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Old 09-15-2010, 12:50 PM   #1
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Joist Bracing/Blocking Q's


is bracing required between ALL joists? I currently have 2x4 cross bracing midspan, and blocking where 2 joist members meet on a girder (2 joists make up the full with of the house, where the girdir is in the middle). There will be a large duct running the entire width of house through on joist bay, so there will not be room for blocking or bracing.

if running pipes/wiring, are the rules for bores and notches in blocking the same as for joists?

[not a bracing/blocking q] are rules for bores and notches in top/sill plates same as for studs?

batt insulation is not suppose to be compressed. So when installing against cross bracing, the bracing will create a gap in insulation. The other option is to push the insulation tight against the blocking to close the gap, but then of course you'd be compressing a triangle shaped portion of the insulation. Which is the better option? I see my current insulation is installed very loosely and there is a huge gap where the bracing is. Doesn't seem quite right to me.

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Old 09-15-2010, 01:07 PM   #2
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Joist Bracing/Blocking Q's


Cross bridging is often specified on plans if joist span is over 8'. It gets nailed on top, the subfloor is installed, and then the bottom gets secured.

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Old 09-15-2010, 01:57 PM   #3
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Originally Posted by epson View Post
Cross bridging is often specified on plans if joist span is over 8'. It gets nailed on top, the subfloor is installed, and then the bottom gets secured.
you're thinking the metal bracing like this which would be difficult to work around:


what I have is the 2x4 bracing nailed to the side of the joists like this:


there are already a few that must have been knocked out by an electrician to run wires and were never replaced. I will be replacing those. But my remodel includes running a large duct through a joist bay that would be too large to use bracing. So my question is would that be ok? Maybe I can use strapping instead?

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Old 09-15-2010, 02:37 PM   #4
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Joist Bracing/Blocking Q's


Has anyone tried the IBS2000 bracing systems yet?
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Old 09-15-2010, 04:22 PM   #5
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Joist Bracing/Blocking Q's


From your State Code:
Prevent rotation (blocking or hangers at ends) ________________________ 2308.8.2
Blocking at intermediate supports __________________________________ 2308.8.2
Joists >2X12 blocked or bridged max 8ft O.C. ________________________ 2308.8.5
No notches middle 1/3 of span ____________________________________ 2308.8.2
Bored holes min 2in from top or bottom or other notch or hole ____________ 2308.8.2
http://docs.google.com/viewer?a=v&q=...h1W5lElSFXE4_w

Notches and holes, Page 2: http://arch.umd.edu/Tech/Structural_..._Guide_A11.pdf

You don’t want a gap. Better to compress some of it with the rest meeting. No gap under floor: http://oikos.com/esb/38/floorinsulation.html

Gap metal or wood cross-bridging or it will squeek……

Gary
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Old 09-15-2010, 05:51 PM   #6
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Quote:
Originally Posted by GBR in WA View Post
From your State Code:
Prevent rotation (blocking or hangers at ends) ________________________ 2308.8.2
Blocking at intermediate supports __________________________________ 2308.8.2
Joists >2X12 blocked or bridged max 8ft O.C. ________________________ 2308.8.5
No notches middle 1/3 of span ____________________________________ 2308.8.2
Bored holes min 2in from top or bottom or other notch or hole ____________ 2308.8.2
http://docs.google.com/viewer?a=v&q=...h1W5lElSFXE4_w

Notches and holes, Page 2: http://arch.umd.edu/Tech/Structural_..._Guide_A11.pdf

You don’t want a gap. Better to compress some of it with the rest meeting. No gap under floor: http://oikos.com/esb/38/floorinsulation.html

Gap metal or wood cross-bridging or it will squeek……

Gary
thanks.

so is that a no to running ducts in the joist space since bracing is required? This is what was suggested by HVAC sub. He wanted to run cold air return in joist space, or more accurately, use joist space as cold air return plenum and line it with sheet metal.So unless I can install bracing inside the sheet metal?

I understand notch/bore restrictions in joists and studs, but my question is if bores and notches in blocking & top/sill plates fall into these restrictions or if there are separate restrictions.
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Old 09-16-2010, 08:18 AM   #7
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Actually acerunner I was talking about your second picture.
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Old 09-16-2010, 10:20 AM   #8
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Originally Posted by epson View Post
Actually acerunner I was talking about your second picture.
ok. when you said nailed to the top, I thought you meant top edge of the joist, where it will be sandwiched between joist and subfloor, which must be the metal type.
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Old 09-16-2010, 10:22 AM   #9
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No problem
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Old 09-16-2010, 11:35 AM   #10
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"so is that a no to running ducts in the joist space since bracing is required?" ------- Yes, I have seen the block removed and used for HVAC, many, many times. As long as it passes inspection.

"So unless I can install bracing inside the sheet metal?"----- No, that would cause air turbulence.

"I understand notch/bore restrictions in joists and studs, but my question is if bores and notches in blocking & top/sill plates fall into these restrictions or if there are separate restrictions." ------ No restrictions. Some science: http://books.google.com/books?id=DWs...olumns&f=false

Top plates: pp.15: http://www.awc.org/helpoutreach/ecou...seV09-2007.pdf

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Last edited by Gary in WA; 09-16-2010 at 03:50 PM.
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Old 09-17-2010, 08:41 AM   #11
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What we have done and supplied in the past was use a 3’’ x 2’ x 1/4’’ thick plate with 6 holes either side to except ½’’ lag bolts and we had no issues as per your reference to page 15.
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Old 09-17-2010, 09:50 AM   #12
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Quote:
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What we have done and supplied in the past was use a 3’’ x 2’ x 1/4’’ thick plate with 6 holes either side to except ½’’ lag bolts and we had no issues as per your reference to page 15.
1/4" is awfully thick. How do you install wall coverings in that area?
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Old 09-17-2010, 09:52 AM   #13
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Originally Posted by acerunner View Post
1/4" is awfully thick. How do you install wall coverings in that area?
By using furring strips
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Old 09-17-2010, 04:04 PM   #14
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Quote:
Originally Posted by GBR in WA View Post
on page 21 of that doc. "And when wider studs are used it's important that they rest completely on a plate. The code requires for the plate to be at least as wide as the studs."

I have a few walls that are furred out around footings as shown in drawing below. Would that be a violation?
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Old 09-17-2010, 06:01 PM   #15
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Joist Bracing/Blocking Q's


Are the walls bearing or just to add insulation behind and hide the concrete footing? How wide is the bottom plate?

Gary

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