DEAR SAM: We live in a 13-year old Levitt-built ranch house that was built on a slab. This winter, for the first time, after several days of extreme rainfall, we have a wet house on the inside. The windows sweat; ice forms between the storm, and prime windows; the front door drips water on the inside, and water fills some of the heating vents about an inch deep. Worst are the ceilings, which drip water around every electrical fixture opening in them. Should we insulate the attice floor? Buy a dehumidigier? Or what should we do?

ANSWER: FOR A WET HOUSE, YOU HAVE MORE THAN ONE PROBLEM, BUT UNFORTUNATELY, YOU HAVE NO BASEMENT THAT MIGHT HAVE BECOME FLOODED. THE WATER IN THE HEATING VENTS, HOWEVER, INDICATES THAT YOUR HEATING SYSTEM IS FORCING AN EXCESS OF HUMIDITY INTO THE HOUSE.

FIRST, YOU MUST REMOVE THE WATER FROM THE DUCTS WITH A WATER EXHAUST VACUUM OR A SUMP-PUM, WHICH YOU CAN OBTAIN FROM SUPPLY RENTERS.

THEN, TURN ON THE HEAT AND FAN TO DRY UP THE HOUSE. YOU SHOULD DETERMINE HOW THE WATER ENTERED THE DUCTS, POSSIBLY FROM THE ATTIC OR FROM THE GUTTERS.

THE WATER IN THE CEILINGS MAY HAVE COME THROUGH THE OPEN LOUVERS OR THROUGH LOSE SHINGLES.

DID YOU HAVE FREEZING WEATHER BEFORE IT RAINED? THE PROTRUDING SHINGLE NAILS IN THE ATTIC MAY HAVE DEVELOPED ICICLES.

THE REASON FOR THE WATER FLOW FROM THE OPENINGS AT THE ELECTRICAL FIXTURES IS THAT THE GYPSUM BOARD OFFERS AN EASY EXIT OF WATER ONLY AT THESE POINTS. IF YOU DO NOT ALREADY HAVE SUFFICIENT INSULATION, AT LEAST 6-INCH-THICK BATTS OR A BLANKET WITH THE VAPOR BARRIER FACING DOWNWARD. IT SHOULD BE INSTALLED IMMEDIATELY. THIS WILL PREVENT THE HEAT OF THE HOUSE FROM ESCAPING TO THE ATTIC AND CAUSING MOISTURE TO RISE TO THE PROTRUDING NAILS.

SINCE THIS IS THE FIRST CIRCUMSTANCE OF EXCESS HUMDITY RELATED TO THE RAINFALL. I DO NOT SUGGEST AN IMMEDIATE PURCHASE OF A DEHUMIDIFIER. IF SUMMER HEAT IS ATTENDANT WITH HIGH HUMIDITY OF 40 PERCENT OR MORE IN YOUR HOME, THEN YOU MAY BE WISE TO PURCHASE A DEHUMIDIFIER.

DEAR SAM: Our home, which we have been renting for eight years, is on the market and we would like to buy it. However, it has these problems:

The baseboards of the bathrooms and other rooms show settling of about one-quarter inch; a crown molding had dropped about 3/8ths of an inch from one ceiling. During the past year the law around the house had dropped by several feet. Is this settling normal?

ANSWER%: THE INSIDE SETTLING OF BASEBOARDS AND CROWN MOLDINGS DOES NOT SEEM UNUSUAL AND CAN BE CORRECTED QUITE READILY BY A CARPENTER.

THE GROUND THAT HAS SETTLED MAY BE ABOVE A SEPTIC TANK. IF YOU DON'T KNOW IF YOU HAVE ONE, CHECK WITH YOUR JURISDICTION'S BUILDING INSPECTION DIVISION. IF IT THERE IS A SPETIC TANK, HAVE THE PIPING INSPECTED. THE PROBLEM CAN PROBABLY BE CORRECTED.

SINCE YOU KNOW THE HOUSE AND ITS CHARACTERISTICS, YOU MAY BE ABLE TO STRIKE A GOOD DEAL WITH THE OWNER, WHOSE MORTGAGE YOU HAVE BEEN PAYING OFF. PAY FOR AN INDEPENDENT APPRAISAL OF THE HOUSE TO BACK UP YOUR OFFER.

DEAR SAM: The paint is peeling from the exterior wood at our house and we have decided to install aluminum siding. Should the wood be removed first? We are concerned about the fit of the aluminum siding.

ANSWER: When put on a new house, aluminum siding does not overlap the trim of the doors and windows, but when applied over existing frame, the installers extend the trim with aluminum moldings so that the fit of the aluminum ends is similarly overlapped. You can visit some completed houses to see what it looks like.

Removing the wood siding would reduce a layer of insulation and would cost entail extra labor costs. I would not recommend it, unless you intended to substitute one-inch-thick StyrofoamTG panels in place of the old siding.

If your house is not old and the present wood siding has not deteriorated beyond peeling paint, it would be better to try to maintain the wood and combat the reason for the peeling. Leaking gutters or excessive moisture may be a simple problem to remedy. It may also be necessary to change the preparatory measures for painting and the type of paint.

Remember, too, that even if you install siding, there will still be wood trim to paint, including window frames and sash, shutters, door frames and doors, gutters and fascia boards, eaves and cornices.

DEAR SAM: As the director of a complex of condominium duplexes with double garages and interior patios, I have a painting problem. Our homes are constructed of insulated exterior plywood panels. This type of construction may be all right for California, where the company first used it, but in the Middle Atlantic coastal area, the wood exterior seems to be taking a beating. The panels, which have latex paint on them, are splitting.

ANSWER: When the builder uses plywood on the exterior siding, I assume that uses addition sheating under it. Check to see if your builder has done this or has not depended on a half-inch thickness of plywood for the full separation between inside and outside structure.

For better structure and insulation of the walls, one-inch-thick Styrofoam(TG) 2x8 foot panels would have provided a moisture barrier and additional insulation.

Two coats of resin oil-base stain would have been better initially. However if you apply two coats of acrylic latex exterior paint after wood-fillers are used to fix the splitting, the problem should be eliminated.