How to leakproof a below-grade wall

Q. We have a bedroom that is partly below grade. The concrete wall leaked during the heavy winter rains this year. What will solve the leakage problem and enable us to repaper the inside bedroom walls? A painter recommended drain tile along the outside. M. E. Cable Sausalito, Calif.

A. If drain tile were to be installed, the ground around the building would have to be excavated to a depth below the bottom of the concrete footing, tile in gravel installed there to ''daylight,'' and the exterior walls waterproofed, ideally with a hot-mop process. That's a lot of work, and it's expensive.

I'd prefer to waterproof the below-grade basement walls from the inside.

Use a cementitious paint-waterproofing process, such as Sealwall or equal. The paintlike material will stop water migration on a sound solid-masonry wall. A hydraulic cement cove where the wall joins the floor is usually an essential part of the process.

If no local dealer has the product, write to Sealwall Products Inc., 36300 Lakeland Boulevard, Eastlake, Ohio 44094. Tel.: (216) 951-3445. The company also will consult with anyone having unusual waterproofing problems.