Adding sub panel to attached finished garage - few questions

[DIRTMCGIRT_VA]

Good afternoon everyone!

I need a little help reviewing my plan for adding a 100A sub panel to the attached garage.

My challenge is that the main panel is on the opposite side of the house from the garage and in the basement which is about 90% finished, so I will need to run the feeder cable about 40' through the basement ceiling (floor trusses). I have successfully drilled a hole from the basement into the garage wall to get a feel for the location, but it's only about 4-5 inches above the garage floor. Is this too acceptable to do? My first thought was to use a 2" LB into the garage wall and bottom feed the sub panel I have also been considering running it inside of the wall and feeding into the back of the box, but have a little concern about how to approach a wire this size going through the top of the floor truss.

Any other issues that you see with my approach from the drawing attached? (purple line represents the SER feeder)

 

[PCustoms]

Is that conduit the full way, or just inside the garage?

 

[DIRTMCGIRT_VA]

Is that conduit the full way, or just inside the garage?

The plan was just inside the garage from the LB to the box.

 

[Innovate1]

No issue with how low it is to the floor that I know of. They may want you to use sch 80 PVC for a little better protection from things hitting it - that depends on the local authorities. I would consider using a 90 bend rather than an LB. If you want to put it in the wall I think that presents a problem with how to keep the LB into the back accessible - don't think you can bury those in the wall. Would need an access panel on the house side. And there are fire wall issues to deal with. Others more knowledgeable will probably chime in. For drilling the floor truss - is that running parallel to the wall? If so some blocking on each side of the hole would prevent any sagging of the top cord. Surface mount conduit would be a lot less work.

 

[PCustoms]

I don't see a scenario where the 90 fits.

An LB down low, inside the garage where it's accessible, seems like a good choice given a surface mounted panel.

You're correct if he comes up the wall the LB needs to remain accessible from inside the house

Edit: post above got me thinking LB inside the wall, but it's not needed with SER in the wall as noted below

 

[sparky 1971]

Since the OP states 1) he's using a feeder cable, 2) the basement is 90% finished, and 3) he's going through the floor trusses, it's pretty safe to guess he wants to use SER cable and if indeed that is the case, it's acceptable to go up the wall and in the back of the panel but that might be more effort than it's worth. The 2" LB method is ok but a 10X10X4 box is probably the easier. Either way, as long as it remains accessible, it's fine.

 

[PCustoms]

Since the OP states 1) he's using a feeder cable, 2) the basement is 90% finished, and 3) he's going through the floor trusses, it's pretty safe to guess he wants to use SER cable and if indeed that is the case

Seeing as how that's literally what he put on his sketch, yeah, safe guess...

 

[sparky 1971]

Seeing as how that's literally what he put on his sketch, yeah, safe guess...

The sketch was blurry when I tried to zoom in with my cheap tablet, now that I'm on the desktop I see that. How in the hell did a 90, LB in the wall, or conduit across the entire basement come into play?

 

[PCustoms]

How in the hell did a 90, LB in the wall, or conduit across the entire basement come into play?

Well I was double checking that he wasn't running conduit the whole way (line was blue all the way across basement) until he crossed into the open garage, then drafted a post, got distracted and quickly changed what I wrote after @Innovate1 posted...

Not sure why they brought up the 90 (no room IMHO) and didn't think twice about an LB not being needed for SER in the wall...

 

[DIRTMCGIRT_VA]

Thanks! I appreciate all of the feedback. I am probably going to remove a small section of drywall from the garage wall and this should give me access to the top chord of the floor truss.

Just to confirm, if I go the route of trying to go up through the wall, is there anything special I need to do to run the cable up through the top chord? Or is it really just matter of drilling a large enough hole to pass through? Also, anything special that I should consider doing to protect the cable inside the wall from the floor to the entrance of the box? I do not mind removing and replacing this entire section of drywall if that's will make for a cleaner run.

 

[sparky 1971]

Thanks! I appreciate all of the feedback. I am probably going to remove a small section of drywall from the garage wall and this should give me access to the top chord of the floor truss.

Just to confirm, if I go the route of trying to go up through the wall, is there anything special I need to do to run the cable up through the top chord? Or is it really just matter of drilling a large enough hole to pass through?

