Mastic Location on a section
Hi, can anyone tell what the mastic and wwf is for the cavity wall, and where are they on the Wall Section?
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We made a video explaining that here
https://youtu.be/dkM6AWE1sls
—Michael Ermann, Amber Book creator -
Where is this question from?
Typically you'd apply mastic (or some other kind of sealant) at the top of the metal base of wall flashing (also called "through wall flashing"). This is the L-shaped line that sits on the foundation wall. The mastic seals the top of the metal through wall flashing to the sheathing. The WRB (water resistive barrier, which this drawing identifies as "sheathing paper") laps over top. The purpose of the mastic (or sealant) is to seal the top leg of the flashing to the sheathing. That way incidental water that gets behind the WRB through all the fasteners (brick ties, for example - not shown in this section) can still drain to the exterior*.
The weep "hole" is that shaded thing in the bottom course of bricks. The terminology is not quite right, because it's not actually a hole. We'd just call what's shown on this section a weep or a weep-vent. What it is in real life is a square piece of plastic mesh that fits in the vertical mortar joints along the bottom course of bricks. If you google "brick weep" you'll see pictures that make it more obvious.
I have no idea what the welded wire fabric would be for in this context. This section shows a typical brick veneer wall. These do not include welded wire fabric. I have probably worked on thousands of these walls. No wire. I wonder if they mean brick ties? Or masonry anchors? These are used to connect the brick to the studs. All brick veneer walls should have them (google "brick ties" to see what they look like), but they're frequently not shown in section drawings. I don't see them here.
If you found this question confusing, I wouldn't stress -- it's just a bad question. (And it's bad enough that I wouldn't trust anything else in this study source, either.)
Christine Williamson
* PS: This isn't typically a whole lot of water (most of the water runs down the exterior face of the brick, some water runs down the cavity behind the brick, and then a very, very small amount runs behind the WRB if it's a "mechanically attached" WRB (any kind we attach with staples or nails, like Tyvek or tar paper). Mechanically attached WRBs are inexpensive and very, very common, especially in residential construction. But not all WRBs are like this! Some are fully adhered or fluid applied. These don't have the same issue with water getting behind them and running down the sheathing (because they're fully bonded to the sheathing). If this same section were drawn with a fluid or self-adhered WRB, the membrane would still lap over the through wall flashing at the base, but we wouldn't need mastic (or sealant) because the fluid or self-adhered membrane would already be sealing the top of the flashing to the sheathing.
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lol! Michael commented right before me... with my own explanation! Hope at least one of the two helps clear things up:)
Christine Williamson
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