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I would like to hear pros and cons of using mastic for a tub surround. I have been told that mastic will hold better during the initial install. Is this true?
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Ted:
Yes, mastic does have better initial "hang time" but its my opinion that you will get much better results, over time, using thinset on an appropriate setting bed. The key to a quailty, long lasting installation is what is behind the tile. You can get tile to stick to thinset...I use it on shower ceilings, it just needs to be the right mix. I never use mastic on anything that is going to come into contact with water or water vapor.
Good Luck....Dave
*I agree with "Creature" (?) That is, I do not ever use any kind of mastic in a "wet area". That includes an area that gets only slight, infrequent moisture. Stick with thinset, pun intended.Also, he/she is so right on re: tile substrate. The key is proper preparation, folks.
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Well, you heard from a couple of thinset proponents, now a dissident amateur.
About 15 years ago I remodelled one of my bathrooms with green sheetrock on the walls and 3/4 plywood on the floor. The floor and walls to about 6 feet are tiled using what the salesman called "floor mastic" (I don't remember the brand). No tile has fallen off, there are no bulges, the grout has stayed put, and AFAIK there's no water leakage, all this despite four showers a day with the water playing directly on the tiled tub surround. No problem with the floor either.
Maybe it's all in the definition of "long lasting": thinset lasts 100 years, mastic only 50.
*Now you get to hear from a professional that agrees with Patrick.We use mastic on shower walls all the time. We have had no failures! We do use a grout sealer on all the shower jobs we do. We use the $100.00 a gallon variety. Sealer is an important part, I think, of a shower job.Good LuckLouis
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Sorry Patrick, but there is no chance you will get 50 yrs. out of greenbd in a shower, it's rotting as we write. I have had to tear out a lot of these and it happens from the inside out, by the time you see any sign of damage, there as been a lot more damage on the inside. In some cases I've had to replace studs, ceiling below and joists were getting pulpy. Tile and grout are porous, which means water is getting thru, the others are right, the substrate is important.
Sorry, Barry
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Ted,
I have just finished my second tub surround and am eager to start my third later this month. I have torn out enough crummy rotten mildewed green board (held up by rotten studs) that I will not even think of using the stuff. I use concrete board and thin set exclusively. I never have had any problem with tiles sticking to the wall with thin set. Doing the job right is nerve racking the first time, but is ultimately fun and rewarding. The best set of directions I have found are in the January 95 FHB.
Incidently, Does anyone know what is the deal with the different grades of thin set? Does it make any difference what grade you use?
Craig Gibons
*Ted, as far as the type of adhesive I think it's a matter of personal preference, mine is mastic for walls and thinset for floors.I would recommend NOT using concrete backer but a product called Denshield. I can't think of the maker right now but it comes in 4x8 sheets and weighs no more than sheetrock AND you can cut it with a utility knife or hole saw for the valves.The substrate is a fiberglass like substance mixed with a gypsum like product.The face is covered with a water proof surface which is slighly dimpled,which helps in the adhesion of the tile to the backer-board. I've been using this product with great success for the last 5-7years.It is more expensive upfront(about $32 per sheet) but look at the sq. ft. coverage from a 4x8 sheet as opposed to the 3x5 or 32"x5 of some makers(32 sq. ft. VS. 15 sq. ft.) not to mention the muscles saved! Geoff
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Gee, alot of different feedback here. It has been my experience that a greenboard (W-R drywall) and mastic tile job in a wet area is a future job for me.
Anyway, I cannot agree with Geoff re: his comment that the type of adhesive used is a personal preference. The mfg. have labored very hard to eliminate this. ANSI and ASTM have explicit specifications regarding materials.
For an authoritive opinion on installation methods and materials, I turn to the Handbook For Ceramic Tile Installation put out by the Tile Council of America. Installation Method B413 details the use of either latex-modified thinset (ANSI A118.1 compliant) or an organic mastic (Type I, only).
