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foiler 09-05-2012 01:09 PM

Tiling on 90 year old plaster wall
I didn't see a 'Tiling' subject anywhere so I guess I'll ask my questions here.

I had asked a question about removing old adhesive on the 'drywall and plaster' board adding my question there not thinking I should start another topic/subject/thread/spoon whatever its called.

Anyway, here's my problem. I'm trying to put up some glass mosaic tile as a back splash. My house is pushing 90 years old so all the walls are lathe and plaster. Walls are solid but not exactly smooth like a piece of sheet rock. Lets say there is some 'character' to their form. Additionally, when I removed the adhesive from the old formica back splash with the paint scrapers, it left some scoring.

I've had a few 'tiling types' look at it and they gave me different opinions. Here is what I would like to know from the wealth of experience out there.

First, is it necessary to use a spackle or plaster of paris to fill in scraps, dents or other defects in the plaster that is less than a quarter of an inch in depth. That is will the mastic/thinset even out the minor defects in plaster. I've had the 'experts give me answers both ways. The second question is what type of 'glue' do I use to put up the tile?

I've been told to use a modified thin set only that can be used for both indoors and outdoors for the moisture properties. And I've been told that the premixed white mastic stuff in a tub and any of the big box stores is fine to use and is a better in wet areas. The tile I am using is .25 thick, is small (18 across in 1 foot square tile) mounted on a net. There is a mix of a few stones but is 90% glass.

oh'mike 09-05-2012 06:47 PM

There is a tie section--I will move it there---

I use white modified----For a back splash you could use a mastic---I prefer white powdered thinnset---

Get a bag of wedges--the mosaic that you describe is rather difficult to install as the weight of the stones will cause sagging.

Use the wedges to keep the lines straight---on drywall small brads help to support the sheets during installation--but that won't work with plaster.

foiler 09-06-2012 12:38 AM

Thanks for your response. Don't seem to be very many folks that know about tiling around here. I'm not sure I understand what you mean by 'wedges'. Are you refering to those spacers they sell in various sizes from 1/8 on up? I've got a bag of 1/8 that match the spacing of the tile I'm using I've been warned about the possibility of sliding when putting glass tile on a wall so, as I have plenty of time and about 20 linear feet to do I intend to lay the first row along the granite counter top and let it dry a bit before putting up the next row above it. I'm not in a rush, I'm old, and slow and intend to do this once, and correctly. Thats why I'm asking questions here. As for the 'thinset' there is at least 6 different kinds. Thinset is a pretty general term these days. Now 50 yeas ago when I did a bit of floor tiling, 'thinset' was thinset.

oh'mike 09-06-2012 02:48 AM

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Look in the tile section at the home depot--they sell little wedges---like the tile spacers

Often the sheet mosaics are not spaced perfectly enough for the use of regular spacers.

foiler 09-06-2012 08:41 AM

I appreciate your response, but, alas my questions remain unanswered.
1. should I or should I not patch scarring on a plaster wall intended for mosaic tile back splash. All markings are 1/8" or less. If the answer is 'yes' then what 'patching' material should be used on a plaster wall that would benefit the inteded tiling.
2. What adhesive should be used for glass tile mosaic on a plaster wall. Modified thinset or a premiex mastic. The only detractor I've heard so far is that mastic isn't 'sticky' enough to hold the heavy sheets of glass tile before it dries so the tile may slide. But I've heard the same story about thinset unless you get a 'certain kind' WHAT KIND?
Been to Home Depot, Lowes and Menards. Asked for 'wedges' they all handed me 'spacers' Is that what your talking about 'yes or no'

foiler 09-06-2012 11:29 AM

Here's some additional info. After looking around at mortar brands available to me I find that MAPEI seems to have a large variety for every situation. The are the only one that actually states on their package for use with 'glass' tile. Not sure if their products are high quality. Havent got a straight answer from anyone yet. Not here either. There are 3 types of mortar in the Mapei line that mentions glass tile with properties that indicate 'nonsag' which I assume is a big issue with heavy 12x12 mosaic glass tile.
1. ULTRAFLEX LFT, which is for 'large format tiles (up to 20x20). It states it is a high polymer, premium, nonsag, low dust mortar general purpose, indoor/outdoor mortar.

2. ADESILEX P10, which has all the properties stated in #1 but specifically states it's for 'mosaic & glass tile. Mentions no other tile types.

3. KERIBOND Dry Set Mortar, also has all the above properties, states that it's for mosaic & glass tile setting and additional states that it is good in intermittent water areas but suggests adding Keralastic. Also states its good for commercial locations which the others did not or referred to 'light commercial'.

So, which do I use? Anyone familiar with this brand, and if not, perhaps the properties. Thanks for your attention

oh'mike 09-06-2012 08:32 PM

Use the number two selection---Mepi is a fine company---

As to the small defects in the od plaster---the thinset will take care of that---

If you do need to do some patching,use powdered drywall mud--- 'Easy Sand' 20 or 45--The 20/45 are the minutes before it's hard--

foiler 09-07-2012 12:50 PM

Thanks for that info o'mike. I'm going to try it out this weekend.

oh'mike 09-07-2012 05:46 PM

Good luck--keep us posted!

