I posted this information on the kerdi Board discussion but since it sheds so much light into Perm Ratings and how they work both in commercial and residential I tohught I would share the same info here.
I'm tiling two new Kerdi Showers in Yaletown as we speak. The shower pans are done with a hybrid approach of Kerdi DS and Noble as a secondary crack isolation layer and Ardex 8+9 as the primary waterproofing product. The walls all have Kerdi and Ardex 8+9 as back up. The showers are totally waterproof and the master shower just passed a 65 hour flood test.
Here is the photo I sent my client at days end yesterday. You can see my white coffee cup in the Kerdi Board niche to the left. If you spend some time here on Terry Love's Forum you will see a common theme. I dislike Jim. Jim dislikes me. I post pictures of construction. Jim does not. Jim is not a pro. I am. Please consider the source of your information and understand the Jim works day and night to promote Schluter and the John Bridge Forum. Sadly I think this his job in his golden years.
Enough about that.
Q: Which is better for a steam shower? Kerdi-Board or Kerdi DS
There is no contest here. Kerdi DS hands down by a land slide. Kerdi DS is what is used in Germany for steam shower construction. Germany is where Papa Schluter was born and the country of origin of the material (Kerdi). So I like to think if Kerdi and Kerdi-Board are not allowed to be used in Germany - why here in Canada? Why here in the US?
I ask a lot of questions and I have found out that here in Canada and the US much of what we have comes from the TCNA. The TCNA is made up of the manufactures of these products. So it is the manufactures that make the rules we follow. I don't think it's exactly the same way in Germany.
Regardless of this. Kerdi and Kerdi-Board are not acceptable in Germany.
Here in Vancouver I order my Kerdi DS at Ames Bros Tile. Ames Bros has been in business here in Vancouver for over 100 years and are members of my local NKBA Chapter (Nation Kitchen and BAth Association). I pay less for Kerdi DS than the average person does for Kerdi at Home Depot. Home depot sells Kerdi for about $3.00 per square foot - about double what I buy it for. Kerdi DS is about $2.20 a square foot. An up charge from roughly $1.50 per square foot.
Remember Kerdi Board in Vancouver at Home depot is $3.75 plus.
Kerdi Board serves a need. It caters to fat, lazy, weak and old tile setters. It also caters to hotels since a typical installer is required to build about 13 showers per day. Foam products are made by everyone.
Laticrete sells them - I've seen their shower base and hate it.
Noble makes them - I've seen their niches and hate them - like Schluter no pre-slope.
Wedi makes them - Never seen them but hate them all the same.
My hatred to the products is not company related it's construction material related.
The sound of water hitting tile in a foam shower creates a sound that can make the hair on your neck stand up. If you need to repair a tile or replace one any hammer strikes will crush the foam. Dumb idea. Crappy product.
They are cheap (just a little bit).
They are light (which is important if your old)
They are fast (if your goal is volume not quality).
I have a couple weeks left in Yaletown and then it's out to East Vancouver for a basement barrier free shower. This shower will be a full Kerdi DS shower with floor heat throughout the bathroom and into the shower. It features Dornbracht shower fixtures and a custom "Whipple LED Shower Niche". You can see it here in rough stages.
Kerdi DS is my new favourite material of choice. I like it because I can order via Ames Bros and not special order it from the States. I like it because here in Vancouver I have local support from Schluter (Bob Weins) and Ardex (Don something). If Noble Company gets their act together and comes up North I will switch back to Noble Seal TS. But really I'm not holding my breath since California is a larger market to them than all of Canada.
Last week Eric from Noble Company did a presentation on waterproofing materials. It was hosted by Jim Olsen of the NTCA. Durning the 50 minute presentation Eric posted this slide. It shows the different levels of water migration in steam showers depending on the Perm Rating of the wall assembly.
Take a look at these numbers.
When you study this chart you can see the lower the perm rating the lower the amount of water can enter a shower's system. No doubt Eric from Noble Company included this slide. During a NTCA presentation Eric can not say his Noble Seal TS is better than Kerdi (it's a presenter rule in the US and Canada) - but it is. Eric can not say NobleSeal TS is better than Kerdi DS - but it is. Eric can not say NobleSeal TS is better than Kerdi Board but it is.
