A sweating garage floor can be a real nuisance than can create a slippery surface and even make your garage damp as a result. If you wonder why your garage floor gets wet, particularly in the spring, then your garage may be suffering from this condition. So let’s discuss what makes a garage floor sweat and what you can do to help stop it.
Why does my garage floor get wet?
Before you make a plan to stop it, you first need to understand what causes it. There are a couple of reasons why your garage floor may be getting wet. The most common is condensation — AKA sweating garage floor.
When relatively warm, moist air comes in contact with a very cool concrete slab, the cold temperature of the concrete will cause the air that comes in contact with it to cool. If the air cools at or below the dew point, it will begin to condense on the surface of the concrete, thus causing the wet and sometimes misty looking garage floor.
As a refresher, the dew point is the temperature at which the air becomes completely saturated. If your concrete surface is cooler than the dew point, it can easily cause the boundary layer of air that comes in contact with it to cool at or below the dew point if allowed to rest long enough undisturbed.
Otherwise known in the concrete industry as sweating slab syndrome, it’s the same condition that causes the outside of a cold beverage container to get wet on a warm, humid day or the surface of your car to get wet when it’s left outside on a cool, damp night.
A wet garage floor generally takes on a darker look due to the moisture and can even suffer from efflorescence as a result. This happens when the moisture that has been absorbed by the concrete travels back up to the surface and evaporates. As it evaporates, it leaves behind white mineral deposits on the surface that the moisture carried with it as it traveled through the concrete.
Sweating garage floors seem to be most prevalent around spring time in areas of the country that experience cold winters. Ground temperatures are still very cool from the winter and tend to keep the concrete cold relative to the air around it.
However, it can also be an issue in areas of the southeast where warm moist air brought in from the ocean comes in contact with relatively cooler concrete slabs during the winter and spring time.
Another condition that can make your garage floor wet is moisture that travels up from under the slab. This is different from a sweating garage floor and is often misunderstood as the same thing. It happens most often with concrete that does not have a moisture barrier beneath it.
Though concrete is hard and dense, it actually has small capillaries within that act like a sponge. If the ground beneath the concrete is wet or has high moisture content, it can absorb that moisture and distribute it through the concrete. Basements commonly suffer this same condition.
If the air above the concrete is warmer, the moisture within it will rise to the surface and evaporate. This can create a wet surface if there is enough moisture. It can also cause efflorescence and just like a basement, it can make for a damp garage as well.
How to test for a sweating garage floor
If you are uncertain whether you have a sweating garage floor or a moisture issue from below your slab, the easiest way to tell is to test for it. Tape a 16” square piece of heavy plastic down to the concrete when it is dry. Make sure to seal all the edges. Leave it in place until your concrete shows signs of being wet.
Remove the plastic and then look at the concrete. If the concrete under the plastic is dry and the surrounding surface is wet, then you have a sweating garage floor. However, if the underside of the plastic is wet and the surrounding surface of the concrete is mostly dry, then you have a moisture problem from below the slab.
Another sure indicator of a sweating slab is if you remove something from the wet garage floor that has a flat surface and you find the concrete dry underneath. An example would be a floor mat or a cardboard box.
On the contrary, if your garage floor looks dry and you remove an item to find wet concrete underneath, then you have a moisture problem from under the slab.
How to stop a garage floor from sweating
Stopping a garage floor from sweating can be more challenging to accomplish than you may be aware. It’s actually a problem involving the physics of condensation that you are trying to prevent.
For example, you cannot stop your garage floor from sweating simply by applying a sealer or coating. The surface of the garage floor will still get wet (sweat) because it is cooler than the dew point. If the air that comes in contact with the concrete has a chance to settle long enough, it will condense regardless if there is a sealer or coating.
In order to stop a garage floor from sweating, what you need to do is eliminate the conditions that make a garage floor sweat to begin with.
Think of it this way. If you park your car outside on a cool night with damp air, the surface will be wet with dew from condensation the next morning. If you wax your car to seal the paint it will not prevent it from getting wet, it will just cause the water to bead up nicely. It’s the same principle with your garage floor.
In order to stop a garage floor from sweating, what you need to do is eliminate the conditions that make a garage floor sweat to begin with. In other words, you need to do at least one if not more of these 5 things.
- Decrease the dampness/humidity of the air
- Increase air circulation across the floor
- Increase air temperature of the garage
- Change the garage floor surface
- Keep the garage door, man door, and windows closed and sealed
So let’s discuss each of these items in more detail, including what may be required.
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Decreasing the dampness of the air
Decreasing the moisture in the air is one of the more effective ways to prevent concrete sweating. If the humidity level in the garage is kept at acceptable levels during the times of year that sweating is most prevalent, then you will greatly reduce the chances of it happening at all.
The best way to reduce the moisture content in the air of your garage is with a dehumidifier. If set to run during the times of year when you encounter sweating, it can greatly help to reduce if not prevent it.
The key is to use the right dehumidifier for the job. For a typical 400-500 square foot garage, we recommend using a unit rated for 2500 ft² spaces or larger.
The reason for using a higher rated dehumidifier is that they will work much more quickly at removing the moisture from the air. Plus, garages are far more drafty than the inside of your home and will continually let in the relatively warm, moist air at a greater pace. Dehumidifiers rated closer to the actual size of your garage will be too inefficient to get the job done.
Also, it’s important to use a dehumidifier that is rated for working in colder temperatures. Many of the in-home units are not rated for temperatures low enough to work in a non-heated space and will freeze up if the temperature dips into the low 60’s.
One of our favorites is the 6 gallon Dehumidifier by hOmelabs. It’s rated for 2500 ft² and works well for a standard 2-car garage. For a 3-car garage or larger, the 9 gallon unit would be better suited.
The hOmelabs units are UL and Energy Star rated as well as rated by the manufacturer to work in temperatures as low as 35°F.
Price the hOmelabs Dehumidifier here
Though larger units such as these emit dry heat when in operation, it is not enough heat to affect the temperature of a cool garage.
Of course, running a dehumidifier requires that you only open the garage door and man doors when necessary. Leaving doors or windows open defeats the purpose of using one.
Increase air circulation within the garage
Another method that can be effective at reducing garage floor sweating is to run a fan to increase air circulation across the floor. If the air near the concrete surface cannot rest long enough to cool, then it will not condense. If it is allowed to rest long enough and form a cooler boundary layer of air at the surface, then it will condense.
A larger sized oscillating fan, like this Huricane Fan pictured above, can move a lot of air.
Let’s go back to the example of a car sitting outside on a cool, damp night. You may have noticed that dew will not collect on the car if you are driving it, but it will begin to collect sometime soon after you park it. The reason is because the air does not have a chance to settle on the surface and condense while you are driving. It’s the same concept with your garage floor.
A lower floor height is good for moving more air under parked cars if necessary, while the wall mount or upright stand will help to circulate more air throughout the entire garage. Just set it up in an area where it will cover most of the garage floor.
If you have a larger garage or more space, a larger wall mount fan is a better choice. They will move much more air and can create a circulation effect when directed towards the floor.
One of our favorite fans that we have used in our garages is the brand Hurricane. They come in a variety of sizes and configurations depending upon your needs.
Price Hurricane fans here
Many times the combination of moving air with a fan and using a good dehumidifier will resist some of the worst conditions for sweating garage floors.
Heat the garage
One option that is not always practical but is worth mentioning is to heat the garage. What this will do is bring the surface of the concrete closer to room temperature. When the conditions for sweating exist (relatively, warm moist air), the concrete will not be cool enough to condense the air that comes in contact with it.
