Have you ever wondered whether you can put paint on concrete while it’s wet? It’s not often advisable to put paint on a surface that isn’t clean and dry, because water can prevent the paint from bonding correctly – but is that also true of concrete?
Can you paint wet concrete? You should not paint concrete when it is wet. Wetness prevents paint from adhering properly, and can cause it to bubble and peel soon after application, even if you apply it in thin layers and let each one dry thoroughly. It’s therefore important to be working with a dry surface, in dry conditions, if possible.
We’re going to use this article to understand why you shouldn’t paint wet concrete, what will happen if you do, and how to deal with concrete that is perpetually wet. This should help to ensure that any paint you apply to your concrete sticks well and lasts for many years.
Is it Okay to Paint Wet Concrete?
You should not paint wet concrete. This is true whether the concrete is wet because it has just been laid, or wet due to rain or ambient humidity. The paint will not stick well to the surface of the concrete, and will soon peel off and look messy. To save time, money, and materials, avoid painting wet concrete.
Paint cannot stick well to wet concrete, because the moisture beneath the paint will create a phenomena known as hydrostatic pressure. This pressure will push the paint away from the concrete, and even paint that appeared to stick well will soon start to peel off, leaving the concrete exposed again and wasting the paint.
It can also damage the concrete underneath, which might mean that you have to tear it out and re-lay it. Obviously, this needs to be avoided, and therefore you should make sure that concrete is as dry as possible before you paint it.
That will generally mean letting any new concrete cure for as long as a month before you paint it. Although concrete dries enough to walk on it within 48 hours in most cases, there will still be moisture in it for as much as a month after it has been laid, and it doesn’t reach its full strength until this point.
That means you need to avoid painting all new concrete projects until they have had sufficient time to cure to prevent problems from arising. It’s better to be patient than to end up redoing the whole concrete surface because you painted it too early.
What If the Concrete Has Been Rained On?
A surface layer of moisture tends to be less problematic to deal with, but you still shouldn’t paint on concrete that has recently been rained on, for the same reasons. It’s important to let the concrete dry as thoroughly as possible before you put the paint on it. You can dry it yourself using a towel, but some water will remain.
Ideally, you should only be painting outdoors when the weather has been dry for a few days, and is going to be dry for several more days. If that isn’t possible, try to cover up the concrete before the rain comes, and keep it covered while the paint is drying. Don’t leave it exposed when the weather is wet.
Where possible, complete outdoor painting projects during the summer. The concrete will dry more quickly, as will the paint, and this increases the chances of you establishing a good bond between the two. If this can’t be done, choose a dry spell and protect the concrete as much as you can.
How Do You Tell If the Concrete is Too Wet?
Sometimes, it’s hard to tell if concrete contains trapped moisture. Fortunately, you can test this by taping a piece of clear plastic over the surface, and waiting until the following day to see how much condensation collects under the plastic.
The moisture in the concrete will gradually be released into the air above, so if you put a large piece of plastic in place on top of it, the plastic will trap this moisture and it will condense against the sheet. You will see the droplets collecting against the sheet, and this tells you that the concrete isn’t ready to be pained yet.
You can use any size plastic square, provided it is big enough to collect some moisture. Make sure you tape the edges down firmly to ensure the moisture isn’t simply escaping from the sides, and wait a full 24 hours before you check it for condensation. This should be enough time for droplets to gather so you can determine how wet the concrete is.
It might be tempting to rush through with the project even if you can see moisture, but don’t do this. You must make sure the concrete is dry enough to hold the paint, or it simply won’t bond.
Can You Use Damp Concrete Primer?
Primer is an important product in many DIY situations, and if you’ve got concrete that is permanently damp because of a moisture problem, you can apply a damp concrete primer. This product is specifically designed to be used after the concrete has been sealed and it will help to protect both the paint and the concrete.
You need to make sure that you have purchased a primer that is suitable for the job, however. Just applying ordinary primer to your concrete will not make it okay to paint on wet concrete. Use damp concrete primer or ensure that the concrete is dry before you start painting if you want to ensure that the paint will adhere.
In almost all cases, it’s better to get the concrete dry first, but if there’s a moisture problem with a concrete floor, damp concrete primer can be part of the solution. You will still need to let new concrete dry before applying this product.
Painting wet concrete will almost invariably lead to bubbles, cracking, and peeling. It can even cause damage to the concrete, so it’s important not to put paint on a concrete surface until the moisture has evaporated. Be patient and use a plastic sheet to test before you start.