Step 9: Sheathing the Roof

It’s been a while since my last update, so it’s time to fix it. I wanted to run electricity first, but it’s a whole other can of worms, so I decided to complete the roof first.

Sheathing the roof included more steps than just laying sheets of OSB and nailing them, and a few issues had to be fixed. Roof is the pinnacle of your building, so not surprisingly every small mistake you made along the way that was ‘good enough’ for the floor or the walls starts to manifest itself in the roof, and you have to deal with it.

So, let’s proceed.

Tools needed: circular saw, miter saw, framing nailer, hammer, ratcheting tie-downs (optional)

Materials needed: OSB, lumber, collated nails.

First, we need to put sub-fascia on rafter overhangs on both sides of the shed and nail them together. Sub-fascia itself runs longer than the shed long side to create an overhang of the roof over the short sides – so you don’t have rainwater running down the falls. First surprise: as I was aligning my rafters over the piece of thread, rafter overhangs became all uneven. Some were within tolerance of a 1/4 inch, but one particular rafter was 1.5 inches out. How the hell did this happen? I don’t have an explanation, must have been asleep at the wheel. Anyway, I marked all rafter overhangs to the smallest denominator and cut them to an equal length. This was a Circue du Soleil act with balancing on the ladder, ripping lumber with the circular saw and keeping cuts straight.

You want to nail sub-fascia slightly lower than the overhang, so that sheathing runs flush over the rafter and onto the end of sub-fascia. I put up both ends of the 18-foot 2×4 with a loop of thread, and then adjusted the height of each end until they were right. Then nail them to the rafters.

Adjusting sub-fascia in place.

Plans called for a soffit, but with the changed roof pitch to a more shallow angle, soffit width increased in size dramatically. I could install plywood as soffit all along sub-fascia, but that would have been a lot of work, and wouldn’t look good. I’m sure people solve this somehow, so I started googling. Sure enough, there are lightweight vinyl soffit panels made specifically for this task, but none are available at any hardware stores around. If you can’t find something readily available at Home Depot, it means only one thing: it’s not used in construction in your region because it is either not up to code, or does not make sense economically or climate-wise.

Turns out there’s a much more economical and aesthetically pleasing solution used in California which was sitting right above my head: open rafters! Open rafters look great, and all I need to do is install blocking along top plate, flush with the sheathing, so you don’t get birds or draft going under your roof.

Blocking installed

Once blocking is in place, we can start actually sheathing. As usual, follow puzzle pattern to increase roof strength.

First sheet in place.

Continue to install sheets, nailing them down at 6” o.c. on the edges and 12” o.c. along middle rafters. Keep a 1/8” distance between sheets on all sides to allow roof for expansion due to heat. Easy to do: just stick a few nails between sheets when you line them up.

Of course, not everything lined up ideally, and a few adjusting cuts had to be made with a circular saw. Also, rafters aren’t necessarily sitting perfectly straight, and you need to man-handle them a bit to line up squarely. I used a piece of wood as a wedge between to rafters to get them in position. Some muscle, sweat and elbow grease – and the roof is coming together.

Pulling end rafters into position.

Next, we need to put sheathing over gable ends, but here’s the problem: gable rafters are pushing themselves outwards, and I need to bring them in a bit and hold in position until I nail the sheathing. I used ratcheting tie-downs to get my end rafters in place.