Metal Roofs and Pests: Where Animals Actually Get In

Every spring I get a version of this question from someone who has had something living in their attic. The honest answer is that metal closes off most of the ways animals get into a roof, and it does nothing about the ways they get in around it. Knowing which is which is more useful than a blanket promise.

How animals get into a roof

They do not chew through a sound roof surface, metal or asphalt. They find an edge that has already failed or a gap that was never closed.

• The eave and fascia. Soft, rotten wood at the roof edge from years of ice damming or a missing drip edge. A raccoon peels it back like cardboard. A squirrel gnaws a fist-sized hole in an afternoon.
• Soffit vents and gable vents. Screens rusted through or never installed. Bats need a gap the width of a finger. Starlings need a little more.
• Lifted shingles. A raccoon lifts the edge of aging asphalt and pulls. Once there is a hole in the decking under it, everything else follows.
• Plumbing boots and roof penetrations. A cracked boot is a doorway for mice and a water leak at the same time.
• Open panel ends and ridges. On a metal roof with no closures, the gap under a ribbed panel at the eave or the ridge is an open invitation for wasps, birds, and mice.

What metal closes off

The lifted-shingle path is gone. A standing seam or interlocking metal shingle roof has no loose edge for a raccoon to get a claw under, and no animal is chewing through steel. The eave is hemmed over metal trim, so the panel edge is not something that can be peeled. On an asphalt roof the field of the roof is a soft target. On metal it is not.

Metal also does not hold the organic debris that insects live in and birds nest on. There is no granule surface for moss, and a smooth panel sheds leaves.

What metal does not do

Here's the tradeoff. The roof is one surface. The soffits, the fascia, the vents, and the penetrations are still wood, screen, and rubber, and they still have to be sound.

• Closures. A ribbed panel has a gap under every rib at the eave and the ridge. Foam or metal closures fill it. They are small, cheap, and skipping them is how wasps, mud daubers, and mice get in under an otherwise good roof. Ask whether they are in the quote.
• Soffit and gable screens. A new roof does not fix a rusted-out vent screen. It should be on the list.
• Rotten fascia. If the eave is soft, the re-roof is the time to replace it. Metal trim over rotten wood is a clean-looking cover on a problem.
• Tree access. Squirrels and raccoons get on the roof from branches. Keep limbs back from the house. There is a separate piece on squirrels specifically.

Bats and birds

Some species are protected, and you cannot simply seal them in or kill them. Bats, in particular, have to be excluded at the right time of year with one-way devices before the gap is closed, or you trap a colony in the attic. If you have bats, that is a wildlife contractor's job before it is a roofer's. What the roof can do is leave no new gaps once they are out. A metal roof installed with closures and sound trim does that well.

Droppings and corrosion

Bird and bat droppings are acidic and eat at wood and asphalt. Metal with a PVDF finish shrugs it off better than either, which matters on the gable end where birds roost. Gutters still collect it. That is a cleaning job, not a roofing one.

Who this matters for

If you have had animals in the attic, a metal roof takes the field of the roof out of play, which is a real benefit, and the rest depends on the crew closing the edges, vents, and penetrations properly. Ask about closures and fascia by name. If you have never had a pest problem, this is not a reason to buy a metal roof. It is something you get along with one.

No roof keeps everything out. A well-detailed metal roof comes closer than most, and it stays that way longer. Now you know where to look.