Slate floor Thinset failing

EdQuinn · 05-01-2012, 07:44 AM

Hi

I have searched the forums and found a few clues but not right on point.

I am putting Vermont slate down in a bathroom and I am having a problem with some tiles not sticking.

Let me start from the beginning I gutted the bathroom to move plumbing around and I rebuilt most of the joists by doubling them up or blocking ever 12-16 inches to stiffen the floor.

I then glued and screwed 3/4 inch plywood to make a new subfloor I then set and screwed 1/2 cement board over the floor.

I had the slate left over from doing the entry ways in the house both are 2 years old and perfect even today. Since the tile was in the house for a while, I washed and scrubbed each piece to make sure no dust was on the tile. I have seen that in a bathroom mastic was not recommended but to use modified thinset

I purchased Versabond fortified Thin set and the Modifier that Versa recommends and they had at the tile store.

I worked with the 1/4 x 3/8 x 1/4 trowel and set the tile. It seemed to go down about as I expected.

Now the problem it is 72 hours later some tiles are not stuck they lift right off. I have not a clue why has anyone experienced this before and if so what did you do to solve it grinding up the old thinset and resetting the tiles is an option but I do not want to do this if there is a bigger problem occurring with the floor.

I have mixed thinset many times before i got it to a nice peanut butter consistency and the rest of the floor seems tight and bonded, today I went up and fond another tile lose and it lifted right off. out of 50 tiles this now makes 8 and they are not in anyone area which is what has me very concerned. When I look at the thinset after lifting off the tile the edges seem lighter and the center seems darker as if it has not cured completely but going back and looking at the first batch of tiles that came up the color has not really changed.

Would appreciate any insight and suggestions thank you

joecaption · 05-01-2012, 11:28 AM

May be a good thing it's happening.
Slate is the last tile I would ever suggest to install in a bathroom.
It's just to poris and would need to be resealed at least once a year.
If you look around in the tile area you will see a bunch of other posted with stain and failing slate tiles in bathrooms.

EdQuinn · 05-01-2012, 11:55 AM

Up till this point I have had great luck with the slate in Bathrooms my first floor has had the slate floor down for 6 years and not a single issue. I do seal it about every other year I just roll the sealer on it is not a high shine but more like the actual stone finish and it looks great. This bathroom also has a shower stall in it not a tub and I put it down with a mastic over cement board back then. This is tile from the same company in Vermont I purchased a pallet of it to do the two entryways and was thinking of the kitchen but my wife decided on a different tile for that. I just have never seen tile lift off almost 100% clean no adherence at all to the thin set. none of the pieces are next to each other either just random. Thinking it maybe something on the tile at this point. Can the thin set go bad? is the modifier the issue was it to wet or two dry (doesn't not seem likely) when a was laying it? Can you use too much of the modifier when mixing will this cause the reverse effect and not stick? Is this a problem with Versabond? should I call them and say hey whats the deal. Hopping to find out and come up with a solution the floor is down except these 3 tiles and I am hopping no additional ones pop at this point or in the future. Should I bother to even try grouting it?

JazMan · 05-01-2012, 05:13 PM

Ed,

Please tell us about this "modifier" you mixed with the thinset. Exactly which product is it and who suggested using it?

You also have an issue with your subfloor, but too late for that now.

Jaz

EdQuinn · 05-02-2012, 07:59 AM

The add mix is made by Versabond same as the thinset it is Thin-set Mortar Admix it states just below that Increases bond strength and performance, Improves Water resistance. Directions say to replace the water with the mix the Bag states to mix one Half gallon per 1/2 bag ad water if necessary.

I forgot to also say that I used Red Guard to coat the cement up 4 inches on the walls I put 2 coats on the cement board before the thin set.

When I did the first floor bathroom I went to Fitzgerald tile in Woburn, MA http://www.fitzgeraldtile.com/ they told me to do it this way in the downstairs bathroom floor. I used a different brand then versabond and do not have the package or jug left around but basicly the same procedure as when I did then a milky white liquid in place of the water. In the foyers I did not use the modifier and the tile still is tight and looks great as is the first floor bathroom.

JazMan · 05-02-2012, 01:17 PM

Ed,

The admix is made by Custom Building Products who also makes Versabond. You misread the instructions. Versabond is a polymer modified thin set, it's already modified so you mix only with water. The instruction on the admix says;

FOR USE AS AN ADMIX WITH NON-MODIFIED THIN SET MORTAR

and then lists the mortars that are unmodified,

Quote:

See the mixing instructions on CustomBlend® or Uncoupling Mat Mortar bag or data sheet for specific directions.

I bet Fitzgerald Tile gave you an unmodified mortar which was the right thing to do.

