Why Did My Wall Paint Blister After The Rain?
Why did my wall paint blister after the rain? Good question! It is one of the most common paint problem we address. It is also an issue we have been battling on the exterior of our own building for over thirty years. So let’s start there.
Why does the paint on OUR building blister? Our problems are probably similar to yours so let’s start at the beginning. When my in-laws opened Rowe Spurling Paint Company at its new location on 67 St. John’s Road in the early 90’s, the building needed some help. After the repairs were made a fresh coat of plaster was applied. THE NEXT DAY the walls were primed and painted so the shop could be ready for its grand opening. And that’s where the problem began. Fresh plaster needs AT LEAST 28 days to fully dry and cure before any primer can be applied. If this step is rushed the excess moisture will cause the paint to blister over time. Additionally, lime in the plaster is very aggressive. If it is not left to cure, it will burn through the colorants in your paint leaving you with white patches all over the house. Sound familiar?
In addition to priming and painting too soon, what else can cause a paint to blister? A crack in the wall, even a small one, can let water in. Think of our stone walls like a sponge. Water gets in through the crack, travels through the wall and when it builds up enough pressure, creates a blister on its way out. Before repainting exterior walls make sure to repair any problem spots, leave those spots to dry and cure then apply a primer and paint.
The third most common reason for blistering paint? A dirty wall! Over time, dirt from the garden, soot from the road or salt from the air deposit themselves on the wall. Paint will not stick properly to a dirty surface so make sure to power wash the house to start with a clean slate. Remember to let the walls dry for at least a day before painting!
Finally, painting on a damp day or when rain is in the forecast can lead to blisters. Good rule of thumb? If you wouldn’t hang your laundry out to dry don’t pick up a paint brush.
What can you do to fix a blister? First, scrape off as much of the loose paint off as you can. Next, run your hand on the freshly scraped wall. Chances are you will see a fine white powder on your hands. This will need to be washed off. On smaller areas you can use a bucket and sponge. On a larger surface a power washer will make the job easier. After you wash off as much of the powder as you can, leave the walls to dry for a couple of days. The next step will be to apply a clear sealer (like our Benjamin Moore Ultra Spec Clear Masonry Sealer). It is thin so it can penetrate in the walls. After the sealer is dry apply two coats of a high quality primer. At home we use Benjamin Moore Fresh Start. After the primer is dry, finish off with two coats of top coat.
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