Moisture and Peeling Paint

Most peeling paint is caused by the moisture. This is particularly true of older homes without adequate ventilation. The problem is usually worst on the walls outside of high moisture rooms, such as bathrooms.

The moisture will migrate through the wall until it reaches the surface of the exterior siding. If that moisture cannot easily escape from the wood, it can push the paint film away from the surface. The problem tends to be worse on walls that get significant exposure to the sun.

When the sun hits the wall, the water expands. On older homes, it is likely that an oil base paint was used at one time. Oil paints do not “breathe”, i.e., allow moisture to move through the paint film.

In addition, on many older homes the overlap between pieces of siding has become sealed over the years. This prevents adequate ventilation of the wall cavity, which in turn keeps the moisture trapped.

Moisture takes the path of least resistance. This generally means pushing the paint film off of the surface. The problem is usually made worse on walls with direct sun exposure. As the sun heats the wall, the moisture vaporizes and expands.

The solution essentially involves improving the ventilation of the wall cavity. This can take several different forms.

One of the easiest is to simply break the seal between the pieces of siding. This may involve removing caulk and the build up of paint. While the gap between the siding boards may be a little unsightly to some, peeling paint is usually more so.

In extreme cases, it may be necessary to insert a small wedge between the boards. This will maintain the proper gap between the siding, and allow the moisture to escape.