However, there is a Caution regarding Substrate Limitations:
"The performance of a properly installed thin-set ceramic tile installation is dependent upon the durability and dimensional stability of the substrate to which it is bonded. The user is cautioned that certain substrate materials used in wet areas are subject to deterioration from moisture penetration. (Reference ANSI A108, AN 2.5.3.2.1) Therefore, while every effort has been made to produce accurate guidelines, they should be used only with the independent approval of technically qualified persons." Notice how they pulled back on their opinion when they made reference to "...qualified persons"?
What this means is, yeah, you can use mastic on greenboard for a tubsplash, but just know that it will be subject to excessive moisture penetration, resulting in premature failure.
You may not see it rotting, but you'll smell it soon enough.
Some anecdotal evidence for NOT using mastic in a wet area: I was asked to checkout one of these jobs. It was upstairs, above the kitchen. The customer wanted to know what I thought about the visible rust in the kitchen flourescents and the powerful moldy smell in the bathroom. (Other than this, the owner had no other evidence of a deteriorating tubsplash) We went upstairs where I pulled a tile off the otherwise fine looking installation with my fingernail. We immediately quarantined the room when we saw a big, white mushroom growing on a wood stud.
On another call, the homeowner explained to me that his young son was in the hospital with a serious respiratory infection caused by fungal spores in, you guessed it, a mastic/drywall tubsplash installation.
I could go on and on and on... this post is already way too long.
I used my chemistry background to establish that fungal spores sure do like the organic mastic. They eat it up!. But how do the spores form in the first place? A dark(inside the wall), warm(heated house), wet(moisture penetration) enviroment is the perfect habitat for mold. That is just what you'll have when you use gypsum board in a wet area.
At the very least, use a backer board specifically for tile installations.
*So assuming that everyone gives greenboard the thumbs down and concrete board the thumbs up how about installation details? Many tubs/showers are on an outside wall. After tearout, do you insulate the wall? With what? Before fastening the concrete board do you attach a 4-6 mil vapor barrier to the studs? Concrete board may not dissolve when wet but I believe water can migrate through it to the framing. And what for fasteners? Double Dip Galvanized Roofing Nails? Screws must be better--so do you go stainless? And then do you use a setting compound on the joints (as opposed to drying). Seems like all these issues must be resolved before debating mastic or thinset. Just thought I'd mention it.Now about that ventilation fan....... Thor.
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Apparently many of the folks on this forum are quite well off and have never ever lived in an apartment or 1950s era house. If you had you would have experienced deteriorating walls and falling off tile first hand. All courtesy to incompetence and cheapness on the builders or homeowners who installed tiles using drywall and "glue". Glue is fine for a tiled coffee table.
If you want a quality job use concrete backer board. Available in many thicknesses. About $10 per 5' x 32" sheet. Use thinset mortar. Glue will last 5-10 years just fine but you and the person who takes the rotted bathroom out will always know you were cheap and shoddy. I like to think I will leave some quality work behind if I drop over dead tomorrow.
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AFAIK??
The unenlightened Rich
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As Far As I Know
*Sorry Barry but i disagree with what ya say cause we install tile in a shower over green board tile is not all porous, glaze tile is sealed,plus if you add acrylic motor add mix to the grout it also makes it stronger and more water tight there is water proof grouts on the market.It called how you prepair the suface of the green board.you can put a polly coat over green board to also seal it there are many ways of doing thigs out there some people like wonder board but if ya install that wrong ya can have problems too as goes for anything.
*the longer the cure time the better grade like theres some out there that set in 45 mins is like a low grade ones that last 6 hours the best grade.the longer it takes the stronger it is but on walls it really don't matter as much as in floors so i better grade is used on floors
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Fred, you seem to be technically literate, judging from your other posts. So, my question to you is: why do you say 15# felt to be "archaic"? Is there something you know that you're not telling us?
I believe that the felt is to act as a moisture barrier. Since there is not any head pressure--or hydrodynamic force as Joe Fusco may be wont to call it--any water that does penetrate through the tile/grout will simply weep down the wall, into the pan, and down the drain. In other words, the felt--if properly lapped--will "shed" any moisture. Of course, a steamroom would be constructed differently.
Since any permeable material is protected from moisture contact there is no capillary movement, so gravity does it's job of facillatating moisture to the drain.
