Sorting through the Liquid Applied Weather Barriers
After a productive discussion on Weather Resistive Barriers behind a masonry wall, I am starting this new thread in hopes of hearing people’s experience and opinion about the newfangled Liquid Applied Weather Resistive Barriers (LAWBs). In the raging debate about housewraps and tapes and claddings, the LAWB solution seems to overcome some of the inherent problems.
Martin has already written on the topic: https://www.greenbuildingadvisor.com/node/17000
Three options are on the table: there is a Tyvek brand product, Tremco has a product called EnviroDri, and Dana Dorsett suggested using 2-part spray foam (not really a liquid, but kind of the same idea.)
Tyvek trains contractors to apply it’s LAWB. Their site pointed me to a single contractor in Ohio, and I got a quote for close to $3 a square foot. (Of course, that’s more than just rolled-on goop: there’s seam sealers and tapes that are incorporated in the process.) That’s WAAAAAAY more than I figured this process would/should cost, but I’m willing to adjust my cognitions.
Tremco neither answers their phone nor responds to their online query form. I can’t seem to find anything on Google that would point me to a contractor or even a place to buy the stuff.
Spray foam? In the range of a buck-a-foot, and I can apply it. But there’s no documentation or manufacturer support for this use, as far as I know.
Would appreciate feedback/advice. Thank you all.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Andy,
There is another set of liquid air barrier products made by Prosoco - Fast Flash, Cat 5, etc.
http://www.prosoco.com/
These products sound really cool. Here is a video by Hammer and Hand, a design build company in Portland, OR talking about using these compounds. It's really a nice informative video.
http://vimeo.com/44143840
I don't about the cost. I assume it is expensive, but sounds very effective.
Andy,
STO corporation has 3 different levels of permeability and two different ways of handling joints in their liquid applied WRB portfolio..
Andy,
If you can apply closed-cell spray polyurethane foam for 1/3 the cost of a liquid-applied WRB, I would choose the spray foam.
The key to longevity and performance with any WRB is to include a vented air space between the WRB and the siding. If you do that, and if the spray foam is conscientiously installed, I see no reason why the spray foam wouldn't work well.
Thanks, Martin. If anyone has experience with any LAWBs coming in cheaper than $3/foot, do let me know!
With spray foam how critical would you say is attending to the seams--spanning with a fabric tape/applying joint compound, etc. How easily will minute movements in the substrate telegraph as cracks through a half-inch to an inch of spray foam?
And just briefly, with flanged windows and doors, could you comment on how those would be installed? Clearly, they'd have to be incorporated as usual into the WRB... can't quite figure out what would be the protocol with such a thick layer....
Andy,
As I recall the STO products are about $100/pail that covers 400+ sq ft. I think any contractor quoting above $1/ sq ft is a rip off! Certainly as a DIY it should be under $0.50 including the joint tapes.
While I was investigating these products, it seemed like a better way to go would be to use the peel and stick membranes (normally roofing) especially for the one time do-it-yourself'er. It's possible that spraying could be easier on certain builds.
No need for spray guns or hunting down limited stock or learning on the go.
You don't need to worry about flashing seams because the membrane flashes everything.
You can also save a bundle as these membranes are commonly stocked and made by numerous vendors, although none are typically permeable.
You also get to progress as needed, working in sections rather than having to spray everything.
Grace makes a permeable version but you have to hunt for it.
I saw a similar discussion on LinkedIn not long ago. Someone posted this video which I thought was pretty helpful:
https://youtu.be/E82kc9nZUuc
We are just finishing up the install of the Prosoco line of Fluid applied WRB here in Seattle and are quite pleased so far. We decided based on seeing a number of local buildings that have already used the product, and also that the product was developed by construction pros and chemists who know our climate. We're using the Joint and Seam for nail holes/sheathing seams, the Fast Flash for window openings, and CAT 5 which is rolled on to the entire exterior.
We are using a rainscreen system along with installing cedar shingles on top of all of this.
Regarding costs, the STO products typically run +/- $100 for a 5 gallon bucket (both the fill and coat products). If you choose to use this for your WRB, then expect to pay ~ $1.00 square foot for materials alone. You need their self-adhesive fiberglass tape at all joints, their Gold Fill at all joints, and their Gold Coat on all surfaces. The tape is a good percentage of the material cost.
