Rainscreen question

[Mark Parlee]

These are pics of the backstop system

see post 15 prior page for Tremco details

[Ted S.]

Ted, Why do you prefer Emerald Coat over the other products?............ Are there drawbacks (besides higher costs) to using a fluid applied air and water barrier?

I don't necessarily prefer one Sto Gold, EmeraldCoat or Backstop product over the other, I think they are all pretty similar. The biggest difference is that the EmeraldCoat was Sto departure from EIFS with this fluid applied air/moisture barrier technology.

The 1995 North Carolina hurricanes all be destroyed the EIFS industry, the industry figured if they were going to get blamed for the water leakage, they better take total control of the cladding system. When introduced, all of these products were exclusively used within the EIFS systems providing complete cladding system from the sheathing to finish vs just the insulation and finish system of the previous NC seacoast failures. This allowed them to really build a watertight assembly as part of the EIFS system.

I always said, if it weren't for piss poor workmanship back in he 90's, we would not have these new fluid applied products.

So after several years of using the Sto Gold in EIFS, someone came up with the bright idea to try it behind brick. I believe that was the event which transpired Emerald Coat so I just have it in my head to go to that product when not being used in an EIFS system.

As far as the Tremco product is concerned, I have little experience with it although plenty of experience with similar products. I am just hesitant of it because of the black color, we just had a problem on a project that used a winter formula peel and stick that was all black, the heat gain was significant and caused some delamination problems. This was in the winter mind you.

As for as disadvantages of fluid applied membranes, thickness consistency, environmental conditions at the time of application and general workmanship would be at the top of the list. The nice thing about sheet applied as that it is one consistent thickness and manufactured in a controlled environment.

[Dick Seibert]

Ted:

With all of these membranes you create a dual barrier by sealing up the outside if you put sheetrock or plaster on the intside. Water is eventually going to get in from the outside, someday, maybe not for 30 years, but someday it's going to happen, we don't build submarines. What about moisture entering from the inside? I've read that it averages 5 gallons per day per occupant, that's hard to believe but I've read it several times.

My liability insurance specifically forbids EIFS, and they won't write anyone who has installed EIFS in the prior 10 years, isn't sealing up the exterior with a membrane the same as installing EIFS? In fact the same companies make it. When failures occur like they did with EIFS aren't the insurance companies going to do like they did with EIFS and refuse to insure the contractors who have installed it within the last 10 years for the next 10 years? When the EIFS thing blew up I had to sign a certificate under penalty of perjury that I had not installed EIFS within the last 10 years.

The prescriptive code doesn't allow it, it is up to the discretion of the CBO to allow it under the discretion he is given under the alternate methods and materials section of the code, I recently posted the code on this issue for Bill Robinson. What I am seeing around here is CBOs allowing in on commercial buildings but not on residences on the basis that commercial buildings run constant ventilation systems, our code now calls for constant ventilation systems but most CBOs are not requiring them or contractors or owners are disabling them because of the noise and cost of running them. According to my electrician when forced to comply with the ventilation requirement they are wiring all fans on constantly (usually bath and hood), then disabling them after inspection. So if you are depending on removing all interior moisture with fans what happens to when the fans are disabled? Moisture in walls equals dryrot.

Why expose yourself to these potential problems and liabilities?

[Ted S.]

Dick,

I don't know the exact status of the insurance industry but there must have been some considerable loosening in regards to EIFS as it is a common cladding at least here in the Northeast. I know two decent size installers, both of which are Sto installers. I live in a house which I designed a cement board stucco system using Sto products, it went on to become "Quicksilver" but I used a number of trim pieces they didn't approve. I told the rep he had no balls, then when they saw my bullnoses, they loved it. Just the other day they send a customer buy to sell the system. That is a dynamite company by the way. Those guys love what they do.

As for ventilation, you know the way I feel. We shouldn't have a shred of insulation in our houses until we can make them so they can dry out on their own and have good indoor air quality.

[Lavrans]

Question- when I looked at using one of the fluid applied systems- I think it was the STO product, I thought they had a fiber tape that was used over seams to flashings? I'm not seeing that in Mark's photos (or maybe it's there, but not showing up?). I would be pretty wary of not having something like that to cover the transition between dissimilar materials.

