When you notice paint peeling around the outside of his house, your first impulse is to blame the paint itself. In most cases this is really not so. Nine times out of ten the trouble is caused either by a structural defect which allows moisture to seep in underneath the paint film or by unsuitable preparation of the surface.
While all outside wall paints are made to repel water, they would not stick for very long to a surface which is endlessly wet underneath. If faulty calking, open seams, leaky gutters or corroded flashing allows moisture to seep into the wall
and drench the wood or masonry behind the paint, blistering and peeling is virtually certain to occur. The moisture in the wall is evaporated by the heat of the sun and pulled outward, pushing the paint off with it. This sort of defect is most easily distinguished by the fact that the paint usually peels right down to the bare wood, rather than just flaking off on top.To fix this kind of dilemma, then you should first fill out or repair all gaping seams and other similar defects. You should then allow for the wall to dry thoroughly prior to repainting. Thorough scraping and sanding is also needed to get rid of the old, defective paint before the new material is applied. Painting immediately over the peeling paint (even when partly removed) will only cause the new coat of paint to peel once more in the near future.
On exterior walls of wood, peeling can often be caused by moisture vapor which gets through the walls from inside the house during times when interior humidity is very high. This often occurs during the winter months when clothes dryers, shower baths and other water-using appliances give off large amounts of water vapor which is cornered indoors by windows and doors that are tightly closed. When this moisture vapor gets to the hollow space behind the siding, it condenses on the cold surfaces and drenches into the wood that leads to peeling later on.
To keep this from happening,
you must make every effort to get rid of all possible sources of extra humidity on the interior of the house. Use ventilating fans in bathrooms, laundry areas, and kitchens. If weather permits, open windows at least once or twice a day on each floor.Since even these measures won’t always prove enough, a lot of experts recommend the use of small ventilating louvers or miniature vents installed in the outer walls. Less than 1 inch in diameter, these vents are set up by merely drilling a hole in the siding, then pushing the vent into place in the opening. One vent is required in every closed-off area between studs to allow vapor to escape freely to the outside without doing any damage.
If only the top layer of paint peels off, leaving the paint underneath still intact, the trouble is most probably due to the paint having been applied when the surface was damp or coated with dust and dirt. This happens oftentimes on the undersides of overhanging eaves, in sheltered parts under roof overhangs, and in other locations which are covered from the weather.
Dirt which gathers on these surfaces is not washed away by wind or rain as quickly as it is on the exposed vertical walls of the house. Due to this, these surfaces must be wiped clean before paint is put on. If these areas are not wiped down with solvent or scoured with detergent solution, the fresh paint will cling to the dirt, instead of on the old paint. As a result, adhesion is really poor, causing paint to peel in less than a year in most cases.
References:
House Painting: Inside & Out by Mark Dixon and Bob Heidt
Painting and Finishing: Expert Advice from Start to Finish by Michael M. Dresdner
© 3/10/2011 Athena Goodlight on Factoidz
