MAMEWorld Forums - The Loony Bin - More garage talk, rafter edition part 1.

Finally finished enough of the little things on the ground to start thinking about a roof. For those following along with their own adventure in mind, the type of roof you are putting up should have been decided already. It's not too late to change things if you must. I priced both prefab truss and "stick frame" (cut everythig yourself). I'll elaborate on the pluses and minuses a bit in this post.

Prefab truss:
Easy as pie to install, lightweight, and fairly sturdy. You can get them with an actual "room" preformed in them as well. They typically call these attic trusses. They are considerably more expensive too. They aren't going to hold as much weight as a majority of stick framed roofs. I'd say prefab is the way to go for low sloped roofs, or if you are dead set on quick and easy. For my garage, attic trusses at the pitch I wanted (10/12) would cost me $1400-$1600.

What a prefab truss looks like

Stick Framing:
This route is not as easy as prefab. It takes a little more math, and a step up in carpentry skill. Those negatives aside it's sturdy as all heck, Leaves you with a nice open attic space, and just looks cooler. I chose this method for my garage as it was $500-$700 cheaper, for an attic that would hold 3x the weight.

What stick framing looks like

Now on to the big question, how the hell do I build it? The first thing to do is draw a mock up of what you have in your head. It can be as simple as a triangle on a piece of paper with some basic measurements. For a square building, you are pretty much going to build this triangle over, and over, and over, and over....

Once you have your triangle, look up your local codes for how much weight this thing needs to hold. This will be your bare minimum spec, build up from here if you want. I found a ton of nice calculators online that figure things like dead and live load, span charts, snow load charts, pitch charts, and just about every other chart you could imagine. Your head is going to spin, and probably hurt. After a few days of reading you should have a decent understanding of what you need to do and how to tie all the numbers together. You could also farm this part out to a carpenter buddy, or an engineer if you are dealing with something tricky.

For my garage I decided on 2"x12"-18' rafter ties. This is quite a bit of overkill for a rafter tie, yes. The bonus in using such thick wood is two fold.

1. 2x12's made the 18' span fine for the weight I wanted to support.
2. Thick rafter ties double as excellent floor/ceiling joists.

I chose 2x8's for the actual rafters as that seemed a pretty common size to use. It also met the load requirements for my village (and then some) for the span it needed to make.

So I have my roof planned and again the question comes up, "How the hell do I build it?" If you aren't familiar with cutting rafters, read. Read a ton. Plan on wasting a board or two practicing as well. It's not hard to do, but it is repetitive. You'll need a good framing square, a pencil, and a saw.

Now before you begin cutting, a little note. The more perfect your cuts are, the stronger your roof will be. On that note, it realllyyyy sucks to have pre-cut all your rafters and find out they are wrong when you try to place them. It also really sucks to have to cut each rafter on the fly, and makes for a long day (an even longer day if the temperature outside is 20F). How do you do both then? Great question. One I asked to a few people. The best answer I got back was "Build a jig."

My fist thought on the matter was "A jig! Why didn't I think of that!"

My second thought was "WTF is a jig?".

To be honest I'm still not entirely solid on the definition of "Jig" myself. It seems to me that carpenters use it to describe anything they don't have a proper name for. Loosely ~I'd~ describe it as anything that helps you make something else. So a jig building I will go....

My jig was more for "quality checking" than cutting as shown below. It did help me see that my plumb cuts were off a tiny bit, which was well worth the 20 minutes and scrap wood it took to build it.

A quick tidbit of advice on making "templates" for your rafters. This is fine to do and will save you a lot of time. The only important thing to note is that you should use the SAME template for every rafter. This prevents "wandering" of your marks. If you used the rafter you just cut to make your next rafter and so on, the last rafter you cut will be nowhere close to the first. I guarantee it. It's the carpentry version of that telephone game you played in school.

To be continued...

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