Ceiling joist, roof rafter layout

[VALENT]

I am going to be using rafters and joists for my simple gable roof. However, I do not understand how the two joists coming from each exterior wall and meeting over the middle wall will have to lay out in order for the rafters to still line up correctly. My question is: how do the joists match up in relation to the rafters?

[dhill]

Set the rafter beside the joists, not on top. Of course, you can set them on top and effectively build your own truss, but it's not necessary. A neat trick is to set the ridge row on top of the joists and mark the place where the rafters will catch on the ridge row before you set it at the peak. That way you'll have the rafters all meeting uniformly without having to take so many measurements. Be sure to stay consistent on the side of the ceiling joists when setting the rafters.

Dusty

[Joe Carola]

There has to be an offset. If you drew a line on the ridge, one rafter you would mark to the left and the othe you would mark to the right. You can't but them oppssite because your ceiling joists are overlapping one another.

The only time you can butt them directly opposite is when you have one continuos ceiling joist, if your ceiling is running the 24' way, then you by 24' joists and put the rafters on one side of the joists then you can butt them at the ridge.

[Dragon]

You can also put a 2X in between the joists on your center wall to bring everything straight again. Personally, I bridge there as well.

[dhill]

Yep, you can stagger those rafters easily enough. Great pics of how to do that Joe.

[conman]

right now im going thru the same deal...Im having a home built and my builder just started on the roof and when i got home from work and saw that he staggered the rafters at the ridge like you show in the picture..i nearly flipped. I'm a 3rd year carpenters apprentice, but not yet ready to build my own place,so I hired a local builder to do the rough framing. I have never seen this done like this. Is it acceptable? Structural integrity? How would you line up collar ties now? Btw..it's a straight gable front to back.

ps..he also used a 2x10 ridge board for 2x10 rafters..isnt the rule 1up? I thought the ridge should cover the entire angle of the rafter cut?

[Joe Carola]

Conman,

You said, "Im having a home built and my builder just started on the roof and when i got home from work and saw that he staggered the rafters at the ridge like you show in the picture..i nearly flipped."



Why did you nearly fip? As I said in my first post with the drawing that has two different ceiling beams you can clearly see that the rafters have to stagger they can't butt eachother. When you have two different ceiling beams that are nailed side by side.

There's nothing wrong at all doing it that way. The ceiling beams are nailed into eachother at the center bearing wall and on the outside walls they're nailed into the rafters that's the way it's supposed to be done. If you have seen that same situattion before with the ceilng beams nailed along side eachother and the rafters nailed at the plate like in my drawing and at the top the rafters butt eachother it's wrong.

If you use one continuous ceiling beam like in the other drawing then they can butt eachother. As for the ridge if you use 2x10 rafters you have to use 2x12 or microlan 1-3/4" x 11-7/8" that you are correct.

Collar ties with the rafters staggered is no problem unless they were getting sheetrocked then you add a block to the rafters to keep the collar ties running straight for sheetrock.

Joe Carola

[conman]

the only reason i flipped is because i personally have never seen anything like that..i always see what dragon had suggested with 2x drops in between ceiling joists to keep the rafters butted at the ridge. In good practice..shouldnt the rafters always be over the studs..with ceiling joists next to them? Youre transfering more weight from the roof than the ceiling
just wondering...

[Joe Carola]

Conman,

I've never seen anyone drop blocks in between ceiling beams before. What is the reason just so the rafters butt at the ridge? I personally layout my rafters over the studs and the ceiling beams off the studs and the ceilling beams are tied into eachother not blocks but if that's how Dragon does it that's fine but I think it's stronger the other way and it's a waste of time to put blocks in. I should say that I just think that it's extra work doing it that way

If I look at 10 different framing jobs you will see rafters over studs on 5 and ceiling joists over studs on 5. If the rafter is off the stud 1-1/2" I see no problenm at all. What about all the trusses that are 2' centers they land in between the studs and also some parts of the country they stick frame 2' centers so you have rafters landing in the middle of the studs. We don't stick frame 2' centers around here.

Joe Carola

[conman]

point well taken...just worried about thrust from snow loads here in chicago..no chance of the ridge movin though ?

[Joe Carola]

Conman,

"no chance of the ridge movin though" ?

I doubt it .

Here's another situation on bigger homes where you have two bearing walls. You would run the ceiling joist from the front of the house to the first beariing wall and then run the ceiling beam from the back of the house to the second bearing wall. These two ceiling joists woud be on the same layout mark.

Now you would run the third ceiling joist from one bearing wall to the second bearing wall and nail them along side the other two ceiling joists and the rafters would get nailed on the same mark as the bearing wall ceiling joists and then the rasfters would butt eachother.

[Dragon]

conman, you shouldn't have a problem with snowloads at the ridge with only a 1 1/2" offset. It isn't my preferred method on roof framing, but it is perfectly acceptable.

[conman]

thanks dragon..thats what i was looking for was another opinion..like i said i personally have never seen this mehod of framing, and when i have 5 grand in lumber sitting on a roof i want to make sure its ok

[VALENT]

thank you (esp Joe Carola) I think I will build the rafters as in your second drawing. This will mean the rafter for the front of the house will be over the wall studs and the ceiling joist on the back of the house will be over the wall studs. So you will see 50-50 on this one house.