The problem with heating a garage, however, is that it can take up to a week for the concrete at the surface to warm. Plus, running a heater for long periods can become expensive since most garages are not insulated. Amazon has a compilation of popular garage floor heaters if you like the idea of heating your garage, even temporarily.
If you are in the planning stages for building a home or separate garage in an area of the country where concrete sweating is common, you may want to investigate radiant floor heat for concrete instead.
Changing the flooring of your garage is arguably the most effective way to stop garage floor sweating. We don’t mean sealing the garage floor or applying a coating. What we are referring to is installing a different flooring surface.
Great examples are interlocking garage floor tiles, vinyl mats, and even automotive approved carpet for a garage. When such a garage flooring system is installed, the surface of the flooring will no longer adopt the temperature of the concrete. Instead, it will adopt the temperature of the air in the room.
As a result, when warm moist air is introduced to the garage, it cannot condense on the floor since the floor will closely adopt the temperature of the air. The other benefit to this type of flooring is that it will help to insulate your feet from the cold temperatures of the concrete underneath.
Seal the garage from drafts
Lastly, you can lessen the effect of garage floor sweating if you take steps to slow down the intrusion of relatively warm, moist air into the garage to begin with. This is particularly helpful when running a dehumidifier and/or fan. You can achieve this by ensuring that your garage door and man door are properly sealed and that windows are kept closed.
For the garage door, a garage floor door seal can be very effective at achieving this goal. It works well at preventing the moist air from traveling across the concrete floor and settling to cool.
Side garage door seals are something to be considered as well. Not only will they help to seal the garage door better, they also work well at keeping blowing rain and other critters from entering your garage.
For your man doors, make sure the door seal gaskets are in good shape. Also, don’t forget an under the door seal as well. Like the garage door, this helps to prevent outside air from flowing across the surface of the garage floor.
Make sure to check for any other areas of your garage that may be drafty or letting in air from the outside. Do not block off or seal any venting that may be required by local or state building codes.
We do realize that the minute you open your garage door to park or exit with your car, you will be introducing large volumes of outside air that may be conducive to sweating. However, many times this air can move in overnight or the early morning when you keep your doors closed. Making sure your garage is sealed properly can go a long ways towards reducing this air from getting in.
Final thoughts
As a reminder, sealing your garage floor will not stop it from sweating, but it will prevent some of the adverse effects such as efflorescence. You will also benefit from easier cleanups and stain resistance as well. Changing the flooring of your garage is the most effective method for stopping it completely.
You may have been surprised by the methods required to help prevent your garage floor from sweating. However, once you introduce one or more of the procedures we stated, you may significantly reduce or stop the problem completely.
Ok so what about a below-slab moisture problem?! How do you fix that?! You told us how to solve the sweating floor problem, but what about a slab that didn’t have a moisture barrier put down beneath it? What can be done about that?
Hello Josh. It can be very difficult to stop moisture that comes up through the slab from underneath. If the moisture is not heavy, the application of a densifier such as this one will slow down and sometimes stop the intrusion completely. If the moisture levels are less than 20lbs of flow per 1000 square feet per 24 hours, then you can apply special moisture vapor blocking epoxy primers to stop moisture. This type of product is more expensive and requires aggressive grinding of the concrete first before application. It’s also important to make sure there is proper drainage away from the slab. Broken water spouts and water that stands up against the slab will cause moisture that is hard to stop as well.
The interlocking tile flooring suggested (the ones that allow for air flow) are a good solution because they sit 1/2 inch above the concrete and allow for the moisture to evaporate while keeping the floor dry. I have to disagree with one suggestion made by the author around matting – which is that if you that down on a concrete floor that has moisture coming up from the ground, it’s going to trap that moisture and cause mildew (unlike the tiles)
Hi John. Just an FYI, sweating concrete is different from concrete that suffers from moisture that comes up from below the slab. Mats work well for sweating concrete because the surface temps will quickly adapt to those of the relatively warmer and moist incoming air. The incoming air will not be able to condense on the surface since the mat surface temperature will be above the dew point. If the slab suffers from moisture coming up from under the slab, then yes, a mat is not a good solution because it will trap moisture vapor underneath.