Don't you worry it will crack over time there?

[Ted S.]

Its in there. The mesh tape is self adhesive, it is stripped in with trowel grade material, once the joints and terminations are detailed, a paint grade product is rolled over the joints and the field. If you look close at one of his photos, you can see the mesh telegraphing through. The light blue product I believe is Backstop by Dryvit.

If you got this stuff on your hands, clothes, tools and in your hair, you'd be impressed with its durability.

[Mark Parlee]

Lav
It's just not showing up.
There is mesh or fabric on all three of these systems.

She stow wraps inside the entire RO; this RO was framed bigger in height and a piece of beveled siding was installed at the sill
the fins are set in sealant the a mesh is applied and embedded in the sto.

I sent you three movies to watch of the process.
Anyone else that wants to see them email me and I will send the download link

Ted, you are correct

[Lavrans]

Nice- yeah, I just couldn't see with my phone- looked like nothing there.

How does this stuff do over time with the penetrations that will occur with the addition of siding? I'm pretty sure it's good initially, but what about 10/20/50 years out? Have you taken any apart after 5 or 10 years? What does the product look like after several years?



Edit- just going to point out that I have used liquid applied systems under tile several times. One product failure, where the material separated into two at the fabric layer (two coats on the deck, then laid mesh into the third coat when wet, then two more coats over the top; each pair of coats being applied perpendicular to the one below it)). The rep who looked at it ruled everything as possible except the material- too thin, too thick, too dry, too wet, too dusty, too hot, too cold. Except that everything was done as per their directions, within the time limits, and in a place with no visible or obvious dust. That was an annoying experience I still haven't really gotten over; I don't trust them very much.

[Ted S.]

How does this stuff do over time with the penetrations that will occur with the addition of siding? I'm pretty sure it's good initially, but what about 10/20/50 years out? Have you taken any apart after 5 or 10 years? What does the product look like after several years?

The question of self healing is a good one, the Sto products mentioned above and the Backstop are non-self healing. I am interested in the Tremco product, there are a number of similar products that are self healing. Mark, is that product self healing around fasteners?

In terms of durability, keep in mind these are commercial systems that have been around for many years, I would not put them in the class of most house wraps, they are simply superior.

[m beezo]

wondering how thick they are? The blue stuff looks pretty thin which makes me wonder about it durability. The black color concerns me also. It looks almost like the spray on basement coatings. But it is a different product?

[Lavrans]

wondering how thick they are? The blue stuff looks pretty thin which makes me wonder about it durability. The black color concerns me also. It looks almost like the spray on basement coatings. But it is a different product?

Mark- they do have pretty strict guidelines for thickness of wet-film and dry film application. I use a wet-film gauge to figure out how thick my application is. They are good to use with anything that is critical, IMO.

[ThingOfBeauty]

Dick, the systems being discussed here are vapor permeable so they are no different than your 60-minute paper in terms of trapping moisture. Of course I know you don't even like plywood so not sure it will meet your approval even with permeability.
I think your worries apply to buildings with Grace Perm-A-Barrier (or any impermeable peel-and-stick) on them, if the insulation is on the warm side of the Grace. But these fluid systems allow moisture to move through them, should be less risky in many situations.

I share the concerns over workmanship and environmental conditions...in fact have seen major problems with both. However on balance they seem a good way to get air control and WRB, if you can get them done right.

Lav, I have seen a well-known liquid-applied waterproofing re-emulsify under a tile floor. The floor had no pre-slope so it was pretty wet, but to see that pink goo under the tiles was really something. I would say a rain screen is a good idea.

Ted, have you seen any destructive testing of fluid-applied membranes under EIFS? That would be a good test of how it holds up wet.

[Dick Seibert]

Dick, the systems being discussed here are vapor permeable so they are no different than your 60-minute paper in terms of trapping moisture

Ted:

You mean even that black tar looking stuff is vapor permeable?

[ThingOfBeauty]

They make both to be fair, that is vapor-permeable and also vapor-impermeable.
Tremco's ExoAir 220 is one of those black fluid applied barriers.
It's permeance is 12, per the spec sheet you can painstakingly access via Tremco's web site:
http://www.tremcosealants.com/applic...d-applied.aspx

That is about the same as Typar, or dry felt for that matter.