DEAR SAM: My four-year-old house is on the river. The other day I had reason to go into the crawl space. To my surprise I found water dripping from the joists and the insulation between the joists was wet, as was the ground. It also looks as if mildew has covered about three inches of the joists. How can this be correct?

ANSWER: The spring rainy season can swell the rivers, causing a high table -- even in a crawl space. (The crawl space usually substituted for a full basement when the builder determines that, because of the terrain, a basement would not remain dry.)

The mildew may have developed during the colder weather when interior floor heat escaped to the area between the joists, causing saturation of the joists abetted by the moisture rising from the ground. You need to improve the soil of the crawl space by removing any organic matter (peat, vegetation, etc.) and installing bank gravel. An inside French drain around the foundation and leading to a low point will permit the flow of excess water from this area.

Covering the ground with a barrier will prevent the rise of moisture to the joists. Cross ventilation by means of louvres on each side is essential.

The wet insulation should be removed and dried out completely before reinstallation. An aluminum foil barrier may be necessary against the underfloor to prevent any escape of heat to the area below.

DEAR SAM: We have lived in a two-story brick huse since 1976. The master bedroom plumbing to the bathroom freezes in the winter when the temperature drops below 10 degrees, especially the hot water line, unless we keep it dripping constantly. We removed the access panel to the tub plumbing and blew in insulation to fill the space under and around the bottom of the tub, but to no avail. Is there no way to reach the pipes in the wall without tearing out the wall? Can I do it myself?

ANSWER: You do not say if the pipes have burst. If they had, there would have been a break in the wall and damage to the ceilings and floors.

I suggest that you remove the plaster or drywall between two studs where the hot and cold water pipes are located. The center lines of the studs will help you cut out the plaster evenly and quickly with hammer and wood chisel. Wrap the pipes with full fiber-glass batts on the outside and over the pipes. As an alternative, wrap electric heating cables around the pipes and connect them to an outlet/switch that can be turned on when the temperature drops below 32 degrees.

A plumber could trace the piping for you and the insulating and the attachment of the gypsum board with bluenails and spackle are easily done.

DEAR SAM: I have just had new galvanized gutters installed on my house; however, I have not been able to obtain any good or consistent advice on painting them. Everyone seems to have a different idea but no one seems to know. Also, what should be used on the inside of the gutters to prevent corrosion?

ANSWER: Perhaps your problem would have been solved most readily (and inexpensively) if you had purchased galvanized gutters with the baked enamel finish applied at the factory. Popular white is available along with many other colors.

The difficulty in obtaining correct advice for painting ordinary galvanized gutters (and rain leadars, too) is that for shipment in bundles, the products are sprayed with an "oil" as a precautionary measure, which is not compatible with paint; hence it must be weathered first for some months or it must be removed with vinegar. After that, you have a choice of oil or water base paint. Both outside and inside may be treated similarly, but an extra inside coat of finish paint could prolong the durability between coats.

Exterior acrylic latex primer and finish are my recommendations, with the finish in the color of your choice. Be sure that moderate temperatures are selected for the painting, so that the metal is not subject to unusual expansion and contraction. Wait 24 hours between coats. For assured adhesion and good durability, be sure that the paint specifies "acrylic, exterior," on the labels, both for primer and finish.

DEAR SAM: when there is a heavy rain, some of it comes down my chimney, past the damper and into the fireplace. Is this normal or harmful? If it's harmful, what can be done about it?

ANSWER: Rainwater should not seep into the fireplace; it could stain the nearby wood floors.

If the outside cement cap of the chimney has deteriorated, the pointing of the opening between the cap and the flue may need replacing.

If this is not the trouble, then the immediate problem lies in the damper. Now that fireplaces are being used more, problems have arisen from heat build-up in the hearth. The usual castiron dampeer may warp from continual expansion and contraction.

Soot and creosote may build up on the damper shelf cover. The cover may not be tight enough in the closed position, allowing rainwater to drip into the hearth rather than flow behind the damper.

A damper should always be open when a fire is lit, even when it rains. If the damper cover has warped, a replacement is available from a masonry supply dealer. Bring the old one along (it detaches) to determine the correct size. The brand name is usually on the cover.

DEAR SAM: We own a home in the Washington suburbs that will probably sell for $55,000. We bought land at Ocean City, Md., near a resort development, where summer and year-round homes are being built gradually. Recreational facilities are available for an annual association fee. We want to buy a modular home and add a garage, porch and sundeck, probably costing up to $50,000.

Can you suggest how to go about this?

ANSWER: Get an expert appraisal of your present house. While your new houses's price may have been set by the builder, you should also obtain a contractors appraisal for building the model and additions you want.

You should check with the development builder about visiting a finished house to make sure it meets your approval. Meanwhile, you should get a lawyer to check the reliability of the contractor and the plans and specificatins of the model you want. Be sure to have him designate the method of payments. The house should be completed before the final payment is made.