Waterproofing with plastic membrane behind durock or durock with Redgard when insulation is spray foam?
user-3370940
| Posted in Construction Techniques on
I am installing a new tub in my bathroom and I have my walls gutted to the studs. I wanted to know if I should use a plastic membrance to cover the spray foam or go ahead and install the durock and then apply Redgard? All of the videos I’ve seen on Finehomebuilding.com have plastic over fiberglass insulation. Should the installation be different for spray foam?
Replies
Why?
Personally I wouldn't use redgard, but if you are choosing to, then:
1. Why would you use Durock as opposed to hanging regular drywall?
2. Why would you need a vapor barrier over your framing and insulation?
The redgard is supposed to be acting as your surface waterproofing membrane. Theoretically no moisture should be diffusing through the wall subtrate or into the wall cavity. Why be redundant with the durock and plastic? Maybe you don't really trust Redgard as it's marketed. I certainly don't.
For the very best tub, shower, tile installation advice, without any attitude, go to the John Bridge site: http://www.johnbridge.com/vbulletin/
I got some great tips and advice there when I was remodeling my showers. They've got some good how to's, and will quickly answer newby questions that get asked over and over. The forum is attended by many tile pros.
The "very best"? You forgot to quailfy that statement with "in my opinion". IMO the site is questionable at best. However, I could see that if you knew nothing about tile work, then you might think otherwise.
BTW, attitudes exists on every site, even that one. If you'r e afraid of a little attitude on a forum (goes with the territory), then you might want to stick to communicating with your pals on facebook.
Wow
WOW, talk about additude on seroids! But, ... as ususal.
We need to know more about
Your walls -- inside walls, outside walls, what construction, what insulation?
Your climate -- where do you live, how cold does it get in winter, how humid in the summer?
minimize water penetration
I believe in minimizing water penetration into any shower substrate, so I'm all for topical membranes. Control the moisture as best as you can.
If your foam is open-cell foam, I recommend that over the studs you use Durock then RedGard. If you are using closed-cell foam, then use Durock and Hydroban.
eliminate water penetration
I also believe in surface waterproofing. If it done properly with the correct material, the type of foam you are using behind the subtrate to insulate your conditoned space shouldn't matter. I recommend Schluter's kerid membrane to eliminate moisture penetration. Most tile work can be thinset over regular 1/2" drywall. If you're worried about the rest of the room's subtrate (painted surfaces) being hygroscopoic, then hang GP acrylic coated dense shield and skim it.
vapor barrier vs non vapor barrier
deadnuts wrote:
If it done properly with the correct material, the type of foam you are using behind the subtrate to insulate your conditoned space shouldn't matter.
It may indeed matter. Now it may not matter where you live, but in my locale, and with my AHJ, it does.
Closed-cell foam is a vapor barrier. So use it with a membrane that is not a vapor barrier; Hydroban.
Open-cell foam is not a vapor barrier. So use it with a membrne that is a vapor barrier; RedGard.
Nice try. The fallacy of your arguement is that Hydroban IS marketed as a vapor barrier membrane. Look it up. It's basically the same idea as Red Gard (CBP), but ust made by a a different (albeit probably better) manufacture, Latticrete.
The reason is doesn't matter is that an effective moisture proof shower system that intends to shed bulk water (and why wouldn't you; it's raining on the inside your house) is going to be, by definition, a vapor barrier. The point your tyring to get at ( I believe) is that one should avoid the use of a double vapor barrier. That is a valid point, but the problem with that in this case is:
1. The double vapor barrier argument only matters if the material between the two bapor barrier "cares" about moisture. BTW, concrete board (i.e. Durock) doesn't care.
2. There is an opportunity for moisture to be, or get introduced in between the two vapor barriers. Kerdi doesn't allow this from the shower side. You might get it from the plastic side. That depends on alot of other factors beyond the scope of shower moisture proofing. Tthat's why I would use the Keridi, period. In every case, no matter where you live. The effectiveness of everyhing that happens behind the Kerdi depends on composition of your ENTIRE thermal evelope; not just whether you use plastic, closed cell foam, open cell foam, etc.
