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How Long Does Concrete Take to Dry
Concrete is usually dry enough after 24 to 48 hours to walk on. For concrete to dry and reach its full strength, it typically takes about 28 days per inch of slab thickness.
Once conditions are conducive for the concrete to cure to 85-90% relative humidity. We say ‘once conditions are conducive’ because concrete that was put down a year ago might have been exposed to the elements for eleven months and only enclosed for the last month.
Since concrete drying time is a major factor in the schedule of most construction projects, shortening that time can save you a lot of money.
Drying is critical when a flooring system is installed over the concrete slab. If the slab isn’t sufficiently dry when installed, the floor might be seriously damaged by the excess moisture.
summary
The concrete curing time takes about 28 days to be fully cured. Differences in weather, mix, other items can slightly change the timeframe of the curing period. The general rule of thumb for concrete drying is 28 days to dry for every 1-inch of slab thickness.
The Difference Between Concrete Curing and Drying
Concrete curing and concrete drying are two different processes.
How Long Does Concrete Take to Cure
The concrete curing process is usually mostly complete after 28 days. However, the concrete will continue to harden further for a significant amount later.
Curing is the process of hardening that begins immediately after the concrete is poured.
Even after the concrete is cured, excess water still must evaporate from the concrete. While it only takes around 28 days to cure concrete, drying can take months.
How Long Does it Take for Concrete to Dry
The general rule of thumb is that concrete takes about 28 days to dry for every inch of slab thickness. Within 24 to 48 hours, the concrete will be ready for foot traffic.
However, as we pointed out above, the conditions need to be right. You’ll need low ambient relative humidity and a consistently warm temperature. You can achieve this by enclosing the space and then turning on the HVAC.
How Concrete Cures
There are many types of concrete, but they all contain three basic components: cement, aggregate, and water.
When water and cement are mixed, a chemical reaction occurs that binds them together. This is what causes concrete to harden. In the process, the concrete becomes porous, and a certain amount of this water becomes part of the concrete.
The water that’s leftover either evaporates or remains in the capillaries of the concrete.
How Concrete Dries
Concrete dries as the water inside it evaporates through its surface. As this water evaporates through the surface, water from deep within the concrete moves through the capillaries and up to the surface to replace it.
As long as the surrounding air can hold more water vapor, evaporation continues. When the surrounding air can’t hold any more water vapor, evaporation or drying of the concrete stops.
How to Speed Up Drying: Before the Pour
Admixtures or the right balance of water can greatly help decrease drying times.
There are a few things you can do before you pour the concrete that will speed up the drying process:
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- Use the correct amount of water in the mix. If there’s too much water, more water will be left over after proper curing that will need to evaporate. That means a longer drying time.
- You can use a high cement content mix to reduce the drying time. However, there is the risk of cracking due to shrinkage.
- Are you using lightweight concrete? Lightweight aggregates absorb a lot of water, increasing the drying time. You can reduce the drying time by replacing these lightweight aggregates with synthetic aggregates that don’t absorb water.
- If possible, don’t use curing, sealing, or bond-breaking agents. They can inhibit evaporation from the concrete’s surface, increasing drying time.
How to Speed Up Drying: After the Pour
Once the slab has cured, enclose the space as soon as possible to protect the slab from absorbing any additional moisture.
While protecting the slab from additional moisture is important, there are a couple of other factors that affect drying after the pour:
- The ambient relative humidity and temperature of the air
- The temperature of the slab itself
The ambient relative humidity is important because it controls whether water can evaporate from the slab. If the ambient relative humidity is too high, your slab won’t be able to dry.
Enclosing the space allows you to use HVAC to control ambient conditions. In cooling mode, HVAC systems act like refrigerating dehumidifiers and usually maintain a 50% relative humidity level, which is perfect for drying concrete. They lower the relative humidity in heating mode by raising the air temperature.
HVAC systems are also a great way to get air circulating the concrete, thereby reducing drying time.
summary
[Tips] How to Speed Up Concrete Drying Time
- Use the correct amount of water in the concrete mix. Too much water can increase the drying time.
- Do not over-trowel or seal the surface. This can block the pores in the concrete, diminish moisture evaporation, and increase the drying time.
- Keep doors and windows closed, the HVAC running, and fans circulating the air.
- You can also use dehumidifiers to remove moisture from the air. This will speed up the overall drying process of the slab.
To really speed up concrete drying time, enclose your slab and ensure the HVAC system is on.
