Home fix-up

Q The slate-tile roof of my sister's home has a leak around the chimney. She feels that the whole roof must be replaced. Can slate roofs be repaired? Also, the slate tiles easily break. Is there a way to prevent this breakage when working on the roof? R. T. Fresto New York There are many ancient buildings in Europe, some of them hundreds of years old, which still perform well with slate roofs. Your sister's problem is probably in the breakdown of the sheet-metal flashing between the roof and chimney, or else in the deterioration of the concrete cap on top of the chimney.

Slate is stone and does not deteriorate with age. It is also a very expensive roof today.

When repairing the roof, be sure to lay down boards or plywood sheets on which to walk, because the tiles are very brittle. What this does is distribute the workman's load over a much wider area.

Q The light gray rolled roofing on my shed is deteriorating faster than the shingled roof of the main house. Both are 17 years old. Is there anything, other than black adhesive, that I can apply to extend the life of the rolled roofing? Richard Bradley Jamestown, R.I.

The material on the rolled roof is most likely a single layer of mineral-surfaced, asphalt-impregnated felt. The shingles on your home will last a little longer because they are lapped when laid up to give at least two layers of protection. I think 17 years of service from your shed roof is quite good. After all, the cost might figure out to about one-half cent a square foot a year.

Deterioration comes from the sun and rain taking the volatile fluids and oils out of the asphalt and leaving the brittle felt mat, which is little more than paper and cannot repel the rain.

To coat it would be wasting money. You could cover it with plastic for a while, but your best choice is to bite the bullet and reroof.

Q We have a gray-green mold on the asphalt-shingle roof of our home. How can we remove it? Marsden Maguire Alden, Mich.

I have personally used a product called X-14, available in paint stores, to remove mildew from interior walls. It sounds to me, however, more like moss than mildew. Moss usually grows on north-facing roofs in winter.

I have been told that any of the ``penta'' family of fungicides, often used on wood-shingled roofs, will stop the growth of moss, but I'm not sure about its effect on a petroleum-based shingle. I recommend that you clean a small portion of the roof and allow it to dry. Then apply a small amount of a fungicide, such as Woodlife. See if it preserves or attacks the shingles over a year's time. Q We are having a problem with tree roots clogging our sanitary sewer. Will the periodic use of a copper-sulfate solution prevent root growth? I've also heard that caustic soda is supposed to work. Do you have any other ideas? Fred W. Whiteman Bay Village, Ohio

I know of no chemicals that prevent root growth. Although expensive, yearly roto-rooting is the best way to keep the drains free. You might consider excavating and repairing the drain as well as doing some major root pruning in the area.

Once the roots have started in the sewer, they will continue to break it up as they seek moisture.

To the real estate editor:

In a column a while ago you mentioned using ammonia or bleach to clean stains. Readers should be aware that if the two are combined, a toxic gas will result. Joe Bailey Sheldon, Iowa

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. Richard A. Kent is a practicing architect and general contractor in southern California.