Edition: U.S. / Global

TRADE SECRETS; The Agony and the Epoxy

By William L. Hamilton
Published: October 22, 1998

NO matter what kind of tiles you buy, the excitement dies hard if they go up on the wall looking like your first set of teeth, with toothpaste smeared fatly across the front.

No one doubts that tiling can be poorly done, especially those who have attempted it. ''When I started out 18 years ago, my first 40 calls were repairs,'' said Stephen Spretnjak, a New York artist and tile worker. ''I learned how to tile by going over somebody's mistakes.''

Mr. Spretnjak did the tiling at Balthazar, the Spring Street bistro, and Pravda, the Lafayette Street vodka bar, which included a hammer and sickle mosaic.

You may not be doing the installation yourself, but you can be aware of how a conscientious tile worker approaches the job, whether using ceramic, stone or glass tiles, in a bathroom or kitchen. Like any adept, Mr. Spretnjak has his priorities and preferences, as he demonstrated on a recent assignment: 300 square feet of tiled surface in a steam room in a loft on Canal Street, which he is tiling with white, 3-by-6-inch subway tile.

The first concern is the wall.

If an existing wall is being tiled, make necessary repairs, most experts advise. Don't expect tiles to conceal damage; they will fall off. If a new wall is being built, as with Mr. Spretnjak's steam room, make sure the contractor uses cement board, which is a fiberglass mesh board imbedded with cement that is waterproof -- much more so than standard plaster wallboard. Mr. Spret njak also specifies galvanized screws for attaching it to the wall studs; Sheetrock screws rust and fail if moisture finds its way inside the wall.

Old or new, the prepared wall must be absolutely level and flat before the first tile goes up.

''No dips, no indentures,'' Mr. Spretnjak said. ''I take the tile adhesive, or mud, as it's called, and smooth out the surface with a big board like it's a plaster wall.''

Before you have tile installed, inspect it, to make sure colors, shading or veining are what you want. Charles Pearl, a tile worker who was completing 100 square feet of tiled surface in a shower enclosure last week in an apartment on Fifth Avenue, recommended that the installer also make a close inspection, ''to make sure that you can actually work with it.'' Mr. Pearl was using 18-inch-square marble tiles.

How many tiles to buy? Calculate the square footage of the space, dividing by the size of the tile. Then add 10 percent to 20 percent. You will lose tiles because of breakage caused by cutting and because of unusable short ends. If you're including a diagonal pattern in your design, add 25 percent because of the greater number of cuts. It is impossible to find exact replacements.

''This is the thing about tiles, even white,'' said Roger Nelson, the general contractor on Mr. Spretnjak's steam room. ''When you get a patch job, you can never match them. It's a horror story.''

Traditionally, tile was adhered with a mud-set, a thick patty of cement. A generation of thin-sets, which are lighter, epoxy adhesives developed in the 1950's, has largely replaced mud-sets, with equal effectiveness, Mr. Spretnjak said. He combs it onto a wall with a notched trowel and then begins applying the tile.

''Start from the bottom up,'' he said. ''Gravity forces down.'' When he is two-thirds of the way up a wall, Mr. Spretnjak stops to take account of how it will finish. ''I'm going to be very concerned about what kind of cut I'll have to make at the top, because it's the most visible,'' he said. ''If I know I'm going to be an inch or two short of a full tile at the top, then I consider a band of decorative trim about a third of the way down, or a molding trim.''

Mr. Spretnjak also installs glass mosaic tile, though the process requires its own precautions and patience. ''It's little bits that reflect light,'' he said. ''When 13th-century tile workers were doing a basilica and they had a saint to be lit by torchlight, they would angle the mosaic glass of the eyes and the hands so that when the light hit, it would reflect and look more real.''

Not an effect you want when you're showering.

To avoid an uneven set to the surface, Mr. Spretnjak lays the tile into the thin-set, tamping and smoothing it flatly with a broad wooden float, ''not your fingers,'' he said, which push individual tiles into the thin-set unevenly.

Larger four-inch-square glass tiles also have their own risks, and a higher installation cost.

''You have to butter the back of each tile carefully with thin-set,'' said Daniel Bonpietro, a tile worker installing tile with Mr. Pearl on Fifth Avenue, ''so you don't see the tooth marks the trowel makes in the thin-set on the wall. You'd see those parallel lines right through the glass.''

Laying the tile is half the battle.

''Grouting's the big frustration,'' Mr. Spretnjak said of the epoxy that fills the thin gaps between the tiles. After the tile has set for a recommended 16 to 24 hours, the grout is applied in strokes across the wall, with a rubber float that works like a squeegee to push it into the gaps while skimming it cleanly from the surface of the tiles.

That's the theory. Grout allowed to dry where it shouldn't -- on, say, the shiny face of a tile -- is there to stay without hard work to remove it.

Colored grouts, in dozens of shades, can approximate a tile color, subtly disappearing, or create a vivid counterpoint. The drawback is that like tiles, they can be hard to match in a repair.

Regularity is the goal. But not always uniformity. Monotony is tile's biggest occupational hazard.

David Ling, a New York architect, employed glass mosaic tile in a recent apartment project to sheathe the undulating form of a wall in a deep, midnight blue. Mr. Ling chose hand-poured, hand-cut Brazilian Vidrotil-brand glass tiles -- available at Hastings Tile, 230 Park Avenue South (19th Street) -- for their artistic irregularity and fluid top relief. He also instructed the installer to interrupt and widen the gridded spacing of the tiles with the knife of his trowel, at random intervals, as the thin-set dried, to create a gentle, schooled swim in the pattern of the wall's surface.

At what price perfection -- whether studiously casual or conventionally square?

Based on square footage, time involved and the labor required for the number and difficulty of cuts in the tiles, the estimate Mr. Pearl offered on his 100-square-foot marble shower, with several built-in shelves and a small tiled seat, was $1,500. This excluded the cost of the tiles and any construction or preparation of the underlying wall. For standard ceramic tile, the price would drop. For stone tile like limestone, which requires sealing, the price would rise. Setting irregular tiles also adds to the cost. Glass -- the most expensive method -- could drive the price up an additional $1,000, Mr. Pearl said.

For a 300-square-foot space like the steam room, Mr. Spretnjak offered an estimate of $2,000.

As in any renovation, invite bids from at least three tiling professionals. ''If somebody is high, ask him to explain why,'' Mr. Pearl said. ''But avoid really cheap jobs. You'll get one. Choose someone who's going to refuse stupid economies, like using Sheetrock in a shower instead of cement board. There's a lot of money involved, and it should come out looking like that.''

Photo: INSTALLMENT PLAN -- Etched marble tiles add detail as both squares and diamonds. (Tony Cenicola for The New York Times)