What Happens If You Paint Wet Concrete?

Concrete isn’t the most print-friendly type of flooring out there, so it should come as no surprise to hear that it is even more difficult to work with while damp or wet!

Though it should go without saying that freshly poured concrete cannot be painted for obvious reasons, moisture or water that is present under a concrete slab can cause a whole host of problems while painting, especially as it’s harder to detect and usually not visible to the eye.

For this reason, if you were to paint wet concrete, then the moisture present underneath the slab can create something that is known as hydrostatic pressure, which is a type of pressure caused by fluid being exerted due to the force of gravity.

This pressure can cause the paint to begin to separate itself from the surface of the concrete, while also potentially causing the concrete underneath to begin breaking itself down.

For this reason, the consequence of painting wet/moisture-ridden concrete can quickly become a very costly one, as it may require you to actually replace the concrete with new.

So, how can you avoid this? One of the simplest ways to check if the concrete you would like to paint is wet or full of moisture is by carrying out a moisture test with a moisture meter.

However, if you do not own a moisture meter then you can also choose to tape polythene to the surface of the concrete.

After 24 hours, if you notice beads of moisture on the underside of the sheet, then you can conclude that there is moisture present within the concrete.

How do you know if the concrete is dry enough to paint?

More often than not, you should usually be able to tell whether or not concrete is dry enough to paint by inspecting the appearance of the concrete.

However, if you are planning to paint it, then we recommend that you carry out a concrete moisture test, as this will help to prevent the costly process of having to repair the concrete if you paint while wet – which can cause the concrete to break down.

We strongly recommend that you use a moisture meter that will be able to use sensors to measure the relative humidity of the air that is trapped within the center of the concrete slab.

The moisture meter will then be able to alert you as to how dry your concrete is, as well as how much moisture is present within the concrete.

If you do this test and discover that the concrete is not completely dry, then you’ll need to give the concrete some more time (23-48 hours) to dry out some of the moisture before you test it again.

By this point, the concrete should be dry enough to be able to receive paint without the risk of hydrostatic pressure occurring, although, if you are finding that the concrete is still retaining high levels of moisture, then you may need to consider moisture mitigation.

Generally speaking, it’s quite rare for concrete to contain no moisture at all, which is why it’s widely considered acceptable to paint over concrete that has small amounts of moisture.

Nevertheless, if your concrete has very high levels of moisture that won’t go away, you may need to consider taking the slabs out and putting new ones in.

How warm does it need to be to paint concrete?

The answer to this question greatly depends on what type of concrete paint product you are using.

In general, as concrete is most commonly used in basements and outdoor spaces, you will need to use an exterior, water-based coating or paint across the surface of your concrete.

These types of exterior paint products offer plenty of leeways, and can often be applied in a variety of temperatures, though the specific temperature range will depend on the paint type, the manufacturer, as well as the overall quality of the product.

However, more often than not, most paints designed to be used on concrete can be applied when the surface temperature is as high as 30-35 degrees Fahrenheit, although there is some paint that will allow you to paint over concrete when the surface temperature is as low as 20 degrees Fahrenheit.

As concrete is one of the most tricky surfaces to paint, we recommend contacting your manufacturer’s customer service team if you’re unsure about what temperature you should paint your concrete in, as this will save you from any costly repair bills further down the road.

When can you walk on painted concrete?

If you’ve recently painted an interior or exterior concrete floor, then you’ll need to give it some time to properly dry before you walk over it.

Usually, you will need to allow the paint around 1-2 days to fully dry before you begin walking or placing any furniture on top of the painted concrete.

As a general rule of thumb, allow the final topcoat at least 24 hours to dry without being touched or walked on, as this will help to ensure that the finished paint job is smooth, even, and professional looking.

On top of that, giving your painted concrete plenty of time to dry will also help to ensure that you do not smudge or damage the paint, which means that you won’t have to worry about having to re-apply.

However, despite this, it’s important to keep in mind that a variety of other factors can contribute to the overall drying time of your painted concrete.

The most common factor that can slow the process down is humidity (moisture in the air) which can cause the paint to take longer to fully dry.

To help prevent this, we recommend trying to keep the area as well ventilated as possible if you’ve painted an interior surface, and the use of fans and even shading if you have painted an exterior surface.

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