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#154059 - 02/21/04 12:02 AM Trenching Concrete Floors  
Joey D  Offline
Member
Joined: Oct 2003
Posts: 259
Arlington MA U.S.
I am on a job in a apartment building where the floors are all concrete. The contractor is framming a few areas in he middle of the ceiling to install recesed lights in. He has cut a 2inch deep trench in the ceiling from one lowered ceiling to the new one. The floors are only 8" deep. Would this be a smart thing to do?


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#154060 - 02/21/04 01:09 AM Re: Trenching Concrete Floors  
crash  Offline
Member
Joined: Oct 2003
Posts: 147
Calgary Canada
The only person who could answer that question is the Engineer who designed the building. If the engineer gave the contractor the go-ahead for this trench and the corresponding repair, then it should be okay.


#154061 - 02/21/04 06:36 AM Re: Trenching Concrete Floors  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I agree with Crash.

Any chance these are precast cement decks?

If yes as long as the pre-stressed cables inside are not cut it seems you can do a lot to them, with an engineers OK.

Without an engineers OK this sounds dangerous.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#154062 - 02/21/04 11:05 AM Re: Trenching Concrete Floors  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
I agree with Crash and Iwire. A structural engineer would need to be involved, and it would seem to me that there would be some specific instructions to the cutting.

Roger


#154063 - 02/21/04 11:54 AM Re: Trenching Concrete Floors  
DougW  Offline
Member
Joined: Jun 2003
Posts: 1,143
North Chicago, IL
I was going to ask if they were Spancrete, or another type of cellular concrete. Taking 2" out of that could be, uh, problematic.

Get a Structural Engineer's opinion.


#154064 - 02/21/04 01:20 PM Re: Trenching Concrete Floors  
u2slow  Offline
Member
Joined: Sep 2003
Posts: 200
Salt Spring, BC, Canada
I work in mainly new highrise construction. Typical floors are 190mm (approx 7-1/2") and having to chip a shallow trench in the ceiling or floor (to bury BX cable or 1/2" ENT) has not been an issue with the engineers or inspectors so long as the steel isn't cut. Usually we don't have to go deeper than 1" or so, unless there's a spot where the rebar is too shallow and we have to go behind it.

Check with YOUR engineer first though [Linked Image]

[This message has been edited by u2slow (edited 02-21-2004).]


#154065 - 02/21/04 08:31 PM Re: Trenching Concrete Floors  
Joey D  Offline
Member
Joined: Oct 2003
Posts: 259
Arlington MA U.S.
Thanks. I was thinking the same.



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