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Old 11-09-2008, 03:20 PM   #1
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Cross bracing


I was wondering if I could add strength to a ceiling joist system by adding cross bracing between the 2x6 joists? They span 13' at an approx. 20 degree angle. Will be finishing the room off and want to make sure the ceiling will support the new sheet rock. I am looking for some overkill as I usually do just to be sure. The roof has been in place for 5 years and no movement wahts so ever so not worried about it in it's present state but when I add the weight of the insulation and sheet want to be sure.

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Old 11-09-2008, 03:30 PM   #2
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Cross bracing


There's more to a truss than meets the eye.

http://www.google.com/search?hl=en&q...2roof+truss%22+

The angles are such that no piece has forces tending to make it slide against any other piece.

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Old 11-09-2008, 04:06 PM   #3
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Cross bracing


It doesn't sound like he's talking about trusses. If they are in fact trusses, do not add additional braces.

If it is a framed ceiling (ceiling joists), you can stiffen it a little bit by adding solid blocking or bridging. I don't see any reason to do so, as the ceiling won't get walked on. Bridging is effective at helping distribute live loads like people walking or heavy furniture, but your ceiling won't have anything but dead load.
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Old 11-09-2008, 06:47 PM   #4
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Cross bracing


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Originally Posted by thekctermite View Post
If they are in fact trusses, do not add additional braces.
Why ?
A few days ago a friend and i tossed up 17 trusses, 22' long and after we where done he told me it would be a good idea to slap a couple 2x4s across the bottom 2x4 of the truss so when i go to sheet-rock it would a sure everything would be 16 oc (i planed on leaving them).
Should i remove these extra "supports" once the sheet-rock is up ?

Sorry to side track this thread.

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Old 11-09-2008, 07:38 PM   #5
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Cross bracing


There should be no reason to add solid blocking into your ceiling joists/ rafters for strenght. I dont think it would really do anything. I have never needed to do it on any of our jobs.
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Old 11-09-2008, 07:48 PM   #6
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Cross bracing


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Originally Posted by iMisspell View Post
Why ?
A few days ago a friend and i tossed up 17 trusses, 22' long and after we where done he told me it would be a good idea to slap a couple 2x4s across the bottom 2x4 of the truss so when i go to sheet-rock it would a sure everything would be 16 oc (i planed on leaving them).
Should i remove these extra "supports" once the sheet-rock is up ?

Sorry to side track this thread.

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I've seen this done before! Years after the fact and no harm was done.
I'd leave them!
If it is to be awhile befor hanging the board, it will keep the truss's from bowing!
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Old 11-09-2008, 08:03 PM   #7
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Cross bracing


Bracing the top chord of a truss usually won't do any harm, as many are designed for sheetrock application, which essentially does the same thing.

Adding braces to web chords of trusses that are not called for in the design can affect the way the truss performs under load. Usually it won't be a big deal though.
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Old 11-10-2008, 02:49 PM   #8
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Cross bracing


Sorry guys I ment they are joists - ceiling/roof combo. We live in upstate NY and just worry about the snow load since 2x8's where not used. Just want to make sure the 2x6's will handle the load of the snow and new 5/8" sheet rock spanning the 12-13' without any further bracing.
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Old 11-10-2008, 06:44 PM   #9
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Sorry guys I ment they are joists - ceiling/roof combo. We live in upstate NY and just worry about the snow load since 2x8's where not used. Just want to make sure the 2x6's will handle the load of the snow and new 5/8" sheet rock spanning the 12-13' without any further bracing.
I live not far from you and am in the process of a similar project as yourself!
In my area the live (snow load is 50 lbs psf. My rafters have an 8' span and I plan to use 2X8's.
I could use 2X6's but 2X8's will allow me to install R21 insulation (6")
If I were you. I would consider installing 2X6's edge sistered to the existing rafters. These would be supported by a ledger board at both ends.
This would help carry the extra dead load, plus the 50 psf live load. And allow space for insulation.
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Old 11-11-2008, 08:28 AM   #10
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Cross bracing