Just drill a hole. It's going to be harder than what you think to fight the cable up the wall and in the back of the panel. Is there a reason you want to do it that way vs just coming through the wall and running an exposed conduit up the face of the wall? I can see doing it if the panel were to be recessed, but not if it's surface mounted and will probably have exposed conduit run out of the top of it for all the garage circuits.

Also, anything special that I should consider doing to protect the cable inside the wall from the floor to the entrance of the box? I do not mind removing and replacing this entire section of drywall if that's will make for a cleaner run.

Nope. Just make sure you have a cable clamp in the back of the panel. If it's a 2X4 wall, the bend will be pretty tight but doable. A 2X6 wall will be a breeze.

 

[larry4406]

Don’t drill an open web floor truss top chord unless you have approval for it.

 

[DIRTMCGIRT_VA]

Just drill a hole. It's going to be harder than what you think to fight the cable up the wall and in the back of the panel. Is there a reason you want to do it that way vs just coming through the wall and running an exposed conduit up the face of the wall? I can see doing it if the panel were to be recessed, but not if it's surface mounted and will probably have exposed conduit run out of the top of it for all the garage circuits.

Nope. Just make sure you have a cable clamp in the back of the panel. If it's a 2X4 wall, the bend will be pretty tight but doable. A 2X6 wall will be a breeze.

Yep, surface mounted and will be running EMT to the circuits... so you're right exposed conduit for the feeder may just be the easiest option.

 

[DIRTMCGIRT_VA]

Don’t drill an open web floor truss top chord unless you have approval for it.

Didn't realize this would be an issue, but thanks for the call out.

 

[larry4406]

Didn't realize this would be an issue, but thanks for the call out.

Rule of thumb - don’t drill or modify any type of truss.

Similarly, don’t drill LVL’s.

With proper engineering, both can be altered, but always best to just leave them alone and find another way.

 

[Stuart in MN]

Make sure to seal well around the penetration from the house to the garage, both for fire safety and to eliminate the possibility of car exhaust fumes entering the house.

 

[Innovate1]

Seems kind of strange to have a floor truss right under an outside wall and on top of the foundation. Seems like in some situations where they are used there would be something needing a hole, perhaps a drain pipe. In that position the truss isn't under much stress as it is supported all along the length so drilling would be less of an issue. Never worked with them though so not sure...

 

[sparky 1971]

Don’t drill an open web floor truss top chord unless you have approval for it.

I'll admit to doing very little residential work and rarely seeing floor trusses; I've worked on a few of them though in years gone by and have never heard anything about drilling holes in them. Maybe I got lucky and the building inspector missed it? The plumbers drill bigger holes than me and drains have to go where they have to go

 

[Innovate1]

Was curious about this and did a quick search. Found this which is labeled repair detail but is about drilling holes in truss joists. Joist must be supported all along the length and there are serious limitations on hole size and loading so an outside wall supporting ceiling and roof would probably be over those limitations. 1" max hole size and 100 lpf loading max. I did a bit of looking for more detail on floor support under an outside wall with floor trusses and didn't find much. What I did find showed the truss directly under the wall with an additional rim board beside it. Still not sure how drain pipes would be handled. In many cases they could be run horizontally to other inside walls to avoid holes in the floor trusses.

https://www.mitek-us.com/wp-content...s/ENG-FLOOR-drilling holes in floor truss.pdf

 

[dscheidt]

I'll admit to doing very little residential work and rarely seeing floor trusses; I've worked on a few of them though in years gone by and have never heard anything about drilling holes in them. Maybe I got lucky and the building inspector missed it? The plumbers drill bigger holes than me and drains have to go where they have to go

One big advantage of floor trusses is that they have lots of empty space. that makes it possible for even a plumber or an HVAC installer to do their thing without cutting members.

 

[Innovate1]

Rule of thumb - don’t drill or modify any type of truss.

Similarly, don’t drill LVL’s.

With proper engineering, both can be altered, but always best to just leave them alone and find another way.