Dehumidifiers
Some facilities have central dehumidifiers that can be used to speed up the drying process. You can also rent portable dehumidifiers and even fans.
Both centrally installed and portable units are available that use one of these methods.
Testing the Concrete for Dryness
You can’t tell if the concrete slab is dry just by looking at its surface because the surface is nearly always drier than the center of the slab. Testing the concrete is the only way to know if it is dry.
Concrete moisture testing has been going on since the 1960s, and today there’s a scientifically proven way to test the moisture content of a concrete slab easily. The test is called “the relative humidity test using in situ probes” and is the basis for the ASTM F2170 standard.
The test uses sensors — inserted into the concrete at specific depths — to measure the relative humidity of the air trapped in the concrete. For slabs drying on one side only, the sensors are inserted to a depth of 40% of the slab’s thickness. For slabs drying on both sides, the sensors are inserted to a depth that’s 20% of the slab’s thickness.
The Wagner Meters Rapid RH® L6 system is an in situ relative humidity testing system that conforms precisely to the ASTM F2170 standard. The single-use L6 sensors are factory calibrated and easy to use.
Once they’ve been installed in the slab and allowed to equilibrate for 24 hours, you can take repeated moisture readings whenever you want. Unlike reusable probes, the L6 sensors never need recalibration.
Free Download – 4 Reasons Why Your Concrete Is Taking Forever to Dry
How Do You Know When the Concrete Is Dry?
You don’t unless you test it. If you’re lucky, it will be dry. However, it often won’t be, so you’ll need to give it some more time to dry and test it again. How much time you’ll give it to dry before testing again is pretty much the best guess based on experience.
The slab will be dry enough to receive the floor covering at some point. Of course, this is an unpredictable process; schedules can slip and costs can mount up.
You can use a moisture mitigation system when you absolutely must install the floor covering, but the drying process isn’t complete. If you go this route, choose a high-quality product that adequately seals the moisture into the slab.
Save time and money by using the most accurate concrete RH test.
Conclusion
Testing a concrete slab is the only way to know if it is dry. The most accurate test for this is the in situ relative humidity test.
Data logging throughout the drying process allows you to detect problems early, correct them, and will aid you in determining what is responsible for slow drying. This protects you from liability.
Trend analysis helps you make accurate projections and create tighter schedules. This saves you both time and money.
Concrete drying time is a major factor in most construction projects’ schedules; when you shorten that time, you save money. Following the tips in this article will help you do that.
(Some of the information is according to the Portland Cement Association)
Are you looking for a concrete calculator to estimate how many cubic feet and cubic yards of concrete you will need to fill your space? Try out our concrete calculator.
Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.
Last updated on June 21st, 2022
800-634-9961
Thanks for publishing this excellent work. Keep up the great work.
Hi Jason,
We are awaiting the builder to lay a top vinyl floor on top of the poored concrete. The builder runs heaters and blowers in our house every day and night to lower humidity (its been about 1,5 week since the last (thin) layer of concrete has been poored to even out the floor). At what humidity level can we progress to lay to vinyl floor? The builder says 50%, but not sure if that is the case. It is currently at 70%. He warned me that too much speed will potentially cause mold in the future. I agree that quality comes first, but I already live there with my kids and speed is important for me as well…
Many thanks in advance!
Arjan
Arjan:
Thanks for the question. I would contact the manufacturer of the vinyl you are having installed and see what their moisture thresholds are for installation. If this is a floating floor, I completely agree with your installer’s perspective that mold could be an issue in the future if moisture is too high. Whether adhered or floating, too much moisture will also potentially ruin the floor.
Good luck.
beton aloka produces lightweight blocks and estimates the drying time of lightweight cement blocks to be two days.
I drilled a 24” diameter hole, 6’ deep and placed a 16” electrical pole into the hole and then filled the hole with cement. Will the cement around this pole every dry?? Maybe after a month?? How long do you think??
Humidity is such a big factor when it comes to drying concrete! So I say amen to that brother. Sucks if you have to seal to prevent blotting but hey if you are going for quality, seal it.
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Hi Jason.
How long do you recommend waiting before polishing a 3” interior slab after poured? I like the industrial look of a concrete floor – just polished.
Thanks!
CC,
Typically waiting at least 28 days for concrete curing is recommended, but there are systems that will allow you to get on much sooner.
