DEAR SAM: What causes roof shingles to lift up or curl during cold weather? One of your columns recommended stapling double-faced aluminum foil between the rafters. Would that help in my case? Does one staple the foil on the rafters which would then leave an empty space between the roof and the foil?

ANSWER: Since older houses may not have utilized the self-sealing roof shingles, there was always the possibility of strong winds lifting the shingles, bending and even breaking them, especially if they were brittle as is the case in the wintertime.

When rain and snow accompany wind, the accumulations beneath the shingles cause the curling; however, if no other damage has occurred, the warmth of the sun should dry the shingles and the curling shingles tabs should return to their normal flat position. Otherwise, dabs of roofing cement are necessary to hold the shingles flat.

The double-faced aluminum foil is intended for better insulation of the attic, both for summer coolness and winter warmth. The foil does not adversely affect the shingles. It may be stapled horizontally to the rafters (usually six inches), or between the rafters, a few inches from the edges. Either way is satisfactory but be sure that the roof louvres are not covered.

DEAR SAM: We need information on pre-fab chimneys. We cannot attach a Franklin stove to the existing single flue that serves furnace. A standard chimney would require that we break our basement floor for adding another flue, which we hestitate to do. By using a Franklin stove on the main floor, we could help heat our home with less fuel oil. We have asked about pre-fab chimneys but have received conflicting information.

ANSWER: You are correct in specifying that an additional flue is needed for use with a Franklin stove on the main floor. For the flue that is viable, you may use "Metalbestos," pre-fab stainless steel. There is no asbestos in this metal piping, despite the name. Eight-inch diameter, 30-inch length will interlock with each extension to the desired length required - through the attic and the roof sheathing to the height approximately of the existing chimney.

At the roof, it will be necessary to install a metal flange for flashing around the pipe, both for weather-tightness and for insulation from any nearby combustile materials (wood and shingles). The diameter of eight inches should readily fit your stove, although other sizes are available from six inches and larger, depending on the municipal building code, which you should check as the first requirement.

Check the Yellow Pages under Chimneys for suppliers.

Write Samuel Fishlyn at P.O. Box 62, 10 Madoe St., Newton Centre, Mass. 02159.