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TurboSAAB
01-12-2017, 07:36 PM
Hi guys!

I am having my small master bathroom completely remodeled.

The bathroom contains a stand up shower. I am VERY fussy with how things are done under the skin. So, of course I'm very fussy with waterproofing. I asked all the contractors I was considering what, if any, waterproofing method they use - kerdi, redgard, vapor barrier behind the cement board, etc.

The general contractor I ended up selecting said that the tile guy installs redgard. My agreement even notes "install redgard to shower walls". Today the tile subcontractor came by to take some measurements and go over our design. I brought up the redgard and he said, to my surprise, that he doesn't like it and doesn't use it. He said he could peel it off with his fingernail and thus doesn't think applying tile to it would be a good idea. He said if I wanted, to tell my contractor to put tar paper or polythylene sheeting on the walls. I know this is a decent option.


I guess the first matter is to find out the discrepancy between what my general contractor told me and what the tile guy he has been using almost exclusively for over 25 years told me. That's a little strange.

What do you think I should do? I'm not at the point of picking contractors, I have already. And this is the tile guy he uses. He seems good and very experienced...I'd need to negotiate with him to get a waterproofing system that I want but also one that he knows how to install and is comfortable with. Other contractors I was considering said that they typically did not use redgard (or anything other than just the cement board) but said that he would certainly use it if I wanted to. But, I picked the guy who made it sound like they always use it...but now his tile guy says he doesn't use it.


I'm also deciding between keeping the shower small (and using an acrylic pan) or enlarging it and having a custom tiled pan. He mentioned that there would be a mud base, a "pool liner" type membrane that would also go several feet up the wall, etc...but didn't get into details beyond that. I've seen online and on this forum diagrams of how that should be done. Not sure how much to challenge him on that or ask for a fully detailed description. This contractor is highly regarded in the area. But, I know that the under the skin stuff often gets overlooked. I'm not worried about a catastrophic leak. I'm worried about subtle water intrusion over the next 25 years that slowly ruin my investment.


Any advice would be greatly appreciated!!

Thanks!

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Houston Remodeler
01-12-2017, 08:26 PM
Al,

Welcome to the forum.

There are many great Pro's who adore and hate RG. The usual factor leading to RG peeling off is not taking the time to remove any dust from the surface before applying. A major concern with any liquid membrane is applying the proper amount.

If you want RG then get RG.

The sheet membrane is an industry accepted alternative to the RG. In both instances, the membrane has to be lapped over the tile flange of the shower pan. BUT if your particular pre-made pan has no tile flange going past the curb, there is nothing to lap the wall hung sheet plastic over. See picture below. IMHO premade pans are no guarantee against leaks.

A custom pan can have a vinyl liner which typically runs 3 to 12 inches above the curb. Any Cement board applied over this membrane will have the fasteners poking through the liner, so going higher up the walls doesn't do any good. When a traditional liner is installed, there is the need for a membrane on the entire wall surface including any benches and niches. That membrane either goes behind the cement board and lapped into the liner, OR (not both) a surface applied membrane such as RG.

Read the shower construction thread in our library. Lots of good info there.

Davy
01-12-2017, 08:33 PM
I would tell him that your agreement calls for Redgard and he needs to use it. Like Paul said, if he would wipe the substrate with a damp sponge and remove the dust, then mix a 50/50 mix of Redgard and water for the first coat, he would find that it will bond plenty well.

TurboSAAB
01-12-2017, 08:38 PM
Thanks to both of you guys for the input!

I have a question in to my general contractor nicely asking for some clarification as to why my contract says redgard will be used but then his main tile guy apparently does not like to use it. That doesn't make sense to me. When I asked about it, he said "the tile guy uses redgard". Odd.

I only worry about pressing him to use the redgard in that if he doesn't like it and has had bad experiences with it, then I feel he may not apply it correctly or will be doing something he doesn't like and thus it won't come out well. But I will try to broach the subject nicely with him.

Paul - thanks for the image. It looks like if he did use the sheet membrane behind the cement board instead of the redgard, and did the membrane sheet liner with the custom pan, it would be a correct job...assuming everything laps properly, as per the image. I will ask about this. I have to be careful, as I do not want to insult a person who exclusively has been doing tile for 30 years. However, it is my bathroom and a big investment for me, and I want it to last...so I have to stand up and be firm I guess.


Thanks!

