too many words by laura lemay

How to Convert an Old Shed to a Chicken Coop in 45,732 Easy Steps (Part Four)

(Part One, Part Two, Part Three)

So you’re probably thinking, “Hey Laura, it’s been a really super long time since you wrote about that shed/chicken coop of yours. Surely you’ve made some progress that you could write about. Surely the shed isn’t just sitting there in your yard, incomplete, in the rain, taunting you with your short attention span and inability to actually completely follow through with a project.”

Yes, well, um.

I will point out that there is a roof (and some siding) on that shed now, and it took me a long time to put a roof on that shed, and that roof is what I want to talk about in this post mostly. But the real reason the whole shed to chicken coop project has dragged on this long is for a particular reason: I no longer have any chickens. I had a family of bobcats come through and wipe me out in August, and I want to write about that, too, because it’s been an important albeit not very amusing part of the story. But for now let’s talk about the roof. And about math.

Rafter Math

When last we left our stubborn intrepid narrator (me) in June in Part Three she had finished the foundation and framing for the walls of the shed, reusing as much of the old wood as possible and widening the shed by about 3 inches. There was a great sense of accomplishment and no small amount of back strain felt by all involved (me).

The next step was to set rafters to hold the roof. The original slanted roof of the old shed (as shown in Part Two) had rafters, thick redwood sheathing, and then about four layers of asphalt shingles. My plan was to replace all that with a simple corrugated (wavy) metal roof. But I would still need rafters.

The existing rafters were 10 foot 2x4s with notches cut into them so that they would sit at the correct angle on top of the vertical walls. The notches are called birds-mouths, and there is some fancy complicated construction math (otherwise known as “trigonometry”) that you can do to figure out where to cut the notches and at what angle. (You know when people say that you’ll never, ever use eighth-grade math ever again? This is where they’re wrong. If you ever want to cut birds-mouth notches in rafters, it will help to remember your eighth grade math.)

About three of the six of my old rafters were in fine shape. The other three were too rotted to use. I figured — no big! Lay the old rafters on top of new 2x4s and use them as templates for the notches. No fancy complicated construction math needed!

But here is where I will bring your attention to that thing back in Part Three where I widened the shed by three inches. The notches in the old rafters no longer line up with the top of the shed. I needed new notches in new places with new angles. I had to do the math after all. Darn it.

I am told that a common framing square has markings on it that are supposed to help you with rafter math. But I don’t actually have a framing square, and, honestly, every time I looked up a description of how to figure this out I felt like despite my actual college degree from a technical school no less I was sitting there in front of the computer slightly drooling and muttering “wut?”

I spent perhaps a month standing around sighing over this, and then I stumbled on a tip in the magazine Home Family Handyman (which, by the way, is total DIY homeowner porn, and if you’re still bothering to read all of my crap here you should be reading that). The tip said you could use hurricane ties — bent metal plates you can buy anywhere — to hold the rafters right on top of the framing, and not have to measure or cut notches at all.


12 hurricane ties: $11.76.
3 10 foot 2x4s: $9.48

After the rafters come purlins, which are just boards that go perpendicular to the rafters to support the roofing panels. I’ll skip this part because it was boring; I used lengths of 1x redwood I had left over from various other bits of the old shed and nailed them in mostly random places to the rafters.

Idiot on The Roof

Which brings us to the roof itself. Wavy metal roof panels come in several different lengths and are 26 1/4″ inches wide. For the length of the roof, front to back, I needed 12 feet of panel. I actually had some eight foot roof panels left over from roofing the barn a few years back, so I ended up buying a few more eight footers and a bunch of six footers. The 8s and 6s overlap by 2 feet to give me 12 feet. Easy peasy.

Width was somewhat more complicated. Math was required (darn it). I had a 10 foot wide roof span. The panels are 26 1/4″ wide, and overlap in the waves in increments of roughly 2 3/4″. I wanted to overhang the roof on either side by 6 inches. How many panels across would I need?

This actually seemed a lot harder when I was trying to figure it out a few months ago, and seems obvious now; five panels to cover the roof itself (width – overlap = ~2 feet; 10 / 2 = 5), plus one extra for the overhang.

Wavy metal roofing panels:
2 8-foot panels $28.50
6 6-foot panels $64.08

To attach the panels to the roof you also need wavy styrofoam filler strips that go between the panels and the purlins, and special sheet metal screws with rubber washers on them.

Filler Strips: $20.74
Screws (3 boxes): $13.29

And now, we roof. I roofed by flinging the panels up from the low side of the shed onto the rafters, and then by standing on a step ladder from the inside of the shed, arranging the panels into the right configuration and then screwing them into place onto the purlins. The last thing I wanted to do was actually climb on top of the roof, for two very important reasons:

  • Metal roof panels are slippery, and that roof is frickin high off the ground. Also, I have neglected to mention that the shed is built on top of the side of a hill, so if I slide off the roof I am not only going to fall eight feet off the shed itself, but down another ten feet into a thicket of poison oak and blackberries. Also, there are spiders there.
  • Framing without siding is NOT STABLE. It wiggles. You may remember from Part Two that I had trouble removing the roof from this shed because it listed queasily around from side to side. It did this a lot putting the roof back on, too, only this time I was up there with an electric drill, standing at the top of an unstable ladder, leaning out over the roof and trying not to be sick. Short of confronting a pack of angry bobcats on the top of a seven foot electric fence with a garden hose and I’ll get to that part in a bit, this was the most terrifying thing I have done all year.

I also occasionally had trouble lining up the screws with the purlins. Whoops.


When the roof was two-thirds done I was arranging the next set of panels on top of the rafters when I noticed something funny. I was going to be about eight inches short. I thought, well, I think I must have done the math wrong. And then I stared at the panels I had already put on for a while and realized that I had overlapped them all by three waves instead of two like I was supposed to.

Oh, crap.

So. I had one of two solutions:

  • Buy another row of roof panels to cover the eight-inch deficit.
  • Remove three rows of roof panels and overlap them correctly.

I went with Plan B, because emotional trauma is always better than spending more money, especially for a shed/chicken coop that was originally supposed to be free. The good news is that putting the panels down for the second time took much less effort, because at that point I was getting used to being terrified on top of a ladder. The bad news is that it took twice as many screws, because I had to cover all the holes I had drilled for the previous overlaps. This roof is very firmly attached to the shed. Very. Firmly. Attached.

The final roof: it’s not perfect, but it’s pretty darn good. Mostly I’m happy that its over.