While at first glance ceramic tile may seem like a rigid, unforgiving form of flooring, it can in truth be one of the most accommodating materials in difficult remodeling projects.

Take this entry foyer. Before we tiled it, the subfloor sloped 1 in. over 6 ft. and was so spongy it had to be patched in two places. To make matters worse, the walls weren't quite square. But working with Club member Jeff Hochstedler, we learned how to make tile look terrific even when the space is flawed. The secret is to straighten out the floor with a bed of mortar using an unusual leveling technique.

Normally, professional tile setters lay a uniform 3/4 - in. - thick bed of mortar by screeding over a pair of runners made from electrical conduit. That's fine if the subfloor is level. When it's not, Jeff replaces the conduit runners with strategically placed roofing nails.

"Sometimes, perfectly level and straight isn't what you are after," Jeff explained. "Using the nail heads as guides, I can cheat the surface so it looks right."

The trick is to spread large irregularities over a broad area so they are imperceptible to the naked eye. But you can't fudge just anywhere.

"When you lay a mud bed for a tile floor, the thinnest part should be no less than 3/4 in., and it should be 3/8 in. lower than the door thresholds so the tile can slip under the thresholds," Jeff warned. You also have to be careful you don't raise the height of the finished floor at a stairway so the stairway does not meet building codes.

Based on the latest Uniform Building Code, stair rise must be between 4 and 8 in. and cannot vary more than 3/16 in.

"Some building inspectors will give you a little leeway, but others will hold you to the letter of the law," Jeff said.
Jeff laid out this tile floor starting at the top of the stairway near the front door because the height of the mud base would be most critical there. It also happened to be the high point of the subfloor. He began by installing a temporary spacer at the top of the stairs. It would hold back the mud and define the space for an oak nosing to be installed later.

Next Jeff drove a 2 - in. galvanized roofing nail into the floor about 3 ft. from the spacer and adjusted its height until the bubble on his 4 - ft. level was centered when it rested on the spacer and the nailhead. As he continued to drive nails at 3 - ft. intervals, it didn't take long for Jeff to discover he could not maintain a perfectly level plane and clear the garage door threshold. So he drove the nails a bit deeper so the bubble on the level was 1/4 off center.

He also confronted the realities of remodeling as his layout approached the carpeted living room at the end of the entry hall. The mud base needed to be

1 - 1/2 in. thick at the end of the hallway wall to maintain a level surface, but the floor would have dropped off unacceptably at the carpeting, so Jeff again adjusted the nail heights for a more gradual and uniform tile/carpet transition.

Later, when he placed the mud, he just grazed the nail heads as he freehanded his strikeoff.

Jeff's boss, Randy Gaulrapp, adopted a similar compromise strategy when setting the tiles. He placed the 12 - in. - square tiles by eye rather than with plastic spacers, enabling him to adjust the grout lines ever so slightly to overcome irregularities in the walls. Minor course corrections are easy with a modular flooring system such as tile but would be impossible with tongue - and - groove flooring or sheet vinyl. In fact, Randy probably is the only one who knows where he cheated to make the layout work.

Back to basics
While our pros finesse the flatness of the subfloor and the spacing of the tiles, other details are firm. The subfloor must be at least 3/4 - in. plywood or 3/4 - in. OSB that is firmly nailed or screwed.

Jeff staples one layer of 15 - pound roofing felt over the subfloor. This slows the curing of the mortar, protects the wood from moisture damage and prevents the mortar from sticking to the subfloor so the two materials can expand and contract independently. Lastly, he staples self - furring metal lath over the felt to hold the mortar bed together as hairline cracks develop (which they surely will).

Jeff also does one other unusual thing to tie the components together: He grouts the gaps between the tiles as soon as the mortar is firm enough to support his weight.

"Grouting the tile the same day helps the grout bond to the thin - set mortar we use to set the tile and it makes the mortar cure slower and harder," Jeff explained. "It also means I don't have to come back the next day."

Sources
- Gaulrapp Ceramic Tile, (612) 428 - 2591