Step 16c – Sheathe/WRB the Gable Ends
The last section of the house to be dried in are the gable ends. The gable end trusses cover an area of the house that is not heated, so it doesn’t need to be insulated. For this reason, I won’t be installing any polyiso foam over the sheathing that covers the gable ends. However, if I simply apply sheathing over the gable end truss, the wall will sink back one inch from the rest of the wall due to the lack of foam. To make up for this, I ripped 2×4’s down to 1″ thick (a normal 2×4 is 1 1/2″ thick) and nailed them to the gable end truss. This not only gave me a better grid to nail the sheathing to, it also moved the sheathing outward 1″ so it matched up with the foam below it.
Here you can see the gable end truss with the 1″ strips and the gable end sheathing just behind it. I added more strips to ensure that all of the edges of the plywood used as sheathing were supported by 1″ strips.
Above you can see how I applied the strips along the perimeter of the gable end truss to fur the sheathing out the extra inch so it matches up perfectly with the polyiso foam below it. With the sheathing fully supported and attached, all that was left was to attach the WRB. I used staples for the areas that were just under the overhangs since they will be fully protected, then lapped the bottom of the sheet 12″ over the sheet below it and taped it down with Tuck tape.
Above you can see the gable end is now completely covered with the Tyvek water resistant barrier. I still need to add more furring strips so that they extend all the way to the roof line. The furring strips will hold the siding away from the WRB, creating a 3/4″ air gap between the two layers. Any water that finds a way to slip past the fiber cement siding will be shielded from entering the house by the WRB, and then dried out by air moving in and out of the gap between the two layers. This water protection technique is known as a rainscreen and has been proven to be extremely effective.