PPD - WALL ASSEMBLY MOISTURE CONTROL
Hi all,
I would greatly appreciate some additional feedback on the question below.
Here's how I thought about it, and unfortunately, I got it wrong. I understand that EIFS is the worst option when it comes to moisture control. However, I assumed that the first assembly wall, although not great, still has components like a weather barrier. On the other hand, the 2nd assembly at the bottom doesn't have any vapor/air/moisture barrier. So, my thinking was that the first assembly might have mold/moisture collected on the exterior, but at best, it would evaporate. However, the third assembly would collect moisture inside, making it the worst assembly.
I would love to hear how you would answer this question and why. Additionally, any guidance on how I should approach this type of question in the exam would be greatly appreciated.
Thank you.
Considering moisture which wall assembly perform better than other?
-
Lemara,
The general consensus right now is that an air space/vapor barrier ext wall is the best. Hard for me to evaluate those wall details without annotations.
Research 'rainscreens'.
Hope this helps!
Rebekka O'Melia, R.A., NCARB, B. Arch, M. Ed, NOMA, Step UP ARE 5.0 Courses
-
Hi Rebekka,
Thank you for the note. I am making an effort to be aware and respectful of the material. Here is sketches for the wall assembly to the question above. So i think both walls not great but #1 missing air space, #2 missing air/weather/vapor barrier, and so which one is worse?
Thank you,
-
Hi Lemara,
This video on water management strategies in walls might help you evaluate these types of questions:https://m.youtube.com/watch?v=UYTCg6IR338
Historically the problem with EIFS (also called synthetic stucco) walls was that they were either adhered or mechanically fastened so tightly to the water control membrane behind them that no drainage could occur. Only a very small amount of water made it past the EIFS (through micro cracks) but the water that did had nowhere to go. It would remain “perched” against the sheathing and water control membrane. At fastener penetrations, it would be driven through and the wall would rot. There were lots and lots and lots of lawsuits. What’s kind of interesting is that now EIFS is quite a low-risk cladding! This is because we learned from our mistakes and enough include a tiny gap behind the EIFS for drainage. We still adhere the EIFS to the wall, but we apply the adhesive is vertical strips and the adhesive itself bumps the back of the EIFS off the water control membrane just enough (like 1/16 inch) for drainage. But lots of people only associate EIFS with failure and avoid it. (People also think it looks cheap and ugly, but that’s a different category of problem:)).
Your second assembly is a “mass wall” (see video). Usually brick veneer walls are “drained walls” (again see video) in that they’re installed in front of a standard wood or metal stud wall. But your example here is installed in front of a concrete wall. This is less common. Water control membranes (which the code calls WRB) are not required for mass walls and are often, but not always, omitted. The short explanation is that mass walls just have an inherently greater ability to store and redistribute water before anything gets damaged.
Hope this helps. The wall assembly stuff is not an enormous part of the exam. But it is a big part of professional practice for most people.
-
This is a different video on hydrostatic pressure that might help you with additional context on why leaks occur:
Please sign in to leave a comment.
Comments
4 comments