My point is the you will always have a vapor barrier for surface waterproofing under tile by definiton. Any plastic film over studs on the inside of face of stud is only going to be seperated by the subtrate material thickness itself (usually 1/2"). Your vapor barrier is effectively in the same plane. I say that because there is no opportunity to introduce a thermal insulating gap in the amount of thickness to combat dew point issues. The only place to do that is in the wall cavity itself. That's an whole other story. We can get into that if you like, but IMO it's not the point of the original post.
??
deadnuts wrote:
Nice try. The fallacy of your arguement is that Hydroban IS marketed as a vapor barrier membrane. Look it up.
"Nice try"?
I don't know how you intended that to come across, but it reeks of sarcasm. If that was your intent? C'mon...
Hydroban is not a vapor barrier. Nor is it marketed as a vapor barrier. You wrote "look it up", so I will. For you:
Here's an exerpt from the manufacturer's pdf:
Uses:
-Shower pans, stalls and tub surrounds
-Steam rooms (when used in conjunction with a vapor barrier)
Water Vapor Permeance: 1.247 perms
It's perm rating is 1.247, too high for it to qualify as a vapor barrier. That's why if it's used in a steam shower as a waterproofing membrane Laticrete specifies you still have to use a vapor barrier to contain the moisture drive from the steam generator. Hydroban is not a vapor barrier.
Jeez, I'm not trying to pick a fight. The guy asked a question.
Hydroban and RedGard are both waterproofing membranes. As is Kerdi. All three of them stop liquid water. But Hydroban is not a vapor barrier. Kerdi and RedGard are vapor barriers, though Kerdi-DS has a much better perm rating than Kerdi.
What steam?
Where in the original post does the issue of of steam shower come up? You're grasping at straws Mongo. The issue is not the 1.25 perm rating not acting as a water (or vapor barrier) for a regular tub/shower surround. Any issue fo vapor drive are going to come from the exterior. Again, I don't recommend using the hydro ban or the red guard. There is no reason whatsoever that you would want liquid water (or vapor) to dry to exterior for a shower system--even for a steam room. If you know of one, please explain your rationale.
As respected building scientist John Straube writes: “The whole reason we’re talking about vapor barriers is not because vapor diffusion control is so important, but because people believe it is so important. The question comes up, have we seen diffusion-related building failures? And the answer is, very few — maybe in rooms with a swimming pool. Assuming that the vapor came from the inside, you would have to have a very high load before you would see a problem. I think that solar-driven vapor is much more important. The moisture is coming from the other side of the assembly.”
Again, ???
I don't understand your combative nature. I'm not grasping at straws.
It seems more that you are tenaciously holding on to your original idea that Hydroban is a vapor barrier, even though Laticrete says that what you stated as fact is indeed wrong.
Of course steam rooms have nothing to do with this installation. The only reason that verbage was used in the post is because that, along with the published perm rating, is the verbage Laticrete uses to say that HB is not a vapor barrier.
It shouldn't be this hard to get that point across.
And now you write:
"2. Red guard needs a DRY film thickness of 30 to get a perm rating of .35. That would mean you would have to paint on the liquid membrane @ 3x's the thickness of regular kerdi (8 mil @ .9 perm) to get this rating. IMO, that doesn't happen in the "real world"."
So even though Custom sells RedGard as a vapor barrier, you infer that RedGard isn't a vapor barrier because no one installs it correctly? Ever use a mil thickness gauge?
Ah, clarity. I believe that I do now understand why you write the way you write.
keep grasping...
I didn't infer that Redgard wasn't a vapor barrier. I clearly stated that it was junk.
And no; I don't use a mil thickness guage. I dont need to. I use Kerdi. It's 8 mil all the time...every time.
