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Why Is the Paint Cracking Outside My House?

The term "cracking" can mean several different things when talking about paint. If the cracks form lots of little squares, it's called alligatoring or crazing. If there are hairline cracks with paint coming off, it's known as flaking. If the cracks are deep and irregular, it is called mud cracking or checking. It is important to understand the difference because they are caused by different things.
  1. Alligatoring

    • Alligatoring gets its name because it looks like alligator skin.

      Alligatoring occurs naturally as paint ages because the paint becomes too rigid to withstand the normal expansion and contraction of the surface. It also occurs when a top coat is applied to a undercoat that hasn't dried properly. Most paint cans list a recoat time that needs to be followed to avoid this problem. Alligatoring can also occur when more rigid paints, like alkyd or oil-based paints, are applied over more flexible paints, like water-based and latex.

    Mud Cracking

    • Mud cracking often occurs when paint is applied too heavily. Paint cans usually list a spread rate, or how much area the paint should cover. Following these guidelines can help avoid spreading the paint too thick or too thin. Mud cracking can also occur in corners of the walls or ceilings because the paint builds up there. Finally, if you painted over a surface that was dirty or oily, cracking will occur.

    Flaking

    • Paint flaking starts out similar to mud cracking and alligatoring.

      Flaking may look like alligatoring or mud cracking in the beginning, but it differs in that the paint starts to come off in small flakes. This may occur if you spread paint too thin or use a low quality paint that doesn't adhere and flex properly. Painting bare wood without priming first can also cause flaking. Painting under conditions that cause the paint to dry too fast will also cause cracking and flaking. Avoid painting when the temperature is over 85 degrees Fahrenheit, the winds are high or if the surface is in direct sunlight.

    Solution

    • Once cracking has occurred, your only option is to remove the cracked paint by sanding, scraping or stripping it away in order to repaint the area. Always follow the manufacturer's recommendations on painting conditions, drying and recoating times, thinning rate and spread rate. Clean the surface thoroughly and allow it to dry before using a quality primer. Follow up the primer with a good quality exterior latex paint.