Ask Woodiwiss: what causes bubbling paint on vinyl and how do I fix it?

Paint bubbling, or “paint blistering”, is the result of low-quality work, paint, or both

As the sun stays up longer and burns hotter over California and the East Bay, some homeowners are noticing the paint applied to their vinyl siding last summer or fall is starting to form paint blisters or bubbles. Paint bubbles on the vinyl siding (or just about any exterior surface), are almost always caused by poor workmanship, low-quality paint, or both.

Our professional painters at Woodiwiss Painting see this a lot as direct sunlight heats up what was fresh paint in the last year or so. Older surfaces that haven’t seen a coat of paint in ten years are likelier to chip and flake off. Whereas more recent paint jobs still have paint with a little moisture and tackiness to it. Like how the surface of a cake that isn’t done yet can expand without cracking versus a cake that’s a week or two old. Even cheap, low-quality paint can work as a sort of ‘paint film’ if it’s new enough.

Some of the most common causes of bubbling paint on vinyl siding include:

  1. Too much moisture. The paint blisters when moisture gets trapped between the siding and the paint. Almost like a bad sunburn on your skin, the bubbling paint will eventually crack and peel. 

Moisture can come from a few different places. If the paint job is recent, perhaps the siding wasn’t dry when it was painted. This is probably the most common cause. We see this sometimes where all the old paint wasn’t cleaned off, or it was humid, hot weather that day, or it rained and the crew didn’t wait or dry it properly.

Improper or inadequate ventilation inside the house can be a cause, too. Moisture can get in around the cracks of the siding. Maybe there’s loose caulking, or the interior walls are damaged and not properly caulked or sealed. Especially large bubbles tend to form near or around exhaust fans and vents,”.

Before we start a job we always look for ways to repair loose caulking, check for cracks or damage in the vinyl siding. We also ensure patched areas are fully ready by sanding, applying primer, and at least two and sometimes several coats of paint. We know the underlying causes of paint bubbling and have never, not once, in twenty years, had to repair or fix paint bubbles caused by our impatience.

  1. Poor surface preparation can cause paint bubbling, too. If it’s not cleaned and dried completely, primed, or receives the right kind of paint, paint bubbles can form within weeks or months of a fresh paint job.

Cleaning off the house’s exterior with warm, soapy water and letting it dry goes a long way. The root cause of a lot of problems in life is usually impatience and a lot of DIY jobs or work done by hasty contractors eager to reduce hours or get in more jobs are quick to ignore the underlying surface thinking the chances of anyone noticing are slim. We take our time like true craftsmen.

  1. Low-quality paint is a leading cause of paint bubbling. This is because cheap paint is less likely to bond well to the vinyl surface. 

When we repair exterior surfaces we start by sanding and chipping away at the old paint. Once the blisters are ‘opened’ our crews can usually tell when the surface wasn’t primed. And sometimes if it was, if they painted before the primer dries — which is hard to tell later — there’s a good chance that’s the underlying cause.

  1. High humidity and direct sunlight causes paint to bubble, pop, and peel. Particularly if the siding is in direct sun for extended periods of time. 

Cheap paint is everyone’s undoing. As the paint dries the water in latex paint evaporates, causing it to adhere to the surface. Low-quality paints have more water than paint, which leaves less to adhere, even if you apply more than one paint coat. 

A paint bubble is almost inevitable in those cases. When the sun turns the siding into a hot surface the paint loses even more moisture. High-quality paint can withstand this because it has more of pigments and materials that stick. Don’t let your paint literally evaporate before your eyes!

Fixing paint bubbles starts with identifying the root cause

To fix paint bubbles on vinyl siding, whether it’s with latex paint or oil-based paint (which are not used in California):

  1. Address any possible moisture issues, seams, cracks, or vents.
  2. Scrape and lightly sand the area with a fine grit sandpaper. Special sanders can be used for large jobs, but blistered paint bubbles are usually sanded by hand to identify any unusual causes to the damaged paint. For instance, water-filled bubbles can be a clue it’s just rain or dew seeping in.
  3. Clean the area and let it dry completely.
  4. Apply a high-quality primer to the surface.
  5. Apply high-quality paint, let it dry, then apply a second coat of paint. Woodiwiss Painting always uses two coats.

We always use paint designed to bond well with vinyl siding, rated for intense sun and UV exposure, and we use a primer designed for exterior use. And it gives you a better paint sheen, too. This is the biggest reason why we never have to repaint a house for bubbles. Like anyone who cares about their workmanship, we want it done right the first time.

Impatience can get the better of people here, too, because people instinctively reach for sanders to speed up the process over a large area. Chemical stripping or a good pressure wash can work if the equipment is up for it, but most people just risk damaging the siding underneath. They end up with a rough texture that can be difficult to repair without it being noticeable later.

Have paint bubbles on your vinyl siding? We know how to get it done right

The summer weather can be hard to work around in some parts of the country. Here in the East Bay we’re lucky to have temperate weather much of the year. 

Still, Spring is a great time to get your home’s exterior painted, whether you have peeling paint, bubbling paint, or just want a new color. Woodiwiss Painting can help with your next outdoor painting project