Playing catch up with the posts about building the house. I went and ordered my sheathing for the walls and roof. There is a newish product that I am using called the Zip system. (zipsystem.com) Basically it is wall and roof sheathing with the house wrap/roof felt already on it, which is pretty fancy.
It also has these little nubs on the edges so you don’t have to worry about expansion gaps like you would with traditional sheathing. Along with the spacers, the board is printed with markers so if you do your walls correctly, you can just follow the guide on the boards and you hit a stud every time while securing it from the outside where you can’t see where the studs are. The kicker is that not only does it have some major time and labor saving factors, it costs a lot less! You have to use their special tape, but its about 1/2 the price of tyvek tape, so that isn’t a big deal.
I priced it out and its much cheaper and then you don’t have to spend all that time house wrapping. The vapor barrier on the zip panels does the exact same thing as tyvek, but its more durable and isn’t prone to being pulled off by inclement weather. It also apparently makes a much better air seal and is LEED Credit Certified.
Traditional sheathing: 18 sheets @$28
Tyvek Wrap: 1 roll $150
Tyvek tape: $100
Roof Felt: $19
Capped Nails: $7
zip boards: 12 @ $19.50 and 6 @ $26
Zip Tape: 2 rolls @ $27
So when it comes to sheathing (which is what the plywood on the outside of the house are called) the trick with it all isn’t the actual plywood, but that you did your framing correctly. If you have done your framing correctly, then the seams of each of your pieces of plywood will land right on the stud. This is important because you need to be able to nail the edge of the sheathing to that stud. There will be some cases where a panel lands on a window, so you will need to place an extra 2×4 piece to have something to nail into, you can see below an example of this.
This photo also shows how in tiny houses we screw and glue our sheathing. Here I used liquid nail on the studs. A piece of advice for anyone who is doing this, help yourself and spring for a air powered caulk gun. I tried to do this for one day and by the end of it I swore I gave myself arthritis because how hard you have to squeeze this stuff. They have a lot of better powered caulk guns for $150-$350, but this gun is $35 and well worth it. To give you an idea of how much you’ll be doing this, I went through about 40 tubes of this stuff while building my tiny house. As far as fastening the sheathing, I used 2.5″ exterior grade screws, every 6 inches on the edges and 12″ in the center (field).
In the video and some of the photos you can see that the sheathing is actually larger than the wall frame. I had the sheathing extend below the wall framing to hide the trailer so that you’d really only see the tongue and fenders, the rest of the trailer is hidden behind, once finished, nice looking cedar siding. I also had it extend above the framing because I could wanted the sheathing to tie into the loft beams, flooring of the lofts, and the silplate. So I carefully calculated the height of all the components listed and a few others, so that when I installed the silplate (that the roof rafters sit on) it was perfectly flush. This
The other key thing to know about the overhang and extension was that this then tied all three systems together to be a very strong unit. Effectively the floor framing, the wall framing and the roof became a unified piece because they all were brought together by the sheathing.