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Is this diagonal blocking providing structural support?

Is this diagonal blocking providing structural support?


  #1  
Old 02-05-23, 11:33 AM
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Is this diagonal blocking providing structural support?

I am checking an existing stud bay to upgrade an electrical panel. Note, a licensed electrician will be installing the new panel. The new panel would be the same width but taller, which will mean it would need to start lower than the existing panel.

Checking the wall, I found that there is a diagonal blocking that would need to be removed for this to work. I'm calling it "blocking" because it is filling the entire cavity between the studs behind the drywall, and is just nailed in.

It's not a contiguous let-in beam going diagonally across multiple bays, but, it's in series and in line with other similar diagonal blocking 2x4s in the neighboring bays. So I couldn't rule out that they might be helping resist compression. It also fills the bay, so it needs to be drilled for wiring -- and this one already has been nearly cut through for the existing wiring (see photo).

It could also be providing fire (draft) blocking but if so a new 2x4 could do the same thing lower down.

I'm in California in earthquake country so I am leery of removing anything that might be increasing structural integrity. I have a lot of doubts this is really doing anything for structural integrity now, but a permit inspector might think otherwise.

So my question is: Is this possibly structural, and I need to add something to replace it; or is it just blocking from construction that can be removed?
 

Last edited by John Panzer; 02-05-23 at 11:34 AM. Reason: typo
  #2  
Old 02-05-23, 12:07 PM
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Most diagonal blocking is intended to resist racking forces, the forces you get when wind (or an earthquake) tries to move the wall sideways along it's length. Because the bottom of the wall is generally securely fastened to the foundation, the top of the wall tends to move out of place so you end up with a parallelogram shaped wall instead of a rectangle. Bottom line, I wouldn't assume you can remove it without compromising your structure. You can get metal bracing that mounts to the edges of the studs; the inspector might let you replace that brace with an X of metal bracing that wouldn't be in the way of all the wires and would probably end up stronger than that hacked up brace.

 
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  #3  
Old 02-05-23, 12:41 PM
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Thanks, that makes sense. There will be a bit under 1/2" of space left behind the newly installed panel once it's in. So it seems possible to fit metal bracing in there.

Opening up the other side of the wall would be a huge PITA for various reasons, so if this is the right approach, I'd hope to figure out something that can be installed from the pictured side. One end would be behind the panel with about 3/8" of space to play with, the other end would have the full 3.5" space of the bay to fasten on to the right hand stud, going that direction.

What's the best way to figure out what options the inspector is likely to pass? (My worry being that if we put something unusual in & fully hook up the new panel before the inspection, then the inspector doesn't believe it meets code, we might be forced to uninstall everything and start over.)

 
  #4  
Old 02-05-23, 02:01 PM
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Is the new panel replacing the existing or in addition to? Some of the cables in the existing seem short already. Where vertically is this wall located in the home (basement, first, second floor)? Is this a load bearing wall? You need to expose the full height of the wall between the studs where you plan to put the new electrical panel to see if it is possible.
 
  #5  
Old 02-05-23, 03:08 PM
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This is replacing the existing panel in-place. I think the main feeder cables coming in from underneath will be okay, given the box will be lower and the electrician plans to put the box in inverted so the feeders come in from the bottom. The other wires in the photo are either very short so it's fine to replace them if needed, or way longer than needed because they're looping way around to come in through the bottom for... historical reasons. So I think it'll end up okay.

I plan to open up most of the bay to take a look at the whole situation once I can clear away some stuff. I know there's no issues above the existing panel, I've run Romex through that space with no problems.

This is a single-story house. I believe given the setup, and the fact that this is present, I should assume it's a load bearing wall.

One piece of trivia: This house was originally built in the 60s, then moved to its current location & placed on a new foundation about 23 years ago. The garage was rotated 90 degrees relative to the main house to get everything to fit on the new lot. So, it's been through a few things . I can never tell whether any given bit of weirdness is for a good reason, or historical accident.
 
  #6  
Old 02-05-23, 04:43 PM
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The best way to determine what the inspector will pass is to run it by them ahead of time. Usually you can can schedule a time to meet with them or talk on the phone. Some of them are real Pita's, others are really helpful. You might get lucky and be allowed to just eliminate the brace given it's just half of one bay. If they get the impression you are trying to do the right thing and not cut corners they are generally more helpful.
 
  #7  
Old 02-05-23, 04:57 PM
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If this is an outside wall, the wood sheathing on the outside nailed to the studs is a better resistance to racking than the angled supports between the studs shown in the photo. If this is an inside wall, racking should not be an issue unless the wall is not connected to another wall at both ends and is load bearing. In this case the angled supports add some resistance to the wall from racking.
 
