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Tom Sawyer Painting

How to properly treat and paint over mildew

Mildew is more than just an unsightly stain; it’s a surface fungus that thrives in moist environments. Simply painting over it is like putting a small bandage on a big problem. The mildew is still alive underneath, and it will continue to grow, causing the new paint to bubble, peel, and chip within months.

If you want to solve the problem for good, you must treat the mildew before a single drop of paint touches your wall.

1. Clean and kill the spores

First, the surface must be properly cleaned. We use a professional-grade mildewcide (or a potent bleach-water solution) to scrub the area. This step does more than just remove the stain; it actively kills the surface-level fungus and its spores to ensure it is fully neutralized.

2. Address the moisture source

This is the most critical step. Where is the moisture coming from?

  • In a bathroom, it’s often a ventilation issue. Is the exhaust fan old or not working?
  • In a basement, it could be a small foundation crack, high humidity, or a leaky pipe.

A professional painter will identify these source issues. While we may not be plumbers, our supervisors (who are on every job site) can spot the problem so it can be fixed before the painting begins. There is no point in painting a wall that is still getting wet.

3. Repair the damaged surface

After the mildew is gone and the moisture source is handled, the wall itself often needs repair. Mildew and moisture can cause drywall to become soft or plaster to crumble. Simply painting over this weakened surface will result in a splotchy, uneven finish. This is where our drywall and plastering services become essential. We patch, sand, and smooth the surface to make it strong and perfectly uniform.

4. Prime with the right product

With a clean, dry, and repaired surface, it’s time to prime. We don’t use a standard primer. We use a high-quality, stain-blocking, and moisture-resistant primer. This special primer seals the surface, prevents any lingering stains from bleeding through, and acts as the first line of defense against future moisture.

5. Paint with a durable finish

Finally, we paint. For high-moisture areas like bathrooms and basements, we recommend premium paints from brands like Benjamin Moore, which are specifically designed to resist mildew and withstand humidity. Choosing the right paint (and the right sheen, such as satin or semi-gloss, in a bathroom) is the final step in protecting your wall for years to come.

Conclusion

Those recurring mildew spots in your home are a frustrating problem, but they can be solved. It just takes a professional process that values preparation as much as the final coat.

The Tom Sawyer Painting team has been helping homeowners in Arlington, Cambridge, and the surrounding areas solve these exact issues since 1985. If you’re tired of the mildew, let’s get rid of it for good.

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