mosaic tiles going down on the floor
#7
My half bath is complete except for the tile work on the floor and the installation of the sink and toilet.  

I have never laid tile in the past.  I ordered this from Wayfair.  The local stores were showing ceramic tiles.  Wayfair had porcelain tiles.

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I am going over a cement substrate.  I am pouring leveling cement this weekend.  

What mastic should I use?  Thin set?

Any suggestions are welcome.
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#8
No mastic... never mastic. Not suited for wet locations and degrades. I personally think it's absolute crap marketed to Harry Homeowner who thinks it's easier. I'd rather do a job once and be confident it will be there longer than I am.

When you say cement substrate do you mean cement backer-board or is the floor poured cement?

First of all, self leveling cement can be very difficult to work with. I pretty much only use it on whole floors or large areas. Build a dam around the edges, including the doorway with wide masking tape. Or if the threshold is already there, protect it with masking tape and pull it off the threshold as soon as it starts to set. It can be a disaster if you aren't prepared and everything prepped. Self leveling sets very quickly. Self leveling tends to have surface tension like water so it bows up on small areas, not so much on big areas. You wind up having to grind it flat once set. If I have small areas to level, I usually use thinset mixed dry so it trowels flat or I use a topping compound cement (make sure you get out any small pebbles first) and trowel it flat. It bonds well but takes longer to set so you have more working time. It's a good idea to slightly sampen the sub-strait before applying whatever you are using to level so the sub-strait doesn't suck the moisture out of your product. You'll get a better bond. Some use a vinyl sealer/primer. I've done it both ways with no issues. Applying mortar/thinset to a dry cement floor can cause it to pull away when troweling.

The pre-mixed thinsets tend to fail. They dry, they don't cure. Powdered thinset cures and gives you a better bond. When in doubt, use a polymer modified thinset. It provides a level of moisture protection and allows for some flexibility, helping to prevent cracks. The stuff at Lowes and Depot are good products.

They will have Gray and White polymer modified thinsets. Use the gray if you are using a dark grout, use the whit if you are using a light grout. Grout is somewhat transparent and there will be thin spots so this helps insure you get the color you want in the grout.

Often times, mosaic tiles are thin. The thinset tends to squish up between tiles... can be another disaster. This is one reason to use the right color thinset. Also, mix the thinset a little dry. Less like toothpast, more like cookie dough. This will help stop the thinset from pushing up between tiles. Another thing, use a small sized square notch trowel for mosaic. I might even go down to 1/8" if they have it. 1/4" would be the largest I use for this. If you use a 1/8", you should probably mix the thinset more like toothpaste, less like cookie dough.
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#9
Yup what he said. I only use mastic on backsplash and not the stuff from the borgs. I use the commercial stuff which holds up extremely well. 

    For that tile I'd most likely go with a 1/4 x 1/4 trowel with white thin set.
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#10
Thank you for the information.

My home was built in 1953.  There is about a 1½" thick poured concrete with chicken wire over the wood floorboards.  I damaged the concrete when chipping up the old mosaic tiles.  (They were really hard to get up and the  tiles themselves were really tough).  I filled the larger divots with patching cement.  But there are a bunch of small to tiny voids that I hoped to get smooth with the poured leveling cement.  

I have built a dam around the waste pipe for the toilet.  The baseboards are not yet installed.  There is a marble threshold and I will tape that as discussed.

After I patched the deep divots I checked for level and ground down the high spots.  The floor is basically level.  Are you suggesting that I  use more patching cement over all the small divots?  I think I would never get it entirely smooth and the spots would telegraph through the mosaic.

Cooler
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#11
Don't worry about the small divots as the thin set will go over that just fine. Only need to worry about the big stuff. 

      I guess your flooring was a old version of gypcrete. I like the idea if the framing is hefty enough. We have a pier and beam house and personally I hate them. No matter what you do there is too much deflection and bounce for me. I prefer a solid concrere slab floor(which I'm finding hard to find in houses in the carolinas). I just like a floor to not give, flex or bounce any amount.
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#12
(04-24-2018, 04:22 PM)Robert Adams Wrote: Don't worry about the small divots as the thin set will go over that just fine. Only need to worry about the big stuff. 

      I guess your flooring was a old version of gypcrete. I like the idea if the framing is hefty enough. We have a pier and beam house and personally I hate them. No matter what you do there is too much deflection and bounce for me. I prefer a solid concrere slab floor(which I'm finding hard to find in houses in the carolinas). I just like a floor to not give, flex or bounce any amount.

The code calls for 2 x 8 for the floor joists.  This house (it was the builder's own home for this development) has 3 x 8 floor joists.   It also have plaster and metal lathe (kills WiFi) and some sort of concrete that defies drilling and 22 nail guns.  The other houses have sheet rock and regular concrete.

But I think the floors are solid.
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