Peeling Paint Mystery

Peeling exterior paint often gets blamed on wall insulation added without a proper vapor barrier (a layer that keeps moisture from migrating into the wall). But that's not the only cause, and it may not even be the main one. If your walls aren't insulated, as one homeowner found after paint failed just three years after application, the real source is likely something simpler: water getting into the wall from a roofing, flashing, or gutter leak.

Materials like plaster, low-fired brick, lime mortar, and wood soak up water and hold onto it for days or weeks. That trapped moisture can keep new paint from bonding well, or push a good paint job off the wall soon after a leak starts. So peeling paint can be a sign of a leak elsewhere in the house, not just a problem with the paint itself.

Tracking down the cause starts with what one expert calls a moisture inventory: a walk-through that looks for every possible source of unwanted water, including combustion exhaust, damp firewood, ground moisture from a dirt crawlspace, humidifiers, plumbing leaks, and rain or snowmelt getting through gaps in the exterior. Checking the roof, flashing, and gutters from a ladder, running a garden hose over the walls while someone watches inside, or inspecting during a real rainstorm can help pinpoint where water is entering. If none of that turns up a leak, the paint failure may come down to condensation inside the wall instead.