There was a development of 6 brand new houses with garages and the only one who had problems with the “sweating” garages floors in spring I assume it was because I was the only one who insulated the entirety of the garage so the inside air of the garage doesn’t balance with the outside air. Soon I open the garage doors I have wet floors because the garage is cooler. Any solution?
Hello Jorge. If your garage is insulated and you are experiencing sweating in the springtime, then it most likely is because your garage is not heated. Your insulated garage is allowing the concrete slab to maintain a lower temperature from the winter cold than your neighbors. When you open the door up in the spring time when relatively warmer air is outside, that warmer air will condense and deposit moisture on the slab when it settles and comes in contact with it.
You have two options. The least expensive would be to run a strong fan across the floor to stir up the air when the weather conditions that are conducive to sweating exists. Moving air does not have time to condense. The other option (since your garage is insulated) would involve heating your garage to a warmer air temperature in the winter. This will prevent the surface of the slab from getting cold enough to sweat in the spring time.
By the information in this article I suspect I have moisture under the garage concrete floor in just one area about 15 sq ft of the NW corner. What steps can I take to solve the problem that has been present since I bought this new construction home?. I’ve had the builder, lawn sprinkler contractor, and landscaper take a look with no solution. I live in the Puget Sound in Washington state.
Hello Gerald. Is your slab below grade or up against a hillside? I assume the builder checked to make sure that no water lines or drain lines run under that part of the slab? Does water drain away from that part of the home? Do you have any type of plans to do anything with the garage floor?
Hi, the back wall of my garage condensates in the middle. One day it’s wet another it can be dry. It is a new building constructed of 325mm cast reinforced concrete 100mm cavity with 50mm Eco therm insulation with a 225mm concrete block and then rendered on the inside. They is no garage door fitted at the moment, would this prevent this patch appearing?? Any thoughts would be appreciated. Southampton England
Hello Leigh. Yes, a garage door is going make a big difference. While the slab temps remain more constant due to the influence of the ground, the surface wall temps are influenced more by the air temps and creating conditions where air will condense.
I live in Wisconsin and in the spring of each year my unheated garage sweats and gets very dangerous to walk on, because it becomes very slippery. In the summer when the humidity is high the problems also occurs. I do not know if it is condensation or a problem below the concrete. My home is only 19 years old and it has happened every year.
If it is coming from under the concrete, how to I correct the problem?
Hello Stephen. Yours sounds like a classic case of sweating and not moisture coming up from under the concrete. You are located in the right area of the country for it as well. If you had moisture from under the concrete that made it as wet as you describe, then you would have it most times of the year. It would also take some serious conditions such as the slab being well below ground, a leaking water line underneath the concrete, and etc. If you have a box or mat on the floor when the concrete gets wet, is it dry underneath when you remove it? If so, then you definitely are experiencing sweating (condensation).
What can I do? Would Drylok work or Epoxyshield?
Hi Stephen. We give a lot to tips in the article to slow down and even stop the problem. As we state, applying a coating will do nothing to rectify the problem. You have a condensation issue and not a moisture issue.
Hi,
I have a sweating garage floor that seems to be exacerbated by old salt from car tires. When the sweating occurs it follows the pattern of where a car would have been parked – there can be very damps spots where car tires would have been and dry spots between them. My hunch is that salt in the concrete is pulling moisture from the air and making a basic condensation issue worse. However, there are no visible salt stains.
Any recommendations for cleaning/removing the salt embedded in the concrete?
Thanks for a great resource!
Hello Rob. Your theory may be correct. We happen to have an article about removing salt from winter garage floors. It includes a product we recommend using. One key to removing the salt is to use a shop vac to suck up the wet salt slurry you create when cleaning. Once it’s sucked up you then rinse. Once you clean the floor to your satisfaction, we would suggest using a densifier/sealer product like the one we highlight in this article. It’s very easy to apply and will help prevent the damage that salt can due to concrete.