  #8  
Old 02-05-23, 05:19 PM
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Thanks. This bay is currently an inside wall, with drywall directly on the opposite side. The bay to the right, however, is the beginning of an outside wall stretching that direction with stucco on the outside. Not sure of the sheathing. It's pretty well anchored though since it's also a corner on the other side of that wall.

I'll try to talk to the inspector ahead of time about it, and see what they say.

I opened up the wall below the existing panel (see photo). After more detailed measurements, and guessing where breakers would be in the new panel: It seems to me that we could keep the actual bottom of the panel JUST above the upper left corner of the blocking. But, I'm guessing the wiring would be a major PITA to deal with if the blocking is there. I will talk with the electrician, who originally said we'd have to move it.

The suggestion of replacing the blocking with a steel X reinforcement in the same vertical location, but behind all the wiring, seems worth asking the inspector about. Would a modified version of https://structurelock.com/product/retrofit-dimensional/ work? Or, if it really isn't impinging on the box itself, perhaps just something like https://www.strongtie.com/wallbracin..._bracing/p/wb?



 

Last edited by John Panzer; 02-05-23 at 05:28 PM. Reason: cut off too early
  #9  
Old 02-05-23, 06:59 PM
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Your second link is more what I was thinking. Your first link is more for stiffening floor joists.
Another simple approach would be to sheath the opening with 3/8 plywood, fastened well to the studs on each side. Then cover that with 1/4" sheetrock. That would provide more racking resistance than the diagonal brace and wouldn't interfere with the wiring at all. 1/4" sheetrock isn't usually carried by the big box stores, but any real drywall supply place will have it.
 
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  #10  
Old 02-05-23, 08:59 PM
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The sheathing approach would be fine, but with 1/4" sheetrock I think I'd run afoul of California garage/dwelling fire separation codes: https://up.codes/s/dwelling-garage-a...ire-separation, which requires: "Not less than 1/2-inch gypsum board or equivalent applied to the garage side"

Or maybe I could use fire-rated OSB sheathing?
 

Last edited by XSleeper; 02-08-23 at 07:20 PM. Reason: Removed link to another diy site
  #11  
Old 02-05-23, 11:57 PM
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I think the short answer is no. Diagonal wall bracing is intended to add lateral support to a wall section across the entire wall not just a piece of diagonal wood in a single bay. Here is an older study look at all the various construction method tested, they are all from top plate to bottom plate.

I love the cover plate being used as a stud plate!

https://www.homeinnovation.com/-/med...NAL__91610.pdf
 
  #12  
Old 02-06-23, 10:01 AM
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Thanks for all the replies, this'll be useful for thinking through options.

I realized after going through a 2 year old email from the electrician that I had missed a key piece of info: They had said "For the sub panel change-out, we would have to remove sheetrock and move a wall stud over about 1". Since this is a firewall, we need to keep the fire rating and encase the sides, back, top, and bottom with a layer of sheetrock. Otherwise, we could surface mount the sub panel on the garage wall to keep the fire rating."

If that's a correct interpretation of the fire code--I assume it is-- then yes, there's no way to replace the current panel without moving a stud over, because there's no fire rated layer between the _sides_ of the box and the studs, and there's no room for any to be added. That's true for any available 200A electrical panel, which come in just one width. (And this will be the case for any construction where studs are spaced 16" apart, which is the case for the entire house here.)

I think what they're saying matches this permit inspection guide for a neighboring city: https://www.buildingincalifornia.com...parations.pdf; page 4, "ELECTRICAL PANEL A 1HR FIRE RATED ASSEMBLY" where it has a recommendation for exactly what the electrician stated, with "NOTE: spacing must be framed over 16” o.c. in order to accommodate thickness of drywall." (Because the standard width of electrical panels is too wide for 16" spacing when you add in the fire rated material they call for.)

Or just surface mount the new panel, and do various things to bring the existing in-wall wiring out to it while maintaining the fire rating of the wall.

I guess the existing panel isn't conforming to the current code.
 
  #13  
Old 02-08-23, 07:55 AM
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FWIW, I now have 3 opinions from 3 electricians. 2 of them say the panel can't be flush-mounted due to the lack of space to add 1/2" drywall around the side to complete a fire-rated enclosure. 1 of them say they used to have to do that but haven't had to do a full enclosure for 2 years.
 
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Old 02-08-23, 08:08 AM
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So the panel is where, in the garage or in the house and what is behind the panel?
 
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Old 02-08-23, 08:54 AM
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The panel is in the attached garage. The other side of the wall is a living room. It's standard drywall on both sides. (& this is in California). I should say I have 2 electricians who interpret the code this way -- cannot flush mount a replacement electrical panel due to new fire codes. A third says that they used to have to bring replacements out of the wall for fire rating in this situation, but no longer have to the last 2 years, and they've been installing them flush-mounted (for replacements) with no problems from inspectors. So that's interesting.
 

