HELP, Tile Mastic not dry after 2 weeks

[martini]

I just retiled my bath tub wall, unfortunately I used green board and so to compensate for its lack of waterproofing I used REDGUARD (waterproofing membrane) and applied the mastic directly onto this. The tiles I am using are 12 by 20 inch and I used a 1/4 inch trowel to spread the glue. After 2 weeks I grouted the tiles, but when I noticed one that was cracked I removed it, and to my surprise the glue was still wet.

Will the glue eventually dry? The tiles seem to be on pretty solid, no moving, will this change when I start to shower due to humidity? Will the tiles fall off or will they stay stuck due to suction?

[Charles Spitzer]

mastic cures with air contact. there's little to no air behind the tiles, so it takes a LONG time to cure, if ever. they will still stay on.

[martini]

Thank you, I appreciate your reassurance regarding this :-)

[SQLit]

Green board is water resistant and the correct product to use in a bathroom. I do not know what redguard is nor how to install it.

When ever I do bathrooms I use a fan to circulate the air.

Can not see the installation so I can not comment on the other questions.

[martini]

I keep reading how Green board should not be used in a tiled bath tub area. Since my walls were already up I asked at HD and was told to use a waterproofing membrane to protect the wall ( I painted on this membrane with a roller which leaves a rubbery film on the wall, thus making the wall waterproof). My fear was that it was due to this waterproofing barier that the mastic was not able to dry (through the wall) as air could not pass through this barrier to dry the glue under the tiles.

The tiles seem pretty secure now, but was wondering how long this could last if the mastic never dried. From a previous post it seems that it is normal for mastic to take a long time to dry and sometimes does not dry and still keeps the tile stuck to the wall.

I will put a fan near the plumbing hole so as to let air get behind the tile walls and hope this helps.

For now, unless I am told that all the tiles will come crashing down, I will live with this and wait it out.

Thanks

[Ajax]

We put a waterproof membrane behind a concrete backer board and the tile is installed to the backer board. I am unfamiliar with the system that you used.

But - I have seen tile installed over other tile, over Formica, and over metal and there was never any problem with the mastic setting in a reasonable time frame - by that I mean within 24 hours.

I can't help but wonder if there might be a problem with the mastic or a chemical issue between the mastic and the rubber film. A few years back one of my tile subs had a bad batch of mastic. He said that after 24 hours that you could still pull the tile off the wall with ease.

He had to remove the tile, clean it, scrape down the walls and clean them, the he re-installed the tile. It was a mess. Fortunately it was not one of my jobs.

[martini]

I doubt the problem was the mastic, but rather the user of the mastic.

I believe 2 factors are contributing to the mastic not drying: First, I must have used way too much glue (it was my first ever tile job and I wanted to make sure the tiles would not fall off, well I must have over done it). Second, the size of the tiles being 20 by 13 is not allowing in any air to dry the mastic.

For such big tiles I should have used a thinset mortar that does not require air to dry or I should not have used a waterproofing membrane so that the mastic could dry through the wall.

Oh well, if you never try you can never learn :-(

[Ajax]

Did you put the tile on with a notched trial? 20 x 13 inches? Or are you in the metric part of the planet?

You most likely should have used thinset mortar instead of mastic, but it might not have adhered the rubber membrane.

[martini]

I am theoretically from metric Canada, but we still use imperial for almost all measurments, go figure. So yes, 20 by 13 inch tiles.

For one wall I used a 1/4 inch square notched trowel, but when I realized that I was almost through my mastic which was supposed to be more than enough for the whole job according to the tile store guy, I changed to a 3/16 inch V shaped trowel for the other 2 walls.

The tiles seem pretty secure now as I already grouted, (thinking after

2 weeks the mastic would be dry), and the tiles did not budge during the grouting.

My main concern is, if the mastic never dries will the tiles stay on? My second concern is, if the mastic never dries will mildew develop? I figure if they are up now, why would they fall? and if there is no air to dry the mastic, there should not be any air for mildew to form.

My choices: Start over now, or wait and see what happens. I'm opting for wait and see

[thetiler]

Your problem is that the tile-store guy was an idiot for selling you mastic to install such large tiles, and the HD person was an idiot for for selling you that "membrane". But don't feel bad...it happens everywhere- everyday.

Ideally you should have used cementboard or hardibacker board, but "greenboard" or otherwise called MR drywall should be OK for many years. With a large tile over 8x8, you should have used multi-purpose thinset. "Greenboard", or MR drywall, has a moisture resistant paper on the surface, which is what you were trying to achieve with the membrane. I've tore out hundreds of rotted tubs and showers made with it, so it isn't a first choice.

Membrane or not, the mastic needs to air dry and cannot. It has probably dried around the perimeter of the tiles enough to hold them, and if no water gets behind them, they probably would never fall off. Suction will hold them, but if moisture ever gets back there the mastic will turn to mush, so I hope you did a solid grout job.

The mystery is this "membrane", and whether mastic will stick to it. Multi-purpose mastic is pretty sticky stuff, and probably you will be OK. I wouldn't take it apart at this point. Get a box fan or something and keep a fan on it for several weeks. My guess is by knocking on it, you can tell where it is bonded and where it is not. For now the moisture will have to escape out through the joints, so having a fan on, or A/C on, will dry out the bathroom air and draw the moisture out.

But......it will take a long time.

thetiler

[Ajax]

Mastic will dry in a sealed bucket if you give it enough time. Tile is porous and most mastics use solvents that will eventually dissipate. Depending on the mastic, it may take some time. My guess is that it really does not take all that much mastic to hold a tile in place.

I think that you will be ok.

[martini]

Thanks guys, I am feeling much better about this problem. I really appreciate your comments.

Now I want the mastic to dry and at the same time not let water get back there.

I guess I should wait before using a sealer on the grout so some air can get through, then again, if even vitrous (glazed) tiles are porous, the mastic will eventually dry through the tile.

I've kept a fan on through a plumbing hole to help dry from the back of the walls, I will turn on my ventillator in the bathroom to help draw out moisture. (With temperatures dipping down to 5 degrees (-15 celsius), I don't want to turn on the air conditioner)

[big mike]

replying to martini, big mike wrote: You should have used half inch trial to get air flow underneath the tile to help dry the Mastic the bigger the tile the bigger trial you need. Put a heater in there to help dry it faster.

[big mike]

replying to SQLit, big mike wrote: Green board is not the correct product HardieBacker or light HardieBacker is the correct product

[big mike]

replying to Charles Spitzer, big mike wrote: It will dry in another week or so

[Wade Garrett]

I once tried to save a few bucks by using a can of really old varnish/sealer I had laying around to finish some nice new interior window trim and molding. It was tacky for a good year and a half! Some years later, you can still feel it ain't right.

[Erik]

replying to martini, Erik wrote: Martini did it every dry?