Paint blisters are one of those problems on a home’s exterior that are hard to miss. You might spot them as small bubbles or raised areas under the paint surface, most commonly on siding, trim, or outdoor fixtures. At first, they seem like a cosmetic issue, but they’re usually telling you something much deeper is going on. If ignored, those blisters can grow, leading to peeling paint, exposed surfaces, and even damage to the material beneath.
In Ottawa, where homes go through hot summers, cold winters, and big temperature swings in between, paint blisters aren’t something to take lightly. These changing conditions create the perfect setup for trapped moisture and heat stress under paint layers. Fixing the problem early makes a big difference. It helps stop further damage and keeps your home’s exterior looking clean and well cared for.
What Causes Paint Blisters on Exterior Surfaces?
When paint blisters show up, it means something likely went wrong underneath the surface or right after the paint was applied. The paint tries to hold on but bubbles form beneath, lifting the paint away from whatever’s below. Most often, there are four common causes behind this problem.
1. Moisture
Moisture is a top reason paint starts to blister. If water is trapped below the surface, it will try to escape once heat or sunlight comes into play. That pressure pushes the paint outward, forming bubbles. Water can get trapped because of:
- Rain or dew that wasn’t dry before painting
- Leaks from inside the home making their way through the walls
- Cracks in wood or siding that weren’t sealed
2. Heat
Painting in the middle of a hot day, especially under direct sunlight, means the paint dries too fast. The outer layer hardens before the inside is done setting. Trapped heat underneath swells and lifts the layer, creating visible blisters. This is especially a concern during peak summer days in Ottawa.
3. Incorrect Application
When paint is applied without letting each step completely dry, it can result in trapped air or solvents that form bubbles later. These mistakes include:
- Skipping drying time between primer and paint
- Painting additional coats while the base isn’t fully set
- Applying thick layers that don’t breathe easily
Each layer needs time to settle, especially in areas where temperature or humidity fluctuate throughout the day.
4. Poor Surface Preparation
Paint needs a solid grip. When painters skip prep like cleaning, scraping, or sanding, dirt and loose debris stay on the surface. That weak base allows paint to lift or expand over time as moisture or heat gets in. Any old, flaking paint left behind could become the gateway for blistering down the road.
These causes often go unnoticed when someone’s in a rush or not familiar with how conditions affect paint. Catching these troublemakers early leads to stronger, better-lasting paint on your exterior walls.
How To Fix Paint Blisters Step By Step
Once blistering shows up, it won’t go away with time—it will only get worse. Addressing it early stops more paint from peeling and prevents exposure to the elements. Fixing it properly means more than a patch. It’s about getting down to the root issue and taking your time to do it right.
Follow these key steps:
1. Check the Area: Inspect where the blisters have formed. Are they along gutters, near windows, or in full sunlight? Look closely at the back side of a peeling bubble. Bare wood might suggest moisture, while old paint stuck to the back signals heat or surface issues. This step helps decide if it’s just that patch or a bigger issue across the entire area.
2. Remove the Blisters: Use a paint scraper or wide putty knife to peel away all loose or bubbled areas. Be gentle and avoid gouging the base underneath. Work your way until only solid, smooth paint remains.
3. Sand the Surface Smooth: Use medium-grit sandpaper first, then switch to fine grit for blending. This step gets rid of rough edges and makes repainting look even. A smooth surface helps the new paint stick properly without bubbling again.
4. Seal and Prime: Apply a good exterior primer, especially if you’re covering bare wood or spots more prone to moisture. A sealing primer gives added protection. Let it dry fully before moving on to the next coat.
5. Repaint Under Good Conditions: Always wait for a cool, dry day when painting outside. In Ottawa, early fall is a great time. Later mornings and early evenings are ideal because direct sunlight is less harsh. Avoid painting just before a rain or if dew is expected that night. Use two thin coats of exterior paint rather than one thick one.
Fixing blistered paint takes focus and a bit of patience, but it’s worth it for a longer-lasting result. Shortcuts only lead to more problems down the road.
Preventing Future Paint Blisters
Avoiding a repeat of paint blisters is all about prep and timing. Ottawa’s shifting weather is tough on exterior paint, but if you stay one step ahead, your finishes will hold up better year to year.
One of the easiest ways to protect your paint job is by using high-quality paint made for exterior use. It sticks better, offers stronger resistance to UV rays, and expands or contracts with the seasons. Cheaper paints tend to peel or bubble under stress and don’t stay intact for long.
Another smart move is cleaning and prepping the surface properly before cracking open the paint can. That means:
- Cleaning away dirt, dust, and surface grease
- Sanding or scraping off any flaking old paint
- Filling in small cracks or gaps to avoid water intrusion later
- Spot-priming exposed patches, especially around windows and trims
Painting in the right conditions helps too. For Ottawa homes, aim for temperatures between 10°C and 25°C. Avoid humid, rainy, or extremely hot days. Think of September as a painter’s sweet spot—summer heat is fading, but winter’s chill hasn’t arrived yet.
Here are six habits that help prevent paint blisters:
- Wash, scrape, and sand the surface before painting
- Use primers and paints that match the material being covered (wood, brick, stucco)
- Seal edges and gaps with caulking to keep water out
- Let each coat fully dry before applying another
- Avoid painting during peak sunlight or immediately before rainfall
- Choose high-quality paint designed for exterior durability
These steps aren’t difficult, they just take planning. Once you get the prep right, maintaining your home’s exterior gets a lot easier in the long run.
Keeping Your Ottawa Home Looking Its Best
Paint blisters are never just a surface issue. They signal that something didn’t go quite right—whether it was moisture hiding beneath the surface, poor prep, or painting under the wrong conditions. Once they show up, the key to stopping them from spreading is taking the time to properly scrape, sand, seal, and repaint.
With Ottawa’s mix of intense summer sun, freezing winters, and frequent rainfall, your home’s exterior battles it all through the seasons. That’s why regular care, spot maintenance, and sound prep work can make all the difference. A fresh coat of paint won’t do much on its own if the area underneath isn’t solid and ready.
Whether you’ve seen a few raised bubbles or are thinking ahead to avoid major repairs, now’s the time to act. Your home’s curb appeal, paint lifespan, and even the protection of your building materials depend on it. By fixing the issue right and following up with proper painting habits, you’ll keep your exterior looking great year after year.
Is your home’s exterior due for some attention? Trust PrimeTime Painters to restore the beauty and durability of your space. Our team of experienced professionals understands the Ottawa climate and knows how to keep your home looking its best through every season. Discover how an expert exterior house painter can transform your property with long-lasting results. Contact us today and let’s give your home the care it deserves.
Is your home’s exterior due for some attention? Trust PrimeTime Painters to restore the beauty and durability of your space. Our team of experienced professionals understands the Ottawa climate and knows how to keep your home looking its best through every season. Learn how working with an experienced exterior house painter can make a lasting difference. Contact us today and let’s give your home the care it deserves.