Why Paint Bubbles and How to Fix It

Paint bubbling on your walls occurs when paint lifts off the surface it’s applied on, causing bubbles or blisters and peeling. It’s a common issue, ruining many interiors and exterior paint jobs, and is an endless source of frustration for homeowners and DIY-ers. We show you how you can fix bubbles under paint and prevent them from forming in the first place.

What causes paint to bubble up or blister?

There’s nothing worse than finishing off a very costly and labour-intensive paint job, only to discover hours, or even months, later, paint bubbling and peeling off the wall. 

The main cause of bubbling is the poor condition of the underlying surface that paint is applied on. The paint fails to adhere or “stick” to the surface, causing it to pull away once dried. Dirt and moisture may accumulate in the bubbles, causing it to peel over time. 

The following are the most common causes of bubbling.

Water

Water prevents the paint from sticking to the surface. Water droplets or leaks from plumbing problems in the bathroom, for example, can cause water-filled bubbles in the paint. 

High humidity

High humidity occurs in houses where ventilation is poor. Excess moisture causes the paint to swell, affecting the ability of paint to stick to the surface. 

In external environments, the sun’s heat will cause excess moisture under the paint to turn to vapour. Because the vapour cannot escape, it will begin to form bubbles under the paint.

In internal environments, high humidity is often found in kitchens, bathrooms, and basements.

Improper surface protection

You must properly prepare the surface before beginning any painting project. It must be thoroughly cleaned of any surface dirt, sanded (to remove any old paint and even out the surface), and completely dried. It’s also important to put a coat or two of primer. Th eprimer’s main job is to provide adhesion or “stickability” between the paint and the surface, making the paint last longer. 

High Temperature

High temperatures will cause the paint to dry too fast, before it’s had time to bond to the surface it’s painted on.

The rule of thumb is if you are painting with oil-based paint, the ideal temperature should be between 7° and 32° C for the next 48 hours. If you’re using latex (water-based) and acrylic paints, the ideal temperature should be between 10° and 29° C.

Also, be aware that sunlight causes exterior surfaces to be 10° to 20° hotter. 

Using the wrong paint

The saying “oil and water don’t mix” is also true when it comes to paint. If you apply water-based (latex) paint over oil-based paint, the latex paint will not be able to stick to the oil-based paint, and vice versa. This causes plenty of bubbling and peeling and an incredibly unprofessional job.

How to prevent bubbling or peeling paint

While it can be fixed, it’s far better to prevent the problem before you paint by thoroughly preparing the surface you’re painting on first to ensure it doesn’t become a recurring problem. We recommend the following steps.

Prepare the area

Clean the area with a sponge dipped in water and detergent to loosen any surface dirt and remove stains. Rinse with warm water and use a rag to dry the area completely before you do anything else to it.

Repair surface holes and cracks

Use a putty and putty knife to fill any visible holes or indentations on the surface. Let it dry completely, then smooth it down using fine-grit sandpaper. 

Add a primer

Primer enables the paint to adhere to the surface it’s painted on. It adds an extra layer between the paint and the surface, protecting the surface material so that the paint lasts longer.

If you’re painting over oil-based paint with latex paint, using a primer will allow for greater adhesion between the two different types of paint. 

Using a primer over new wall surfaces such as drywall (plasterboard) or wood will also improve the ability of paint to stick as drywall and wood are highly porous, and will absorb paint if the primer is not applied to it first.

Please note, primer is not the same as paint. The main difference between them is that primers contain chemicals to enable the paint to stick to it, while paint contains colour pigments that provide the colour, as well as other materials that provide durability under different types of weather conditions.

Let the primer dry completely before adding paint.

Paint

Stir the paint slowly using a wooden stirrer. Try not to stir too quickly for too long as this will create air bubbles in the paint. 

Using a roller brush, carefully and gradually apply the paint. Slow down if you see any air bubbles forming. 

If you are painting over narrow or smaller surfaces, use the correct size brush and apply with even strokes.

How to fix paint bubbles

Before you make any repairs, make sure the paint has completely dried. This may take a few weeks, depending on the type of paint used. Lay some drop cloths on the floor to collect debris, and make sure you are wearing a mask and goggles, and that the room is well ventilated. 

You need to take proper precautions when scraping off old paint. Dust or fumes from old paint may contain lead, which is hazardous when inhaled or swallowed. Professional painters use proper protective equipment such as a correctly fitted respirator or a good quality mask from a reputable supplier that meets Australian standards. Make sure the equipment you buy is suitable for the job you are undertaking.

Remove blisters by scraping and sanding

Start by scraping off the paint with a putty knife. Start at the centre and work your way outwards. Ensure any old paint shavings are correctly disposed of afterwards.

If the surface is uneven, you may need to also sand it to smooth it down.

Remove the source of moisture

Remove all sources of moisture that may be contributing to the bubbling. You may need to contact a plumber if there’s a possibility of leaks occurring in your plumbing.

Ensure there’s proper ventilation by installing vents and exhaust fans to lower humidity in the area. 

Lastly, ensure the ambient temperature is between 7° to 32° C if using oil-based paint, and 10° to 29° C if using water-based (latex) paint, and avoid painting in direct sunlight when outdoors. 

Achieving professional results takes know-how and skill. Book a free, 30-minute consultation with us and let us give you expert results without you needing to lift a finger.