We have just completed the roof on massive 6000sqft+ custom home. The home had interior ceiling height of 14′ through the center section and 9′ exterior walls. This raised the center of the structure roughly 27 feet from the deck to the peak at a 7/12 pitch. In order to help speed the project along we decided to use truss for most of the roof. Now that you have some background, here is my problem.
There was an area in the home that transitioned from a 9′ ceiling to a 14′ ceiling. The truss company could not engineer a truss that would work. My solution was to stick frame the area and tie back into the valleys. The span of the run of the roof was close to 21′. I opted to use GP lvl plated tji for the rafters. I birdsmouthed them and plate blocked them in accordance with the manufacturer’s recommendations.
After installation the GC informed me that the method I used in cutting the tji was in violation of the IBC. He says the only allowable method is to use a beveled double plate. I won’t argue that his method is acceptable, but I would think a reinforced birdsmouth with Simpson brackets would be better at stopping the slide.
A little help here please. I can’t find anything in the code that backs up what he is saying. Am I wrong here? Do I need to eat the costs of replacement?
Replies
What state do you live in? The reason I ask is that you need someone to answer who has access to your exact flavor of the code.
With engineered products, normally the manufacturers recomendations is what is used by the building inspector. Further, I thought it was OK to notch TJI rafters for a birdsmouth, as long as it is only at the bottom end of the rafter - ie not a mid-span bearing point, etc. Plumb squash blocks need to be installed though. Here in NC we are currently using the IRC 2000 code (NC modified), which has very little (and vague) verbiage on wood I-joists for rafters, and basically refers to the manufacturer design specs.
I think you are in the right as long as you did it to manf. specs, and especially if your building inspector is OK with it.
He is right about local inerpretations.but this might help to further communications with him.
My memory of TJI specs for rafters is about twenty years old. i think that back then, they did not allow such noitching as you have done. if your GC is that old, he may be going on outdated info and memory, so you might be able to simply tactfully bring him up to speed. I have had a couple subs enlighten mne on new changes. Just don't approach it adversarily, and be backed up with documentation.
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Yes, this fellow is in his mid sixties. I believe that is most likely the issue.
I live in an unincorperated area in missouri. The only building codes we have here are enforced by the fire marshall. (fire blocking, egress, etc.) Although, having been the victim of many a harsh city inspector from days past, I believe that knowlegde of codes is essential. But more importantly I would never consider erecting anything unsafe. I have quite a few years of experience, but I don't think that I will ever know everything about framing.
I had the honor of working for an older guy who was a large general from St. Louis. I was a little younger and eager to learn all he was willing to teach. I asked him once who it was that he had gained the most knowlegde from throughout his career. He replied " the lowest laborer I have. The guy running a wheel barrel, carrying bricks, or using a shovel". " every time I get stumed, can't figure how to do something, or need an easier way I'll look for the lowest laborer I can find". He isn't confused by code, or experience. He'll flat tell you the easist way to get it done. Even if it aint right it'll make you think in a different direction....... You know what,... he's right.
Thanks piffin.
Go here for some reference information. http://www.trusjoist.com/PDFFiles/2025.pdf
I don't see in the Trus Joist information, nor have I ever seen in anyone's engineered joist details, a birdsmouth detail for seating rafters on plates.
I see sloped plates, and I see blocked ends wherein the bottom flange is cut horizontally where it comes to bear on a not-sloped plate. No birdsmouth though, no matter how reinforced.
Are your bottom flanges cut so that a horizontal "seat cut" of the flange bears fully on the plates?
Gene Davis, Davis Housewrights, Inc., Lake Placid, NY
OK - you got me curious so I had to go look it up... look at this page: http://www.gp.com/build/product.aspx?pname=Wood+I+Beam%e2%84%a2+Joists&pid=1390&hierarchy=pc, scroll to the bottom, and click on the first document in the list. Once viewing the .pdf document, look at page 28, diagram R4 & R6. Ya gotta be careful when talking about engineered lumber as you need to use the directions that go with the brand of stuff you are using.
Assuming that Carl has had a very good look at his local code book, I think that he should say to the GC - "show me in the book" - in a slightly more tactful way, as Piff suggested.
It amazes me of how many guys don't own, have never seen, don't bother to read, etc, etc, a code book, and strictly go on "well my brother in law said", and "I once had a BI tell me" and "the place where I used to work". Yea, some of those are good resources, but I like to see what is on paper too. Matt
I should have been more clear. Trus Joist allows a birdsmouth detail, and shows it in their specifier's guide, but the bottom flange must bear fully on the plate. The webs are reinforced with appropriate thickness material.
If the thread initiator had said, "we did the birdsmouth detail exactly per the manufacturer's literature," I wouldn't be commenting here, but he didn't.Gene Davis, Davis Housewrights, Inc., Lake Placid, NY
We have used both methods, both recommended by the manufacturers, without a problem from the building inspector. I think that the gc is jerking you around. If you did follow the manufacturers recommendations, I bet that they might provide an engineer stamped detail of the installation that would be acceptable by any code at no cost as a customer service to back up their product. It might be worth persuing this if the gc wants to play hard ball.
Just using my common sense and my experience with wood eyes. The blocked flange is supposed to bare on the plate completely. This prevents the joist from failing due to web-flange separation. I've notched the joist after the blocked bearing point on a sixteen inch member only on the overhang side. It seems to me that a fairly easy alternative for you would be to block out the web both sides, but more importantly gusset the joist flange to flange with 3/4 inch ply. This should transfer the bearing point properly. I would come about four feet from the seat towards the ridge. You can always talk to an engineer and ge a spec'ed repair. I hope I can get back to sleep 5:00 comes early. Edit: After looking at the GP manual I see that I the bootom flange can be cut and I think that you should be all right .
Edited 6/21/2005 10:45 pm ET by quicksilver
Here's the GP installation guide.
http://www.gp.com/build/DocumentViewer.aspx?repository=BP&elementid=4372
The allowable roof details for their products are on page 28 and 29.