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Correcting Common Paint Problems: Checking and Mildew

Here are tips and suggestions on how to correct common paint problems. Homeowners all over the country experience these types of problems. Take the time to read the instructions carefully and follow them and you can correct many of the paint problems around your home.

Checking of a Painted Surface

  • Checking usually occurs on a painted plywood surface. As the plywood veneer ages, it cracks from repeated expansion and contraction. This weathering and aging causes the painted surface to check.
  • When checking occurs, the entire checked area must be sanded smooth. The job will be easier with a power sander.
  • After the sanding is complete, prime the bare wood with one coat of good grade undercoat.
  • Fill all holes, cracks and seams with a good grade of caulking compound.
  • After the caulking compound and undercoat paint have dried thoroughly, apply one layer of a good grade of outside house paint.
  • In cases where the plywood is extremely aged, you may need to replace the wood completely.
  • If new plywood is mounted, you can prevent it from checking by sanding the surface of the new plywood smooth.
  • After sanding, apply one coat of a good grade of latex wood primer.
  • After the primer has thoroughly dried, apply one or two coats of a top-quality outside house paint.

Mildew On Paint

  • Mildew is caused by a combination of high humidity and high temperature that creates a growth of fungus on the paint film (see image).
  • Completely remove mildew from the surface. If you simply paint over it, the mildew will grow right through the new coat of paint.
  • Make a solution of 1/3 cup of powdered detergent and 1/2 cup of household bleach mixed in one gallon of warm water.
  • Scrub the entire mildewed surface thoroughly using this solution. Scrub the area vigorously, then rinse lightly with clean water.
  • Apply one coat of a good grade of undercoat paint, and allow it to dry.
  • After the undercoat layer has thoroughly dried, apply a finish coat of mildew-resistant outside paint or a top-grade of latex outside house paint. This procedure will remove the mildew problem.

Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the National Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.

For home improvement advice, visit JS West Lumber & Ace Hardware Sonora, Ca. or visit and click on the Answers@Ace icon. Answers@Ace is an online resource with information for do-it-yourselfers about hardware and home improvement projects. The Everyday Projects section has pictures and detailed, step-by-step instructions for this and many more home improvement projects.

To speak to an Ace Hardware advisor in Sonora call: 209 532 7446.