Do-It-Yourself: Warming up a cold concrete floor

By Gene Austin
Saturday, September 18, 2010

Q: We added a room to our house that has only a concrete slab for a floor. The slab gets so cold in winter we are unable to use the room. How can we make the room comfortable? -- Vicki

A: Cold concrete floors are a rather common problem, and there are several approaches to warming them up. A few of the methods are expensive or not practical for some homes. One of the most recommended systems requires digging a trench around the outside of the slab to below the frost line, which in some climates can be several feet down. Panels of foam insulation are then glued to the perimeter of the footings and the slab. For details on this method, go to and put "slab-on-grade foundation insulation" in the search space. In some states where termites are a serious problem, special precautions need to be taken in insulating a slab perimeter, since termites can tunnel through the insulation to reach wood.

A second rather costly method is to retrofit the slab with radiant heat.

Still another method that can add several inches to the thickness of the floor is to attach foam insulating panes to the surface of the floor and cover them with finish flooring. For information on these methods, search the Internet with phrases like "retrofit radiant heating" and "insulating the surface of concrete slab."

There are a couple of methods that can add some comfort to the room at moderate cost, assuming that the slab does not have a moisture problem. One of these is to lay Comfort Base panels, made by Homasote, over the surface of the floor. These panels are only about 1/2 -inch thick and are small enough (4 feet square) to handle easily. Cover the panels with a thick carpet and pad. For details, go to Cork tiles, generally about 1/2 -inch thick, can also have some insulating ability and add comfort to the floor.

Q: There is a room in my house that never seems to get warm. I think it needs more insulation, and the heating system serving it needs to be connected properly. I can't afford to do both. Which should I do first? -- Doug

A: If this one room is very important to you, I'd say to get the heating working first. But if the whole house is under-insulated, you would probably be better off to bring the insulation up to modern standards. You don't say where insulation is needed, but attics and floors are usually the first priorities.

Q: I have asked waterproofing companies for prices on a backup sump-pump battery, and they estimated the cost at $1,500 to $2,500. Should a battery cost that much? What about the backup pump? -- Sanjiv

A: You can buy a complete battery-powered sump-pump system for $750 or less, not installed. This includes the battery, charger, pump and some other accessories. I wouldn't consider any of the really inexpensive systems, some of which sell for less than $200, but the better-quality pumps should do the job. Installation shouldn't add a great deal to the cost.

QUICK TIP: Most do-it-yourselfers know the value of duct tape for quickly making many types of repairs. A new line of Scotch tough duct tapes from 3M gives a choice of superior tapes with unique characteristics. The five varieties include a tape with "extreme holding ability," a tape that is supposed to leave no residue when removed, a transparent tape, a heavy-duty all-weather tape, and one that excels at hanging poly sheets and tarps when painting. A company spokeswoman said they are also "UL approved for HVAC uses," which apparently means they can be used on heating, ventilating and air-conditioning ducts -- a task ordinary duct tapes can't handle without drying up and coming loose. The tapes cost more than ordinary versions, but the special functions may make them worth the extra cost. Questions and comments should be e-mailed to Gene Austin at Send regular mail for Gene Austin to 1730 Blue Bell Pike, Blue Bell, Pa. 19422.

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