Why Does Exterior Paint Peel?

Knowing the answer to this question will help you maintain your home’s exterior. The most common cause of peeling, not surprisingly, is water.

Water vapor that accumulates beneath paint or primer separates these coatings from the surface. This, in turn, leads to cracking. A snowball effect ensues: Water seeps through small cracks, which causes bigger cracks. Peeling paint eventually lets you know that something isn’t right.

How does water get underneath the coatings in the first place? Substandard caulking is one possible explanation. The importance of using top-quality caulk, and applying it skillfully, cannot be overestimated.

Keeping water vapor out of a house’s outer walls is easier if there are plastic vapor barriers between the drywall or plaster and the framing. This is less often the case in older homes than in newer ones. If peeling occurs near or in a bathroom, shower-related dampness is likely at fault. One way to reduce the area’s moisture level is to put in an exhaust fan. In general, if part of the house is consistently damp, then the origin of that dampness must be discovered and dealt with.

The undersides of a roof’s overhang, commonly known as soffits, are vulnerable to leaks from flashing or gutters. Fascia boards are equally susceptible. Wide enough metal flashing — between 4 and 6 inches wide, to be precise — may keep both safe from harm, provided it doesn’t let water get past the fascia.

Some varieties of wood siding shouldn’t be painted; T1-11 are rough-cut cedar are examples. If you or someone else has painted these or similar kinds of siding, peeling may result. In cases like these, staining is the proper approach to sealing the wood. This is mainly because it’s extremely porous, which makes it more likely to crack if painted.

Water Isn’t the Only Culprit

As in human relationships, incompatibility between paint layers can be a recipe for disaster. For example, a surface finished with alkyd or oil paint must be treated with primer before being covered with latex or acrylic paint. In intense sunlight, oil paint, which becomes fragile over time, tends to crack. Latex paint, on the other hand, is fairly elastic. When the sun heats an exterior wall, it expands along with the wall itself.

What does it mean that latex and oil paints are so different? If the former is applied over the latter without primer between them, the latex’s stretching may pull the rigid oil paint off the wall. This can expose the wood, which leaves the surface at the mercy of the elements. Not a situation you want in New England in February — or at all, really, no matter where you live.

Other Reasons Paint Peels | Learn more about house paint prep

It may seem like a no-brainer, but using interior paint on an outside wall can result in peeling. So can painting an exterior in subzero temperatures, or applying paint to an unclean surface. Whatever the nature of your project, make sure to identify all trouble spots before priming and painting. No peeling paint or surface defect can remain if your work is to be successful.