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You should never paint concrete while it is wet, and that isn’t just because it will be messy to do so.
It’s very important that the concrete is dry before painting over it, or else the paint won’t stick properly, and you’ll have issues with it down the line.
Suppose the concrete is wet or even just slightly damp. In that case, the paint won’t be able to grip onto the surface properly, and it will be prone to peeling off after a little time, making the paint completely ineffective and the job a complete failure.
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The paint might also start peeling off in patches so that the concrete surface will look uneven and worn and not in good condition overall.
That is why it is super important to ensure the concrete is 100% completely dry before applying a coating of paint. If it rains, for example, you should, on average, allow for a full 24 hours before painting to ensure it has had enough time to dry.
It is also why you have to be aware of the weather conditions before painting a concrete surface, as you have to time it so there is no rain and that it is warm enough for the paint to be applied properly to then dry fully.
So basically, if you paint wet concrete, the paint will not be applied properly, as it won’t grip onto the surface as well as it should. Therefore, the paint will likely begin peeling off after a little time, and the paint job will fail.
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Okay, so it’s super important to make sure the concrete is completely dry before you start painting it, or else the paint won’t stick properly and will start to peel off very quickly.
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But how do you know if the concrete is dry enough and ready to be painted? How much time do you have to let it dry? And what if it’s just a little bit damp? Let’s get right into it!
There are some obvious ways of knowing if the concrete is dry enough, such as touching the surface to see if it feels wet or waiting an appropriate amount of time after rain or other weather conditions to be certain that it’s properly dry.
But moisture and dampness, conversely, can be pretty hard to spot and, therefore, can’t be confirmed simply by looking or touching.
Instead, the concrete floor will have to be tested for dryness, which professionals almost always do so that the job can go ahead successfully. This test, which has been used since the 1960s, is still the most reliable way of testing the dryness of concrete to start painting over it.
What the test does, is measure the moisture within the concrete by using situ probes. These probes are sensors inserted into the concrete at different specific depths to pick up the amount of moisture trapped inside.
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So, for example, if the concrete slabs are only drying on one side, the sensors are inserted at a depth of 40% of the overall thickness. And if the slabs are drying on both sides, then the sensors are inserted at a depth of 20% of the overall thickness.
These probes then need to be left for quite some time to properly calibrate and ensure the results are reliable enough. Usually, they will be left for 24 hours.
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If you don’t have the means to test the concrete, then you won’t be able to know 100% for sure whether it’s completely dry or not, so beginning the paint job will always be a bit of a risk.
But if you’ve allowed for a good 24 hours after washing the concrete, and it’s nice and warm and sunny, then chances are the concrete will be dry, and it should be completely fine to paint over!
How Warm Does It Need to Be to Paint Concrete?
When painting concrete, especially outdoors, it’s very important to be aware of the weather conditions and to time the job just right so that the weather is optimal for painting. So basically, it needs to be dry and warm so that the concrete is fully dry, and the paint can be applied and then left to dry.
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But how warm does it actually need to be for you to paint concrete?
Ideally, you should schedule your outdoor paint jobs so they are done during the summer when it’s more likely to be warm and dry. The warmer it is, the faster the paint will dry, but also the better it will dry, as the cold can cause it to form cracks!
Also, the warmer it is, the less moisture and dampness in the concrete, and the better the paint will hold.
Most paints require it to be at least 50 degrees Fahrenheit warm outside to be applied effectively, especially coatings that are water-based. However, some paints can be applied in temperatures as low as 35 degrees Fahrenheit, so it’s all about finding the right paint for the right circumstances.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When Can You Walk On Painted Concrete?
Once you’ve painted the concrete, you need to wait until it is fully dry before walking over it or placing things on top of it. On average, the first coating of paint will take around 12 hours to fully dry, during which time it should be left to dry undisturbed.
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If you’re adding extra coatings of paint, they might take the same amount of time or slightly less, and they should also be left to dry undisturbed.
And to finish off the paint job, you will usually use a top coating or sealing layer, and it’s important to check the information as each will take a different amount of time to dry, on average.
But on top of this, if you want to avoid the risk of scratching the newly painted concrete surface, you should wait around seven days before walking over it with shoes or placing furniture on it.
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