Starting the roof was fairly simple. We had already placed the roof joists so that every seam of 4x8 OSB would hit a joist, so we really just threw the sheets up there and glued and screwed them down.
Since we had spaced the joists so that they lined up with the OSB seams, the joists on the edges ended up rather close to the parallel frame. We placed insulation in those gaps on either end before we sealed it up with the OSB sheathing.
The first piece of roofing we added was the trim on the low edge of the roof, called the Eave Trim (see invoice below). The trick with anything dealing with water is to imagine the flow and build accordingly. This will come up again with framing and flashing the windows. Basically, you start from the bottom and keep layering up from there so that any water running down won't get caught on any edges. By starting with the Eave Trim, we were able to layer the underlayment over the edge of that trim so water could still flow down over it.
Next we added an underlayment that I got from a local metal roofing company. It's called Titanium PSU 30. It's advertised as such: "PSU30 is a high & low temp. professional grade self-adhesive synthetic roofing underlayment for protection from Wind-Driven Rain, Water, Snow and Ice Dams. Use under all: Metal, Tile, Slate, & Shingle roofing".
We started from the lower edge and rolled it out, sticking it down as we went, attempting to keep out all the air bubbles. As dictated by the manufacturer instructions, we overlapped the second layer 6 inches over the first.
At $110 for a 200 sq ft roll, I just couldn't justify buying a second roll only to use another 15-ish sq ft of it...so we ended up using left over strips of window flashing to seal up the exposed bits of sheathing. Not very pretty, but I figured that if it's good enough to keep water out of window trim, it could keep water out of my roof. Right?...
We placed two layers of window flashing along the top edge to make sure it was sealed up tight.
After we got a satisfying amount of flashing and underlayment stuck down tight, we started installing the metal roofing! I purchased my roof from North American Metals, Inc. and honestly I wouldn't recommend them. They weren't very helpful with questions and whomever it was that answered the phone every time was quite rude. However, their prices were the lowest I could find in the Portland area. Maybe that's why. Anyway, I purchased "26 ga. Premium 12-inch Tight Lock" standing-seam concealed fastener roofing panels. Below is a copy of my invoice. It totaled to $463.37 for 107-7/8" x 300" of roofing, trim, and all fasteners.
We started with the "back" of the house (opposite end from the tongue of the trailer). Each panel was screwed down and the next panel snapped down over the previous panel's ridge.
Dad used some weird piece of metal he had lying around (in his hand below) that he placed under each panel on the low side of the house to ensure we were keeping the same amount of overhang on each panel.
It all came together really quite quickly!
The overhang turned out just right all the way down.
Next up - roof trim!