This is, as you may surmise, a defense of felt as a moisture barrier.
*Fred,If it were my shower I would not have a problem using 15#felt as a moisture barrier. If you want, install the durock over the OSB then use thinset to install a membrane called Nobleseal TS or Dalseal TS (same thing) over the durock. Once the thinset cures, you can install tile directly to the membrane with thinset. Cost for the membrane is between 1.50 and 2.50/sf.Dave
*Sorry to disagree, but NobleSeal is a crack suppression membrane for installation on horz. surfaces, ie, floors.There are trowel-applied liquid moisture barrier membranes available, but these are more costly in material, require more labor than roll membrane, and increase "downtime" until dry.
*Nobleseal CIC is a crack isolation material. Nobleseal TS (and Dalseal TS) is a CPE (Chlorinated polyethelene) waterproofing membrane for thin bed tile installation. Fred, I would use your EDPM without hesitation if you avoid any seams or penetrations on horizontal surfaces or below the water lines. Put a slight pitch in the seat to drain it. I build all my showers with seats. I love to sit down in a hot shower after a days work.
*Fred, Now I'm not sure the reason for the question. I'm assuming some part of the enclosure is on an exterior wall. Since the cement boards are vapour permeable and I've read several places that 15# felt is, I'd think you would want a vapour barrier rather than relying on the osb. It seems the epdm would do this but no personal experience to know the specific problems. (I'm comtemplating a similar problem and was moving toward taped greenboard for air vapour with 15# felt and cement board over.)
*None of the above. I have replaced all the mastic /greenboard in my house that was put in by an unknowing tile contractor, before I knew any better myself. I have used backer board on an occasional job, but in my own house everything is now floated. I think it is a superior method on all counts but price, but you get what you pay for.
*Mike - Maybe your clime makes this a moot issue but do you use an air or vapour barrier behind the mud bed? - since it doesn't seem that the mud itself would be impermeable.
*Yes. I prefer solid backing for 2 reasons. First it allows a one coat float. Second I'm not a good enough plasterer to get mud to stick without it. So from the studs out.Plywood (or greenboard) 15# felt lapped generously. If I had EDPM laying around I might use it.(vinyl pan to above the flood line and on all horizontals within the range of water) Mud Tile One of the greatest advantages to a float, is that any irregularities can be fixed. I have always found it difficult to shim sheet material a little here and a little there. With a float you just shim screeds perfectly and the mud ends up perfect. Plumb, square and level.I am a firm believer in mechanical waterproofing (i.e. membranes and flashing) as the first barrier. Sealants must be the second barrier.
*I float my walls the same as Mike except that I comb out some asphalt gum behind the 15# felt with and 1/8" notched trowel. I am assuming he uses metal mesh of some type in his bed. Floating works well for me because alot of my tile is installed in older homes where the walls aren't nice and plumb. By floating I have complete control over the setting bed, and I think its fun.For a durock installation on an exterior wall I install directly over the greenboard..from the studs...vapor barrier, greenboard, asphalt gum,15#felt,(yes I would use EPDM if it was available) I would probably skip the gum if I used EPDM, durock, tile.This may seem like overkill but the last thing I want is to be back fixing a leak.I also like a seat in my shower...for alot of things!!Dave
*Dave, I use expanded metal lath, because it is easier to get the mud to stick and as I said I am no plasterer. But, as you probably know, you have to get it right side up, so the mud slides into the mesh and not out. Another advantage to floating is that penetrations can be confined to vertical surfaces. On a slightly different subject, since you brought it up, Nobleseal/Dalseal TS is acceptable for exterior application over wood. I checked with the manufacturer's rep. before I did this and got an ok. I have done a few decks this way, some over living areas. Technically it is not an approved roofing material, but since PROPERLY applied it is a positive waterproof membrane, and it is covered with tile, I think this is a moot point. I don't have to worry about freezing here in So. Cal. but if you do, you need a tile that will take the freeze.
*Good memory Mike...thanks for the info.Have a great week.Dave
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I would like to hear pros and cons of using mastic for a tub surround. I have been told that mastic will hold better during the initial install. Is this true?