Flooring Tile - tile install questions

am putting 12x12 ceramic tile in upstairs bath. have scraped up old vinyl and cut underlayment. would appreciate any input on several questions before i start doing permanent damage:

1. subfloor is plywood, and vinyl came up no problem. scraped and cleaned pretty well, and am thinking/hoping that small, thin patches of vinyl adhesive that remain on plywood are ok to cover with thinset when putting down backerboard?

2. when underlayment is down, should i fill expansion gap around walls and tub with silicone sealant? all the way to top of underlay?

3. the floor is gonna be higher when done: thinset, 1/4 in. underlayment, more thinset, then 1/4 in. tiles. this may be a plumbing question, but in mind's eye am seeing look on my face if commode won't sit right when tile is laid... is adding some height to the flange a routine task?

4. tiles are glazed, but they are not slick, shiny, perfectly flat tiles. would you add a sealant to the tiles, or is putting sealant on glazed tile a waste?

great forum! mtia

1. Only if most of the floor is clean. You can remove remaining adhesive with a solvent.

2. I wouldn't. Caulk the baseboard after you put it back down.

3. Pull up the toilet before you start. When finished tiling, add an extension ring to the existing flange before reseating the toilet. It's all easy.

4. A waste.

P.S. I'm just an electrical guy messing around in the tile forum. I don't mind a bit if you real tile guys want to set me straight. I have tiled several bathrooms and have my own wet saw. It's fun.

Pretty good, for an electrician ;)

1.) Get as much of the old adhesive as possible. Use "play sand and a sander with 60-80 grit to get up any big globs. Put duct tape on the soles of your shoes, so you can peel it off and not track glue residue or totally ruin your shoes. Sprinkle the sand around on the adhesive, and hit it with the sander. The play sand is a media for the adhesive to attach too, and not back to the surrounding adhesive.

2.) Yes! Most everyone skips this important step in the prep! The expansion gap left from cement backer board installation should be sealed, before the the first tile is set. You don't wantmoisture to get under the cement board and on the wood subfloor. Use 100% silicone. The real stinky stuff.

3.) ¼" cement board? I don't recommend it for floor use, only walls & counter tops. If your floor has any deflection movement, the grout will crumble out later, and worst case, tiles pop or crack. The practice of doubling wax rings hasn't failed me yet, but I am by no means a plumber. It wouldn't hurt if you can undo the screws holding it to the subfloor and see if you have play room to anchor it through the cement board, and into the subfloor.

4.) Glazed tiles are not absorbant to take a sealer. The glazing is the sealer. Porous tile and stone get sealers, if desired.

thanks guys - glad i asked: sanding proved that a lot more adhesive was on that floor than i thought...

gut instinct told me to just slap another wax ring on the flange, so was glad to hear that suggestion... will see how it sits and maybe do the extension ring...

the underlay is "hardibacker" if that makes any difference regarding it's 1/4 in. thickness...? figured on top of thick plywood subfloor would be okay? but will reconsider before laying down..

cheers...