Roof Rafters and Collar Ties

I wanted to do a quick overview about the rafters, the collar ties, and explain so that you understand the importance of all these things and how they interact with one another and what keeps the roof of your house from collapsing on you. That's what's really important. Take a look at this

Here you can see, this is one of the big main rafters that goes all the way up

It connects against the ridge board right there. And then of course the corresponding rafter goes down, down, down, down, and it rests on

the outside wall. And of course the rafters are toe nailed into the top plate of the wall

But if you didn't have, and you can see those toenails right there, well, we'll kind of

go out there. You can see those two little nails down there in the center of the frame

But that's not enough to hold those rafters in place if, you know, once you put all the

weight of the shingles on there and the snow, and what wants to happen is this rafter, the

the weight, you know, is bearing down on the rafter, and it wants to make the rafter go down

which would kick out the wall. In other words, that wall down there that the rafter is resting

on is now plumb, but if you didn't figure out a way to stop that rafter from coming down

believe me, the wall would just kick out. It would just, the top of the wall would end up in the

trees. So you do that, you stop that by adding in this horizontal member right

here. We call it a collar tie. You might call it the attic floor joist or you

might call it the ceiling joist if you were down below, you know, in this room

because you looking up So it really like three things but it a primary structural element for this roof so that we don pull apart and we don collapse the walls And you can see

what happens, it actually becomes the bottom of a triangle because this collar tie right

here passes underneath the floor right here on that black line and it comes out right

there and connects to the bottom of that of the rafter. So it's basically the third leg of the

triangle. And if you remember from your high school geometry class or trig, in physics

triangles are really, really strong structural elements. Now what happens is you have to nail

you have to connect this collar tie to the rafter. And we have put five 16-penny nails

through the collar tie into the rafter, and we did the same thing over here. We put another five

nails going this direction. So there's ten nails that are connecting that together. There are other

ways to make roof rafters stable. You could put the collar tie up a little higher. You could put

it up here. You can put gusset plates up here. The ridge beam itself can be supported and take

a lot of the weight. There's all different ways to skin the cat. But I just want to tell you that

this collar tie is very, very important. And if you're in a house and you're thinking about

doing some demolition, don't start cutting into these things or you'll collapse your roof

So that's just a little bit of overview as to why all these different components are important

and just, you know, keep that in mind. And if you just use some common sense

you're going to have a nice, strong building, you know, for the shed or house

or whatever it is that you're building. And just keep it all in mind

It's that simple. I'm Tim Carter for AskTheBuilder.com