Why Is My Paint Peeling?

By: Jeanne Huber, This Old House magazine (Page 4 of 4)

Photo by: Anna Palma

The paint on the house Dee rents went from bad to horrendous. When he moved in, there was a coat of latex over several coats of oil, and it was beginning to peel. He recommended stripping it down to bare wood, but the landlord didn't want to spend the money. So Dee scraped off all the loose paint, spot-primed and repainted. Before long, the south wall looked like a disaster zone.

Photo by: Anna Palma

Dee confers with paint-company experts about the peeling paint.

An American house wearing eurpean paint.

Photo by: Anna Palma

When a paint job costs $40,000-as it did on the 5,529-square-foot Victorian in Concord, Massachusetts-you just pray it lasts. The walls and trim were scraped to bare wood, primed and coated with two layers of oil paint imported from Europe.

At the Paint Quality Institute near Philadelphia, odd-looking fences test how paint performs on wood, aluminum and even faded vinyl siding.

What the research reveals: TOP: Adding zinc oxide to paint helps it resist mildew. MIDDLE: Earth tones outlast bright colors because they don't break down in sunlight. BOTTOM: Clear finishes are short-lived because sunlight gets through, breaking down wood fibers.

Alligatoring

CAUSES: Natural aging of oil paint; undercoat was wet; or top coat is harder than the base (such as alkyd enamel over latex).

REMEDY: Strip to bare wood, prime and paint.

CAUSES: Wall painted while in sun; wall has moisture problem; surface was damp (for oil paint) or humidity was high (latex). REMEDY: If blisters go down to wood, fix the moisture problem. Scrape, spot-prime, repaint in shade.

CAUSES: Low quality or excessively thinned paint; poor surface preparation or lack of primer; latex dried too fast because temperature was too cool or wind too high. REMEDY: If cracks are on surface layer alone, scrape and sand; then prime and repaint; otherwise strip to bare wood.

CAUSES: Use of latex over more than three or four layers of oil paint.

REMEDY: Strip to bare. Or scrape, prime and repaint with latex-but expect unscraped parts to peel later.

CAUSES: Moisture in wall; poor surface preparation; low-quality paint; surface was wet (oil paint only) or blistered.

REMEDY: Fix moisture problem, scrape, sand.

CAUSES: Paint was too thick; surface or weather was too hot; uncured paint got wet or humidity rose; undercoat was dirty.

REMEDY: Scrape or sand to remove wrinkles. In hot or damp weather, wait longer to recoat.

When Michael O. and Phyllis J. Hunt bought this 1858 Greek Revival in Lafayette, Indiana, they ripped off asbestos shingles and found thickly painted yellow poplar underneath. Michael, who runs the wood research program at Purdue University, followed the advice of Forest Products Laboratory and restored the old siding with new paint.

After removing the old paint with a rotary grinder, Michael Hunt coated the wood with a water-repellent preservative, then a latex primer. He finished up with two coats of latex paint. Five years later, there is still not a flake in sight.

Browse Images

On Newsstands Now

In the Magazine

Reinvent your rooms with color

A Perfect Paint Job
Spring is a great time to repaint, says Mark T. Knaebe, a chemist at the Forest Products Laboratory in Madison, Wisconsin. "I like it because you can be fairly sure you'll finish the job before it gets too cold." As co-author of "Finishes for Exterior Wood," a book summarizing the lab's 75 years of paint research, Knaebe knows a quality job takes time.

He recommends starting with a quick test to determine the extent of the work. First, choose an inconspicuous place where the paint is worst. Clean the surface, let it dry and paint a small patch. The next day, press on a Band-Aid and then quickly pull it off. If the tape is clean, it's safe to repaint after scrubbing the whole house. If the tape pulls off all the paint down to bare wood, the house needs to be stripped before it's repainted. If just new paint comes off, the old paint is too chalky and you'll have to coat the whole house with an oil primer first.

For houses with some flaking but not enough to require stripping, remove loose paint with a scraper and a power washer, taking appropriate precautions if you suspect the old paint contains lead. Sand all bare wood and exposed paint edges or the new paint will be thin there and will chip in no time. Scrub the walls with water and kill any mildew by using a solution of one par household bleach to three parts water. Rinse and let the wood dry.

Most painters would simply prime and then paint at this point, but Knaebe recommends coating bare spots with a water-repellent preservative specifically labeled as compatible with paint. The repellent will limit shrinking and swelling of the siding due to moisture. Three sunny days later, you can prime the bare spots or coat the whole house. (If you've stripped all the paint, latex primer is recommended.)

Apply the finish coat soon. Soap-like compounds can form on oil primers in as little as two weeks. If there is a longer delay, scrub and rinse before applying the top coat. Two coats will probably be needed with latex, Knaebe says. Before painting, check the air temperature and the weather forecast and make sure they're compatible with the weather guidelines on the label. Weather that is too hot, too cold, too humid or too windy can undermine the best prep work.