NobleSeal TS is by far the King of the sheet membranes for showers. Look at the chart.
Remember the email from Bob Weins? Here it is again.
The facers on the Kb are waterproof, the facers are a derivative of kerdi and have similar properties. The foam has additional benefits such as perm or vapour diffusion. Kerdi has a per of approx .74 / Kb .45
Sent from my iPhone
Commercial Projects Manager Western Canada
604 790 8746
So if the Perm rating from Kerdi is 0.74 and the Perm Rating for Kerdi-Board is 0.45 here is the amount of water for each using the example above as the size of the shower.
A Steam Shower Built with Kerdi would let in 28.42 Oz of water (28.42 oz )
A Steam Shower Built with Kerdi-Board would let in 17.28 oz of water (17.28 oz)
Lets look at my favourite two steam shower systems. Kerdi DS and NobleSeal TS.
Kerdi DS Perm Rating is 0.19
NobleSeal TS Perm rating is 0.05
To meet the new specification for commercial steam showers the membrane needs to be less than 0.50. I find it interesting that Kerdi Board is listed at 0.45 (meeting this requirement) but is not recommended for commercial steam showers. Maybe it's because the cardboard layer gets soaked before the vapour retarder is slowing down water vapour? Hmm - what do you think?
So if we use Kerdi DS and NobleSeal TS in the same example we get this data
A Steam Shower Built with Kerdi would let in 28.42 Oz of water (28.42 oz = roughly one full bottle of wine)
A Steam Shower Built with Kerdi-Board would let in 17.28 oz of water (17.28 oz = roughly 2 glasses of wine)
A Steam Shower Built with Kerdi DS (perm 0.19) would let in 7.3 oz of water (7.3 oz = roughly one glass of wine)
A Steam Shower Built with NobleSeal TS (perm 0.05) would let in 1.92 oz of water (1.92 oz = roughly 1/4 glass of wine)
To meet the requirement for commercial steam showers you need a perm rating of 0.50 or less. With the example above this would equal 19.20 oz of water or roughly 3/4 bottle of wine.
Pretty clear to see which is the better material and why we recommend only Kerdi DS and NobleSeal TS to our clients.
A typically steam shower session is under thirty minutes for most of my clients and most use their steam shower one to two times per week - so this data is very close to an average steam shower. Lets look at a larger steam shower - commercial size. Maybe 8-15 people.
20' x 15' x 9' foot print. Lets say it runs for nine hours every day. The size of the steam shower is say ten times bigger.
A Steam Shower Built with Kerdi would let in 255,780 Oz of water (255,780oz = roughly 9,837 bottles of wine or 428 cases (12 bottles per case)
A Steam Shower Built with Kerdi-Board would let in 155,520 oz of water (155,520 oz = roughly 5,981 bottles of wine or 271 cases (12 bottles per case)
A Steam Shower Built with Kerdi DS (perm 0.19) would let in 7.3 oz of water (657 oz = roughly 25 bottles of wine or roughly 2 cases (12 bottles per case)
A Steam Shower Built with NobleSeal TS (perm 0.05) would let in 1.92 oz of water (264 oz = roughly 10 bottles of wine or less than one case of wine (12 bottles per case)
What do you want in your next steam shower? Now with Kerdi Board you are wetting the cardboard layer so your wall assembly is weaker. With a Kerdi DS and cement board shower nothing weakens in the backer board. With a NobleSeal TS and concrete board layer nothing weakens in the backer board.
Not sure how Jim will twist this data but as always you should double check the facts. Eric the presenter of this class can be reached at Noble Company. His email is Eric Edelmayer <email@example.com>
Tell him John Says Hi.
Take another peak at this failed Kerdi Board Steam Shower....
Take another peak at the tent card on display at Fontile. Best you understand all the facts before reading things a marketing team puts in front of you.
Advertising cards say - Vapour Tight & Vapour Retardant I don't think so.....
A little knowledge is a dangerous thing. Jim is claiming someone at Schluter told him a slice in Kerdi Board is OK. Jim is not a pro. I have bought Kerdi Board to prepare a new test - a second round of Kerdi Board is coming. If you would like to see all the other Kerdi Board tests I have done - you can access the pictures here:
Kerdi Board Testing
Kerdi-Board testing pictures located at the link above