I think I understand what you are saying. Right now I have the 2x6's off of the ledger board on the house supported by the metal joist hangers and it goes down to rest on 2 2x6 cross members. So what you are saying is to twin up each 2x6 joist with a new 2x6 joist and screw them together. Won't that limit the insulation value? I was actually thinking about furring the 2x6 another 1.5" to make room for more insualtion. I live near Elmira, NY so I don't think our snow load is as great as someone closer to the Buffalo or Rochester area. Thanks for your reply and look forward to clarification.
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Old 11-11-2008, 12:03 PM   #11
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I think I understand what you are saying. Right now I have the 2x6's off of the ledger board on the house supported by the metal joist hangers and it goes down to rest on 2 2x6 cross members. So what you are saying is to twin up each 2x6 joist with a new 2x6 joist and screw them together. Won't that limit the insulation value? I was actually thinking about furring the 2x6 another 1.5" to make room for more insualtion. I live near Elmira, NY so I don't think our snow load is as great as someone closer to the Buffalo or Rochester area. Thanks for your reply and look forward to clarification.
Note: I was suggesting that the new rafters would be installed under, and to the edge of the old ones. But, if this would lower the ceiling (5 1/2") too much the new rafters could be sistered beside the old ones. This would of course reduce the insulation area plus limit the thickness of the insulation also!

I live in the lee of Lake Huron in Ontario, Canada. We do have a heavy snow load from streamers coming in, off the lake.
I assume that your rafters are supported by a double wall plate (2-2X6's). This should be adequate support.
I have my doubts that 2X6's are good enough for the span that you have.
I would install ledger boards, both at the house and at the outside wall. Then hang the additional rafters from metal hangers at both ends.
One advantage of the new ledger boards would be support for the drywall.
Fastening the new rafters to the old wouldn't be a necessity, but strapping them together with metal plates may have advantages!

Last edited by Wildie; 11-11-2008 at 12:09 PM.
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Old 11-11-2008, 12:50 PM   #12
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Cross bracing


I do have a ceiling height issue but would rather be safe than sorry. What about putting new 2x8's up next to the 2x6's hang with joists hangers and notch out the end of the 2x8's to fit into the existing cross bracing. Thanks for the help. Any knowledge on crawl space insulation?
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Old 11-11-2008, 03:14 PM   #13
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I do have a ceiling height issue but would rather be safe than sorry. What about putting new 2x8's up next to the 2x6's hang with joists hangers and notch out the end of the 2x8's to fit into the existing cross bracing. Thanks for the help. Any knowledge on crawl space insulation?
I find that your reference to cross bracing confusing! I assume that you are referring to the support from the wall, where the rafters lie. Cross bracing to my mind is diagonally placed strips of wood placed between joists. In the form of an 'X'.
By the way. just confuse the issue, if roof sheeting is supported by horizontal framing, these are referred to as rafters. Whereas, if they are supporting a floor above, or an attic, now they become joists. And if they are on a second floor that is unfinished they are referred to as collar ties, until they are used to support a finished ceiling and then they become ceiling joists.
See, when your mother said that life is not easy, this is what she was referring to.

Anyway! back to the problem at hand.
2X8's sistered to the 2X6 rafters is likely over-kill. Another option would be to install another set of 2X6 rafters in the center of the existing rafter bays. Glueing them to the roof sheeting.
This wouldn't be good from an insulating point of view.
But would maintain the ceiling height.
As a compromise, you might consider using 2X4's edge to edge to the 2X6 rafters. These I would glue together.
Again this will drop the ceiling 3 1/2", but would allow R20 insulation, plus an air gap.
About crawl space insulation. At my place I used ROXUL brand insulation held in place with wire pins.These pins have a flat perforated base. A dab of construction adhesive is placed on the concrete wall and the base is pressed into this.
24 hours later, the insulation is pressed onto the pin. A vapor barrier is hung over the top and then the the vapor barrier and the insulation is held in place by a 'press' nut!
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Old 11-11-2008, 04:38 PM   #14
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Cross bracing


Thanks for all your help just a dumb heating guy on this end no way trying to impersonate a builder. Thanks again
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Old 11-11-2008, 10:10 PM   #15
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Thanks for all your help just a dumb heating guy on this end no way trying to impersonate a builder. Thanks again
I'm an electrician (ret) trying to impersonate a framer!

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