I have an interlocking floor in my 2 car garage which I installed years ago. I am now finding a lot of excess water under the tiles and I am not sure how to keep the cement floor dry especially after a snow storm or heavy rains which are brought in by our cars. I have a ceiling fan and I used a leaf blower under the tiles in an attempt to dry out the cement floor but I need a better solution. Help!!
Hello Bruce. Are you saying that you never used to have water under the tiles until now or are you just now noticing it? Has something changed that is allowing water in? It can take a while for a lot of water to evaporate under the tiles. It generally is not an issue since the tiles cannot mold or mildew. If you are that concerned about it, you can disconnect one large section and pull it off to the side or out to your driveway and then sweep the water out or use a wet/dry shop vac.
Hi,
My daughter bought a house in December. When inspected during the summer months prior to purchase the inspector found no issues with drainage. The basement had been newly refinished for the sale.
The house is in NYS and when we had winter thaw and heavy rains in February she discovered water coming up from the floor in all areas of the finished basement. The flooring that was put down was completely ruined.
After having an engineer inspect the floors he said she was the lowest lying property in the area and the hydrostatic pressure was causing the issue. She got a report from building inspector for the town that had not been filed before sale stating that there had never been more than 4 inches of water in the basement at any given time. That sounds like a lot of water to me.
She has one pump running and has , of course, not replaced the floor. Is there any solution other than French drains to solve this problem?
Thank you
Hello Jane. we are sorry to hear of your daughter’s basement issues. Hydrostatic pressure is a powerful force. Unfortunately, there are no sealers or vapor barrier blocking coatings that can be applied from within the basement that will stop that much moisture. The moisture mitigation must be tackled from the outside first in order to be successful.
Hello,
I have an office space on the first floor of a building and just below our Space we have a company which runs it’s hub room with AC running 24/7.We have started to notice cold water on the tiles of my floor after they started operational which has ruined the furnished floor.We had asked them to do some sort of under deck insulation which they don’t seems to oblige. Please advice if anything can be done on my floor which will resolve this issue for me?
Thank you
Hi Rahul. Your suspicions are correct. The air conditioning from the space below is cold soaking the underside of your floor which is causing condensation. I would suggest getting building management involved. Your floor needs to be insulated from the cold air below or the problem will continue. In the meantime, you can try running small fan across the surface of the floor to reduce the condensation.
Hi , I have an 2 bay open cartlodge style garage with a power floated concrete floor . Being it has no doors I get airflow but this time of year with cold nights and some sunny days the slab condensates and is very slippery. I believe its is dew point issue and not moisture coming up even though no membrane was put down as it’s very hard to put a membrane over the steel raft without piercing it. Is my only solution the interlocking floor ?
Hello Andrew. One option you have would be to apply a clear MMA acrylic coating like this one here with anti-slip grit mixed in the final coat. These type of coatings are very durable and easy to apply. They are not as durable as epoxy, but if you are only parking your cars and not doing too much mechanical work, they hold up well. These are applied in thin coats, with the final coat getting the anti-slip grit mixed in. Two coats are generally sufficient. The concrete will still get wet from condensation, but it will not be slippery.
I live in the coastal SE, about 30 miles inland. My problem is the floors sweat from both condensation and moisture coming up through the slab which has no vapor barrier.
W have tried dehumidifiers but they can’t keep up. Floor fans help a bit. Even installed an industrial side wall fan.
Not only does the floor get wet, sometimes 1/2 inch of water! But everything inside gets wet from condensation.
I think what is happening is the floor gets cold, water is saturating the slab and when any warm air comes in it lifts the mpisture from both the air and slab so a double whammy!
Will a sealer/coating help seal out the slab moisture? I’m at my wits end, everything in the garage is rusting.