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Had a 14×48 slab poured inside an existing building with a garage door and a side door. The previous floor was wood and over the years animals would get under it, etc. so always wanted a nice slab to put a 4 post lift on, instead of the previous wood floor. This was poured 6 days ago. The building is insulated and outdoor temps around 85 deg and humidity around 50 %. I left the garage door open a few feet for airflow and the side door open and temp inside will be around 77 deg. Should I be doing this for this first week or so? If I don’t open the garage door and side door humidity inside the building is around 70% and will get into the 80’s if I don’t open anything.
Just wondering.
J,
Thanks for the question. I can think of no reason why having airflow and lower the humidity in that building early on would cause any problems at all. Let me know when the lift is in so I can come use it. Enjoy.
This is the best write up on how to speed up the concrete dying time.I really loved it and thank you very much for sharing this with us. You have great visualization and you have really presented this content in a really good manner.Keep sharing such informative articles in future.
It was interesting when you talked about how mixes with high cement content are able to dry more quickly after they’re poured. My husband and I want to have a concrete driveway installed for our new vacation home since we think that would look more elegant than the current gravel one. Asking about cement content should help us find a knowledgeable contractor for the job, so thanks for sharing this info and giving me the idea!
Hi,
Long story I’ll make it short. The flange under our toilet broke off clean from the bend. I went to hardware store bought ready mix concrete patch to fill the small space around the bend. Do to the fact The bend is still intact with no damage I need to drill the flange into the concrete8 for toilet bowl to be held down. I poured it at 2 pm and left it to dry it’s been about 4 hours and is still drying. So my question is there a better Process To help accelerate the pro cces! Thanks
Arturo:
So based on this situation, you don’t care about dry, you care about hard so you can drill into the concrete. Depending on the type of mix, you may be able to drill in a few days. Good luck.
Jason,
My question isn’t about moisture but maybe you have an opinion.
I just poured a 3 1/2” thick 7’ x 4’ slab with #5 rebar spaced at 8” in both directions suspended 1” from the bottom. The slab is going to cover a 6’ x 3’ block septic tank for my hunting camp. I know that’s a small tank but I’m the only one that will be using the camp. Do you think 28 days will be long enough for the slab to cure before it can be lifted into place? The slab was poured on the ground and framed with 2x4s, I put a plastic sheet underneath before the pour. I used Quikrete High Strength concrete mix from Lowe’s. It will be exposed to the elements but covered with a plastic sheet. My camp is in central Florida.
Thanks
Jim:
Thanks for the question. Based on the specs, properly proportioned Quikrete High Strength is rated at 4000psi. Comparing it to a tilt wall construction process, 3000psi seems to be about the only technical number I can find that may have some relevance here. With that, 28 days seems to be reasonable. One thing you need to be careful of though is moving the slab, no matter the compressive strength. I would do some research on tilt wall placement to get some pointers. Good luck.
I am building a redwood party fence in the backyard. I hear it take 24 hours for the cement at bottom of wooden posts to dry and harden. Is there an additive at hardwire stores that quickens the drying time, say in 4-5 hours?
Ray:
Thanks for the question. I would go with a fast drying concrete like https://www.homedepot.com/p/Quikrete-50-lb-Fast-Setting-Concrete-Mix-100450/100318521 They claim it sets in 20-40 minutes. Good luck.
Jason
I just filled a sunken living room space with 7 inch’s of concrete and wanted your advice on curing time before installing Luxury vinyl tile. My concrete guy says 30 days. The floor installers are painting a rubber type membrane on the concrete first then the plastic moisture barrier then the LVT. Do you think 30 days is enough time in our air conditioned home for curing, I was leaning toward more time maybe 60 days, its a real inconvenience but we want to make sure the new concrete has cured.
Appreciate any advice, we are in Florida and keep our inside temps around 74 in the summer.
Keith
Keith:
Thanks for the questions. Curing and drying are two very different things. Your concrete guy is correct on the curing side. Usually, it takes about 30 days for the concrete slab to reach about 80% of its specifics structural strength (curing), but there is still plenty of water left in the slab to dry to an acceptable level for the finished floor product. The flooring system you are installing should have maximum recommended moisture levels within their written installation documents. I would consult this and then perform the appropriate moisture tests to ensure you are within those limits. Good luck.
I’m kind of shocked at this article. After a pour, concrete does not dry, it cures. Moisture must be retained in the concrete for proper curing and hardening. In fact, installers often cover concrete to help it retain moisture for the required time period. For proper curing to take place, the 28 day rule of thumb is typical for standard concrete, regardless of the thickness, since adequate moisture retention promotes curing through the slab. Once cured, then removal of moisture so flooring can be installed is a later concern, which I suspect is the intent of your article. I hope nobody here tries to immediately dry their concrete as you’ve directed and then ends up with a damaged slab because they did not leave adequate time + moisture for curing.
