Minnesota code timeline · Roofing · 2000

Roof Ice Barrier Membrane in Minnesota Roofs Installed Before 2000

Minnesota's climate requires a waterproof membrane along the eaves to handle ice dams. Roofs installed before the requirement often do not have one under the shingles.

By Karl Espilseth, Founder, Tarn · Updated

What it is

An ice barrier is a self-adhering waterproof membrane applied directly to the roof deck along the eaves, underneath the shingles, extending far enough up the slope to cover the area where ice dams form. It is different from ordinary felt underlayment in that it seals around the nails driven through it, so water sitting on top of it has no path down into the deck.

Why it matters

Ice dams are a function of climate, not workmanship. Heat escaping into the attic melts snow on the upper roof, the meltwater runs down to the cold overhang, refreezes there, and builds a ridge of ice that backs standing water up under the shingles. Shingles shed water running downhill; they do not seal against water sitting still and pushing uphill. That is the specific condition the membrane addresses, and it is why the code requires it in Minnesota's climate zones and not in warm ones.

What's worth doing next

The membrane is invisible once the roof is on, so the practical question is when the roof was last replaced. If it was reroofed after 2000 it almost certainly has one. If the last permit predates that, this is worth raising at the next reroof rather than as a reason to do one early — the added cost at the time of a planned replacement is small, while tearing off a sound roof to add it is not. Interior signs worth noticing in the meantime: staining on the ceiling near exterior walls, or water showing up at the top of a window frame after a thaw.

I built Tarn as a homeowner, not a code official. Everything on this page is sourced to published Minnesota law and linked so you can check it yourself.

Minnesota uses a single statewide building code, so these requirements are state law rather than city ordinance — they apply the same way across every Minnesota city Tarn covers, except where noted. Code changes are also prospective: they apply to work done after the change, not retroactively to homes already standing. A home that predates a standard isn't out of compliance with anything. It just predates it, and that's worth knowing before you buy.

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