Wow… you are right about getting the double whammy, Jeff. Unfortunately, you cannot apply a coating to a slab that is emitting moisture from below. The moisture will cause the concrete under the coating to deteriorate and the coating will peel. Your only option is to apply a densifier. Assuming that the surface of your concrete is in good shape, the densifier will help to block off and close many of the capillaries within the concrete that allows the moisture to travel to the surface.
I live in a condo with 2 units. I live on the north side, my neighbor on the south side. Her garage never ever gets wet. Mine is wet a lot. If it is rainy or damp outside, my garage is wet. Neither of us leaves our units much. I do open my garage door one time a day to go get the mail. She is mostly home bound so doesn’t open hers near as much. She also keeps her home heating at 74 in the day and 60 at night. I keep mine 62 all day and night. I have fell so many times and gotten badly hurt on the floor. Is the fan or dehumidifier the best answer? Why would my side be so much worse?
Hi Elaine. There are a few reasons why you can be experiencing this. First, your northern facing garage does not get any direct sun and will stay much cooler than your neighbor with the southern facing garage which gets direct sun for most of the day. A cooler garage means a cooler slab. If relatively warmer moist air comes in contact with a cooler slab, it can condense when it comes in contact with it. This is more prevalent depending on what part of the country you live in. Using a fan to move air across the floor is the first step we recommend to combat this issue. You may also want to get yourself a carpet runner for the garage that you can walk on. This one from Amazon works well for that.
Thanks for a great article! Very informative.
The foundation of our house is concrete…it sweats bad…how can I stop this…
Hello Linda. We list the various methods to slow down or stop sweating in the article.
Our cabin has a concrete floor on good drainage that gets cool but not sweaty except one painted surface in the centre of the room. The painted shamrock surface gets drops of water on it during humid weather. We are considering installing a new raised flooring to warm up the floor. Is this a viable option?
Hi Peter. Yes, you should be fine. Sweating is due to moisture in the air condensing on relatively cooler concrete surfaces. It’s not due to moisture from below the slab. Installing raised flooring will stop the condensation and keep the new floor surface warmer than the concrete.
My daughter is buying a townhouse in Houston TX, and we noticed some bubbling of the Sheetrock above the trim on an interior wall and bowing of the glued down vinyl plank flooring.
The seller opened up the wall thinking it may be a water leak but no pipes in wall. Had a GC come in and he pulled the flooring up and found a wet slab.
The GC has pulled up the whole floor which was all wet (over 800sqft) and has dehumidifier and fans running to dry – then plans to put a sealer/barrier on before we go back with a floating vinyl floor with an attached moisture barrier.
The unit was built in 1978, likely no under slab moisture barrier, is in the middle of 6 units – and the neighbors report no issues. The unit was a rental and has been empty for several months – with no heat or ac on until went on market.
A comment made was that the lack of conditioning in the house during this period could have created the floor moisture. Does this sound valid?
Once all of this work is completed would the house staying conditioned keep the problem from returning?
Or does this sound like a bigger problem of moisture coming up through concrete and will continue?
Hello Deb. The fact that it’s a middle unit with that much water in the concrete while the neighbors don’t is suspicious. It makes us think that there may be a leaky main drain for the units or leaky water pipe under the slab. I would request that it be tested for such leaks before anything else is done. Professional plumbers usually have the equipment to run such tests. No, the lack of conditioning the air in the house would not have that kind of effect.
Hello
The back addition to the home has tile over the concrete and each spring and summer the grout between the tiles are wet as they get darker as if I had water spill.
Im not sure if water is coming from under ground. Any recommendations?.
Hi Violet. What you need to do is a simple moisture test during the time of year when this happens. Tape an 18″ square piece of plastic to the floor when things look dry. The idea is to cover as many grout joints as possible. Seal all the edges with the tape. When the grout joints on the outside of the plastic show signs of being wet, pull up the plastic. If the grout joints are dry under the plastic, then the wet joints are from condensation on the surface. If the grout joints under the plastic are wet or the underside of the plastic is wet, then you have a moisture issue from under the slab.
