What is the cause of paint flaws and how to fix paint problems such as alligatoring and blistering?

Alligaloring can be caused by applying a second coat of paint before the first has dried. Or two incompatible layers may have expanded at different rates. For a mild case, sand and fill the area with exterior spackling compound. For a severe case, strip the paint.

Blistering that occurs soon after painting may be the result of hot, direct sunlight, which dries the paint’s surface, trapping solvents before they can evaporate. After the paint dries fully, scrape off the blisters, sand, and repaint early or late in the day. Later blisters usually result from moisture in the siding. Locate the cause: excess house humidity; water from damaged roofing, flashing, or caulking; moisture from the ground. Correct it before repainting.

Chalking is a powdery surface residue. Many exterior paints are meant to chalk; it allows rain to carry away dirt. If it’s down to the paint layer below, brush the chalk off, coat with a primer-sealer, and repaint.

Crusting and flaking on a masonry wall result from a moisture-caused granular buildup under the paint. Clean the area with a wire brush and scraper. Then, wearing gloves and goggles, scrub with a mixture of 1 part muriatic acid and 2 parts water. Rinse well and let dry; correct the source of dampness. Before repainting, apply a masonry sealer.

Peeling results from painting over a greasy or dirty surface or from moisture getting trapped beneath the paint. Scrape and sand the surface. Before repainting, correct any source of dampness. On masonry, peeling can have the same cause as crusting.

Running and sagging are driplike formations that occur when you apply paint too thickly. Prevent them by making sure to brush out and smooth each paint stroke. Sand off dried runs and sags before repainting.

Wrinkling occurs from applying a paint too thickly. The surface dries first, then wrinkles when the paint under it dries. Sand the surface smooth and apply a thinner coat.