Houston Remodeler
01-12-2017, 08:47 PM
3- If he is a true professional he will have no problems showing you how he did things properly.

2- As long as he does an industry accepted installation I'd skip pressing on the RG unless you hire someone else.

1- General contractors tend to take the "general" part of GC too literally and don't have much specific knowledge about anything. My guess the GC parroted your mentioning of RG, has no idea how its installed, or the names of any other waterproofing methods or details.

TurboSAAB
01-12-2017, 08:57 PM
Yea...I can ask him to show me how he'd do the custom shower base...maybe even include the image you attached here and ask if it would be like that. He did mention a sloped mud base, vinyl liner (he described it like a pool liner), etc. But I need to ask him more details...need to ask also how the curbs will be created. Has to be mud/cement over the wood, right? No cement board here?

And as far as industry accepted installation - so if he still pushes back on the redgard but does the plastic sheeting behind the cement board, and everything is like in the diagram you attached, I guess I'd leave it alone and consider that a very good installation.

Regarding the general contractor, I'll have to see what he says about saying redgard is included but then his own tile man saying the opposite. I had to question him on that, waiting to see what the reply is.

TurboSAAB
01-12-2017, 09:02 PM
By the way, he did mention that there are sheet membrane systems that get embedded in the thinset that in his opinion is better than the redgard since it gets embedded in the thinset.

So I was thinking great, sounds like kerdi, that's good!

So I then say, "you mean like Kerdi?". So he said he's not sure of the names, there are several, but explained very generally how they work.

But I was thinking that if he didn't even know the name of it, how familiar is he with it - I know kerdi has very specific installation procedures.

Houston Remodeler
01-12-2017, 09:08 PM
Sounds like you're ahead of the GC :tazebro:

Houston Remodeler
01-12-2017, 09:12 PM
There are a few ways to do the curb

Thins to look for;

1- A pre-slope of drypack under the liner (as shown in the picture)
2- Notched studs where the liner goes OR furred out wall studs. You do not want the bottom of the cement board bulged into the shower.
3- If the classic liner is used, check out the curb details in the shower construction thread. NO cement board inside or atop the curb.

TurboSAAB
01-12-2017, 09:26 PM
Haha..


One last question...

If he does go with the plastic membrane behind the cement board, and I have a shampoo niche put in, how would he waterproof that? Would he at least have to use a paint on membrane there?

Thanks for all this help!

Houston Remodeler
01-12-2017, 10:49 PM
He could bulge out the plastic OR use a surface membrane in that area usually painted quite larger to overlap the sheet plastic behind a fair amount.

TurboSAAB
01-13-2017, 06:51 AM
One other question...

...if he does indeed go with simply putting some plastic sheeting on the studs behind the cement board...I guess the fact that the plastic sheeting is tacked to the studs and the cement board is screwed to the studs through the plastic sheeting is considered acceptable and not a realistic means for moisture to enter the wall?

Houston Remodeler
01-13-2017, 07:44 AM
Correct, which is why epoxy coated cement board screws are critical in this case. Drywall screws would rust

MAPEI - Technical Service
01-13-2017, 09:12 AM
If he just doesn't care for the product, not the concept of liquid applied membranes you can certainly use our AquaDefense (http://www.mapei.com/US-EN/Tile-&-Stone-Installation-Systems/Waterproofing-Membranes/Mapelastic-AquaDefense).

TurboSAAB
01-13-2017, 09:59 AM
He seemed to think none of that stuff was necessary. He said the tile is glazed, there's thinset, the cement board is 1/2" thick, etc. Now I know none of that is waterproof...I would think a 30 year tile guy would too.

So I pressed a little bit, and he said I could have the general contractor hang some felt paper or plastic sheeting on the walls before he gets to the job.

Just wondering also if the general contractor hangs the wall plastic first, that the tile guy would make sure to lap the shower pan liner under the wall plastic.


I'm going to nicely email him and ask if he is averse to other coatings (hydroban, Aquadefense, etc). If he really pushes back I will ask him to describe the full membranes that go right into the thinset that he mentioned (yet couldn't recall the names...even though I know the names).

Worst case, I'll accept plastic sheeting behind the cement board as long as everything is done correctly. Probably better to have him use a method he is familiar with instead of one I insist upon and then he does a bad job with it due to not having experience using it. In other words, if I insisted on Kerdi, and it would be his first Kerdi job, plastic sheeting behind the cement board may be better.

