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Old 11-24-2008, 11:31 AM   #1
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Second floor framing(collar ties too high?)


As a Newbie to these forums, I'd like to say a "hello" to all, and a "great site" to the webmasters.

Background:
We bought this 1400sq ft house almost a year ago, and have had a busy(and fun) summer working on just about everything. I'll post some pics later. The seller had done a few improvements recently but there was still quite a bit of work to make the place more conventional.

The house was professionally inspected before closing, and the ceiling showed only two small nail pops: natural for an 18year old second floor addition. The paint was dirty enough for us to think that it had not been touched in quite a while
The inspection report mentioned the "second floor could have been built incorrectly", but the framing was passed by the city, after all.....

Present:
Over this summer, nail pops and cracks started showing up along the rafter-collar ties intersection.
A reputable engineer said that the collar ties should not have been placed higher than 1/3rd up the rafters. The seller probably altered the construction at the last minute which the final inspector never noticed.

To tie the walls together, they recommended either installing three exposed beams, or lowering the ceiling to a conventional eight foot height.

Any suggestions on the construction fixes and/or recourse? Thx John
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Old 11-24-2008, 11:45 AM   #2
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Second floor framing(collar ties too high?)


Collar ties prevent your rafters' tails from thrusting outward when loaded, and tie them together so they load the top of the wall vertically. The code generally requires that collar ties/ceiling joists be placed in the bottom third of the roof's height. They're most effective at the walls' plateline of course, and the higher they are the less effective they are.

The engineer's idea of adding some beams down lower is pretty valid. My only question/concern is did he/she give you any idea on how to attach the beam to the rafters? You'd need to know that. The connection would need to be pretty strong since the beams are working in tension and there won't be very many of them. The beams could be made very decorative, and could be trimmed in wood or sheetrock. Lighting could even be incorporated on them if you wanted.

The other option is of course to frame in a conventional ceiling and create attic space up there, or floor space if the pitch of the roof would allow installation of floor joists. The ceiling or floor joists would certainly keep the rafters from thrusting outward.

Nail pops don't concern me. They happen. There's very little movement occurring at the joint between the rafters and the collar ties...If there is a failure occurring, it would really show up in the walls I think.

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Old 11-24-2008, 11:49 AM   #3
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Second floor framing(collar ties too high?)


Some other guys will be along in a little bit w/other opinions, but to me it looks like there's still some information that could be helpful in determining a course of action. I can think of two different things that could be going on -

1. The outside walls are bowing out, allowing the ceiling rafter/joists to sag. In this case a pertinent question is are there any other walls or parts of the structure that join the outside walls of this room that keep them from bowing out? I see what looks like a wall on the left, is there any difference in the cracks, etc on one side of the room versus the other?
2. The outside walls are supported, but the ceiling rafters/joists are just sagging under the weight of the ceiling, roor, etc. If this is the case, tying the walls together won't help, you'll actually have to install some perlings too with bracing up from the beams to hold the roof/ceiling up. Do you know what the joists are made of (2x6, 2x8, etc.)?

I'm sorry for answering a question with a question, but you could be having more than one problem, and if you don't fix the right one.....
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Old 11-24-2008, 12:14 PM   #4
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Second floor framing(collar ties too high?)


Purlins will not usually prevent ridge sag or wall thrusting due to their angular orientation. If the rafters are overspanned, then purlins would be in order.
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Old 11-24-2008, 12:33 PM   #5
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Second floor framing(collar ties too high?)


Agreed. What I'm going for is if the walls are staying true, and he's seeing cracks, etc, it could be from over-spanning the rafters or ridge sagging. If that's the case, to your point, a purlin (didn't know how to spell it) with bracing down to an added beam could be the ticket. Also to your point, that kind of stuff can be made to look pretty cool it it's done right. It's tough to tell exactly how far the un-supported span goes, but based on the ceiling fan and widows in the pic, it looks like it could be on the order of 10-12 feet, which is a little far for my taste if they 2x6's on 24" centers at what looks to be a fairly shallow pitch.

From the pic, it looks like there's a wall corner on the left that runs pretty close to all the way up to the collar-tie point, which I would expect to help that side of the room, regardless of the mode of failure.

My $.02....
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Old 11-24-2008, 02:15 PM   #6
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Second floor framing(collar ties too high?)


My 2 cents would be to get that engineer back on the project and heed their advice. I had to put in 4 beams ( at plate level ) in a situation somewhat similar to yours in a vaulted roof ( like yours)that previous owner cut trusses to vault. Bottom line is you either use a ridge beam or tie the walls together using 3-4 beams at plate level to stop rafter thrust. I used 4 beams at plate level and engineer signed and stamped off on it. Where are you located?? Do you have a high snow load?? Roof pitch? Rafter length?? This is all info a good engineer will know and be able to design a proper fix.
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Old 11-24-2008, 10:14 PM   #7
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Second floor framing(collar ties too high?)


