What to do when home insulation gets soaked; sealing a chimney

Q Four years ago we insulated our century-old clapboard house by having cellulose blown into the walls. Recently a heavy rainstorm made clogged gutters overflow, sending torrents of water into the walls and soaking the insulation. Workmen, in repairing the gutters, told us the insulation has not settled. Will the moisture rot the wood studs? Should the insulation be removed from the inside or outside, if necessary? What should we do? Robert Baker Malden, Mass.

The degree of wetness and the subsequent drainage of the stud cavities may determine the answer to your questions. Certainly any continuing dampness of the framing should be avoided, not only because of the potential damage to the structure, but also it could trigger mold and an unwelcome odor.

I am surprised that the insulation has not settled. If it were my house, I'd verify the workmen's opinion that it has not.

Should the insulation have to be removed, its access, whether from inside or out, should be determined by a comparison between the interior and exterior wall finishes. Likely, the removal would be through an outside access. If your 100 -year-old framed walls have a fire stop at mid-point, insulation removal would then have to be from above that midpoint as well as from above the bottom plate.

Before doing anything drastic, I'd have the insulation contractor make an on-site inspection and recommendation. Further, ask a local veteran builder for advice on how best to remove the wet insulation, if indeed it has to be removed and replaced.

The water problem may be covered under a residential insurance policy. Get in touch with your insurance agent before proceeding with any corrections.

This problem may serve to raise a red flag to homeowners who have gutters on their houses. All gutters should be seasonally checked and cleaned in order that rain water may flow freely.

Q Our 5-year-old home has a 3-story, used-brick chimney. Pieces of the brick, especially during the winter, tend to break and peel off. We've been told that this is due to water penetrating the brick, freezing, and then thawing. The exterior chimney surface was originally coated with silicone, but last year we coated it with another product, which did not work. Is there something we can use to stop the brick from disintegrating? Barbara Marek Lake St. Louis, Mo.

Among our most faithful consultants is the Brick Institute of America in McLean, Va. Here is a response from its director of marketing, Charles N. Farley:

''The chimney problem described is not an uncommon one. The previous advice received regarding freezing and thawing is correct, while the source of the water is in error. What often happens is that the thin layer of cement mortar usually used on the top row of brick, which seals against the flues, has probably cracked or loosened from around the flue tile.

''This is caused by the expansion and contraction of the flue tile as it is heated and cooled by fires in the fireplace. Rainwater can then leak into the cracks and run down the inside of the brick.

''Silicone applied to the outside only makes the problem worse by trapping the water inside.

''The proper remedy would be to replace the chimney cap, if necessary, or at the least to caulk around the flue tile with a good grade of resilient material, such as polysulfide, butyl, or silicone rubber.''

The brick institute's Technical Notes on Brick Construction, 19B, revised June 1980, discusses a prefabricated chimney cap in preference to a poured-in-place cap, metal rain caps, and preferred sealants.

Q My nearly completed, lakeshore vacation cottage has a crawl space under the floor. The front side of the cinder-block foundation has no drainage tile or is not below the frost line, or both. Consequently, the floor inside has raised slightly. How can I correct this problem? Lillian Porter Silver Spring, Md.

The actual cause of the raised floor needs to be pinpointed, whether it's frost, original poor construction, expansive soil, or the absence of drainage. It may take a seasoned builder or engineer to make that judgment. An expert can only decide on a cure after he knows the actual cause of the problem, not before.