Flaking Paint on Outside Walls
Cracking, flaking paint on outside walls is one example of what pros call paint failure. It's a tough world out there, and there are many ways for a once-beautiful coating of color to take a wrong turn and become ugly. Flaking is a different malady from alligatoring, as are chalking, wrinkling, leaching, mottling, blistering… Sadly, most failures require nothing less than starting over with a clean slate. It's important that the painter learns from his mistakes so the new paint can enjoy a long life of successful protection. It's what all good paints deserve.
Flaking paint on outside walls is not the same as peeling or bubbling paint, and proper diagnosis is the first step to a cure. Flaking paint looks as though something has caused the paint to crack into small pieces, almost like shattered glass (specifically tempered glass, which breaks into tiny chunks, not pointed shards). Once this happens, little bits of paint begin flaking off the surface. The failure can start with hairline cracks and affect just the topcoat, but eventually the cracking penetrates deeper, typically down to the bare wood or other material.
There are several common factors behind flaking paint on outside walls. One of them, you've probably heard, is cheap paint. It simply can't stand up to the daily attacks from weather and temperature changes. Even if the old paint was high quality, if it was applied too thin or was thinned (diluted) too much, it'll eventually crack and flake off.
Applying paint directly over bare wood is another mistake that leads to flaking paint on outside walls; you need to start with a quality primer that's compatible with the surface material AND the paint that will cover the primer.
Primer is also critical before applying a new latex (water-based) paint over old layers of alkyd (oil-based) paint, as latex and oil can be too different to make it together over the long haul. Oil paint is less flexible and never stops curing, while latex cures within weeks and remains relatively flexible; as the latex expands and contracts with the wood below, it can cause the oil paint to crack. A primer coat serves as a buffer between the two to keep things copacetic.
Finally, painting an exterior when it's too hot and/or windy can result in the paint (particularly water-based paint) drying too quickly, leading to cracking.
Actually, there's really only one solution for flaking paint on outside walls: getting rid of the failed paint and starting over with new primer and paint. Good primer and paint. Begin by scraping, brushing and/or sanding all of the failed paint from the surface (see note below about lead-based paint).
If, after a thorough removal job, you still have areas where the old coating is tenaciously bonded to the wood, you can probably prime and paint over it. Sand to make sure it's smooth and clean, and feather the edges to erase the transition between bare and painted areas; if you leave a hard line where the paint stops it will telegraph through the new coatings.
Clean the wall thoroughly, apply new primer and paint—as directed—and watch with pride as your new coating matures into the strong protector it was meant to be.
Note: If your house was built prior to 1978 or you have any reason to suspect the walls may contain lead paint, have a sample of all of the paint layers tested at a local accredited lab. (Just call and find out what they need for a sample.) Removing lead-based paint requires special techniques to ensure your safety. You can have the paint removed by a qualified professional or do it yourself, but be sure to follow local and EPA guidelines for all treatment and handling of lead paint.
Philip Schmidt writes for Networx.com.
Updated May 9, 2018.
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