from how you asked them. Not knowing just how moist your floor is my answer may not help, but I’m going with what you have given me.
    The article addresses your question, as would the paint can. For sure you need to paint wherever the soil touches the concrete, but painting everything is really the best approach.
    Now, tell me why you are elevating your foam wall insulation, and supporting it with brick? I can’t know if it’s a good idea until I know why you are doing it. It seems it may be overkill, but I’ll know more later. And when you glue the foam insulation consider using Bostik’s Best glue. Whatever glue you use make sure it won’t melt the foam.
    You didn’t address how you were going to finish the walls once you insulated and vapor-proofed them. If you are going to use drywall as the finish, with your plan you don’t have a good way of attaching it to the wall. Why not consider nailing or gluing 2″x2″ strips to the walls, insulate between them, and then you can attach the dry wall to the wood strips.

  20. The gap at the bottom of this system pays attention to letting any moisture escape that might be found between the wall and insulation.
    A 2 x 4 wall will be built and placed next to the hard foam and covered with drywall painted with vapor barrier paint.
    I am unsure where the moisture might come from: through the poured foundation wall or from condensation on the wall from interior air.
    I was going to insulate between the studs in the wall with kraft back fiberglass. It has a lot of embedded energy cost to make it. I may use blown cellulose which I am going to use on a Habitat house we are building.
    The whole idea is avoid any mold.
    Thanks for the advice on the glue.

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