Humidity is the first thing to plan around
In an average year at Charleston, NOAA's engineering weather data counts about 1,820 hours with the wet-bulb temperature at 73°F or higher and about 3,372 hours at 67°F or higher. Wet-bulb temperature folds heat and humidity into one reading. When it's high, the air holds a lot of moisture and takes up little more from a wet coat of paint.
Those counts describe NOAA's Charleston figures, not conditions inside your house or on your porch. But they explain why so much of a painter's planning here is about moisture.
Mildew comes off before paint goes on
Mildew grows on painted siding, soffits, porch ceilings and shaded trim, and it grows through new paint if it isn't removed first. Paint applied over it can also lose its grip. A sound exterior bid includes:
- washing with a mildew cleaner, not just water;
- rinsing it off fully, so cleaner residue doesn't stay under the new coat;
- giving the wood or masonry time to dry before primer or paint;
- a finish product that contains a mildewcide, which many exterior paints do.
Ask the painter which cleaner they use and how long they'll wait after washing.
Drying, recoating and dew
A latex coat dries by losing water to the air. On a humid day, it loses it slowly. In practice that means:
- the recoat time on the label may not be enough, and a painter may wait longer between coats;
- work often stops earlier in the afternoon, so the coat has set before evening dew;
- the north and shaded sides of a house can stay damp from the night well into the morning.
Inside, the same air moves through open windows. With the air conditioning running and windows closed, paint dries more predictably, but it still needs some fresh air to clear moisture and odor. Bathrooms and laundry rooms, which already run damp, benefit from a paint made for high-humidity rooms. The interior painting page has more.
Choosing a finish for damp conditions
Glossier finishes shed water and wipe clean more easily, which helps on trim, doors and porch ceilings. Flat finishes hide surface flaws but hold dirt and mildew spores more readily. Many homeowners split the difference by putting a satin or low-sheen product on siding and something glossier on the trim. Our sheens and finishes guide goes through the trade-offs.
South Carolina's registration rule
Under South Carolina Code Section 40-59-20, the law lists painters and wall paperers among residential specialty contractors, who must hold a Residential Builders Commission registration when the work on a home exceeds the amount given in the card below. South Carolina LLR's Residential Builders Commission lists Painters/Wallpaperers as a specialty contractor classification covering the application of materials common to the painting and decorating industry, and says a registered specialty contractor may hold up to three classifications.
You can ask a painter whether they hold that registration. We don't check registrations for anyone.
Older paint
EPA's Renovation, Repair and Painting Rule applies to anyone paid to do work that disturbs paint in homes, childcare facilities and preschools built before 1978. The fact card gives EPA's wording. If your house dates from before then, ask the painter how they'll set up and clean up when they scrape.
What to ask before you sign
- How will you remove mildew, and how long will the house dry before painting?
- What will you do if a coat hasn't dried by the label's recoat time?
- What time of day do you stop to stay ahead of the dew?
- Which product and sheen are going on siding, trim and porch ceilings?