The sun does most of the damage
Ultraviolet light breaks down the binder that holds paint together. As it does, the surface turns chalky, colors fade and the film gets brittle. In San Antonio, with long, bright summers and few cloudy days, a south or west wall can look tired years before the north side of the same house.
You can see it by running a hand across a sunny wall: if your palm comes away colored, the paint is chalking. That's the first sign the coating is wearing out.
Heat makes everything move
Wood siding and trim expand in the afternoon heat and shrink overnight. Caulk and paint have to stretch with them. Cheap caulk and stiff paint crack along joints, and once water gets into those cracks, wood starts to rot from behind.
Heat also affects how paint goes on. Paint laid on a wall that's been baking in direct sun can dry before it bonds, which shows later as blistering and lap marks.
Humidity and sudden storms
Gulf moisture means muggy mornings and heavy downpours between dry spells. Moisture trapped in wood or stucco pushes paint off from behind, and damp, shaded walls grow mildew and algae.
The ground moves too
Much of the area sits on clay soil that swells when it's wet and shrinks in drought. Foundations move a little with it, and stucco and drywall crack. Painting over a crack hides it for a season at most.
How to make a paint job last here
- Wash the house first. Paint doesn't stick to chalk, dirt or mildew.
- Replace rotted wood instead of painting over it.
- Repair stucco cracks properly so they don't open straight back up.
- Use flexible caulk at joints that move.
- Choose exterior coatings made for strong UV, and lighter colors on the sunniest walls.
- Paint each side of the house when the sun has left it, not when it's baking.
- Keep sprinklers off the walls and gutters clear.