I Joists For Roofing, Questions

ApgarNJ

hey guys,
i've framed several times using I joists for flooring, but never for roofing, we are going to be building a work shop addition and the span is 27' and the plans call for I joists but don't give any other details on blocking, overhang, birdsmouth etc. I have a few questions. how do you attach the i joists when you are taking a shed roof(with ijoists) and fastening it to a another roof that is a 12/12 pitch? do you just put a 2x ledger and fasten that to the 12 on roof and do they sell hangers for all types of pitches? we are taking a 2.5 on 12 shed roof and going to a 12 on main roof for part of the shed, the rest of the shed roof butts to a gable end wall of the existing house. I'm sure that on this area we just bolt a ledger to the gable end wall and use I joist hangers with web stiffeners.

ok, on the other end, what's the best way to fasten a soffit and fascia boards to the end/bottom of the i joist as it's overhanging the outside wall?

i'm starting to wonder if it would be faster to frame this whole thing with LVLs for rafters and skip some of the expensive hangers and web stiffeners that are required for i joist roof framing.

I know the LVLs would be costly but saving labor is a good thing. what are your thoughts? how much longer does it take to frame a roof with i joists?

since this is my first time using these for a roof, i'm open to all suggestions you guys who frame with these all the time have.

Thanks again
Dan
NJ

genecarp

What is the reason for not using good old 2x 10 doug fir.

i just noticed the 27', that may be a problem, ask the architect if he can re engineer to use normal lumber

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JonM

http://www.lpcorp.com/ijoists/profes...tallation.aspx


Google is your friend...

woodworkbykirk

ive done it on a few jobs, but not in a while

we had to set a engineered beam then hang the TJI's off of the beam using special hangers they make, at the plate where it sits you cant make a birds mouth, we made up canter strips ripped on a bevel to match the roof slope, and for the tail cuts we cut them off just past the plate, filled the web then screwed 2x4's to that which then had the plumb cuts for fascia on them, blocking was required in between at the plate as well

Joe Carola

Yes you can. Scroll down to the bottom right and zoom in where it says "Roof Framing Detail" and look at 2H and 2I.

http://www.owldistribution.com/pdf/E...all%205902.pdf

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Joe Carola

Joe Carola

Dan,

All this information should be on the set of plans drawn by the Architect. Since they're not call him up and tell him to give you what you need because he HAS too. Either way all you have to do is use the installation guide from whatever brand truss you're using.

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Joe Carola

Aframe

Pretty simple blocking details found in installation instructions from manuf. ^^

LVL's will be a lot more $$ and weight for you to handle and load for framing below roof. Two people can easily handle a 27 I joist, prob not LVL so there goes the labor saving.

get the install booklet or print out the instructions so you'll have them with you while you do the job.

woodworkbykirk

interesting, because when we did it we had the weyerhauser rep come to our office for a toolbox meeting to go over how to frame up a roof with TJI's, he specifically told us to do it with canter strips

ApgarNJ

thanks joe.

i had read the LP install instructions on their website. the plans don't show much about connectors or hangers. they do show a metal hurricane type strap but i'm more concerned with the longer cut where the shed meets the steeper roof framing, and how to secure the. i know how we do it with regular lumber but not sure if the angled hangers work for all different types of angles. the ones i have seen in the past seem to be for certain angles like a 45 deg. etc. seems like the time consuming part is filling in the web part with plywood. the blocks between joists at the outside wall plate can just be left over scraps of i joist material.

looks like we'll have to cut a block of wood in between each block at the webbing out at the fascia board in order to fasten to it.

Joe Carola

Where the 2.5/12 pitch I-joists sit on top of the 12/12 pitch existing roof, you can nail down a ledger from 2-2x's so that you have full bearing. If you put web stiffeners in, I'm sure that would be alright, but just ask the Architect for that detail because like I said before, hes HAS to give it to you. It's his design and his plans.

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Joe Carola

ApgarNJ

thanks joe!!

neolitic

But it's always best to have a
real plan before you ask him!

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(Sorry....it seems there really are dumb questions)

Kgmz

Is this a permitted job?

Because when the inspector comes to inspect this, he is going to want to see the engineered plan for TJI's. Then he will look at the details of the plan to see if it was installed right.

All TJI packages come with engineered plans if it was engineered by the I-joist manufacturer. And even if a Architect engineered it, the I-joist manufacturer will still check to see if his engineering is Ok, and still supply their own plans and details, stamped by their engineer. And the engineered plan and details should have been delivered with the TJI's.

Now all this does not mean you can't buy the TJI's without having it engineered. Someone could just get some TJI's from the lumber yard and not have it engineered. Especially for something simple like a roof where you just need a bunch of TJI's the same length.


So make sure that this thing is engineered to protect yourself later.

ApgarNJ

I believe they are LP I Joists, not TJI. I will take the plans to my lumber yard and they can contact LP on what exactly the plan should be and what I will need.

when you guys brace these, do you just use left over scrap of the I joist? whenever we used these for floor spans in the past, we always used the left over cuts for braces and nailed through the top/bottom of the joist. not the webbing.

Timuhler

I've used I-joist rafters on two houses and I'd do it again. A little more prep work, but much lighter and straighter.

I prefer to rip bevelled strips and nail those to the topplates to avoid a birdsmouth.

http://picasaweb.google.com/TimothyUhler/Lot35Muirkirk

ApgarNJ

yeah. we have a 2 1/2 pitch on this shed roof, so there wouldn't need to be much of a bevel. it would be much faster to do that along a 35 ft. wall than to cut a birdsmouth into all of them. i was even thinking of angling the top 2x6 of the double top plate, and put a wedge between the two top plates.

Joe Carola

Just cut the top of the studs with a 12° angle on them and your done. No beveling or wedge.

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Joe Carola

72chevy4x4

wouldn't that create a little bit of a cant when installing the sheathing? suppose it depends on the eaves detail...

ApgarNJ

we would just hold the sheathing down because the soffit will cover that area if the top most plate is angled.