Attaching a metal gangbox to a concrete wall


Old 10-14-19, 11:01 AM
Thread Starter
Join Date: Jun 2007
Posts: 129
Received 0 Votes on 0 Posts
Attaching a metal gangbox to a concrete wall

After a storm surge flooded my basement, I had electricians rewire it. Near a sump, they installed a 1 gang box for a pump.

Some time later, a crew installed ducts for an AC system; the air handler and the ductwork semi-hid the outlet in a sort of cul de sac.

As a result, it was some time before I realized that the gangbox wasn't actually attached to the wall; it just hung from the wire/conduit.

The people who put the ducts in might have removed the strap that held the metal conduit in place--it looks like there are screw holes where it used to be, though WHY they'd have removed it, I have no idea. But I cannot see a trace of how the electrical box had been attached, so I can only assume the electricians overlooked that.

So, what should I do? De-power the outlet, remove the top, and mark where the holes on the back are and put in two tapcons? (autocorrect insists on making that "falcons" Use construction adhesive to put a block of wood back there and attach the box to the wood? Something else?

I do have a drill-driver, though I don't have a masonry bit of the right size. I'd like to avoid drilling into the wall if I could--I've dealt with leaks so many times over the years that I have a sort of mental block against making more holes. Is there some sort of mounting strap that would work?


Name:  box.JPG
Views: 40
Size:  66.9 KB

Last edited by PJmax; 10-14-19 at 05:04 PM. Reason: resized/enhanced picture
Sponsored Links
Old 10-14-19, 01:10 PM
Join Date: Oct 2015
Location: Ct.,USA
Posts: 1,223
Received 33 Votes on 28 Posts
You will need to rent a hammer drill to make a hole in concrete for a tapcon. If the holes in the metal electrical box are diagonal, use two tapcons (else 1) with diameter of 1/4 or less and 1 inch long, Don't drill holes close to one another as the concrete may crack between holes. Use a ratchet to install tapcon (need hex heads) because you have to push and turn at the same time. Another method of fastening to concrete is using concrete nails installed with a concrete nail gun. I have no experience using this method.

Last edited by beelzebob; 10-14-19 at 01:14 PM. Reason: hit save by mistake
Old 10-14-19, 04:19 PM
Geochurchi's Avatar
Join Date: Nov 2012
Location: USA
Posts: 4,036
Received 18 Votes on 18 Posts
Drill a couple of holes and use either Tapcon or plastic anchors, you certainly will not create a leak.
Old 10-14-19, 04:43 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,967
Received 59 Votes on 52 Posts
You also need to attach the conduit to the box using the proper connector. (EMT or PVC)

So, what should I do?
Get your "electricians" back to properly finish the job.
CasualJoe voted this post useful.
Old 10-14-19, 06:04 PM
Join Date: Nov 2015
Posts: 1,232
Received 18 Votes on 17 Posts
Could that conduit be just used to sleeve NM cable?
In that case, conduit doesn't need to be connected to the box given that the NM cable is properly attached with a strain relief.
Old 10-14-19, 06:33 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,967
Received 59 Votes on 52 Posts
If it is EMT it is required to be bonded to the equipment ground. This is normally done by attaching it to the box using a connector to the box and bonding the box.
Old 10-14-19, 08:15 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,948
Received 32 Votes on 27 Posts
Looks like a PVC sleeve to me.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes
Ask a Question
Question Title:
Your question will be posted in: