Home fix-up

Q We have a 30-year-old home with a crawl space under the floor. Every fall I close the outside vents to prevent the water pipes from freezing. In midwinter we get frost all along the sill and the adjacent floor joists. This has caused some dryrot, but I don't dare to open the vents or the water pipes will freeze. Any ideas? Walter W. Phillips Harpswell, Maine I recommend you insulate between the floor joists with at least R-19 fiber-glass batts which have a vapor barrier face. The vapor barrier should be on the outside.

Further, wrap the pipes with foam insulation. The foam is split so it can be installed on existing pipes. This will eliminate the spread of dryrot, even if you close the under-floor vents. Q I am having trouble locating shingle nails for an asphalt-shingle roofing job. In our area, with its salt air, I'm concerned that copper wouldn't last as long as the roofing itself while some of the locally available monel metal boat nails have heads which are far too small. I would also like to know if any special material under metal roofing is necessary to prevent condensation or is special grounding to prevent lightning damage necessary? Henry Dunseith Mattapoisett, Mass.

Hot dipped or electroplated galvanized iron shingle nails are the best product for putting down asphalt shingles. If they aren't readily available, consider using 4-penny galvanized box nails run through small galvanized washers to increase the head area. These should last as long as the roof.

If using metal roofing, underlay it with 30-pound asphalt saturated felt paper. You would be wise to install a lightning rod; or at least run a ground cable down from an eave of the metal roof.

If you have a question about designing, improving, or maintaining your home, send it to the real estate editor, The Christian Science Monitor, One Norway Street, Boston, Mass. 02115.