Hi there.
I’m in southwestern Ontario where the temps are extremely cold in winter and extremely hot and humid in summer.
I’m about to pour a slab in my newly constructed shop, and am planning on putting double bubble foil wrap under it, along with piping for infloor heat.
I wonder if you think this will be suffice. I’ve strongly considered styrofoam panels but have drawn the conclusion it could just be a waste of money. My only concern is that it may sweat in the warmer months.
After reading through your site, I think I’m fine to move forward without styrofoam, and just the wrap.
The surrounding area is relatively high and dry, with no concern of moisture under the slab. My thought wAs If im wrong and have sweating, I could just fire up the Infloor heat and it would
Solve it quickly.
Looking for your opinion.
Hi Nic. Have you read the many articles about foil faced bubble wrap? Here is one as an example. I do know that it will work well as a moisture vapor barrier if that is your primary intent. In terms of using it to insulate the concrete, I don’t think it’s going to do what you want it to do. About the only ones promoting its use are the companies that sell it. This is a quote from a concrete engineer with over 40 years of experience who lives in central Maine; “In heated structures, particularly with in-floor radiant, a minimum of 2″ of rigid board insulation is typically placed under the slab. You can use either XPS or EPS as long as it meets ASTM C578. In cold climates, rigid insulation should also be used vertically on your frost walls if you have them to keep frost from getting under your slab through the walls“.
Regardless, the radiant heat will take care of the concrete sweating. If you warm up the slab during the times of year when sweating is most prevalent, the moist air will not be able to condense on the surface and cause you problems.
Hi, I need your help please for my garage floor.
I live in Boston and i have a 2 car garage that also 2 floors. It has a garage door and 2 windows on the first floor and 1 window on the second floor. The 2nd floor ceiling also has air vents in the ceiling and the 2nd floor of the garage is insulated and the first floor is made from cinder blocks.
The structure is probably more than 75 years old.
My problem is that on some parts of the floor I get moisture (wet spots) and it happens even when it hasnt rained for days.
In fact, I notice it happens when the humidity is high.
I’ve been told by folks who have come out to look at it that it’s from water around the garage rising from under the garage and that I need to do the garage floor over and add a vapor barrier. But I cant believe that cause it happens even when it hasnt rained in days.
Another guy came out here and said I have to seal the floor, and that seems more likely, but I need someone to tell me if sealing the floor really stops moisture in the air from forming on the floor?
I believe its related to moisture in the air forming on my floor, but need help.
How can I fix this please?
I’ve been dealing with it for years.
Hello Bill. Before I answer the question I want to make sure I understand this correctly. Is the structure a 2 car garage with a living space of some sort above? Is the garage floor and entire structure above grade on fairly level ground?
Hi, I too am struggling for a fix on 2 car, heated garage (26’x26′). Walls and roof line ceiling are insulated (no “ceiling”, just goes directly up to roof line). I have done your checks and confirmed its concrete sweating / humidity issues.
wet floors and severe dampness started in early May and hasn’t gone away. Seems to be getting worse with the summer…oh and BTW I live 100ft from the ocean in MA :(. so quite humid area.
I only have 2 gable end vents (no room for soffit vents). Thought maybe I didn’t have enough airflow at the peak so I added a gable exhaust fan. That didn’t help at all. I have even tried to seal up the gable vents..no change either.
I am at my wits end with this garage and moisture issues. Don’t know what else to do beside try a dehumidifier, but I am very reluctant to run one of those for the REST of life (or garages life)
THanks,
Matt
Hi Matt. Sometimes the best solution is the simplest. Have you tried running a fan yet to blow air across the floor? If the air is moving, it cannot rest long enough to condense.
