Several Steps Needed to Correct Flaking Wall

QUESTION: I have a problem with a concrete block wall. The paint on it has become a chalky disaster over the years and is flaking off. What can I do to prevent this from happening again when I repaint the wall?

ANSWER: The cardinal rule when it comes to painting any concrete surface is that dirt, grease, oil and old chalky and flaking paint will quickly follow the deterioration of the old. Professional steam cleaning is a good start, and if this doesn’t do the job, try wet or dry sandblasting.

Once the wall is cleaned and dry, latex, oil-based, oil-alkyd or rubber-based paints should adhere. Latex is most commonly used because it breathes and isn’t damaged by alkalies often found in concrete. To waterproof and seal your block walls, you may want to use a product like Thompson’s Water Seal. The maker suggests applying the sealer and then waiting at least a week before applying oil-based paint.

Floor Covering Won’t Disrupt Radiant Heat

Q: I have a home with radiant heating (cement slab floor with embedded circulating hot water), and I want to replace the existing vinyl tile in the kitchen. I would like to use slate, quarry tile or something similar, but I’m concerned about the chance of disrupting heat transfer and increasing energy requirements and cost. What do you recommend as the best covering for this type of floor?

A: Any floor covering that you like will do fine. We checked with the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and they say there would be no appreciable increase in energy use regardless of the type of floor covering.

The response time of a radiant heating system to changes in thermostat setting is normally slower than that of a hot water system with baseboard or free-standing radiators, or a forced warm air system. By covering the floor, you will slow down this response time slightly, but you will also increase the mass of the heated floor so it takes longer to cool down. Thus the end result will be almost no perceptible change in heating costs.

For further information on any home problem, write to Popular Mechanics, Readers Service Bureau, 224 West 57th Street, New York, N.Y. 10019.