Weatherization Nation 7: Rainscreen on a Roll

September 12, 2019

Mesh sheeting creates a drainage space between the siding and weather-resistive barrier (WRB) allowing walls to dry much faster which makes them last much longer

Welcome to ProTradeCraft’s Weatherization Nation. A show about building smart from the start. Last week we were drying in the roof with a combination of peel and stick membrane and a synthetic roofing underlayment called Protec. 

We went over a couple of critical flashing details and some storm-proofing extras.

This week,  we’re going to cover the walls with a high tech rain screen product called DrainVent. It creates a drainage space behind the siding so any water that sneaks back there can be directed away from the house. It installs a lot like home-wrap with a few differences.

Let’s look at it in animation land. 

Sketch Desk: Rainscreen uses gravity to protect walls

The WRB provides a drainage plane to shed liquid water, and the DrainVent rainscreen creates a gap between the siding and the WRB so that water drops out of the picture. Fortunately, when the water seeps into the ground, it will be carried away from the house buy a well-crafted footing drain.

Installing siding tight against the WRB can trap water causing the siding to fail early, and it can push water through any minor holes in a WRB.
At the bottom of the DrainVent, fold the flap up and under the mesh, to prevent any bugs from moving in.

The facing is a filter fabric that can act as a mortar stop, as explained in the ProTradeCraft Demo Home

Tom Baida: So what that filter fabric does, is in the case of stone and stucco, this will serve as the intervening layer. Typically you're installing a weather barrier first, and then some sort of intervening layer, whether it's a black paper, or in this case, this filter fabric will serve as that secondary layer.

And what that filter fabric does is ensure that no mortar infiltrates through into the honeycomb, into the entangles mesh, in order to ensure that you get that proper draining and drying that your after.

At the bottom of the vent, fold the flap up to prevent any bugs from moving in.  With the HomeWrap doing double duty as an air barrier and an extra rainscreen layer, the durability of this wall is nothing to bark at.

Git er Done: Fasteners, seams, and rainscreen installation details

Tom: What we try to do is minimize the fasteners because normally we just want to get this up on the wall, understanding that the cladding will go on soon after. So we want to try as best we can to avois additional holes in our weather barrier. 

So what the installation guidelines call for is a fastener at the top, toward the bottom, and one in the center every other stud.

But before fastening theDrainVent, it needs to be positioned. Snap a line 48 inches above the bottom of the housewrap to keep it level. 

The DrainVent can be rolled over the whole wall and cut around the windows. When they get to a door, they cut the roll, smooth the DrainVent over the wall and staple it into place. 

It turns out, the second course aligns with the tops of the windows, so they can piece in the rainscreen between windows and pretty much roll full sheets over them.

Before overlapping the edges, Christiano does something that many contractors have never done: he reads the instructions.  

In them, he verifies that fasteners should be kept away from windows and doors.

Christiano: Staple six inches from the windows and six inches up.

Keeping fasteners back from windows and doors eliminates a lot of holes in critical flashing tapes. 

He also verified that the edges do not overlap, but instead they but each other. The waterproofing is already done at this point; this layer is strictly to allow drainage.

Overlapping edges would create a hump that would make installing the siding difficult.

The bottom flap folds down but is only is important if using stucco or lick-and-stick stone veneer. 

The crew continues placing DrainVent between and around the windows before they climb up the big ladders to put up some long swaths of the rain screen. Again, it is set to just but the course below, not to overlap it.

The seams do not need to be taped unless using stucco, in which case you’d tape the vertical seams. 

Next week we’re going to wrap up season one of Weatherization Nation with some blower door-directed air sealing and a quick recap of the season.

 

Previously: Roof Dry-in, Flashing, and Underlayment

 


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