Need new flooring over concrete? Got questions about moisture testing? Today we’ll answer one of the most common questions we receive from homeowners preparing to install laminate or luxury vinyl plank (LVP) flooring: “How long should you wait before installing laminate or LVP over new concrete?”
There’s nothing worse than having your concrete poured, getting excited to install your new flooring, but then having to wait. Everyone wants to know how soon they can lay their flooring, but if you install laminate or LVP flooring too early, you may run into trouble down the road.
Concrete’s surface may feel dry within a couple of days, but inside the slab, moisture can remain trapped for weeks or even months. Below we go into more detail about why waiting for the proper amount of time is so important when installing laminate or LVP flooring.
How Long Does Concrete Take to Dry?
As mentioned above, new concrete contains excess moisture. During the mixing process, water is added to activate the cement and allow for workability. Some of this water evaporates during curing, while some moisture remains inside the slab.
Installing laminate flooring too soon after the pour can cause issues with moisture wicking from the concrete up into your new flooring. If not given adequate time to dry, concrete can cause a number of problems for your flooring such as:
- Buckling
- Warping
- Mold
- Mildew
- Adhesive failures
- Loss of warranty
How Long Should You Wait?
Concrete begins to cure as soon as it’s poured but continues to release moisture and harden for years to come. Many people believe that 28 days is long enough to wait before installing flooring over a new concrete slab. While it’s true that concrete will typically reach most of its strength after 28 days, it can still retain moisture well past that time period.
Factors that affect drying time:
- Slab thickness
- Mix Design
- Humidity levels
- Temperature
- Job site conditions
- Ventilation
- Vapor barriers
Don’t Guess, Test!
Every slab is different, and concrete can dry at different rates. Just because your neighbor was able to install laminate flooring over their concrete porch after 30 days doesn’t mean that you can do the same. It’s always best to have your concrete professionally tested to ensure that it has reached acceptable moisture levels.
How Do You Test Concrete for Moisture?
There are a few different ways you can check whether your concrete is ready to have flooring installed over it. These methods include:
Relative Humidity Tests
One of the best and most accurate ways to test concrete for moisture is by using relative humidity testers. This requires small probes to be inserted into the concrete and can check for moisture levels beneath the surface.
Calcium Chloride Test
Calcium Chloride is a simple and affordable way to help determine how much moisture is being emitted from your concrete slab. This quick test will help you get a general idea of whether your slab has too much moisture.
Concrete Moisture Meter
While not always 100% accurate, concrete moisture meters can help you identify “problem areas” on your slab. These meters provide a quick and non-destructive way to screen your concrete and see if there are any high moisture readings.
Slab Thickness
Just like a thick cut of meat takes longer to cook than a thin cut – thicker concrete slabs can take significantly longer to dry than something that is only an inch or two thick. A general rule of thumb is that concrete can take about a month to dry per inch of thickness.
Will Florida Weather Impact Drying Time?
Yes! Believe it or not, Florida’s humidity can actually play a role in how long it takes your concrete to dry. Humidity works like this – if the air is already saturated with water moisture, it will take longer for your concrete to dry.
Installing a vapor barrier under your concrete slab can also help reduce moisture from coming up from the ground. A vapor barrier is usually installed during the initial build process.
Do You Need a Vapor Barrier?
The installation of a vapor barrier can help reduce the amount of moisture rising from the ground but it’s still recommended to have your concrete tested. Just because your porch has a vapor barrier doesn’t mean that there isn’t excess moisture.
How Long Should You Wait?
When it comes down to waiting for a concrete slab to dry, you really can’t go by any set amount of time. Concrete may be ready to accept flooring after 28 days, but trapping moisture can lead to problems down the road. If you have questions or concerns about your slab, we recommend calling a professional to come out and evaluate the moisture levels of your concrete.
If you are unsure if your concrete is ready to have flooring installed, reach out to the pros at Custom Concrete Prep and Polish. We offer concrete preparation, moisture testing, grinding and leveling as well as flooring sub-floor preparation services. Contact us to learn more.
