I have a question abou Collar Braces. Here in southern Louisiana every parish (same thing as a county) uses a differant building code. We are currently building a house in an area which uses Southern Standard. We have talked with several framers in the area and found that the local inspector has a fetish about the collar braces. We have always put the collars toward the top (upper 1/3) without a problem. It appears from talking to the other framers that this inspector wants the collars exactly 1/3 down from the top. One framer said that he was required to install 22′ long collar braces, and then had to “brace” the braces. My question is what does the Southern Standard actually say about the collars? Do they go in the upper 1/3, or exactly 1/3 down from the top? Also, is the 1/3 measured to the lowest purlin or to the plate? Thanks.
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That's an interesting set of questions.
I've always been taught that they should be no more than one third of the way UP the rafter, in other words, the bottom third. You are probably allowed higher because of no snow load way down there.
The important thing that counts for you is what the inspector requires. Find out from him and do it. Fighting the inspector is a lose lose game. If he's wrong on paper and you win, you will still lose later, somehow or other and for you to fight to keep the collar ties in the upper third instead of one third of the way exactly doesn't make sense because it puts you in a position of trying to build a weaker structure instead of a better one.
I would assume the reason for an extra brace on a 22' long collar was to keep it from flopping around with such a lonnnnnnnnng span.
Excellence is its own reward!
Collar ties....equal.......top third.....and right at top thrid..as your inspector requires...would be building it the best it can be.........
and I don't care if ya have snow or not.....we do here...and it's still a collar tie.....so upper third it goes......just like I learned way back when in trade school......
I remember questioning the logic at the time.....like a longer triangle would make for a stronger triangle.......but I remember being corrected and shown the logic behind the upper third answer........which I've new lost forever......so I'm just left with the text book that says.......top third.
Actually....the logic ran akin to...collar ties are to strengthen the ridge system.......ceiling joists are to strengthen and keep the walls from seperating. Ceiling joists got down...collar ties go up.
A roof/ceiling w/o ceiling joists(vaulted) is a different animal..that's gotta be engineered different.
Jeff
Jeff
..............Al-ways look on......the bright......side of life...........
.......whistle.....whistle.......whistle........
Piffin is getting "collar" ties and "rafter" ties mixed up. Rafter Ties go at the lower third to keep the walls from spreading. Collar ties go in the upper third to keep the rafters from blowing up and away from the ridge. I was raised in Oklahoma where tornados are their biggest concern. The purpose for collar ties are minimal. That is why only the southern standard requires them. In the case of high wind, most soffit have a continuous vent, but the roof only has a certain number of vents. If "extreme" winds were to occur, it would be posiible for the force of the wind to come up through the soffit and blow out the top of the roof. Hence, the need for collar ties. That would be to keep the roof from seperating at the ridge. Florida did a study and found that a large number of house failures during hurricanes were from the wind pushing out on the roof. Most carpenters only think about the forces outside of the house i.e. snow load. Collar braces are actually more affective tight against the ridge, and in the case of cathedral ceilings metal straps would be just as affective.
No agreement on this one boys. Your 'collar' is the top plate, the ring that holds the house together. Placing a horizontal tie in the upper third of the rafter does absolutely nothing to stop plywood from being torn off the rafters in an uplifting wind and very little to prevent outward spreading of the walls when the rafters are loaded. It might help tie rafters together at the ridge though so we are probably back to regional differences. I did assume you meant collar ties
The lower in the framing system it is, the more it resists the forces that contribute to outward spread on the walls when there is no structural ridge. Those forces are greater in heavy snow country which is why you find more specifics for different placement in the north country.
So it seems like if it is in the upper third, it is a rafter tie and in the lower third, a collar tie?.
Excellence is its own reward!
http://www.taunton.com/finehomebuilding/pages/h00011.asp
Scroll down about two thirds of the way in this article for the part about collar ties and rafter ties. According to it, I'm wrong on my terminology. Continuing education! In over thirtyu years, I've always heard ALL these horizontal members called collar ties and never heard the term rafter ties.