I built a mock-up wall using the Prosoco product. The one thing I really like about the Prosoco system is that it does not require fiberglass reinforcement tape (reduced installation labor). The cost of their joint filler and flashing compound is roughly comparable to the STO tape and fill system; however, the pricing differs in a big way when you look at the coating products.
STO Gold Coat ~ $100 / 5 gallon bucket
Prosoco CAT 5 ~ $500 / 5 gallon bucket
Coverage is comparable for these two products. Practical application rates are approximately 500 sq. ft. per bucket, at least when used over plywood. Textured materials, like OSB or CMU, will have lower coverage.
Thanks to everyone who has contributed here--at this point I think I'm going with STO. Where I am, their distributors offer great customer service so far, and the combination of cost, DIY application, and online tech support has swayed me to them.
As I mentioned, I looked into the liquid Tyvek, but apparently it's only available to trained installers, which, of course, is not a bad thing but it did skew the cost factor out of reach.
Haven't had time to investigate other brands. Have to work and sleep sometime.
I've also decided to not try Dana Dorsett's idea of using expanding foam, since I'm just not brave enough nor experienced enough to go rogue, and the STO system may come in cheaper anyway.
The STO guy I'm talking to is recommending Emeraldcoat, which seems to be the same as Gold Coat in every way except with a higher permeability (6 perms vs. 15). Says that's important behind masonry. Whatever--a guy selling STO at another place told me I need Gold. This is just how it is in this field.
For added protection, I'm considering overlaying STO DrainScreen (3d drainage mat with another WRB) on the southwest and southeast walls, with the expectation that it will help with the sun-driven vapor issues (and provide additional protection against clogging mortar droppings...)
Just as long as it stops raining here soon....
Daniel,
"You need their self-adhesive fiberglass tape at all joints, their Gold Fill at all joints"
NO and NO! STO also allows the elimination of the self adhesive tape and elimination of the Gold fill by substituting their mesh tape embedded in Gold coat or Emerald coat. Yes the joint treatment is a good percentage of the costs, about 50% but not 75%. I guess it's ok to expect to pay $1/ sq ft and be pleasantly surprised when it's closer to $0.50/sq ft.
Andy,
Have you looked at Greenguard DC14 instead of the STO drainscreen. I like it because it, in addition to providing drainage adds a significant vapor retarder preventing solar driven moisture from moving inward.
Followup a few weeks later: I am nearly finished installing the Sto system. On top of my OSB SIP panels, the distributor's tech guy (a LEED AP) suggested going over it first with Emeraldcoat, then taping the joints with Gold Fill and mesh, then a second coat of Emerald. Cost of all this is somewhere around $1.25/sq.ft. in materials. I feel confident that I'm getting a durable and uninterrupted exterior air barrier that also happens to be waterproof, with enough permeability to allow drying if necessary. FWIW, since I'm cladding with full-thickness limestone, I will also be overlaying a drainage mat (probably Sto's Drainscreen, which comes in cheaper than anything else I've seen, at 60 cents/sq.ft.)
It's not hard to apply, but it is labor intensive. I have chosen to roll rather than spray the Emeraldcoat since I'm moving slowly, in stages. There are several options for joint treatments, and they're all compatible. The joints are very time consuming and the results aren't pretty, mostly due to the rough nature of OSB. The system wraps into all the rough openings, so that's a nice bonus. I've installed nail fin windows, without any other flashing or pans, and will be sealing their tops and sides with Sto Fabric embedded in Emeraldcoat.
Concerns? First and foremost, I worry that OSB is too rough to achieve a perfect pinprick-free membrane without many coats. All of Sto's videos show the product applied over foam or other smooth surface, although their literature says OSB is an acceptable substrate. Perhaps spraying would be more effective, but would also empty the pails too quickly. Part of me wonders if there's any functional difference between this stuff and plain old latex paint--it rolls the same and at 17 has the same perm rating. I also wonder if I shouldn't have just gone with 30-lb felt and been done two weeks ago for 90% less money.
Learning lots; everyday I prove the old saw that the more you know, the more you realize you don't know.