However, I still don't think this mistake would cause some of the tiles to not stick. Even not having the required double layer of subfloor shouldn't cause a bond failure.

Quote:

I washed and scrubbed each piece to make sure no dust was on the tile.

So, what did you wash the tile with and when?

Maybe you let the thin set dry up and skin over before you set the tiles. Maybe the backer board was very dry and you didn't moisten it before you spread the thin set. Maybe you didn't "key-in" - "burn" the mortar to the floor with the flat side of the trowel before gauging it. Maybe the tiles were damp or you washed with detergent. Did you back-butter the backs of the tiles just before setting them into the mortar? Maybe there is way too much flex in the floor. Did you install the cement board into thin set mortar or just fastened to the subfloor?

Could be other things too.

Jaz

EdQuinn · 05-02-2012, 07:12 PM

Hi

Thanks for that info on the modifier.

I scrubbed the tile the week before with a green teflon pad and hot water then let them dry for about 3 days some a week they were layed out in a clean sheet of plywood to dry. I used the kitchen sink one box at a time I did not use soap or any cleaner and the pad was from a new package that I picked up when I bought the thinset.

I have ground out the thinset and reset the tiles yesterday all seems AOK today until i started tapping the tiles and found 2 new ones that were just sitting on top and not a speck of thinset on them same you can see where I gave them a slight twist and a slight push the ridges from the trowel were flattened down. I looked at the tiles all over not a clue.

As far as the mortar skinning I mixed small batches layed about 15 sg of slate cleaned the edges around the work and went and mixed up more I did this a total of 4 times same mix same ad same peanut butter consistency smooth and held a peak.

Also the tile was in the house for a week from the garage sitting to warm up and reach house temp. They were in Cardboard boxes still on the original shipping pallet.

Could the quarry have introduced something in the cutting like an oil maybe? I honestly can not see or feel anything but just at a loss also the tiles I mounted vertically around the floor held tight not one fail and the only thing I did differently was to use a smaller notch trowel that I had that was smaller to work in the 6 inch area around the floor. So far the reset tiles look and seem fine I did wire brush them a but to just break the smooth surface up a bit hoping to improve the grab area a bit no bgouges just a light brushing.

I also had some issues with the thinset adhering to the redguard as I was troweling it down. it seem to slide in laces as I used the flat edge before combing it with the notched edge. Could the redguard be effecting the thinset? I ordered this from them on line got it in March 2012

JazMan · 05-02-2012, 10:46 PM

It's either bad mortar or installer error, it's usually installer error.

If it was bad mortar, none would stick. I think it should have still worked ok even though you mixed it with the additive. Call Custom Building Products @ 800-282-8786 and ask them if mixing that way cause a chemical failure some how. Also get the ID numbers on the bag which will tell them where and when it was made. When did you buy it?

I listed several posible reasons for your problem. You only addressed a few. I can see a few things that I would have done differently like; You said you gave the tiles a slight twist. You may have mixed it too thick. Did you let the mix slake before you used it? You're supposed to set a few tiles, then remove them to check for thin set transfer, you didn't do that, sounds like. Did you key-in or burn in the thin set?

Jaz

EdQuinn · 05-02-2012, 11:15 PM

Let see the bag was purchased in March of 2012 with the modifier. I did let the mortar slake for about 10 minutes then ran the mixer on my drill another couple of minutes to make sure the mix was complete and no lumps. I was taught years ago to lift the first few to make sure the bonk is true the first three I set and lifted and needed a stiff putty knife to break the bond. I was also told to give it a little wiggle as you set it and then level it to the surrounding tile with a little pressure I did that with all the tiles. As I said I worked in small batches to make sure the working time was minimal maybe an hour with each batch so no the mix was not dry it troweled smoothly and the tops stayed non of the tiles look like the mortar dried first since the mortar was slightly flat at first I thought it may have been to wet but it troweled well and the channels are obvious under the tiles.

I will check with the company this was stock from Home Depot and I suppose who knows how long they had it especially in this economy. It was not a damaged bag it looked recent not old. I still suspect their is something on the tiles one I reset 2 days ago came u again today I threw that one in the waste pile and took another. I will let you know if this one holds. I am putting this rough side up but no big voided ones the underside is smooth as if sawed which is why I am still leaning on something on the tile. but the colors look good and true no real stain looking pieces and no one color group seems to be an issue either. Can I use a cleaner on the tiles in the future and what would some one recommend? how about running a wire brush over the underside to rough it up a bit ? Yes I keyed in the thinset with the flat edge before flipping to the notch trowel. As I stated I was a little concerned when doing that in some ares the Redguard seem to be a little stippery to it so I went back over a couple of areas a couple of times before switching to the notched side and raking it. could I have picked up some residue from the red guard on the Mortar? or could I have a reaction to the Redguard with the mortar and do not know it ? I red the spec sheet on the Redguard and feel really certain I followed those instructions to a T but I do not have a lot of experience with it only the second time around.

very certain the mortar did not sit for more then an hour during the tiling and it was slaked over 5 mins and remixed to check for lumps I set the timer on the stove for each batch.