The two problems that I'm still trying to get my head around:
How is it even possible to have a 22 foot long collar tie if by definition, it is in the upper third? By the time you get into a 66 foot wide building, trusses come into play instead of stickframing.
How does a collar tie stop the plywood and roofing from lifting off? It holds the frame together but the ply still ligts if not nailed right. The studies I remember from Andrew and Hugo showed that the codes were fine but builders and inspectors were getting by with piss poor nailing off.
.
Excellence is its own reward!
As far as the 22' collar ties... That was from the inspector not knowing what he was talking about and made the framers install them 1/2 way down. As far as the structure is concerned. If the wind reaches the point that it would start tearing something up inside of the roof. Would you rather lose the connection of the rafters to the ridge, which would destroy the whole roof, or have a couple sheets of plyboard blow off the top of the house in order to relieve pressure? The plywood would act as a pop-off valve. I didn't come up with this, an engineer did. don't blame me. The reason I sent the question in, is because I don't own the Southern building code. I use the International as my main reference. The Parish that we are building in has just recently adobted the Southern Building Code. The inspectors are retired state troopers whom have never built a house in their life. Are you starting to see the problem. All I am asking is what exactly does the Southern Building Code say about Collar Braces.
After ssearching all afternoon, I don't find any specifics.
I guess you have to buy the code book for a hundred bucks or let the inspector tell you..
Excellence is its own reward!
We use the new Florida Building code but it's an update of past codes with new stuff specifically for high velocity wind areas. The Section on roof and ceiling framing is still the same as it was in the 1994 SBC (the oldest code book still on my shelf) with the same numbers: 2309.1.7 Collar beams of 1x6 boards shall be installed in the upper third of the roof height to every third pair of rafters.
Collar ties...beams...what ever...upper third....
size the rafters right for the span.....and they don't need the extra help at the bottom.
Jeff..............Al-ways look on......the bright......side of life...........
.......whistle.....whistle.......whistle........
Jeff, sizing the rafters has absolutely nothing to do with whether the walls need to be tied. You could build a roof with 6"x12"oak timbers only fourteen feet long and laid @16"oc on a 12/12 pitch but if there is no structural ridge, they WILL spread the walls and let the ridge sag over time. That is the reason for the ties, whether you call them collar or rafter ties, and for that purpose, the lower third of the rafter is the best place.
I know I've learned from being challenged here and doing the research to find out why I'm finding this confusion out here. It's because we started out talking about two different things. In northern states and mountain areas with heavy snowload requirements where loads do push the ridge down and the walls out, we have always been more concerned with keeping the walls from spreading. In sounthern areas without snowload problems but with more frequent tornadoes and hurricanes, uplift is the greater concern and placing the ties in the upper third is the answer..
Excellence is its own reward!
Once more..with feeling...
Collar ties....or collar beams......upper third.
Vaulted ceilings.....mean structural ridge......and ya better pay close attention to the rafter size/span.
Non-structural ridge.....means flat ceilings......with ceiling joists....with...or without...collar ties...in the upper third.
If I can remember way back when....this thread was about an inspector?
If he said upper third.....the inspector...was also right.
Jeff
..............Al-ways look on......the bright......side of life...........
.......whistle.....whistle.......whistle........
I think the problem with the inspector is that the inspector wants the "collar tie" in a spot that is exactly one third of the way down while the builder wants to argue with him whether anyplace in the upper third zone is ok to save a few feet of 1x6.
I said same in my first reply - inspector is right enough to not be worth the hassle of arguing with him. He'll win one way or another.
Like arguing with your wife, when you win you lose. But if you know how to lose, you win..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit. The second is to look things in the face and know them for what they are." --Marcus Aurelius
well..in that case.....I'd say you're 100% right.......as I was taught.....it's Upper third.....as in..anywhere in the upper third....just not lower.
but...like ya say......if ya can....put them at exactly 1/3 down...and maybe everyone will be happy. ...not the biggest of changes to be made for a happy bld inspector.
Jeff..............Al-ways look on......the bright......side of life...........
.......whistle.....whistle.......whistle........
What I find interesting is that a 1x6 is called a BEAM.