Q. We have linoleum tile on our family room concrete floor 3 feet below ground level. Dampness has caused sections to lift. We got in touch with several flooring dealers who have given us all kinds of advice, but no two were alike. We need to have this 20-year-old floor fixed. What do you recommend?
Michael Assaly, North Chelmsford, Mass.
A. ''While many of our floor coverings can be installed on below-grade concrete floors, they must be dry in order to obtain a secure bond,'' writes Joan M. Greiner, customer relations correspondent, Armstrong World Industries, Lancaster, Pa.
Traditionally, linoleum flooring has been a no-no on below-grade slabs.
Moisture migrating to concrete triggers alkali, which may repel ordinary tile adhesives. Three ways to prevent alkali disposition in a new slab are: (a) pour crack-free slabs, (b) use a vapor barrier and capillary break, and (c) use as low a water-to-cement ratio as practical. There is no sure way to tell if your slab met those criteria 20 years ago when poured.
The key to successful laying of resilient floor on existing concrete slabs on or below grade lies mostly in using the proper adhesive. Thoroughly assure yourself that the adhesive to be used in your new below-grade resilient floor installation is approved for such use by the manufacturer and your contractor. Place no new flooring until a reliable contractor has visited the site and given a written guarantee that his flooring will not lift.
To learn about resilient flooring, write Armstrong at P.O. Box 3001, Lancaster, Pa. 17604. Ask for pamphlets Nos. F-5595-981M, F-5061-382J, and F- 5683-1281L.