Last edited by John Panzer; 02-08-23 at 08:56 AM. Reason: additional info
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Old 02-08-23, 02:32 PM
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I have 2 electricians who interpret the code
So what does you local building dept say?
 
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Old 02-08-23, 03:21 PM
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Your link to California codes is being blocked or is incorrect.
Maybe you can just post the reference code number and it can be looked up.

I hate to just jump in in the middle of a thread but I can't see the need for putting sheetrock between a METAL electric panel and a stud. The metal panel to wood stud is already a fire resistant installation.

And as for that bridging below the panel..... take it out.
It's providing little to no support. It's like my first boss would say.... it's all for the big act.
 
  #18  
Old 02-08-23, 11:45 PM
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Sorry about the link. The code is R302.6, "R302.6 Dwelling-Garage and/or Carport Fire Separation", I think. Added relevant part as an image. The piece they're quoting is "1/2 inch gypsum board or equivalent applied from the garage side" of shared garage/dwelling walls for fire separation. I think this gives 1 hour fire rating, so I am guessing you'd need something 1 hour fire rated as an equivalent -- but getting that rating is tough, apparently. It isn't just individual parts that get fire ratings, it's pieces in an assembly -- like gypsum board 1/2" screwed to 2x4 studs and sealed with no holes.

I can understand why a thin sheet of metal alone isn't 1 hour fire rated, because the issue isn't just will the fire destroy the metal, it's whether the heat will be conducted through the metal to what's behind it and ignite that, bypassing the otherwise-insulating sheetrock that's around the metal. I could see the studs the panel is touching charring and catching fire more easily.

All the electricians agree the diagonal blocking can be removed with no ill effects, so I guess this thread is now on to a completely different question.

I will check with the local building department once I have all the proposals in hand -- the question is going to be "which of these solutions can meet code" I think. So far I have 4 electricians and 4 different proposed solutions, including "this isn't an issue". The fourth electrician has now proposed putting it flush in the wall, and covering it with a second fire-rated door slightly larger than the panel door. So then it'll basically be in a little airlock, which will protect the metal from fire.










https://up.codes/viewer/california/c...lanning#R302.6

 
  #19  
Old 02-09-23, 01:59 PM
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The thin metal panel is the best possible fire stop. A fire stop is just a fire delay-er.
The only true fire stop is metal or a masonry type product..... like brick, block, cement, etc.
Not even sheetrock is a true fire stop. It just delays the fire's travel.

I have several "high end" towns that I work in that require cats... fire stops in walls.
A full sized block is installed midway between floor and ceiling.
An electrical panel that fills the bay is its own fire stop. Nothing further needs to be done.
 
  #20  
Old 02-09-23, 10:51 PM
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No argument from me, and one electrician agrees with you. I think the person whose opinion counts here will be the inspector & how they interpret R302.6, though. I guess I should ask them.
 
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Old 02-10-23, 10:41 AM
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So what does you local building dept say?
That's the only one that matters regardless of anybody's opinion or interpretation or experience in their home town!
 
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Old 03-16-23, 09:45 PM
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Just to close this out: I managed to talk to the local building inspector today, very nice guy. He agreed that in my situation, upgrading a panel in place, there's no need to surface-mount the new panel to maintain the garage/dwelling fire separation. He suggested putting an extra drywall sheet behind the new panel (between it and the inner drywall of the living room) if there's room, which there probably is, and normal fire stop measures like fire putty otherwise. He also pointed out the same thing as noted above -- the metal door is pretty fire resistant.

In the course of researching this, I also found https://www3.iccsafe.org/cs/committe...E_15_04_16.pdf, which seems relevant:

"The separation is not a fire-resistance rated assembly. Section R302.6 simply requires a layer of 5/8” Type X gypsum board on the garage side. Openings and penetrations through walls or ceilings separating the dwelling from the garage are to be in accordance with Sections R302.5.1 through R302.5.3. These provisions are also prescriptive requirements. Section R302.5.1 addresses openings, Section R302.5.3 addresses duct penetrations, and Section R302.5.3 addresses “all other penetrations” of the separation between the garage and dwelling. Section R302.5.3 requires such “other penetrations” to be protected in accordance with Section R302.11, Item 4. Even though Section R302.11, Item 4 specifically mentions only vents, pipes, ducts, cables, and wires, the intent is that penetrations of the 5/8” Type X gypsum board membrane by such items, as well as other similar items, be fireblocked by simply filling the annular space around “the penetration” with an approved material to resist the free passage of flame and products of combustion. The material filling the annular space is not required to meet the ASTM E136 requirements."
 
  #23  
Old 03-17-23, 12:17 AM
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I managed to talk to the local building inspector today, very nice guy.
They usually are until you try to slip something past them!
 
 

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