Q. Our 125-year-old Victorian house with a mansard roof still has its original built-in gutters. A workman has suggested he put tin over the gutters because of a bad roof leak in a thaw and rainstorm last winter. To prevent more leaks,do you think we should remove the shingles from the roof, cover the sheathing with tar paper, and then apply new shingles? Miss Helen Adair Delhi, N.Y.
A. Electric heat tapes on the edge of the roof above the gutters may relieve the ice-melt problem, but it is expensive, takes a bundle of Btu, and may not be entirely effective on your particular mansard roof.
I'd take the workman's recommendation to apply tin over the old gutters before investing in electic heat tapes.
In this column on Feb. 23, 1979, Howard M. Deer of Minneapolis responded that he had solved the ice-dam problem on his eaves by making sure that the attic insulation was tight to the outside perimeter of the house.
Otherwise, interior warm air passing through to the roof edge melts the snow, which then freezes at the edge of the roof. An ice dam is created which forces any subsequent melt water up under the shingles; thus, the leaks.
Mr. Deer explained that a fully insulated attic area makes the snow melt uniformly and the water is carried away by the gutters. It saves on heating costs as well, he reported.
In your own case, make sure that the attic insulation is tightly set to the attic perimeter extremities.
This column on Jan. 26, 1979, also contained a response from Stephen C. Smith of Madison, Wis., who said he solved his roof ice-dam problem by adding a cupola at the ridge. The result was an increase in cold-air circulation in the attic.
In that same issue, Guy C. Crooker of Portland, Maine, said he threw rock salt on the roof above where the water was getting into the house. The ice-dam problem was fully solved, he said, adding that the salt had not damaged any of the vegetation, although salt might damage copper gutters.
Undoubtedly, your guttes are copper, since they were installed before the Civil War and have lasted all these years. Besides, rock salt is not practical on your two- or three-story Victorian home.
If these suggestions prove unavailing, you may need to remove the shingles for a couple of feet to remove the shingles for a couple of feet or so above the gutters. Then apply an appropriate metal or composition sheet over the sheathing. Install new shingles thereon.
The critical waterproofing point is where the new sheet meets the existing gutters.
That joint must be absolutely watertight. To make sure it is watertight, I suggest you hire a professional sheet-metal firm working in conjunction with an experienced roofer.