Siding in Portland
Sebago Lake, which the Portland Water District describes as Maine's second-largest and deepest lake, is the primary water source for nearly all of the district's customers. The district says the water is clean enough to be exempt from the Safe Drinking Water Act's filtration requirements, one of only about 50 of 13,000 U.S. surface supplies serving unfiltered water. That is a fact about the city's drinking water and nothing more; this page is about the outside of the house.
A siding job here comes down to three questions. Will the wall stay put when the wind gets under it? Will rain that slips behind the panels find its way back out? And will the material, the fasteners and the caulk keep working through a long run of freezing and thawing? The rest of this page takes those one at a time.
The station behind the numbers
Every figure below comes from NOAA's engineering weather data for its Portland station (elevation 62 feet). At Portland, NOAA lists:
- a 50-year basic wind speed of 110 mph, measured as a 3-second gust at 33 feet;
- a 100-year rainfall rate of 2.3 inches per hour;
- about 78 freeze-thaw cycles in an average year;
- a 99% winter design temperature of 2°F;
- a 1% summer design temperature of 84°F, with a mean coincident wet-bulb temperature of 70°F;
- about 74 hours a year with the wet-bulb temperature above 73°F, and about 495 hours above 67°F.
These describe the station's record. Your own lot, its exposure and the trees around it will shape what your walls actually see.
Wind first
A 110 mph design gust at the Portland station is the number to bring up with every bidder, because siding usually fails at its edges and fastenings rather than in the middle of a panel. Ask each contractor:
- which nails or screws they will use, how long they are, and the spacing they follow;
- whether that schedule comes from the product's own instructions for higher wind zones;
- how starter strips, corner posts and J-channel will be secured at the ends of walls and under eaves, where wind tends to pry first;
- whether the product line offers a high-wind version and what it would add to the price.
Loose fastening is correct for vinyl, so the panels can slide as they warm and cool. Loose is not the same as under-nailed. A good installer can explain both in plain words.
Rain and the layer you never see
NOAA's 100-year rainfall rate at Portland is 2.3 inches per hour. Heavy rain pushed by wind will reach the sheathing behind any cladding at some point; the wall stays sound when that water has a clear path down and out. Ask for these in writing:
- the water-resistive barrier, with seams lapped shingle-style so the upper sheet always laps over the lower;
- flashing at the head of every window and door, and kick-out flashing wherever a roof edge stops against a wall;
- a drainage gap, rainscreen mat or drainable wrap, and its cost as a separate line;
- how dryer vents, outlets, hose bibs, meters and cable entries will be sealed and flashed;
- what the crew will do if tear-off turns up soft sheathing, and the price per sheet to replace it.
Seventy-eight freeze-thaw cycles
The Portland station averages about 78 freeze-thaw cycles a year, and its 99% winter design temperature is 2°F. Each cycle lets any water caught in a joint freeze, expand and open the gap a little more. That is why the small details earn their keep: caulk rated for the cold, sealed cut ends on fiber cement and engineered wood, and enough clearance at the bottom of the wall that snow piled against it does not sit on the lowest course for weeks.
Vinyl turns brittle in hard cold and can crack if a ladder or shovel hits it. If the work runs into late fall or winter, ask how the crew handles cold panels and whether paint and sealant can still cure at the temperatures on the label.
Summer is part of the story too
At the other end, NOAA puts the Portland station's 1% summer design temperature at 84°F, with a mean coincident wet-bulb of 70°F, and counts about 495 hours a year above a 67°F wet-bulb and about 74 above 73°F. Sun on a dark wall heats siding well past the air temperature, so vinyl needs room at corners and channels to grow. Ask what gap the installer leaves at each end and whether they change it on a warm day.
Matching a material to the job
- Vinyl: light, low upkeep and quick to install. Needs correct loose nailing and careful handling in the cold.
- Fiber cement: takes paint well and resists rot and insects. It is heavy, cuts make silica dust, and every cut end needs sealing.
- Engineered wood: lighter than fiber cement and easy to work, with sharp profiles. It depends on sealed edges and good ground clearance.
- Cedar or other wood: a traditional look that needs paint or stain on a schedule and a close eye on the lower courses.
Ask each bidder what they would put on your house, why, and for the maker's installation guide they intend to follow.
City permits and paperwork
Ask the contractor which City of Portland permits the job needs, who will pull them, and whether an inspection follows. Ask for proof of liability coverage and workers' compensation, call your own insurer if you have questions about your policy, and check that the business name on the bid matches the name on the contract.
Reading the bids side by side
Have every company price the same list: tear-off and disposal, the product with its grade or thickness, the weather barrier and any drainage layer, flashing, trim, soffit and fascia, the sheathing allowance, permits, cleanup, a start and finish date, and both the product and workmanship warranties. Lay the bids next to each other and go line by line. When one total is far lower, the difference is usually a line that is missing rather than a better deal.