What paint should I use on basement drywall in New Brunswick to resist moisture and prevent mildew growth?

Use a high-quality 100% acrylic latex paint with built-in mildew resistance for basement drywall in New Brunswick — brands like Benjamin Moore Aura Bath & Spa, Sherwin-Williams Duration Home, or similar premium lines formulated for high-humidity environments are your best options. NB's Maritime climate pushes summer humidity to 70 to 85 percent, and below-grade spaces trap that moisture against cool foundation walls, creating ideal conditions for mildew growth on painted surfaces if the wrong product is used.

The key properties to look for are mildewcide additives built into the paint formula (not just on the surface), moisture resistance rated for high-humidity spaces, and a satin or semi-gloss sheen. Flat and matte finishes absorb moisture and provide more surface texture for mildew to grip, while satin and semi-gloss finishes create a smoother, less porous surface that resists moisture absorption and wipes clean more easily. For basement bathrooms, semi-gloss is the clear choice. For general living areas, satin offers a good balance between moisture resistance and a softer visual appearance.

Primer matters as much as the topcoat. Apply a moisture-blocking primer designed for below-grade or high-humidity spaces before your finish coat. A quality primer seals the drywall paper face, which otherwise acts like a sponge for ambient moisture. In NB basements, where the air behind the drywall carries humidity from the foundation wall, unprimed or poorly primed drywall develops mildew on the back side of the paper facing — a problem you will not see until it is severe. Use a mildew-resistant primer specifically, not just a standard drywall primer.

However, paint is your last line of defence against mildew, not your first. The real protection comes from the wall assembly behind the drywall. If your insulation is rigid foam board or closed-cell spray foam with a proper vapour barrier on the warm side, and there is an air gap between the foundation wall and the framing, your drywall will stay dry and paint choice becomes less critical. If fiberglass batt insulation is sitting against the foundation wall — common in older NB renovations — no amount of mildew-resistant paint will prevent the mold growing behind the drywall in the trapped moisture. Fix the insulation assembly first.

Humidity control in the finished space is equally important. Run a dehumidifier in the basement from May through October, keeping relative humidity below 50 percent. A properly sized dehumidifier for an 800-square-foot NB basement should handle 50 to 70 pints per day. Without active dehumidification, even the best paint will eventually develop mildew in NB's Maritime summers.

A few practical tips for painting NB basement drywall: apply two coats of your finish paint over the primer for complete coverage and maximum moisture resistance. Allow each coat to dry fully — in a humid basement, this may take longer than the label suggests, so run a dehumidifier or fan during the painting process. Avoid painting in spring when humidity is at its peak and the basement is at its dampest. If you notice musty smells or discolouration on existing painted surfaces, do not simply paint over them — clean the surface with a mildew-killing solution first, identify and fix the moisture source, then reprime and repaint.

Paint for an 800-square-foot basement (walls and ceiling) typically runs $300 to $600 for quality product, or $1,500 to $3,000 if you hire a professional painter. This is one area where a capable homeowner can handle the work themselves, as long as the drywall is properly installed and the insulation assembly behind it is correct.

---

Looking for experienced contractors? The New Brunswick Construction Network connects homeowners with qualified professionals:

• Thirty Four Renovations
• Gionetterenovations