A metal roof lets go of its snow, which is most of its appeal here and most of its risk. This page covers the panel types, the slopes each needs, where sliding snow lands, going over an old roof, and the towns and districts that limit metal.
Metal shows up on every kind of building in southern Maine, from barns and camps to new houses and, in a few historic districts, restored roofs that were metal to begin with. Its pull in this climate is easy to see: a smooth, steep metal roof clears itself of snow, and a roof that does not hold snow does not feed an ice dam.
The same habit is its main drawback. Snow that slides comes down all at once, onto whatever is below the eave. The sections below take the decisions roughly as you will meet them: which kind of metal roof, the slope each one needs under the 2021 code Maine enforces, where the snow will go, what may be laid over an existing roof, and the local rules that steer the look of a metal roof or rule some types out.
Which one fits depends on the house more than the metal. A steep cape or farmhouse can take any of them. A low porch roof or shed dormer is standing-seam territory. In a district where the street face has to look traditional, metal shingles may be the only metal allowed.
Snow on metal tends to hold until the sun or a thaw breaks its grip, then leave the roof in one sheet. Before the panels are ordered, walk the eaves and ask what is underneath:
The weight is real. The Maine Emergency Management Agency notes that a cubic foot of ice weighs about 62 pounds, and it asks owners to clear large icicles hanging over doorways and walkways with care.
Inspection of the snow guards' attachment belongs on the list each fall, along with the gutters.
The code's design table sends its ice-barrier answer to a short list of roof coverings. Footnote h of Table R301.2, as posted by the Town of Topsham, points to the ice-barrier rule in six covering sections: wood shakes, wood shingles, slate, roll roofing with a mineral surface, metal shingles and asphalt shingles. Metal shingles are on that list. Metal roof panels, standing seam included, are not.
So, by the letter of the code, a panel roof in a town whose table says Yes is not held to the ice-barrier rule that a metal shingle roof is. The panel maker's installation instructions still decide what goes under the metal, and the code requires roofs to follow them (R904.1). A low-slope standing-seam section, or a valley where two metal slopes meet, collects meltwater the same way any roof does.
The question for a quote is concrete: what underlayment the maker calls for under these panels, where any self-adhering membrane goes, and how the eave, valleys and walls are flashed.
The 2021 code has more room for metal here than for shingles. Section R908.3.1 allows a recover in a few cases, two of which are about metal:
Section R908.4 has a catch for wood roofs. If the new roof leaves a hidden space that could burn, the whole old surface must first be covered with gypsum board, mineral fiber, glass fiber or another approved material, fastened down.
The flat bans in R908.3.1.1 still apply to metal: nothing goes over a roof that is soaked or too far gone to be a sound base, over slate or tile, or over two existing coverings. And the frame has to carry the added weight, an item on Topsham's re-roof checklist. Going over an old roof also leaves its condition, and the deck's, unknown.
Every town page under roofing by town notes its historic review where the research found one.
The few towns that print a design wind speed give 115 mph (Topsham, Yarmouth, Raymond) or 120 (Westbrook), and Portland's records hold gusts up to 78 mph. A metal roof stays on through the attachment: clip spacing in the field and tighter spacing at the eaves, rakes and ridge, set by the panel maker's tested layout for the wind speed at the house.
Many houses here sit in the salt air. Old Orchard Beach's seven-mile beach puts many of its buildings in direct sea air and wind; Saco's Camp Ellis and Ferry Beach, Biddeford Pool, Kittery Point and the Casco Bay islands are the same. For a house like that, ask which metal and coating the panels use, which fasteners and clips, and whether the panel maker's warranty terms say anything about distance from salt water.
Two more details belong on paper: what happens where the metal meets a chimney or a wall, and how the ridge is vented and closed against wind-driven snow.
Rooftop solar and a new roof are best planned together, and towns here treat the panels as a structural question:
An array also changes where the roof's snow ends up, so the eave plan above applies to it as well. If the roof under the panels is near the end of its life, it is usually wiser to replace it first.
Often, yes. Snow tends to hold on metal until a thaw or sun loosens it, then leaves in one sheet. Plan for where it lands: doors, walkways, decks, lower roofs and gutters. Snow retention fastened to the panels, set to the panel maker's instructions, is one answer.
In some cases. The code allows standing-seam and similar systems that carry their own loads to go over an existing roof, and metal over wood shakes with a fire-barrier layer. It still bars any roof-over on soaked or worn-out roofing, on slate or tile, or on top of two existing layers.
The 2021 code allows standing seam down to a quarter inch of rise per foot. Lapped panels without sealant need 3 in 12, or half an inch in 12 with sealant in the laps, and metal shingles need 3 in 12.
The code's ice-barrier rule names metal roof shingles but not metal panels, so on a standing-seam roof the panel maker's instructions decide what goes underneath. Ask for the underlayment and any membrane at the eaves and valleys to be spelled out in writing.
It depends on the district. Brunswick's guidelines allow a return to metal when old photos show the house had it, Freeport exempts copper in its design review districts, and Gorham's Village Center allows metal made to look like shake or shingle but not flat or corrugated panels facing the street.
Metal roofing across greater Portland and southern Maine, from Casco Bay and the York County coast to the Sebago Lake towns. Each city has its own page with the permit rule and code edition that apply there:
Sources: MUBEC residential code (2021 IRC with Maine amendments), Chapter 9: R904.1, R905.4, R905.10.2, R908.3.1, R908.3.1.1, R908.4 (UpCodes copy) · Town of Topsham, 2021 design criteria with Table R301.2 footnote h · Town of Topsham, residential re-roof inspection checklist · Town of Topsham, photovoltaic firefighter access to the ridge · Maine Emergency Management Agency, severe winter storms (icicles) · Town of Gorham, Land Use and Development Code (Village Center design standards) · Town of Limington, zoning ordinance (manufactured housing roofs) · Old Orchard Beach (seven-mile beach, buildings in salt air), as summarized in the pack's place research · Town of Brunswick, Village Review Overlay District design guidelines · Town of Freeport, Design Review ordinance · Town of Richmond, Land Use Ordinance Article 4 (Village District) · Town of York, Historic District Commission guidelines · National Weather Service Gray, Portland's strongest wind gusts · Town of Yarmouth, solar permitting checklist (115 mph, 60 psf) · City of Westbrook, code FAQ and solar permit (60 psf) · Town of Kennebunk, residential solar permitting requirements · City of Portland, historic preservation review. Codes, programs and prices change; confirm the current rule with your city before you rely on it.
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