There are sometimes prescriptive guidelines for LVLs and probably less common for trusses (post 19) that allow limited size holes without any engineering (or technically it's that the engineering has already been done). For example this:
https://www.bc.com/wp-content/uploads/2019/06/LVL-1-Versa-Lam-Hole-Chart.pdf

 

[larry4406]

There are sometimes prescriptive guidelines for LVLs and probably less common for trusses (post 19) that allow limited size holes without any engineering (or technically it's that the engineering has already been done). For example this:
https://www.bc.com/wp-content/uploads/2019/06/LVL-1-Versa-Lam-Hole-Chart.pdf

Yes.

But does Billybob, Jimmy-Jo, and Julio have these at the ready when his first motive is what’s easiest for him? Their motive as a piece worker, hourly is maybe if I vandalize this truss I can save 20 minutes and 4’ of wire….; maybe no one will see it.

Best to always first find another way, and only when 100% boxed in and sounded the alarm, cut/drill only after approved details and have the red stamp at the ready for inspection.

I have had my share of dealing with this **** at the day job. Just best to have a hard stance of NO! Almost always another way and people are just too close minded.

 

[mm08822]

Yes.

But does Billybob, Jimmy-Jo, and Julio have these at the ready when his first motive is what’s easiest for him? Their motive as a piece worker, hourly is maybe if I vandalize this truss I can save 20 minutes and 4’ of wire….; maybe no one will see it.

Besides...why else I bring me chainsaw to work???

 

[larry4406]

Besides...why else I bring me chainsaw to work???

Thought he was roughing in hvac that day instead…..

 

[PCustoms]

Besides...why else I bring me chainsaw to work???

Thought he was roughing in hvac that day instead…..

Ever notice the hole a framing hammer leaves in and I-joist is just about the perfect size for 2-3pcs of 12/2?

 

[larry4406]

Ever notice the hole a framing hammer leaves in and I-joist is just about the perfect size for 2-3pcs of 12/2?

They used to have round knock outs in them about the size of a hammer head. Helps if Neanderthal can align the hammer with the knockout. Haven’t seen the knockouts in years.

Neanderthals? Yes I see them and mouth breathers daily. I question the **** that goes on in these houses and shake my head. Then I say to myself, “these are same people that **** all over the toilet and think it’s fine”.

Perspective….

 

[Innovate1]

Yes.

But does Billybob, Jimmy-Jo, and Julio have these at the ready when his first motive is what’s easiest for him? Their motive as a piece worker, hourly is maybe if I vandalize this truss I can save 20 minutes and 4’ of wire….; maybe no one will see it.

Best to always first find another way, and only when 100% boxed in and sounded the alarm, cut/drill only after approved details and have the red stamp at the ready for inspection.

I have had my share of dealing with this **** at the day job. Just best to have a hard stance of NO! Almost always another way and people are just too close minded.

Good points. I have seen some pretty sketchy things where someone just hacked out stuff to run something through.

 

[Skooterj]

Why would you ever need to drill a hole in a floor truss for wires????? I almost(almost) get it for a toilet flange, but wire is flexible enough to move 2.5 to 3.5 inches around the top cord.

 

[dscheidt]

Why would you ever need to drill a hole in a floor truss for wires????? I almost(almost) get it for a toilet flange, but wire is flexible enough to move 2.5 to 3.5 inches around the top cord.

It happens when the wall is directly on top of, and parallel with, the truss. There's no way to get into the stud bay without drilling a hole in the top (or bottom) chord.

 

[larry4406]

It happens when the wall is directly on top of, and parallel with, the truss. There's no way to get into the stud bay without drilling a hole in the top (or bottom) chord.

That’s when you stop, get the site foreman, and wait for further direction. Don’t just say eff’it and blow a hole thru. Very common to move joists/trusses to accommodate trade roughs.

We back charge trades 100% for stupid **** repairs. I give them notice to take their stuff out before repairs. If they don’t, well we show their work the same level of care when effecting repair.

 

[dscheidt]

That’s when you stop, get the site foreman, and wait for further direction. Don’t just say eff’it and blow a hole thru. Very common to move joists/trusses to accommodate trade roughs.

We back charge trades 100% for stupid **** repairs. I give them notice to take their stuff out before repairs. If they don’t, well we show their work the same level of care when effecting repair.

that's great. How is that supposed to work when the guy drilling the hole doesn't know there's a truss there, because the floor already has sheathing on it? Or in a remodel? or the drawing tells them to put their stuff their? Serious question.

