After living in this house for 17 years without a problem, now, after every snowfall and for weeks later, even when no snow remains on the roof, we have a brand-new problem of water steadily coming through in at least two places: one attic valley where it runs down an inside beam of an addition-roof, and one attic knee-wall where it finds its way into a second-story window frame and has damaged the wall in that room and in the room below. Our roofers say the cause must be ice-dams from heat-loss, which must have been caused by their removing the old cedar-shakes roof under the old metal roof when they stripped the roof for the new shingles (they added a new plywood base which has a slightly shorter projection than the old metal roof had, new Tyvak "breathable" sheeting, and new wood framing to mount the shingles on). They say the new roof isn’t leaking, but the ice-dams are making water back up and then come inside the walls of the house.

So they say the answer is more insulation everywhere, but we’re sceptical, since we haven’t changed anything else about our living habits and we’ve never had the problem before. Most of the third-story is plaster-finished living space from a century ago so insulation would be hard to place , and we don’t usually even have any heat on in the third storey or in the second-storey room with the bad leak into the window frame (we do have heat on in a nearby room under the very same slope of roof, but it has not had a problem).

At present we’re just trying to get through the winter by having the lower few feet of snow shovelled off our new roof soon after a storm; this reduces the amount of water but does not stop it. We have tried to find roofing experts, engineers, etc. without luck to advise us on the problem, since we paid a great deal for this "Cadillac" 50-year plus roof and do not want to spend another winter terrified every time it snows lightly. We are so worried that we are seriously thinking of going to all the expense of having the whole new roof ripped off and replaced by standing seam again, which might dump snow on the nearby sidewalk, but might allow us some peace of mind. We can’t afford to do this, but neither can we afford to have our house rot around us.

Has anyone else encountered this problem, that when you put a new but similar roof on you changed the environment of your old house so that the old ventilation was no longer adequate? Would just taking off the last few rows of metal shingles and extending the roof projection underneath farther beyond the walls help the front roof-wall area? What would help the valley on a different side?

We’re at our wits’ end, and would appreciate any suggestions anyone might have.

Your roof is not similar, only the material is. Original roof was solid from eave to ridge so any ice formed would just keep backing up the roof without penetrating. New roof is pieces which allow the ice to form and move underneath and then leak in the house.