NOAA's Rochester numbers
NOAA's engineering weather data for Rochester lists a 50-year ground snow load of 47 pounds per square foot and about 58 freeze-thaw cycles in an average year. In an average year at Rochester, NOAA counts about 726 hours with the wet-bulb temperature above 67°F and 165 hours above 73°F, a measure of how many muggy summer hours the city gets.
The snow load is a structural design figure for the weight of snow on the ground in a rare case, not an everyday amount. It's here because snow that piles against a house and melts is hard on the paint at the bottom of the walls. The other two numbers describe what the paint lives through each year.
Where snow sits against the house
Snow banked against siding, piled on porch floors or drifted onto window sills keeps those surfaces wet for days at a time, and each melt sends water into any open joint. In a repaint, ask the painter to pay attention to:
- the lowest course of siding and the trim board along the foundation;
- sills and the bottom rails of windows and doors;
- porch floors, steps and the bottoms of porch posts;
- the ends of boards where they meet trim.
These are the places paint usually fails first, and the places where repairs, primer and caulk earn their cost.
Freezing and thawing through the shoulder seasons
About 58 times in an average year, the air at the station crosses freezing. Water in a crack freezes, swells and widens the crack, and the next thaw lets in more. A tight, unbroken film keeps that from starting. That's why scraping back to sound paint and priming every bare spot matters more than the color of the top coat.
The shoulder seasons also limit the calendar. Every exterior product has a lowest temperature for air and surface on its label, and the coat needs to stay above it while it cures. Cold nights can end a painting day early even when the afternoon is mild.
Muggy hours in summer
Humid air slows how fast water-based paint dries, and the station's muggy hours come in summer, when most exterior painting is done. Late-day dew can land on a coat that hasn't set. A crew that stops earlier on sticky days is protecting the work. Ask how they plan the day's last coat.
Minnesota's remodeler license law
Minnesota law requires a residential remodeler license from the Department of Labor and Industry for a person who contracts with an owner to improve existing residential real estate by providing two or more special skills, and the statute lists interior or exterior painting among those skills. Minnesota law also exempts specialty contractors who provide only one special skill, and persons whose gross annual receipts for those skills do not exceed $15,000, from the residential contractor license requirement.
Read together, the two statutes mean whether the license applies depends on the business and the work it takes on. It isn't something we decide. If a firm tells you it holds a Minnesota license, you can ask for the number.
Bid questions
- Which walls, trim, porches and sills are in the scope?
- What repairs come before primer, and are they priced separately?
- What primer goes on bare wood, and how many top coats?
- What's the earliest and latest you'll paint in the season, and why?
The exterior painting page has more on preparation and timing.