Quote:
Originally Posted by thekctermite View Post
Purlins will not usually prevent ridge sag or wall thrusting due to their angular orientation. If the rafters are overspanned, then purlins would be in order.
whats a purlin?
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Old 11-24-2008, 10:17 PM   #8
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Second floor framing(collar ties too high?)


Quote:
Originally Posted by thekctermite View Post
Collar ties prevent your rafters' tails from thrusting outward when loaded, and tie them together so they load the top of the wall vertically. The code generally requires that collar ties/ceiling joists be placed in the bottom third of the roof's height. They're most effective at the walls' plateline of course, and the higher they are the less effective they are.
does that mean that if you have ceiling joists, you dont need collar ties? what would be the best means of connecting joists or ties to the rafters, nails or bolts?
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Old 11-24-2008, 11:07 PM   #9
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Second floor framing(collar ties too high?)


Quote:
Originally Posted by feralfreak View Post
whats a purlin?
A purlin is an intermediate ridge of sorts. It is 2x dimension lumber oriented horizontally under the midspan of the rafters, which allows them to span longer distances than they could without midspan support. Purlins are supported by 2x struts, usually at an angle, down to bearing walls or beams.
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Old 11-24-2008, 11:16 PM   #10
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Second floor framing(collar ties too high?)


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Originally Posted by feralfreak View Post
does that mean that if you have ceiling joists, you dont need collar ties? what would be the best means of connecting joists or ties to the rafters, nails or bolts?
Yes, usually. There is no better collar tie than a ceiling joist attached to the rafter heels at each side of a roof. Except in the most extreme conditions, a few 10d nails are perfectly adequate to secure the ceiling joists to the side of the rafter heels.

Collar ties are getting more common as houses get bigger and more cut up. The ceiling joists only work in tension if they're all on the same plane and run in the same direction. That was common in 1950's ranch homes, but is less common these days. Differing ceiling heights make it much more challenging to use the ceiling joists as collar ties. Some engineers specify both, which is usually overkill. But, it is a room by room situation in a lot of cases. Collar ties are often required in parts of a house where continuous ceiling joists aren't there or where the ceiling joists change directions.

Bottom line, collar ties and ceiling joists is great. Ceiling joists is usually great. Collar ties (in the upper 2/3 of the roof) alone requires some engineering.
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Old 11-25-2008, 06:37 PM   #11
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Second floor framing(collar ties too high?)


Thanks for the responses. The rafters are 2x10's 24in on center. On the second floor, a little less than one quarter is boxed in for a beautiful sunny bathroom with two skylights, and the rest is a giant room.

There is some ridge beam sagging, as well as pronounced rafter sag in the center of the roof(I should have described the situation a little better.) The engineer was first talking about putting in a ridge beam initially, but then mentioned the exposed beams, and I got a little lost at that point.

I was wondering what the best solution is:
1)Replace ridge beam only.
2)Replace ridge beam, and add exposed beams. There would be one 30ft run which might look strange.
3)Replace ridge beam, and lower ceiling to 8 foot. A wall might probably be necessary in the center, and the bathroom skylights would be lost.

Last edited by Stillwerkin; 11-25-2008 at 06:41 PM.
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Old 11-25-2008, 06:37 PM   #12
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Second floor framing(collar ties too high?)


The house was purchased in December of last year. The shingles are in good shape, but the roof was covered with snow during the inspection period.
We are in Michigan so a little "overengineering" wouldn't be a bad thing. I wouldn't mind some attic space, but don't want to lose the bathroom light and open space effect.

The only closing contingency I asked for was to cut down a Siberian Elm which was getting ready to take out the power lines to the whole block, but the seller(and my Realtor) finked out on that.
I also found out from a neighbor that the seller had repainted earlier that year, so this was a "previously known issue". I don't really want to pursue the seller unless necessary, but I'm a little ticked at the situation.

Last edited by Stillwerkin; 11-25-2008 at 06:39 PM.
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Old 11-26-2008, 02:43 PM   #13
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Second floor framing(collar ties too high?)


Sagging ridge and sagging rafters, I'd say it's time to get the engineer back on site and ask him to work up a bracing plan for you. If you want the open vault, I would expect it could be retained, but undoubtedly with some exposed structure. If I were to guess, I'd say something like engineered wood beams (i.e. LVL's) spanning at some interval (every 10', 12', etc) with purlins installed maybe mid-rake with braces down to the beams. If the cross-beams were sized appropriately, you might even get away with running a brace up in the center through the flat part of the ceiling to the ridge to brace it up. You wind up with kind of a truss-like structure exposed, which could be made to look pretty cool too. All this would have to be tied securely into the existing framework and supported properly - which is another place an engineer might come in handy.

Even if you go with a conventional ceiling, you're going to have to either build a load-bearing wall to brace from, install purlins to take out the rafter sag, and brace up the ridge....and you don't get the cool effect of the elevated ceilings.

Once you get a good plan, have somebody bid it for you, then go after the seller for some or all of it.

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