Hi Shea,
Thanks for reply. I just put a big fan on the floor in corner. I will let it run and monitor it over the next few days!!
Great!
Hi, I’m looking at getting garage tiles like you’ve suggested, but do I get the vented ones or the ones that are non vented (no holes in them)? Thank you in advance!
Hi Rick. Either style will work great as the surface will always be at or close to the relative air temperature and not the cooler concrete.
Cool thank you so much 😁
Hi Shea,
I’m getting ready to do my concrete garage floor with rustoleum rocksolid. I’ve wrote to you on different threads of yours. I made the concrete sweat this morning as I had a window A.C. unit on low all night and opened the garage door this a.m. to do the floor and it sweat pretty bad in a couple spots. Will the vapordike and poly flooring be ok to put down with this condition when it dries up? There was no rain or moisture coming up it literally happened in a couple minutes because the slab was cold and I introduced the warm air. If I am not mistaken this condition is okay for the flooring as opposed to moisture coming up. Correct?
Thanks,
Mike
Hi Mike. Because your surface prep was grinding, this will have allowed some of that surface moisture to be absorbed by the concrete. Just make sure it’s bone dry before you apply it and you will be fine. In case you have not read the data sheets on VaporDike, you can access them here.
Thanks Shea. I appreciate it.
Let us know how it turns out, Michael!
You’ve been awesome at answering questions. Thanks!
So im in Florida (super humid) and during heavy rains water floods our yard near the slab. We have water coming up from the slab and getting moldy under our mats.
We have a home gym so the mats have gym equipment on top of them (plus the mats are 100lb thick rubber – not easy to move and clean often).
We are planning to move within 3-4 years so looking for temporary or less expensive solutions.
I worry that trying to get water not to sit on the slab wouldn’t even work, as its probably so moist in the ground anyway (just a few miles from the ocean) and this issue is year round, not just rainy season.
So we are thinking maybe just covering the floor in thick plastic, tape it down, and mats on top with protect us, and get professional cleaners whenever we move and the plastic comes up..
Any other ideas or tips?
Hi Scott. Many Florida homes sit on soil that drains very well due to the sandy composition. According to one of our Sponsors (Legacy Industrial) who is located in Florida, slabs rarely have issues with drawing moisture up from below due to the good drainage. However, flooding is a different issue and concrete will soak up moisture like a sponge when that happens. Taping plastic down is not going to solve the issue other than providing a different surface for mold and mildew to grow. It will keep it off the mats, but it will proliferate under the plastic. The only solution that would keep mold down to a minimum and keep it off the mats would be to lay a sub-floor of polypropylene interlocking floor tiles. The underside of these tiles are designed to allow air flow and water drainage. This will allow moisture to escape and prevent the growth of mold. You can then install the mats right on top of the tiles.
Thanks for your reply! My mats have a tiny space for air circulation already (but clearly not helping or not helping enough).
So with the tiles that are not vented, will they still likely provide enough circulation. Will putting mats on top prevent any benefit from the vent regardless?
Do you have any specific tiles you would recommend?
Side note: Since we always get water up (different amounts) not just during rainy season, is there something else we should do to check for water? It’s not sweating because it only builds up in the center of the mats.
Thanks again!
It’s not surprising that you get wet spots under the center of the mats even when it’s dry, Scott. All concrete will contain very small amounts of moisture that escapes as moisture vapor during temperature changes. The mats are very effective at preventing the moisture vapor from escaping. It can only make it out where the seams are and is why it tends to collect in the center.
The interlocking tiles will provide airspace between the concrete and the mats which will allow that moisture vapor to escape. Any additional moisture that develops due to flooding will linger for a while, but it will have a chance to evaporate due to air circulation and not being trapped tight under the mats. In terms of tiles, as long as you stay with a product that is manufactured in the U.S., we recommend purchasing a budget tile and not a premium tile in your case. This one here by Garage Flooring LLC is a good example and about the least expensive available.