I understand your point, Mondo, that HB is not technically a vapor barrier because it does not fall below the threshold of 1 perm. I should have stated that it is marketed as a water barrier rather than a vapor barrier and I stand corrected on that minor point. However, the larger point is that is marketed to do the same thing Kerdi does which is to be used as a surface waterproofing membrane under shower tile installations. Whether it is technically a water barrier or vapopr barrier is a small degree of difference (.25 perm) that is inconsequential in terms of its use in normal showers. Remember, vapor drive is not an issue in regular showers.
Let me illustrate the fallacy of using HB (or Redguard for that matter) for surface waterproofing. It is fullly recommended for surface waterproofing regular shower conditions (the point of the original post), but not recommended for steam rooms unless it is used in conjunction with a vapor barrier. Think about that for a minute. It is saying that it is okay to use it in steam rooms in conjunction with something like kerdi or kerdi DS, but not by itself. Well, Kerdi or Kerdi DS can do the job all by itself without the aid of Hydroban. Why would anyone (but an idiot) use it in conjunction with? That's like a garment manufacturer marketing a nylon windbreaker as keeping you dry in a rain storm as long as you are wear it in conjunction with a rubberized overcoat. Well, duh!
Anyhow, that is but another reason I recommend (in all cases including steamers) Kerdi over HB or Redgard. It installs just as easy (if not easier) and is relatively cost effective to install. Both HB and RG are (IMO) junk. Kerdi reaches the threshold of a water barrier and a vapor barrier all the time, everytime. Further (and to the point of the OP) this negates the necessity for a polyetheleyne or tar paper liner under the tile substrate and the type of wall cavity insulation becomes a moot point.
The end...
deadnuts wrote:
Let me illustrate the fallacy of using HB (or Redguard for that matter) for surface waterproofing. It is fullly recommended for surface waterproofing regular shower conditions (the point of the original post), but not recommended for steam rooms unless it is used in conjunction with a vapor barrier. Think about that for a minute. It is saying that it is okay to use it in steam rooms in conjunction with something like kerdi or kerdi DS, but not by itself. Well, Kerdi or Kerdi DS can do the job all by itself without the aid of Hydroban. Why would anyone (but an idiot) use it in conjunction with? That's like a garment manufacturer marketing a nylon windbreaker as keeping you dry in a rain storm as long as you are wear it in conjunction with a rubberized overcoat. Well, duh!
I agree that Hydroban shouldn't be used in a steam shower. I never wrote that it should. I don't use RedGard, however...RedGard Is a vapor barrier, so it could be used by itself in a steam shower. Or for simple waterproofing in a non-steamer if appropriate. Kerdi? It's a fine product. I used it in my own walk-in shower when I built it 15 years ago.
deadnuts wrote:
I like this forum; it compells one to sift through the B.S.
Here are some facts you brings up and that folks should be aware of:
1.Kerdi DS has a very low perm rating (.18) but it's application is for continuous use steam rooms. Its mil thicknes is 20. So it's basically for commerical applications. it has no bearing for residential construction. It's a fine product, but there is no sense in even bringing it up as methood for getting under the 1.0 perm rating threshold for vapor barriers (not that it matters in regular shower areas anyhow) for residential applications.
So when I wrote that if the OP desired a material with a perm rating better than Kerdi, he might want to look at Kerdi DS, that's BS? Because Kerdi DS has no place in residential construction?
This is where you are being close-minded. There's a residential architectural firm in this area that specs out shower wall topical membranes as having to have a perm rating less than 0.5, doesn't matter is it's a steamer or not. That's where K-DS comes in handy. Does it have bearing with regards to the OP? I don't know. I simply offered it to him as an option. It's another material, another membrane with a different set of numbers behind it. Just in case. It's simply about offering options.
The construction world isn't all about you and what you think is crap and about you methods and your favored materials. Nor is it all about me. There are different strokes for different folks based on our building locations, circumstances, surroundings, working conditions, etc. One size most definitely does not fit all.
consider taking your own advice
You might call it 'the end', but you don't know how to mind your own advice.