Jeff:
Thanks for the comment. I am fully aware of the facts that you cite regarding drying, curing, and hydration. The assumption in this article is that the 28-day curing window has passed because most projects wouldn’t even think about attempting an expedited drying concrete drying process until the building shell is near whether tight, which in my experience, is at least 28 days. Thanks again and I will look to see about making this delineation more clear in the article.
Jason
I do like it when you said that dehumidification is one of the best ways to quicken the drying speed of the concrete because it will reduce the dew point so that the moisture in the concrete will evaporate. The only problem is that we do not know how to do this since none of us in the house knows anything about concrete works. Perhaps, we can ask the contractor that we will hire since we want the driveway to finish by the time dad returns home next week.
I do like it when you pointed out that the reason why concrete takes time to dry is because the water trapped in it needs to fully evaporate first. We really want to make it so that the concrete flooring will be dry a day or two after it has been poured, so I want to know what we can do. Perhaps, we can reduce the amount of water in the concrete but not in an exaggerated way so as to avoid adverse effects. I will talk to the contractor about what we can do. Thanks!
Hello Jason,
I had a problem with moisture coming up through an old slab foundation in a bedroom, I had the slab removed and re- done, added a moisture barrier and repoured the slab. How long should I wait before adding flooring like laminate or anything else on top.
J:
Thanks for the question. It all depends on how long it takes for the slab to dry to an acceptable level for the laminate. Concrete dries based on ambient conditions, not on a clock, per se. Reasonable air temperatures and relative humidity in the environment are more compatible with concrete drying. This being said, measuring the moisture in the concrete is the only way to know whether the conditions in the concrete are acceptable for the finish installation. I would consult the laminate manufactures installation guidelines for this specific information on what those maximum moisture levels are and the methods of measuring they will accept. Good luck.
Jason
We are having a similar problem with Denise Supple, crazy as it may seem. We had a water leak 16 years ago in a hallway and the water pooled in the only room that had a wood floor under the existing Laminate flooring. The leak was fixed at the time as was the only place in the laminate flooring that had buckled, in the office. Fast forward to 2018, we are doing a little remodeling in our office and we pull up the laminate flooring and what do we find?? Water, moisture, mold, disinigrated wood. Guess the flooring contractor 16 years ago missed something. Everything was pulled up 3 weeks ago and we are down to the concrete slab, our moisture readings are so high that we as well have been unable to put a new laminate floor in the room. After reading your response to Denise, we felt a little better and we purchased a dehumidifier and have been running that for 2 days, the humidity in the room seems to be rising, but moisture is leaving the room so I’m a little unclear how this whole process is actually working. We live in sunny Arizona, where record temperatures are upon us. We also have a high powered carpet dryer running in the room. I’m assuming we just need to be patient, my small project turned into a huge project that in the end will be a good thing. We had a company come out to do a leak test (just in case) and no leaks were found thank goodness. Any other suggestions you could offer would be greatly appreciated.
Lolos:
Thanks for the question. Yes, patience is a big part, but based on my experience with older construction (in AZ, even newer construction at times), patience may not even be enough. This may be more of an issue than just the water leak from 2002. At times, slabs are/were constructed either without vapor retarders directly beneath the slab or if they had them, they have long since degraded due to the various materials used. Unfortunately, without this retarder, moisture vapor from the soil has direct access to the bottom of the slab which can lead to issues as you describe. I would continue the process you are doing, but I would also look to have someone (geotechnical engineer?) come out and do core samples of the slab to verify there is an intact vapor retarder. If there isn’t, all that you are doing is for not. Good luck.
Jason
Hi , don’t know anything about pointing inbetween my patio slabs .The young man put this dry ciment i brushed it in how long does it take to dry
Thanks for the comment. Dry is a relative term and is based off of the ambient conditions. I would have this discussion with the young man that poured the slab.
Thanks,
Jason
We had a leak in the hot water pipe in the cement foundation. We had the leak fixed. We had engineered wood on top on the cement which was all pulled up. The problem now is that the flooring guy will not install the new wood flooring because the moisture in the cement is reading really high. Our contractor brought in the dehumidifiers and ran them for a week. The moisture in the cement is still very high. Do you have any suggestions on how to dry the concrete? We had a leak detection company come back out and there is not a new leak. We can’t seem to make any progress.
