I was told to return an all purpose 3 gal tub of mastic that lowes guy recommended for inside alcove shower/tub ceiling 3x5 area.. Should I use unmodified thinset mortar ?.. I am using 6x6 porcelain tile on 3/8 hardibacker screwed to the ceiling and 9" surround at the top of an acrylic wall/ tub surround.. Is the unmodified thinset preferred for tiling on cement (hardibacker) or use modified thinset on the hardibacker board..? i'm going to get white or which ever shade closest to color of tile (almond in my case) .. another project I have is on the 1st floor bathroom,the subfloor is 5/8 plywood should i use modified thinset for setting the hardibacker 1/2 to plywood 5/8 subfloor followed by the manufactures screw instructions/fiber tape slightly spaced seemed to floor joists? And lastly,go back to unmodified thinset (almond) for setting the 12x12 floor tiles to the cement hardibacker? or just use modified thinset mortar throughout? thank you in advance

ballengerb1

On cement I use unmodified thinset but on Hardiebacker I use acrylic modified thinset. On the cement floor you may want to consider Ditra as your base. Schluter-DITRA - Schluter-Systems By the way, you can use 1/4" Hardiebacker on the floor rather than 1/2" inless you needed to build up.

jon123

ballenger, So I should not use regular thinset over hardibacker on the ceiling inside the alcove tub area? Again , this is the first ceiling tile project I'm doing and should use the acrylicpro adhesive or similar knowing it is likely easier working upside down.. also, today I installed 1/4 EZ grid hardibacker over the existing 1/2 sheetrock using a left over 1gal. can of acrylPro ceramic tile adhesive applied v notch 1/4 and screwed it tight using the durock 1 1/4 screws so I know it will be ready tomorrow. Glad I waited before trying the regular thinset to ceiling. I do believe it will be much easier working with the acrylic adhesive. One last thing, i'm using 1/4 spacers on 6x6 porcelain tile, should I keep off the inside corner ceiling about an 1/4" tiles look alittle better than a 1/4 thick , so once the ceiling is up and set I'm going to use an adhesive caulk around the perimeter before continuing the walls ( about 10") around the tub unit. thank you again

massplumber2008

JON...use 1/16th tile spacer on the 6x6 tile....maybe 1/8".....but not 1/4" (thick grout lines can crack..especially overhead! My opinion). AND tell me...how did that cast iron tub drop in...hmmm...? Ballenger will answer the questions you asked him...I am sure. Keep in touch.

jon123

Mass, today is snowin day, can't get to lowes or depot for the modified thinset.. I had the right stuff in the first place but my dopey brother said return the mastic 3.5 premix and modified thinset for the cheaper regular thinset mortar! ..so today I'm holding off until I can again return this (unmodified)thin set 50lb. bag for a (modified) thinset I had the first time! I am going (overkill) as he put it with the modified thinset. besides I went to hardibacker site and this is what they recommend. As for spacing, I agree staying thin on the grout lines, however, the (project director) my sister, wants 1/4 grout line. Main family bathroom still on hold, waiting for the plumber to change out the roughin valve and waiste lines from lead/cast to pvc as planned,can't do much until than. I have the tub tarped in backyard. The other bathroom home project underway is the upstairs room. Spackling done, today start ceiling paint approx,1000sq ft. of ceiling painting today. Also, just replacing old blistering masonite crap board with 6x6 unglazed porcelain tile. shower tub upper portion flange 10" of wall/ 3x5' ceiling. I am guessing the best startoff is finding center on the 3x5 ceiling.. lay out with size spacer count out to cut corner tiles It works out about an inch less off each end to wall on the 5' layout.. from bullnose , full tiles to backwall shorties?

jon123

mass, i'm going to check up on the spacing again, if it were me i'd certainly go thin on the grout line, but she wants the same size spacers showcased in the store. I tried to tell her thinner is best but she wants 3/16 -1/4 space she seen displayed in lowes where we picked up the tile. I doubt i'll be tiling today , will double check do alittle more DD .. later today painting, she's sponge mopping the dust now preping for painting. heavy snow shoveling today in the nnj area

ballengerb1

You can use any spacing your wife wants but nromal installation you use the 1/4 spacer for 12x12 tiles. I'd use a premixed grout that is stain proof, its about $24 for a 5 lbs. tub but it will not shrink, crack or stain and it will hold better when you do your overhead work. I would not use a 3 part expoxy overhead. Remember, thinset on concrete and modified acrylic thinset for Hardiebacker, Wonderboard or plywood. When your side wall meets the back wall you should keep the tiles spaced the same as you have done on the surface, 1/4" in your case. Do not grout this verticle seam, use a silicone caulk that is mildew proof. DAP makes some good ones called PLUS.

jon123

hey ballenger, now you really got me thinking, could you please review this link Removing grout from Venetian Stone - InfoTile Forum and specifically the poster cindea about her grout situation.. I will have to now re-think the bag of sand grout the lowes guy recommended too. thanks

jon123

ballenger check this tileguybob tile for shower walls - InfoTile Forum diffinitely getting the modified thinset for everything in both bathrooms. thank you again! might be too busy for lowes tonight with all this snowmelt.. will get it all tomorrow. Tonight I want to research some links for the materials in question. check this tile out what she picked and please give me your opinion for the bathrooms.6" x 6" Porcelain Rialto Beige Tile BN OUTCNR thanks much good buddy!

jon123

I also read on hardibacker site to wet sponge hardibacker prior to applying modified thinset.. i'm going with 1/4 notch trowel. later!