VANCOUVER BC’S PREMIER RESIDENTIAL PAINTING COMPANY
VANCOUVER BC’S PREMIER RESIDENTIAL PAINTING COMPANY
At Dunbar Painting, we know that paint blistering is one of the more telling signs that something went wrong beneath the surface. Those bubbles rising up from your walls or siding aren’t just cosmetic. The paint film is separating from the substrate, and every week you leave it untreated, the damage underneath has more room to grow.
Blistering almost always comes down to moisture or heat. Understanding which one you’re dealing with determines everything about how the fix gets approached.
Moisture blistering is far more common, especially here in the Lower Mainland. When water vapour migrates through an interior wall to the exterior, it pushes the paint film away from the surface as it tries to escape. The same process happens when oil-based or alkyd paint gets applied over a surface that wasn’t fully dry.
On the exterior, hydrostatic pressure near the foundation can draw ground moisture up through the wall cladding, causing blistering that creeps upward from the base of the house. Bathrooms and kitchens generate their own moisture pressure from the inside, and without proper ventilation, that humidity finds its way into walls.
The telltale sign of moisture blistering is depth. If you scrape or pop a blister and the damage goes all the way down to bare wood or substrate, moisture is almost certainly the culprit. Fixing the paint without fixing the moisture source means the blisters will be back within a season.
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Heat blistering is more straightforward. It happens when paint gets applied to a surface that’s too warm, typically in direct sunlight on a hot day, and the solvent evaporates too quickly before the film can properly bond. Heat blisters tend to be shallow. When you peel one back, you’ll hit another layer of paint rather than bare substrate, which tells you the adhesion problem is confined to the most recent coat rather than driven by a deeper structural issue.
Blistered paint won’t resolve on its own. Left alone, blisters pop and leave behind rough, cratered patches that eventually lead to peeling and cracking across a wider area. The repair process varies depending on the cause, but the core principle holds: you need a clean, sound surface before any new paint goes on.
The affected area gets scraped and sanded down until the finish is smooth, then primed and repainted under appropriate weather conditions. Since heat blistering doesn’t involve a deeper moisture issue, this is generally a contained fix once the surface is properly prepared.
Moisture-related repairs go a step further. The source of the moisture needs to be identified and addressed first, whether that’s failed caulking around windows and trim or inadequate ventilation in an attic or bathroom. Repainting over an unresolved moisture problem is a short-term fix at best.
Surface preparation is where most DIY attempts fall short. Scraping away only the visible blisters without feathering the edges leaves ridges that telegraph through the new coat. Every bare wood area needs to be primed before applying a topcoat. Bare wood that absorbs paint unevenly is a reliable setup for adhesion failure down the road. On heritage homes and older wood-clad properties, this prep stage often involves more sanding and caulking work than the painting itself.
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The most effective prevention is good preparation and correct application timing. Starting with a surface that’s clean and fully dry, and making sure caulking around penetrations is intact, dramatically reduces the risk. On the interior, proper ventilation in kitchens and bathrooms does more to prevent paint failure than any product upgrade.
Paint blistering is fixable, but the repair is only as good as the diagnosis behind it. At Dunbar Painting, we take the time to understand what caused the failure before we touch a brush. If you’re seeing blisters or bubbling on your home’s interior or exterior, give us a call at 604-788-3382. We’ll figure out what’s driving the problem and make sure the next paint job is one that lasts.