Denise:
Thanks for the comment. Consistent environmental conditions (temperature and humidity), air movement across the surface of the concrete, and dehumidification are key. The problem may take longer than a week to rectify. Another option to discuss may be a better adhesive or moisture mitigation product that will allow the floor to be installed in its current condition. It may be worth the discussion.
Thanks,
Jason
I have a brick floor that was flooded with about 2″ of water when a washing machine hose failed. The flooded floor lasted about 7 hours before we got home. It’s about 600 sq. ft. of brick flooring. We had a professional crew come in and remove all the old sealer about 10 days ago. They had to re flood the floors to do their work. How long should we wait before applying the new water-based sealer? The mortar between the brick is still wet. There is a visquine (sp?) barrier under the slab.
Carlotta:
Thanks for the comment. I really can’t give you a timeframe on how long it will take the brick to dry. I would talk with the manufacturer of the sealer and tell them the situation to get their input. I can tell you though, air movement across the surface of the brick and good environmental conditions will help the process.
Thank you,
Jason
We have had a water leak in a heater pipe in our bungalow, we have concrete floors and have industrial dehumidifiers and drying fans, but still struggling to dry the floor. The drying company say they need to skim the floor by about 2 mm. Do you think this will help to dry the floor. The bungalow was built in 1988.
Barry:
Thanks for the comment and sorry for all of the issues. I can’t say that I have ever heard a recommendation to skim because a floor was too wet, nor do I understand how it would work unless they theorize that the excess moisture on the surface can be utilized in the matrix of the skim coat. I understand drying, so for me, I would stay the course with drying. The other way may be effective, but I’m not sure.
Thanks,
Jason
Joe,
we had a concrete floor done in our backyard. It has been 3 months and it still looks like patches in it. Is it because it’s not dry yet?
i called the company and they said it’s take time to dry. They just finished sealer coat yesterday. The cement pour was about 31/2″.
please help. this company i am not happy with. all they care for is money.
Thanks,
kundan
Kundan:
Thanks for the question. I can’t say for sure, but my best guess, based on the information you provided, is that the concrete hasn’t had enough time to dry. I hope this helps.
Thanks,
Jason
Jason Spangler
As the parking lot pavement is always cracking , we are considering pouring concrete onto a parking lot area at a business park which will be driven on by cars and occasional lighter delivery-type trucks. The tricky part is closing the parking lot so the concrete product can set up properly, all without driving the tenants into despair.
Do you have any thoughts on this process?
Thanks
Joe Ebin
Joe:
Thanks for the comment. I think your best bet would be to get in contact with a local concrete finisher and get his/her input on this. I would imagine that with some concrete design modifications (faster curing, higher compressive strength) and timing (weekend pour, holidays) you could pull it off without a hitch.
Jason
We have built a new house….well still building….we took over after the contractor was done with the drywall. The drywall was completed about late October. We didnt do the flooring until after Christmas. We came in in may almost ready to move my mom into her new house and the flooring had buckled. We someone for moisture under the floor. We’ve had plumbers and everyone out. We can’t figure out why the concrete is now retaining moisture. It wasnt before. It doesn’t flood, it sits high. Its been over 100 degrees alot this summer. We live in West Texas so it’s not humid. We just can’t get it dry. You leave something on the floor, come back the next day and it’s damp underneath. We are at a stand still. Noone seems to be of any help around here. My dad passed away so this is my mom’s mother in law house. Right now we are all living out of boxes trying to this figured out! What do we do??
Kimberly:
It would be easier if you just give me a call. I am in the office Monday-Friday 7:30am-4:00pm PST. Our office number is (800) 634-9961 and you can ask for me directly.
There were various leaks in my tank wall external side. After repair, all the repair points are having moisture content over 6% due to which I am unable to start the coating. Will blow drying the specific point help in reducing the moisture content ?
If the ambient conditions, temperature and relative humidity are reasonable levels where they can “accept” additional moisture, then moving heated air across the surface will help (how much is anyone’s guess). Left to its own though, the ambient air may become saturated to the point that it can’t accept any additional moisture.moisture, thus eliminating moisture movement from the surface of the concrete. Also, should you stop the heated air during this time, the likelihood of the moisture moving from the air back into the surface of the concrete is high. This is one of the reasons why some type of dehumidifier is critical in this process.
Jason