John Bridge
01-13-2017, 10:02 AM
Every major tile products company has a liquid membrane. I recommend RedGard, Aqua-Defense and Hydro Ban from Laticrete. All are great products if directions are stringently followed. :)

TurboSAAB
01-13-2017, 10:07 AM
Should I imply he doesn't follow the instructions if he thinks Redgard stinks?


A little peeved because I chose this contractor because he told me the tile guy uses Redgard when I asked about it when I was deciding between contractors.

John Bridge
01-13-2017, 10:11 AM
Al,

Someone asked whether the guy doesn't like the product or whether he's against the liquid membrane concept altogether. If it's just that he prefers another product to RedGard that's fine. Every setter I know has his own favorites. :)

TurboSAAB
01-13-2017, 10:16 AM
Hi John,

When I asked about the Redgard to confirm he'd use it as per the general contractor, he said it was bad, explained how it can peel off. He then did not bring up other paint on membranes, he instead explained how the tile is glazed, there is thinset, he seals the joints, and the cement board is 1/2" thick. I know in my head as he's saying this that none of that means waterproof.

When I persisted a bit, he mentioned that there are membranes that get embedded in the thinset that are better since they won't come off (but he did not remember names...surprised, since even I've heard of Kerdi) and also said the general contractor could just lay some building felt or plastic sheets on the studs if I really want.

zeaflal
01-13-2017, 10:55 AM
he instead explained how the tile is glazed, there is thinset, he seals the joints,
I think you may have found the root of the problem. And possibly the source of future problems.

TurboSAAB
01-13-2017, 02:13 PM
I think I got some good news.

The tile contractor called me back and we discussed the waterproofing options. Very happy to hear that he was happy to explain everything to me and was open to my wishes for upgraded waterproofing.

He said he was looking at a video of the Kerdi system (because I mentioned it in my email), and gets the basic principle, but didn't like a few thing about how it was installed at the lower corners in particular.

But, he did say that he uses a similar type of applied to thinset membrane called Noble Seal. He said he's used it several times in the past year or so. He said he often uses it on handicapped bathrooms where the entire bathroom floor needs to be waterproof.

So, Noble Seal applied to my cement board shower walls will be just as good as Kerdi? I get the feeling it's like Ford vs Chevy. Everyone will have a preference....and if basically equal, I'd like to let him use what he is comfortable with and has experience with.

HooKooDoo Ku
01-13-2017, 02:47 PM
Al,

I'm just a DIYer... that finished in a basement bathroom on my own (with some lessons from all the great people here in this forum).

I used AquaDefence... and I learned that you can indeed peel it up with a finger nail. But went you do that, you are effectively pulling that tiny piece of membrane with what might amount to 100psi of pressure (perhaps 1lb of force over an area 0.1" x 0.1").

But when you put a 12"x12" tile up that weighs perhaps 5lbs, that's only 0.03psi of pressure.

rmckee84
01-13-2017, 05:10 PM
Noble makes some very good products, as long as they are installed properly you should be good to go. If you use this guy try and document the process. I know that can be difficult with work and responsibilities of your own. If you aren't able to be around while the prep is being done request pics be taken so you can keep for your own records.

jadnashua
01-13-2017, 06:17 PM
Noble has been in the business of membranes maybe even slightly longer than Schluter. Both are quality products and will work well IF installed exactly as specified in their installation manuals. Noble's product is a bit thicker than Kerdi, making seams stick out further, and IMHO, making it a little harder to get the tile flat across them, but it can be done. Noble uses different materials to make their seams verses Schluter, so it's one more product to buy (much more expensive than thinset for the seams!), but has an advantage in that you can start tiling or flood testing almost immediately verses having to wait 24-hours for the thinset to cure enough prior to flood testing a Kerdi shower (something you should insist on).

The key with any system is knowing AND following the instructions.

For any painted on waterproofing, the installer should have (and use!) a wet film thickness gauge to verify proper coverage. The two coats MUST be installed between the min/max specified, and there's no way to tell that visually. Too thick is just as bad as too thin with them. IMHO, it's much easier to have a pinhole leak with a painted on one than a bad seam with a sheet membrane, but that's my opinion.

