Video: How to Hang Airtight Drywall (3 of 3)
Hanging the Walls: Install polystyrene Energy Blocks behind electrical boxes, and cut back the cured spray foam before taping
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Produced by: Colin Russell and Daniel Morrison
Justin: Hanging drywall on an exterior wall uses the same fundamentals as hanging the ceiling, but there are more holes: electrical outlets, windows, doors, and service chases. Before hanging the walls, cut back all of the canned foam applied to the ceiling perimeter, any obstructions around windows, and if not done on the pre-construction walk-through, seal all of the gaps between framing members.
Myron: Remember, you want to keep things clean, because wherever the adhesive is going to be used, it won’t stick as well if it is dusty and dirty. We’re going to have a seam up here, and then another seam right down here. That way, our butted seams are falling in the window frame area.
Justin: Again, the face of the studs gets a thick bead of adhesive. Windows get the royal treatment. Use both latex caulk and polyurethane construction adhesive.
Myron: I’m going to be careful that when I apply the adhesive, I want it to actually intersect with the caulking that we have on here so that we get a continuous seal. You’ve probably noticed that I am really piling on the adhesive and the caulking. The tip here is: this is not the place to skimp on materials. Use plenty of it, because we really want to make a good seal.
Justin: Place the left edge of the sheet into the corner and then lay the rest of it flat against the framing, caulk, and adhesive.
Myron: Looks good. It’s important that when you fasten the drywall, you put it right into place without moving it around and smearing the adhesive.
Let’s be careful not to smear it. I want to go right where I want to put the top edge in first. I’m good here.
I know that we have used drywall adhesive and caulking around here to form a nice air seal, but we also need to properly fasten the drywall. This actually holds the drywall tight against the framing and into that caulking and adhesive, which makes a real nice tight air seal.
OK, I’m putting the panel right into place. Once again, because I don’t want to smear the adhesive, I have to lift it up slightly. You can’t fit drywall in tight, so you’re always going to end up with that little gap. But we’re going to use that to our advantage, and have that as a little gap that we can foam and get a really good seal along the bottom edge.
One thing I really like about using a latex drywall adhesive is that you actually have quite a bit more open time, so we can apply the adhesive to the entire wall, and even take a half hour later and still be hanging it.
You never know what you're going to run into on these remodeling jobs. Here we’ve got an old window, and the framing didn’t line up. So this is not the place to skimp with the adhesive. Put a good bead on there so you get a good seal.
OK, I’m going to go right into my corner before we go into the wall tight, all right?
I have three outlets in this wall. So all I did was, I just attached the top edge. Now I am going to cut them out. Because if I actually attached the bottom edge, I’d be making the drywall very tight, and when I cut the outlets out, they are going to bust open.
A drywall router is a very fast way to cut out an electrical outlet. But you don’t want to go so fast that you make an error and overcut this outlet. So just take your time, even if it takes a little longer than you think it should. At least you don’t have a repair to deal with later.
Justin: After the cutouts are made for the boxes, seal the drywall opening to the edge of the box opening. First, brush out the dust so that the caulk can stick. Then apply a generous bead of caulk around the perimeter of the box. Smear it in with your finger to make sure the opening is sealed.
Myron: Another great way to really insulate and isolate these electrical boxes is to use something that is called an Energy Block. I buy them online. They are pretty inexpensive, and they fit right around the box. You cut and fit it around the electrical wires. Adhere it to the wall with adhesive and fill in any gaps with spray foam, and you’ve got a nice tight seal.
Justin: It is not just windows and electrical boxes that can make a wall tricky. This big conduit which runs from the electrical service panel outside to the breaker panel inside presents a bit of an obstacle. To best treat this, we removed the fastening brackets so that we can slide a sheet of drywall behind it. Don’t box out the chase before the drywall because this introduces long cracks in an otherwise continuous plane.
Myron: That’s the last piece. Now all we have to do is seal the perimeters. I’m foam sealing all the larger gaps, but right along this top edge here I have only maybe an eighth of an inch. So once I get up to this point, I’m going to switch over to caulking that.
Well, you can see that I’ve got the caulking actually globbed up there pretty heavily. When we come in to tape this, it’s not going to be good. I actually just want to push it in there. So I’m just going to use my finger and level it out.
To complete the air seal on this job, all we have left to do is tape the seams and the inside corners, just like we would on any other drywall job. But this job is better, because it's airtight drywall.
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