Router Forums banner
1 - 15 of 15 Posts

·
Registered
Joined
·
2,666 Posts
Discussion Starter · #1 ·
Is there a builder in the house??? We're creating a 4-12 pitch roof to go over the front eight feet of our deck. The pitch is supposed to be 4/12 (or 4-12, not sure how it's supposed to be formatted) but neither of us is sure what angle I need to be cutting the rafters/beams.

We're using the Sam's Club Arlington 12x12 as a guide, but of course, that's a kit, and we're having to make all the cuts ourselves. (This should prove to be interesting, since I'm a craft person, not a carpenter.) The rafters are being done in cedar, since they're lighter, and will make it easier for the guys to put up. The braces are treated lumber. The posts, while should have been 6x6 in my opinion, we were told the 4x6's Ken bought (or even 4x4) would be sufficient. Not so sure on that, but everyone we've talked to has said we're good. The roof is metal, painted, from Menards.

So if someone can tell me what angle I need, how how to figure it out, that would be great. Below is where we currently are, (ignore the condition of the paint on the house, that's still up in the air as to what we're doing, and the yard... it will get purtier when we're done.) And the example we're following on the roof. For those interested, we're using the Sam's Club Arlington Gazebo plans as a plan.

P.S. before someone says something, yes, there is an electrical wire at the one end. This wire should have been raised years ago, I was told, because it's really even too low even for my umbrella on my deck. I have a request into our power company to either raise it to a safer level, or move it.
 

Attachments

·
Registered
Joined
·
2,666 Posts
Discussion Starter · #3 ·

·
Registered
Joined
·
4,625 Posts
Barb...will you be putting an overhang on the sides...?

If so, you will need to cut out a "bird's mouth" in the part of the rafter where it intersects with the wall. The bird's mouth will sit on the upper horizontal 2-by and then the rafter gets toe-nailed.

Take a look at this site for all the particulars...angles, lengths, overhang, bird's mouth, etc... It also has a calculator for all the components for different style roofs.

https://www.blocklayer.com/

Good luck...
 

·
Registered
Joined
·
2,666 Posts
Discussion Starter · #6 ·
You need a speed square.
Here is just one of many videos.
https://www.youtube.com/watch?v=CnngQFYXU6U
Got a couple of those, Bob... just never knew what all the stuff on there was for, or what they meant :lol: just learned that last night when I went you-tubing to see if I could get some assistance. Ken is having a cow over all this. These are the moments I almost wish I could just pay a contractor to do this stuff. But, oh well. *shrug*
 

·
Registered
Joined
·
2,666 Posts
Discussion Starter · #7 ·
Barb...will you be putting an overhang on the sides...?
I'm pretty sure the answer to that is yes, if I recall the plans we're using as a guide.
 

·
Registered
Joined
·
4,625 Posts
Barb...just be careful to not over-prepare the lumber...some things are best left for "at-the-time".

For example...the rafters shouldn't be cut until the walls are framed and up and the ridge beam is up. Reason being that you need to know the exact measurement of the ridge to the top 2-by of the walls (rafter length)...and the distance may change a bit from one side to the other depending on how accurately the ridge beam was installed...then you can more accurately cut the bird's mouth and overhang so there are no "wavey's" in the fascia board.
 

·
Registered
Joined
·
2,666 Posts
Discussion Starter · #9 ·
@Nickp Okay, I'll try not to get my knickers in an uproar, then. I want to do the notching in the 2by rafters for the cross beams that will go across them, but will wait till we get measurements. No walls, just the framing around the top, then the rafters, and metal sheets at the top.
 

·
Retired Moderator
Joined
·
16,385 Posts
If you are using a chop saw to cut the angles then you need the angle which as Lee said is 18.4 degrees. But if you aren't using a chop saw to make the cuts then the easiest way to do it is by using a framing square and a set of stair gauges. You set the square on the edge of your material so that the 4" mark on the short leg is lined up on the edge and the 12" mark on the long leg is lined up on it also. Once it is set like that you tighten the stair gauges onto the square and you are set to go. It will cut the correct angle board after board. They are called stair gauges because that's what they are the handiest for but they also cut rafter angles including what's called a bird's mouth notch where you cut out a notch that sits on the top of your wall. Marking along one leg will give you a vertical line once the rafter is hoisted into place and marking along the other leg will you a horizontal line. Here is a short vid that shows them in use but it wouldn't hurt to check a few out until you understand them. The math is actually really simple since every angle is constructed using a rise (y axis) and a run (x axis). That is what you are doing with the square. You are setting the buttons to match your rise and run.
 

·
Registered
Joined
·
8,956 Posts
Just make a plywood pattern, draw 12" and then up 4"(square),draw a line connecting the ends and you have a 4/12.

The above is called the level cut for the birds mouth and the raise of the rafter. For the ridge and the tails where the overhang is, is a 12/4 cut (plumb cut). It is all right here:

https://www.wikihow.com/Cut-Roof-Rafters
 

·
Registered
Joined
·
1,890 Posts
It's not necessary to know how to use a framing square or what the pitch is. As long as you are not working from a blueprint everything is up to you. Simply hold the rafter up until the pitch looks right. Then nail a board against the back of the building to hold the board at that height. Now take a level and draw a plumb line at the top this will be your angle for the ridge (when cutting move the line down 3/4 of an inch to compensate for 1/2 the thickness of your ridge board). Next, go down to where the rafter hits the wall and trace where the top plate meets the rafter this will be your birds-mouth cut. You do the tracing on the end of the building so that you can use the top plate to trace against. If you are not familiar with the birds mouth or ridge look them up. If you are going to have a fascia then let the rafter overhang and use the level to determine the angle to cut in order to have it straight up and down. As far as using cedar for the rafters, if it's the weight that you are concerned about you shouldn't be. One person can easily handle a rafter. all you do is set it on the outside wall and lift it up and nail it to the ridge board.
 

·
Registered
Joined
·
2,310 Posts
Do the winds ever blow above 40 where you live? Consider attaching your rafters with metal rafter ties as well as toe nailing. Some metal ties of the posts to the caps as well. These are all places where the connections just aren't strong enough without them, and leaving them out will only save you about $20, so well worth the cost. 10 years ago, a neighbor lost his deck roof in a strong thunderstorm here, that he had built only 2 years before (no metal ties). Unfortunately, it also destroyed his truck when it landed.

Charley
 

·
Registered
Joined
·
15,459 Posts
I'm probably too late but don't notch the rafters! I'm not talking about the birdmouths, I mean those notches to receive the horizontal strapping. They substantially weaken the rafters and if done on a house roof would invite a total rejection by the Bldg. Inspector.
The strapping gets nailed/screwed onto the top edge and the resulting gaps on the ends are covered by the fascia or bargeboards applied to the outside rafters.
 
1 - 15 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top