One more question how long should I wait on this to grout do you think?

JazMan · 05-02-2012, 11:23 PM

You can grout the next day after you decide if you're gonna seal it or use a grout release or what ever?

Did you butter the back of each tile before setting into the notched thin set on the floor?

Jaz

EdQuinn · 05-21-2012, 11:39 AM

Sorry for the long delay took some time to sort this out

OK first off mixing the ad mix to the thin set I have should not have been an issue.

2nd I did not back butter all of them because after the first few and what appeared to be a solid bond when I had to use the trowel to lift the first few I did not feel it was necessary. I maybe wrong but read on

What did happen is the lot that the thin set came from was recalled for insufficient cement in the mix. Home Depot never took this pallet out and instead sold most of it apparently before the complaints came rolling in. Home Depot was very nice at refunding the $12.59 since I still had the receipt ( whoopee for them they just lost a return customer)

What I then had to do was pull up all the tiles and grind the surface which I did with a lot of work and a grinder and a sonic tool I had. (Ouch my knees) I then applied a floor leveler to take care of any of the gouges (I was careful But) and then reapplied the red guard over the floor. I then went to the tile place I mentioned and bought thin set and re applied it I first put down a thin coat with a 8" wide putty knife and then troweled it on with the notch trowel. Oh yes not ad mix to this bad they solid me the right product for the slate. then I started laying the tile which I also cleaned off with a wire brush on the grinder. Now the only tiles I back buttered were the edge and the wall tiles to make sure I had no voids in this area. I then put three coats of sealer on after the thin set dried then grouted. Easiest grout job I have ever done Grout also from Tile Store. Then 2 coats of high gloss sealer over the top after 3 days of dry on the grout.

It came out perfectly and is is water resistant the water beads right up no penetration what so ever the tile guys at the tile store suggest a re-coat every 2 years and it should remain water resistant. One other thing I wanted to mention the redguard although expensive went on like a dream I used a brush not a roller to help assure a nice think coat and it cut the time and work substantially and I really liked working with it even when laying the tile. I will send pictures as soon as we are done with all the fixtures.

But this was a bigger project then I expected thanks to my taking the convenient route and trying to make one trip at HD Never Again.

Thanks for all the advise lets hope this lasts till I resell it. 4-5 years

framer52 · 05-21-2012, 11:54 AM

Quote:

Originally Posted by EdQuinn

Sorry for the long delay took some time to sort this out

OK first off mixing the ad mix to the thin set I have should not have been an issue.

2nd I did not back butter all of them because after the first few and what appeared to be a solid bond when I had to use the trowel to lift the first few I did not feel it was necessary. I maybe wrong but read on

What did happen is the lot that the thin set came from was recalled for insufficient cement in the mix. Home Depot never took this pallet out and instead sold most of it apparently before the complaints came rolling in. Home Depot was very nice at refunding the $12.59 since I still had the receipt ( whoopee for them they just lost a return customer)

What I then had to do was pull up all the tiles and grind the surface which I did with a lot of work and a grinder and a sonic tool I had. (Ouch my knees) I then applied a floor leveler to take care of any of the gouges (I was careful But) and then reapplied the red guard over the floor. I then went to the tile place I mentioned and bought thin set and re applied it I first put down a thin coat with a 8" wide putty knife and then troweled it on with the notch trowel. Oh yes not ad mix to this bad they solid me the right product for the slate. then I started laying the tile which I also cleaned off with a wire brush on the grinder. Now the only tiles I back buttered were the edge and the wall tiles to make sure I had no voids in this area. I then put three coats of sealer on after the thin set dried then grouted. Easiest grout job I have ever done Grout also from Tile Store. Then 2 coats of high gloss sealer over the top after 3 days of dry on the grout.

It came out perfectly and is is water resistant the water beads right up no penetration what so ever the tile guys at the tile store suggest a re-coat every 2 years and it should remain water resistant. One other thing I wanted to mention the redguard although expensive went on like a dream I used a brush not a roller to help assure a nice think coat and it cut the time and work substantially and I really liked working with it even when laying the tile. I will send pictures as soon as we are done with all the fixtures.

But this was a bigger project then I expected thanks to my taking the convenient route and trying to make one trip at HD Never Again.

Thanks for all the advise lets hope this lasts till I resell it. 4-5 years

Just a note to everyone. the thinset has a code stamped on the bag. it is best to check and not use old thinset.