The difference between the conventional shower with a liner verses a surface membrane shower is that while both have a waterproof pan, only the ones done with sheet membranes are waterproof the entire structure. This means the whole thing can dry out MUCH faster, and that means less susceptible to mold. Mold requires moisture, food, and the spores. Well, you'll have plenty of surface moisture in a shower, and there will be some soap scum, oils, etc. accumulate in places, and you can't get away from the spores except maybe in a clean room...so, your goal should be to minimize how much and how long moisture sticks around...can't beat stopping it immediately behind the tile and the thinset holding it in place. The vast majority of moisture first, doesn't penetrate to the bottom of the grout, and can evaporate in between uses. CBU or deckmud (on the pan and curb) will try to wick the moisture down into it, and tend to stay damp longer. A conventional clamping drain with weepholes, it is not uncommon for the weepholes to eventually clog up, and moisture can then accumulate in the pan. Much of that can be forestalled by proper build techniques, but a surface applied sheet membrane doesn't use that type of drain and there's not 1-1.5" of porous deckmud underneath the tile to accumulate anything...it's a waterproof membrane.

Dave Gobis
01-14-2017, 07:46 AM
Short history lesson. Noble and NAC were the pioneers of sheet membranes. Laticrete was the pioneer of liquid waterproofing.

TurboSAAB
01-15-2017, 11:03 AM
I thought of another quick question regarding the use of Noble...or any other sheet membrane like Kerdi, etc...probably even more of an issue with Noble since it seems to be thicker...


If the sheet membrane is used under the tile in the shower area...and the adjacent parallel walls also have continuing tile, does that extra thickness of the sheet membrane cause a problem? Or, is that simply "lost" in the thickness of the thinset?


I guess this is something for the tile guy to worry about...I just like to be aware of all concerns.



And, HooKooDoo Ku, that is an excellent point regarding being able to peel off the roll on coatings with finger nail as not really being relevant. I bet one can peel the surface off of cement board too!
Thanks!
Alex

TurboSAAB
01-15-2017, 02:42 PM
Another follow up...

The general contractor got back to me. He said he has 3 different tile guys he uses, depending on availability, that have differing views on the necessity of waterproofing the wonderboard in showers. He had quoted me the redgard because I asked for it and it did not increase the price very much. He said the tile guy for my job is not a fan of redgard, but he never really discussed it with him because I'm the first customer to have asked for it. He said in 25 years of making showers, they never had a call back for water getting in a wall. I was now quoted an extra $1450 for a kerdi and/or Noble membrane system.

Now, if he has 3 tile guys with differing views on the necessity of waterproofing the wonderboard, wouldn't it be reasonable for me to ask for the opinions/potentially use one of these other tile guys on my job? It seems like redgard would be more budget-friendly and get the job done.

What do you think?

jadnashua
01-15-2017, 02:54 PM
The TCNA has numerous recommended methods of building workable, reliable showers. Some of them utilize surface waterproofing materials, but not all do. The key here is partly what you want and understanding the benefits of one technique verses another, not as to if they will work as all of them, done properly (and that is key) will provide a long-term, reliable outcome.

Personally, I prefer a surface applied sheet membrane. This makes the entire shower waterproof. A conventional shower construction only waterproofs beneath the tile setting bed on the floor, leaving the rest of the shower to be water tolerant, but not waterproof. But, you have to consider that you don't fill a shower up like a tub, so just having the pan be waterproof works, and gravity will direct the rest down the drain. CBU is not damaged by becoming damp, and with a barrier behind it, that, along with gravity, will prevent damage to the structure (again, if it is installed properly).

Building a shower isn't technically hard, but it is VERY detail oriented...mess up one seemingly simple requirement, and it COULD fail...doesn't mean it will fail, but it could under some circumstances. The combination of knowing and UNDERSTANDING those requirements, and being able to execute them properly is where the skill comes in. BOTH are required.

Most of the membranes are fairly thin...Kerdi is about 8mils. Noble TS is about 30mils, or nearly 4x thicker. For that thickness, it gives you a little better vapor barrier and (maybe) a little more resistance to damage during installation prior to the tile being installed, but just like having 1/8" thick glass verses 1/2" plate...both are still waterproof. Then, consider that it is sandwiched between two rigid surfaces, and once installed is protected from abrasion and punctures. It gets more complicated when making seams, and that is where the extra thickness can become problematic as in a corner, you might end up with a layer of overlaps 3x thick not counting the bonding material between each layer.

TurboSAAB
01-15-2017, 03:26 PM
Thanks for the feedback!!