 

[larry4406]

that's great. How is that supposed to work when the guy drilling the hole doesn't know there's a truss there, because the floor already has sheathing on it? Or in a remodel? or the drawing tells them to put their stuff their? Serious question.

Nail patterns on floor sheathing show you where the joists are if you bother to look instead of blow and go.

Bang a hammer on the floor as you slowly move across the floor; the sound will change and you’ve found the joist. Same way you wrap your knuckles in the wall to find a stud.

Look up from below first. Measure the joist layouts. Reference off something that you can transfer to another floor.

Really it’s not hard.

Can’t go down with a wire? Go up jump a couple bays then go down. Oh - yeah there went 50’ of extra unbudgeted wire…BFD.

When you are the one having to fix messes like this you quickly developed a strong distaste for job site stupidity. I’ve kicked many off the job with request for them to never return. I take their picture so I know who they are and include it with the immediate notice to vacate and their back charge invoice.

 

[mm08822]

Nail patterns on floor sheathing show you where the joists are if you bother to look instead of blow and go.

Bang a hammer on the floor as you slowly move across the floor; the sound will change and you’ve found the joist. Same way you wrap your knuckles in the wall to find a stud.

Look up from below first. Measure the joist layouts. Reference off something that you can transfer to another floor.

Really it’s not hard.

Can’t go down with a wire? Go up jump a couple bays then go down. Oh - yeah there went 50’ of extra unbudgeted wire…BFD.

When you are the one having to fix messes like this you quickly developed a strong distaste for job site stupidity. I’ve kicked many off the job with request for them to never return. I take their picture so I know who they are and include it with the immediate notice to vacate and their back charge invoice.

Wouldn't be the first time an 1/8" pilot hole for reference saved my ***. It can also save a lot of time.

 

[larry4406]

Wouldn't be the first time an 1/8" pilot hole for reference saved my ***. It can also save a lot of time.

And you can drill a small hole “Up” safely from below to see where you are. By drilling up, you are not blind and know exactly where the joists are. Then tape measure to ensure proposed pathway is sound.

It’s amazing what a little bit of common sense and foresight can achieve.

 

[mm08822]

up/down, left/right, in/out......it's like magic!!

 

[PCustoms]

It’s amazing what a little bit of common sense and foresight can achieve.

 

[DIRTMCGIRT_VA]

Follow up question... I know that the NEC requires that the SE cable be supported and secured ever 4.5' the same as NM, but I assume that the fact that the ceiling is finished across a 20' section would allow for the cable to not be secured for that 20' distance. So the idea would be to secure on both unfinished sections as required, but not required in the finished section? Would this be a correct assumption?

 

[75gmck25]

Are you able to get up there and look through the unfinished ceiling area where you want to run the SER?

I have to assume the SER will run parallel to the floor joists above, and in most basements the joists have X-shaped cross braces between the floor joists. If you can get the SER up high enough to guide it above the X-bracing, it won't be secured by clamps, but it will not drop down and rest on the drywall ceiling below.

 

[DIRTMCGIRT_VA]

Are you able to get up there and look through the unfinished ceiling area where you want to run the SER?

I have to assume the SER will run parallel to the floor joists above, and in most basements the joists have X-shaped cross braces between the floor joists. If you can get the SER up high enough to guide it above the X-bracing, it won't be secured by clamps, but it will not drop down and rest on the drywall ceiling below.

Well, the floor actually has trusses and not joists and the goal is to run the cable through the trusses as they run perpendicular to the path that I need to take. So it will be supported by the bottom chord of the trusses at the very least. My challenge is just the fact that I won't be able to "secure" it to anything through that section without removing sections of drywall along the way.

 

[sparky 1971]

Well, the floor actually has trusses and not joists and the goal is to run the cable through the trusses as they run perpendicular to the path that I need to take. So it will be supported by the bottom chord of the trusses at the very least. My challenge is just the fact that I won't be able to "secure" it to anything through that section without removing sections of drywall along the way.

It doesn't have to be supported where going through the trusses and above the ceiling. 338.10(B)(4)(1), which will refer you to
334.30(B)(1)