Ask a builder: Swimming pool floor material

Q. I am building a swimming pool. Should I use a regular mix of cement to plaster the pool or is there a special swimming-pool plaster? If so, where can I buy it? John P. Garvey Albany, N.Y.

A. Cement comes in a bag and, along with sand and rock, is one of the ingredients of concrete. Whe mixed together with water, they form concrete. A "cement floor" is a frequent misnomer.

Now, concrete is impractical to use as a plaster because concrete contains coarse rock.

You can buy swimming-pool plaster from a pool-supply company. It is specially mixed for subsequent use underwater. Among other fine ingredients, it usually contains tiny chips of marble, thus adding durability and beauty to the pool.