tile floor prep

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Old 01-20-17, 06:33 PM
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tile floor prep

Hello again all. Need help with new project. I will be renovating upstairs bathroom. New porcelain tile floor, replacing bathtub with tiled shower alcove. Couple of questions for you experts. I noticed czizzi said you should have 3/4" plywood + 1/2" plywood + thinset +1/4" backer board + thinset + tile. So my question is what size trowel opening should be used for laying the thinset that goes under the backer board? I assume the two layers of plywood should be laid in opposite directions, is that true? Also will be using a KBRS brand tileable shower pan. Not really a pan but some sort of composite material which must be set into thinset as well. Any tips you guys can give me on shower installation and tiling the shower would be greatly appreciated. How do you drill holes into porcelain tile (such as for shower door installation)? What type of thinset to use. Buying the tiles at Lowes. Are there different types of thinsets for use on shower floors and walls due to high moisture? Again you guys were such a help when I did my hardwood floors that I had to come back for help with the tiling. FYI I have tiled in the past. did my kitchen tiling a few years back but am a little paranoid about the moisture level when doing a shower/bathroom floor installation. Thanks in advance.
 
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Old 01-21-17, 06:10 AM
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If you currently have sound 3/4" flooring and 16" floor joists then a single 1/2" backer board is more than sufficient. Screw the snot out of the flooring.

And to make your shower selection a bit more confusing, consider using Ditra or in my case Prove membrane. It's the absolute best option.

They state you can install over drywall and I have no reason to doubt, but I went with 1/2 CUB in the shower, sort of belt and suspenders concept.

With the membrane installed you have an absolute sealed space, no water leaks, nothing to ever worry about.

This is my walk in shower!

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Old 01-21-17, 08:10 AM
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Hey bobby, give us a link to the shower pan you are planning to use and also the relative sized of tile you are going to use on the shower floor and walls. Sometimes the shower floors are limited in the size of tile that can be used due slopes and angles to get the water to the drain. Plywood layers should be set in the same direction which is perpendicular to the joists but offset from one another with the second layer screwed to the first but not the joists. 1/4" x 1/4" trowel should be sufficient for the 1/4" backer board screwed with appropriate backer screws - this is also offset from the top ply layer and screwed to the ply not the joists. Use backer tape and thinset on the joints between backer. Don't install too tight to the walls leave a little gap. In you have not, remove any baseboard molding. Use a thinset from a dry bag and mix to order, stay away from anything premixed. A modified thinset should be fine unless you are going natural stone at which we would want to pair the correct thinset. Use a vapor barrier either painted on or placed on the wall before the 1/2" backer goes up. Mesh and thinset the seams and corners. A key tip would be to make sure everything is smooth, studs are not out of alignment so that when laying tile on the walls, you don't have to deal with bumps and humps.

Make any adjustments to plumbing stub outs so they land in a pleasant way on a tile. Easier to cut on a grout line then drill a hole in the middle of a tile. I make a story board that lists the space and distance between the tiles so that everything lines up nicely. Start on the second row of wall tile with a ledge board so that you can return and cut the first row the fit. This helps take out any variations in level of the pan/base as the first row is cut to fit.
 
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Old 01-21-17, 09:20 AM
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https://www.showerbase.com/pages/the-shower-kit

that is the link to the shower "pan"

Planning on 12 x 24" porcelain tile for shower walls, hex pattern mosaic tiles for the shower floor (hex pattern approx. 1" meshed together by backing), 6 x 24" tiles for bathroom floor. All are porcelain. Is any size spacer acceptable? Would like to use small 1/16" or 1/8" to keep grout lines small for easy cleaning. Also a subway pattern meshed together for perimeter of bathroom floor to add some decoration ( maybe two rows of the smaller subway tile.) Should I have one row of regular tiles first and then the decorative 2 rows. Should the tile (shower walls) go all the way to the ceiling? The shower kit comes with all waterproofing materials needed.
Another question is why can you not screw the top layer of plywood to the joists as well as the first layer? Same with backer board? So definitely consciously do not screw top layer to joists? Thanks again
 
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Old 01-21-17, 09:58 AM
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Haven't used that pan system but watched the video and it you are overly conscientious about the waterproofing sealer you should be OK. It did not go into detail about screwing the base and curb down so try to look into that.

For tiles that big, very important to have a super flat and beefy floor structure. Any unlevel area over 24" will give you grief when you go to lay the tile.

Old Floor prep called for a mesh embedded slab of concrete on top of a layer of tar paper so that the tile floor was isolated from movement of the wood subfloor to prevent cracking. Modern backer systems also need a way to isolate movement so that your floor does not crack out. By NOT tying everything to the same joist, the different layers of ply and backer are not fighting against different expansion and contraction rates and provide for a unit that moves in unison and prevents buckling and cracking. The thinset under the backer board acts like 1000 little hands to support the backer so there are no voids or areas that will flex. Multiple layers of ply stiffen the floor to remove any deflection that may occur between the joist themselves.
 
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Old 01-21-17, 02:58 PM
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Thanks to Czizzi and Marq1. Czizzi should I put a layer of felt paper between the plywood and thinset layer under the backer board. Do I need a plastic vapor barrier between the backer board and the studs of the shower walls? One wall is an exterior wall with insulation the other two are interior walls.
Also drilling into the porcelain tile to install shower doors does indeed scare me ha ha ha. Do you use diamond impregnated drill bits or something similar. I have read that masonry bits do not work well on porcelain tile. Also how to "start" the hole without it drifting? Are there template/bushings available for this? Thanks for all the help. I owe you a steak dinner ha ha ha,at least.......
 
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Old 01-21-17, 06:45 PM
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On the floor, no felt paper between the thinset and the ply. For the longest time I was able to use glass bits to cut through tile. First do a small pilot hole with the smallest bit and then increase to the size you need. If that doesn't work as some porcelain tile is tough as nails. In that case check back, I had some bits but don't remember exactly what they are. Every diamond bit has disappointed me to date, so don't waste your money.
 
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Old 01-25-17, 03:36 PM
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So Czizzi....... the backerboard on the floor just gets installed in the thinset layer? No screws into the plywood subfloor? Again do I need a plastic vapor barrier between the backerboard on the wall and the studs? Again I really appreciate the assistance.
 
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Old 01-25-17, 03:53 PM
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I noted one faux pas in the video. Nowhere was there consideration for grab bars. Always install 2x12's between each stud bay at about 34" centered in height before you put in your backer board. I, too, am a little leery about the backer installation without lumber in the stud bays behind everything. It is a weak point and you definitely don't want flex there.
 
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Old 01-25-17, 07:06 PM
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So Czizzi....... the backerboard on the floor just gets installed in the thinset layer? No screws into the plywood subfloor? Again do I need a plastic vapor barrier between the backerboard on the wall and the studs? Again I really appreciate the assistance.
Thinset and screw the backerboard down wtith screw designed for your backerboard of choice.
 
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