I'm a little surprised that since I asked for redgard and it was put into my contract several months ago that the tile guy (out of 3 options) selected for my job was the one who doesn't like it. My other option is to spend $1450 extra on a sheet membrane.

The general contractor also added that if water gets behind my tiles, there are bigger problems, because the tile will start to become loose.

I thought water is expected to get behind the tile, why would that alone make it loosen?

I want to be firm here but not fight the guy too much. He is extremely experienced. While my family in the past was in the home-building business, I personally have not built bathrooms. I get the feeling they think I'm just reading stuff on the internet and don't know what I'm talking about.

evan1968
01-15-2017, 04:27 PM
The general contractor also added that if water gets behind my tiles, there are bigger problems, because the tile will start to become loose.


You need a new GC along with a new tile guy.

He is extremely experienced
You might want to rethink that statement. To some of us here that have been reading this thread, he doesn't seem to be.


I get the feeling they think I'm just reading stuff on the internet and don't know what I'm talking about.
You just happen to be on a site that has some of the most knowledgeable and experienced tilesetters in the country. Maybe the GC and his 3 guys that do tile might learn a thing or 2 by being on here.

It's your money and your project. Get what you want.

TurboSAAB
01-15-2017, 04:38 PM
By experience I mean 30 years of experience and a generally very good reputation in the area. That's why it feels funny telling him to do things differently than his suggestions. I had 3 contractors bid the job. 1 said he didn't use any additional waterproofer, 1 said he typically does not but has used regard and would if I want it, and the one I chose said "the tile guy uses redgard" when I asked. So, that was a factor in my selection. Not just for that 1 detail, but to me it implied an overall good attention to detail. So, the recent developments are a little confusing to say the least.

I think I will ask him to use a different tile guy on the job. If he quoted regard so easily like it was a matter of fact, I presume that means that one of his tile guys does waterproofing. Knowing I requested it, I would have thought that person would have been selected for him job.

TurboSAAB
01-15-2017, 05:12 PM
I think the external sheet membranes are out if he wants to charge me $1450 to add that feature while redgard was included in our initial price/agreement.

So I need to decide if I want to press on that, or at least insist on plastic or tar paper being used behind the cbu.

One thing I didn't think of - has anyone who has used redgard (or any of the coatings) tell me how bad the odor is? My wife is pregnant and this bathroom is our master bathroom, the door is literally a few feet from her side of the bed. if it's a short lived thing, we could just have her sleep elsewhere for a day or 2 I guess.

Thanks!

TurboSAAB
01-15-2017, 06:10 PM
I'm literally looking right on Custom Building Products website (makers of Wonderboard, which is being used for the shower) and it says right there that building felt or plastic sheeting must be used behind the product, or redgard on the surface. Is it too much to ask for a product to be installed as per the manufacturer?

Houston Remodeler
01-15-2017, 06:45 PM
Not at all. In fact its REQUIRED.

When you get to court, the manufacturer's instructions reign supreme. :usflag:

Far above "we've done it this way for 30 years"

jadnashua
01-15-2017, 07:27 PM
As I've been saying...it's not hard to build a proper shower, but it is very important to follow the manufacturer's instructions on the products selected AND to abide by known, industry approved methodology. Those that do not do that are either VERY lucky there has not been a problem, or the customer didn't realize there was a problem (some don't show up until the next remodel), or it happened beyond the year or so the guy typically gives for a warranty, and was never contacted.

A properly built shower should last until you decide to remodel it...not for it failing to perform.

If you'd considered something like KerdiBoard verses the cbu you have, while the materials are more, the labor is way less, and it would have been, IMHO, a higher performance shower. Personally, the delta costs in materials to go Kerdi verses RedGard is way less than the upcharge, and, once you've used it, the labor to install it is higher, but with probably $1000 of that upcharge in labor, that's nearly 2 days...someone that knows what they're doing, it's less than one...sometimes, way less. If you used KerdiBoard and can use the foam pan, you'd be ready to tile it in hours except for the fact you want things to sit 24-hours before you flood test it. If you used WediBoard, you can flood test that same day.

TurboSAAB
01-15-2017, 07:29 PM
Houston Remodeler - I see on your website that you use the HydroBan coating. Do you how the odor of this product compares to Redgard as it is installed? If I end up getting them to use a coating, I may want to go with Hydroban instead since my wife is pregnant and the bathroom is our master bathroom. Reading online, it does seem to be lower VOC and meet more environmental certifications. Even if we go with the sheeting behind the wonderboard instead, I'd push for the niche part to be treated with a surface waterproofer. Thanks!