I'm not surprised to hear the old "different strokes for different folks" argument whenever someone runs out logic. Sorry; that rational doesn't accomodate B.S.
It is B.S. to bring up Kerdi DS for someone who is not considering a continuous steam unit in their house...let alone no steamer at all. I don't care who it is.
It is B.S. to bring up catering to an AHJ that inspects on personal preference. Our inspecters inspect on the code. That happens to be the IRC. I don't allow them to deviate from that without disputing it to a higher level. The entire document doesn't mention Kerdi one single time. If you have to cater to someone that doesn't understand surface waterproofing or vapor drive, then I would question why you choose to put (or leave) yourself in that position.
Finally, it's B.S. to talk about a particular level of vapor permeance (beyond water proofing ) that should be used for a regular shower (not steamer) based on what kind of wall section or cavity insulation one is using. I've certainly never seen the IRC dictate the conditions under which a shower enclosure needs to allow water vapor to dry to the inside, let alone the outside. That's where, my friend, the real B.S. started--and should end.
Cheers!
Mongo,
Remember Andy's tagline? Trying to teach a snot nosed kid the difference between a vapor barrier and a vapor retarder seems to fall under it.
KK
yep...
Good ol' andy.
I'm trying to follow Andy's guidance. Guess the easiest way to follow is to simply be done.
re-check your supporting data
I did some additional research on some the facts you use to defend your positon Mondo. That's one of the reason I like this forum; it compells one to sift through the B.S.
Here are some facts you brings up and that folks should be aware of:
1.Kerdi DS has a very low perm rating (.18) but it's application is for continuous use steam rooms. Its mil thicknes is 20. So it's basically for commerical applications. it has no bearing for residential construction. It's a fine product, but there is no sense in even bringing it up as methood for getting under the 1.0 perm rating threshold for vapor barriers (not that it matters in regular shower areas anyhow) for residnetial applications.
2. Red guard needs a DRY film thickness of 30 to get a perm rating of .35. That would mean you would have to paint on the liquid membrane @ 3x's the thickness of regular kerdi (8 mil @ .9 perm) to get this rating. IMO, that doesn't happen in the "real world". And good luck proving you have evenly appled for this mil thickness if you do have failure in the Red Gard. Conversly, the Kerdi membrane is installed as 8 mil everywhere--every time.
I guess that is why Custom Building Producets only warranties the product only (not the10 yr full tileinstallation like Schluter does) for only 1 year. IMO Red Gard is junk...and also why I wouldn't even bring it up as a waterproofing option for showers. IMO, the the only reason you would use it is you're cheap or ignorant--or both.
Get used to it. Par for the course with deadnuts.
Bi Polar if you ask me.
Yes, either plastic or #15 tarpaper will work just fine. Neither tile nor cement backer are waterproof so you need to stop the water before it gets to the insulation. Red Guard on top will stop it before it gets started. You can also save a little time and money and use Denshield instead of the cement board as long as you use Red Guard on top. Kerdi works well too but will cost you about $600.00 more than the other methods and isn't really any better.
fuzzy math
Kerdi membrane is about $2/sq. ft with thinset. Typical tub/shower surround is approx. 75 sq. You do that math. It ain't $600 more than other methods. Also, it's better because Schluter guareentes it for 10 years--material and installation! IMO, you won't find that warranty with every other system.
I've done the math on every Kerdi shower or tub I've done. And my figure is right on. I like Jerdi, just not the price .
maybe use a calculator
Really? They must have burned down the school house just to get you out of the third grade.
Any kind of plastic membrane is only as good as the penetrations, use 15# felt.
There shouldn't be any penetrations with a shower waterproofing system-except plumbing fixtures. And Schluter makes gasketed components to handle those for the Kerdi system.
what a bunch of BS
Dan, you're talking about plumbing leaks here; not shower surface waterproofing. No material or best construction practices are designed to combat that issue.
You're so far off base that it isn't funny.