I have a duplex with a wrap around gravel driveway, and a detached 4 stall garage directly behind the house (so there's a bit of a parking area in between). It's a little over 42' from the house to garage, and this is replacing an existing metal conduit that got a short in it last winter.

I'm planning on running 2 1/2" conduit out there this weekend. I'm not sure what setup I want out there yet (sub panels, a few 20A lines, etc), but I'll be running both unit's cable through that conduit, leaving plenty of room for expansion, and I want the conduit in the ground before winter, as I can always run the cable later.

A few questions:


How deep should I bury the conduit? I'm pretty sure local code is 18", but should I go deeper as a gravel driveway/parking area is on top of it?
When the conduit comes out of the house... how should I seal around that to prevent leakage as this will be under ground? Is a tight hole and caulk good enough? What about where it goes into the garage (above ground, explained next)?
I'm planning on doing the run straight from the basement to the garage, then one of those slight curve 90 bends out of the ground right in front of the garage's brick veneer, then a hard 90 into the garage (street elbow, I believe?), then another hard 90 up the inside of the garage wall into whatever I plan on putting there (so there will be a bit of conduit poking out of the ground into the garage). Does this sound reasonable?

1. table 300.5 tells us that burial under a driveway is 24" to the top of the pipe.

2. hydraulic cement around the conduit and some tar on the outside facing the earth should do it

3. the "hard" 90 is called an "LB". Be sure there is no chance of the exposed conduit being damaged by a car or other means. Remember that all removable covers are required to be accessible.

1. table 300.5 tells us that burial under a driveway is 24" to the top of the pipe.


You're looking at the wrong column.
It is 18".

The 18" is only for dwelling type purposes a garage is not a dwelling type purpose it is a class "U" use since one cannot "dwell" in a garage

It still falls under a dwelling setting. It is an accessory building to a residence.

I have NEVER heard of a residential garage not referred to as a dwelling setting. A residential garage IS for "dwelling related purposes".
Besides, it is not going under the garage, it is going under the driveway.

Under Location of Wiring
Method or Circuit

"One- and two-family
dwelling driveways and
outdoor parking areas,
and used only for
dwelling-related
purposes"

18"

I thought this site was to help out people with questions, not a pissing contest. I'm trying to help these folks, and you insist on correcting me. I'm giving answers straight out of the 2005 NEC. If you are that much of an expert, stanfortyman then I suggest you apply to the site "JUST ANSWER", where you are paid for your opinions. In the peoples republic of New Jersey, where I am an inspector, a garage is absolutely not considered a dwelling use and we require 24" of cover whenever the conduit is under a driveway or parking lot. I know that in some states they consider a garage a dwelling space, but we interpret things differently than the rest of the world I guess. Besides, the property is a duplex, more than likely an income property, and unless he lives in both units simultaneously, this is considered non owner occupied, hence a commercial use.

New Jersey. I should have figured.

No, no pissing contest at all. All I see is someone who cannot be corrected, and takes offense when they are.

I only correct what I see is incorrect. I like folks who are asking questions to have the facts, not someone's opinion.

What you are enforcing mr. inspector is NOT required under the 2005, 2008, 2002 or ANY other version of the NEC.

The text I provided is directly from the 2005 NEC. Right in T300.5.
Are you seriously telling me that where it says:

"One- and two-family dwelling driveways and outdoor parking areas, and used only for dwelling-related purposes"

... you do not think this applies to one and two family dwelling driveways??

What planet are you from? Oh yeah, I forgot. New Jersey.

In the peoples republic of New Jersey we have the uniform construction code which modifies the various codes to suit the liars, I mean lawyers, who write the ucc... we don't require arc faults in the prnj... and I've been informed that soon the equipotential bonding grid referred to in 680.26 c will no longer be required either... not my idea, I assure you, but that's how we are do things in nj. For example:the requirement for the recep and light required in 210.63 and 210.70 for hvac units has changed twice since 2007. Sorry if I seemed like a jerk before. When I'm arguing with out of state contractors all week because "we don't do it that way in pa. del. or n.y." you get the picture. I guess I had a workweek flashback. Again, apologies

Well I find it refreshing to see such humility. I also apologize for coming off harsh in my replies. I should have been a bit more tactful.

I found out long ago on boards such as this that there ARE many locally amended codes. More than I ever imagined.
When I make replies I just quote direct NEC. Unless the poster makes their location known and asks about local codes, it is impossible to tell if they need special information.

BTW, welcome to the board. :)

DMOZINGO Were you planning on running PVC? I strongly advise you do since it's more easily worked with. Good luck with your project.

Thanks for the replies guys. I ran the conduit today. I ended up running 2" PVC and using LB's in front of the garage, inside the garage, and in the basement. The final height varied some (it was a gravel driveway and the trencher wasn't totally cooperating), but it averaged to about 19" below the surface. Slathered the tar sealer stuff all around the pipe going into the basement.

The pipe was 2" ID, so like 2.25" OD, and after boring a 2.5" hole, there was only about 1/8" wiggle all around the conduit, not enough room for cement or motor. Good tip though, never heard of that hydraulic cement.

The old conduit was metal and only 2" (!) below ground, which I'm fairly certain is original and just finally shorted after about 40 years. Either way, this new setup is a hell of a lot better.

Hoping to get to the wiring within the next month or two. I'm sure I'll have some questions on that too.

Thanks again!

Glad you got it run OK. Yes, hydraulic cement is great stuff. I always have some on the truck.

Sorry for the little diversion. Electricians can be some high strung guys and it shows sometimes.
It also shows you how things can vary from place to place.

Have fun.