Bud Cline 09-08-2012 12:29 PM


Don't seem to be very many folks that know about tiling around here.
There once was but they have all been run off by less-knowledgeable belligerent participants and moderators.

Ninety years of living with plaster walls must surely also included ninety years of living with painted plastered walls.

No one has mentioned the paint issue thus far. The paint is the risky part. Tile adhesives and paints are never very compatible. The paint should be severely scuffed prior to installing any tile adhesive.

Pre-mixed tile adhesive in a bucket is never a good idea. This is also referred to as "mastic". You don't want to use mastic with glass tiles. You must use a quality modified thinset and mix it yourself.

If your substrate is only nicked here and there you shouldn't need to correct it.

Sagging with those tiles is an issue no matter what thinset you use so you don't have use a non-sag thinset.

You will need spacers between the counter-top and the tile (mat). Wedges would also be very handy. Spacers and wedges ARE NOT the same thing. Home Depot sells wedges AND spacers. You will also need spacers between the sheets of tile. The wedges and spacers sold at Home Depot are in the area with the tile trowels.

Here's your next problem. The tiles formatted the way you describe can be an issue once they get wet during installation. So you can't screw around after you begin. The webbing that holds the tiles together uses a water soluble adhesive and once the sheets get wet from cutting on a wet saw (assuming you have a wet saw) the tiles begin to fall off of the webbing so be careful.

The moisture from the thinset will also melt the webbing adhesive but that should (not) be an issue once you have the sheet in place. After a few minutes you won't be able to move the entire sheet because when you touch it only the tiles you are touching will move. That's kind of a pain but it's do-able.

Mapei products are top-of-the-line products, not to worry.
Ultraflex LFT is not necessary.
Have no idea what the Adesilex is.
Kerabond IS NOT a modified thinset and shouldn't be used.

If you want an inexpensive recommendation based on what appears to be available to you I would suggest Mapei's Ultraflex II.

Also...of most importance is the size of the notched trowel you choose to use. Anything having notches greater than 1/8" X 1/8" X 1/8" could mean trouble. You DO NOT want thinset purging between the tiles as you apply them to the wall. Spread your thinset evenly and IN ONE DIRECTION ONLY, nice and neat. You may have to look in the "wood flooring" department to find the 1/8" trowel because home centers just don't get-it.

Good luck!:)

foiler 09-09-2012 10:15 AM

Thank you Bud for your detailed response. Thank you for taking the time. I'll have to hunt for those 'wedges' you mentioned. I didn't understand their use from other posters and couldnt find them at any of the 3 big box stores here. Now I know they are used to help hold the bottom row of tile up. I'm not in a hurry to do this. I intend to do the bottom row first and allow them to dry in place before putting tile above. Also, I was aware of the paint issue and it was a question I had. Part of the are is painted with a latex about 2 years ago. So, I intend to use a palm sander and go after that so that it is well scuffed. As for the thinset, the one you last mentioned, UltraFlex II is available. The one I was leaning towards and was recommended by Oh,Mike is specifically made by Mapei for glass tile backsplash. I has all the properties that UltraFlex II has except it states on the package its for glass tile, mosaics. I will examine both of these products closely before buying. As for the trowel, the only one I have has 3/16th V teeth. Its marked for flooring. Is that one too big? I'll recheck for anything smaller.

Bud Cline 09-09-2012 10:58 AM


I intend to do the bottom row first and allow them to dry in place before putting tile above.
I wouldn't suggest doing the job in that fashion.
Those tiles aren't perfect and they aren't adhered to the netting perfectly. You will need the ability to adjust tiles from time to time and this is only possible if the adhesive is still fresh and the tiles are movable. I would recommend that once you begin you keep going.


The one I was leaning towards and was recommended by Oh,Mike is specifically made by Mapei for glass tile backsplash. I has all the properties that UltraFlex II has except it states on the package its for glass tile, mosaics.
Do what you want. Ultraflex II will work. Thinset manufacturers have realized that people aren't all that confident these days and they sell more product if the bags clearly says; "This is for this and this is for that". My guess is the only difference in the two products is the printing on the bag. Generally information about which thinset to use should come from the glass tile manufacturer, they all have their own recommendations.


As for the trowel, the only one I have has 3/16th V teeth.
I personally wouldn't use that trowel but again, you do whatever you think is correct. The proper trowel in this case WOULD NOT be a "V" notch trowel. ONE MORE TIME...I would use a 1/8" X 1/8" X 1/8" SQUARE NOTCHED TROWEL. A "V" WILL NOT deposit the necessary amount of thinset onto the wall.


I'll have to hunt for those 'wedges'...
The wedges are readily available at Home Depot. Buy the soft rubber type. They can be placed back-to-back to create a wider gap if need be but that shouldn't be necessary with your tile.

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