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Why Does Paint Crack and How to Prevent It

Posted by Victoria Yardley on

Why does paint crack

Painting your home can be a big job and it's not always as simple as just opening a tin of paint and laying a brush to walls. There are other elements to consider in order to avoid any complications. In this article we take a look at a commonly asked question in the world of painting and decorating which is ‘why does paint crack’? Hopefully getting to the bottom of this will help to provide you with tips to avoid this issue in the future. 

Why Does Paint Crack?

There are actually a number of reasons why paint might crack. This can range from low quality paint to damp and moisture or even poor application. Fortunately, it is possible to prevent your paint from cracking and achieve your desired finish if you prepare and apply the paint properly.  Here are three of the main causes behind cracking paint: 

Fresh Plaster

The main reason why paint cracks is due to poor preparation on fresh plaster.  Fresh plaster needs to be totally dry prior to applying paint.  It also needs to be primed before adding emulsion. Fresh plaster has a very porous surface with many teeny tiny holes which will quickly absorb the paint if it has not been prepared properly first.  These little holes needs to be ‘filled in’ first or the paint will be absorbed and at worse it can cause cracking, at best, it absorbs too much paint which can be expensive. Preparation can be done in one of two ways:

  • Use of a good quality primer
  • Application of a mist coat

NEVER EVER use a cheap contract matt to prime or mist coat fresh plaster (or any time really!). There is a huge misconception that using cheap contract paint to prime a surface is a good thing.  It isn’t!  In the words of our Technical Director contract matt ‘is the devil’s work’.  What happens is that an already very porous surface is painted with a cheap, chalky and unstable product to produce a mist coat. This then offers up a very porous, thirsty surface and as the top coat sinks into the wall it has to work very hard to perform well, and this is why oftentimes paints crack.  

Insufficient surface preparation

The first way you can prevent paint cracking is by ensuring that you have sufficiently prepared the surface. Whether the surface is a wall or a ceiling, the preparation is more or less the same. Preparation generally depends on the current state of your walls, if there is already visible cracking it is important to remove any previous layers of paint and smooth out the surface using the right tools such as a sander or scraper. Next it is important to pre coat the walls with an appropriate primer.

Another important thing to check before painting is to look for any exposure to damp or moisture. This is because damp is a common culprit behind cracking paint. If you do have damp be sure to resolve this issue first before painting the affected area.

Poor application of paint

Another possible answer to the question ‘why does paint crack’ is poor application of the paint. Over thinning your paint and applying too thin of a layer can cause the paint to split and crack. Conversely, using a heavy hand to apply paint that may be too thick can lead to what is known as ‘mud cracks’. This is where the paint has been applied too heavily and creates an uneven surface that can look lumpy and is more likely to crack as the walls of your home expand and contract . A good way to avoid this is to ensure you have left adequate drying time in between each coat.

Low quality paint

Another cause of cracks in paint is the use of low quality paint. Low quality paint can cause cracks because it has inadequate adhesion and flexibility meaning as the paint dries, cracks can appear. Over time the paint will become more brittle anyway, regardless of its quality. This means at some point pretty much all paints may need replacing and updating over time. However, the lower quality the paint is, the quicker cracks are likely to appear. This means it can end up costing more in the long run as you are more likely to have to touch up and repaint it sooner.

Why does paint crack: FAQs

How do you keep paint from cracking?

There are a number of ways to keep paint from cracking. This involves the correct preparation and checks. You want to make sure that there is no damp affecting the walls in question, next you should check the quality of the existing surface is in an adequate condition to be painted. If not it is important that you prepare the surface so it can be painted. Next you should prime the walls prior to painting and when you do get to the point of painting, be sure to use a good quality paint. 

What happens if you paint over cracked paint?

Like anything, fixing the root of an issue is more likely to stop it recurring than doing half a job and not properly resolving the cause. This goes for painting and decorating too. If you paint over already cracked paint the issue may appear resolved at first, but it is very likely that the same crack will just reappear. We always suggest removing the cracked paint correctly and applying a high quality primer before repainting. This is the best way to prevent cracks appearing in the future. 

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