Cut Rafters Sit On Wall Top Plate Or On Top Of Floor Sysstem?

wallmaxx

I learned framing in the residential Houston, TX region starting 1989. We always cut all of our roofs. All of our rafters were placed directly on the walls next to the joists (that ran parallel). The rafters received two toe nails into the plate + 2 face nails into the joist + 2 face nails from the joist back into the rafter. We added kicker blocks for the perpendicular sides. Back then the nails were all 3” .120 ga. Smooth brites. For vaulted and raised ceilings – this way for sure.

Then when I was in Clarksville, TN, a framer I worked with would completely joist out the structure, including a rim joist, then he would run a 24” rip of sub flooring along the entire perimeter where the rafters would land, followed by a 2x6 sill plate, glued and nailed to the subfloor and rimjoist. Then the rafters were nailed to this 2x6 plate. Every 4 feet he would nail a short 2x4 back down to the nearest parallel joist as a lower rafter tie. He was a big time commercial hotel and apartment framer and I think he did it this way when you are working with floor trusses and the like.

Both ways have pros and cons. Which way do y’all put up your rafters and what are your thoughts?

For flat ceilings, I like the second method. I’ve even floored an entire attic (2x10 first floor ceiling joists).

reveivl

I do it the way you do, rafters birds-mouthed on to the plate, nailed down and sideways. No blocking though, for intake roof ventilation from the soffit.

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framergreg

yes , second that.i always cut the rafter and nail to ceiling joist. the reason for putting the 2xon a deck /flooring from my old school teachings was to get added insulation in the rim of ceiling joist if hgt wasnt issue.

Joe Carola

Most of the time the rafters are on the top plates. I've framed many house and additions also where they sit on top of the second floor joists. One reason is because of the first floor windows having transoms or circle tops above and the soffit would be into the windows, so the plans will spec the rafters on top of the ceiling to raise the soffit.

Another reason is because we have to install several layers of freezeboard trim above the windows with dental and crown molding, so you need the height for that.

Another reason is if you use I-0joists for the ceiling joists and the slash cut would be greater than the amount you can cut, so therefore the rafters sit on top.

Here's a couple pictures of a house I framed and trimmed with the rafters on top of the ceiling joists because of all the exterior trim. We needed the height above the windows.

Attached Thumbnails

     

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Cole

Damn Joe, Post Some More Pics!

For me the rafter birds mouth sits on top of the top plate!

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Mr. Constructio

I think it depends on the project at hand, most blueprints tell you what height the rafters should be set. If you have a house with 8' walls and a 10/12 pitch roof then you would have to raise the roof system up to clear the windows, I have built 4' knee walls around atop the walls to sit rafters on, but thats how it was supposed to look , just depends on the situation which way to frame it.

Floordude

When I framed, the blueprints dictated this.

We did it both ways, depending what the architect had a vision of.

One thing we ran into a lot, was it looked good on paper, but had no strength designed into the architects drawings.

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neolitic

Have used knee walls for insulation depth, and trim details like the others. Only time it made sense to frame the roof off the joists, like your Tenna. friend, was for story and a half houses.

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A W Smith

Exactly. follow the plans or whats shown on the elevations. lets say the elevation shows a narrow 6 inch band of Azek frieze that lines up with the head of the window under the soffit. Suddenly by banding the ceiling joists and in effect raising the entire roof 10 inches you have ruined the look of the elevation. Speak with the owner or architect before you decide to make a change from what is shown on the plans.

KentWhitten

Yeah, I'm coming in late, so nothing more than what's been said. Either way, depending on the situation is fine. And if there is an architect, he supersedes anything you know is right. Let him be the wrong one, not you.

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RobertCDF

Trusses... Almost all the time. Cut roofs are rare and only in a few places. Never the whole house. But thats just me and here.

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wallmaxx

A pdf of the image below of rafters on floor system


A pdf of the image below of rafters on the plates

kpatrix

I like to stay above the joists. I've never used 24" rips of subfloor but I have double plated on top of I-joists and pony walled to match on more than a few houses.

Sometimes it means changing the roof pitch to make it more shallow in order to clear second floor windows, but it's better IMO for beams and trusses so that you don't have to have roof cuts. It's the only way with some Joists an beams.

Timuhler

It depends for us. We'll do that on the frame we started yesterday.

Normally we put them on the wall plates.

I tried to post links, but can't until I hit 15 posts

osborn

I had an inspector turn me down today for framing with a plate above the ceiling joists. I have done it that way tons of times in new builds(bonus room over the garage).
This job we had to demo the roof framing due to water damage from the fire dept. The house next door burned and the fire dept hosed the attic of this house to prevent fire.
The widows are high. I put a plate above the cj to keep the soffit from being below the window.

Joe Carola

What was his reason?

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osborn

She wants an engineer to say this is an approved method.

Joe Carola

Did you cut back the ceiling joists and put a box on, or did you just add blocking in between the ceiling joists?

Did you nail hurricane ties on, or put angled braces nailed to the rafters and ceiling joists?

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osborn

I cut the cj s back to the top plate and blocked between. No ties required in this area. We added collar ties also.
She wants us to have an engineer inpect the whole job and ok it.
I have crossed paths with her before. She normally inspects the high rise work. All work there needs engineering. Shes just trying to cover herself at the cost of us paying an engineer. She even wants to know if our paslode gun nails are ok(3 inch .131)

rusty1986

Done it both ways. Putting the rafters on a plate that is sitting on the joists allows more room for insulation.