Draw a full-scale mockup and snap a line with fascia in mind
When sheathing a roof, the first step is to snap a line so that the first row goes on straight. But if you snap it at 40 inches, then the sheathing will not project over the subfascia or true fascia. This opens the door to the possibility of water damage by letting gravity work against you.
Don't do that. Gravity can be your buddy.
In this video, Ben Bogie shows how to visually calculates where to snap that first line.
- To figure out the sheathing snap line, swing the square over to the pitch of the roof, in this case, it is a six-pitch, and strike a line right there.
- Then we're going to use a scrap of 2x4 to space off the square and strike a line there.
- This indicates the truss tails extending past the walls.
- measure from the edge of the plywood (outside of the wall) over to whatever the overhang will be and square a line up to indicate the end of the truss tail.
- Add an inch and a half for subfascia, and strike a line.
- Add the thickness of the true fascia, 15/16 in., in this case.
- Mark the thickness of the roof sheathing, 1/2 in. in this case, and strike that line
That completes the drawing of the whole eave. Ben likes to keep the bottom edge of the roof sheathing above the outer edge of the fascia, in case there are little discrepancies in the framing so he marks a line about a quarter inch in from the outer edge of the fascia.
Hold the 48-inch mark on your tape measure to the outer edge of the plywood and look to see where the end of the truss tail falls. It is at 45-3/4 in.
Measure up the rafter 45-3/4 inch from the cut end of the truss tail and snap a line along the trusses. This indicates the upper edge of the first row of roof sheathing—leaving enough overhang that the subfascia and fascia will tuck neatly underneath when the time comes.
—This tip was captured live on Professional Remodeler's 2017 Model Remodel.