TurboSAAB
01-15-2017, 07:31 PM
jadnashua - so you're saying its strange that redgard was included in my initial quote but the kerdi/noble membrane system was now quoated at $1450 extra? It's not a huge shower. (It was quoted as Schluter Kerdi Noble Seal TS.....which are 2 different products, assume it meant either/or).

Houston Remodeler
01-15-2017, 07:32 PM
Once cured there is zero odor. That takes about 24 hours. Then it gets covered with tile.

My analysis has shown that every waterproofing method comes in right around the same price per SF until you add labor. The more labor the higher the final price, as Jim explained.

Unless you hire me, then my price is high to begin with . : )

TurboSAAB
01-15-2017, 07:35 PM
PS - wish some of you guys were in my area, or I checked/read this site before even thinking of redoing the bathroom. :)

Houston Remodeler
01-15-2017, 07:39 PM
Al,

We probably do have forum Pro's in your area. If you want to find one, start a new thread (linked back to this one if you'd like) with a title such as "Installer needed in (location) for new construction, GC is a bonehead"

Please add your geographical location to your User CP with is linked in the dark blue bar above. That way it stays with you from page to page without getting lost.

TurboSAAB
01-15-2017, 07:45 PM
Good point. My only concern is not necessarily wanting to cancel this job that I had booked now for several months that starts in a few weeks. And I've kept my location hidden to protect all involved...didn't want to publicly criticize anyone, really just wanted advice/make sure my job was being done right.

But you do bring up a potential option. Hmmm... I probably should have started here for my contractor search. Maybe I'll find out that one of the forum members in my area is one of the other 2 tile options my guy uses :)

Houston Remodeler
01-15-2017, 07:51 PM
Checking the NTCA membership (http://www.tile-assn.com/search/custom.asp?id=2759) is a good start

Houston Remodeler
01-15-2017, 07:53 PM
PS - wish some of you guys were in my area, or I checked/read this site before even thinking of redoing the bathroom

if we had a nickle..... :gerg:

TurboSAAB
01-15-2017, 08:06 PM
I'm going to nicely put my foot down w/ the waterproofing and see what happens. Hopefully I don't need to then make a post in the pro section of the forum :)

JerseyDIYguy
01-16-2017, 11:58 AM
Al, one suggestion is to ask your GC to get details of how each of his subs usually waterproofs the showers they build. Those answers should be extremely telling in terms of the subs' level of knowledge and ability to build a shower that will last. No need to fight or insult your GC, just insist that he provides you the info.

TurboSAAB
01-16-2017, 06:10 PM
Guy replied to my email that they'll do the plastic behind the wall and treat the corners and niche area. But totally disregarded my question about why I was told "the tile guy uses redgard" and the the tile guy who shows up doesn't. And I asked him to clarify the 3 different waterproofing views of his 3 different tile guys. So, need to talk on the phone. Really feel like my requests are not taken seriously. Going to ask exactly what you suggest, Warren.

Houston Remodeler
01-16-2017, 07:49 PM
The GC is hiring these guys, the GC is 100% responsible

Davy
01-16-2017, 09:02 PM
If you have to, tell the GC you don't want anyone showing up on your job until you get some answers.

evan1968
01-16-2017, 09:19 PM
Yo Alex!:lol2:

TurboSAAB
01-16-2017, 10:26 PM
Yo Alex!
Got in touch with him actually :)

jadnashua
01-17-2017, 05:15 PM
A few questions to ask:
- what TCNA shower build process is going to be used?
- what products are being selected?

Then, a statement in the contract should be:
The shower shall be built using one approved TCNA build methodology and shall follow all selected manufacturer's installation requirements. If you want a specific one, you'd want to state either the products you want to use, or the method (which does not specifically indicate a particular product, but does indicate a class of material - i.e., the TCNA does not list brands in their specs, only methods, some of which require specific products without saying it).

This takes most of their wiggle room out of the equation, and gives you a leg to stand on. Note, there is an implied expectation that the 'professional' will do a professional job, and that means what I wrote above, but IMHO, stating it gives you a bit more force when they say, "We've been doing it like this without problems forever" and you find that it is not following the manufacturer's installation instructions.