Stairwell Deck...

[jusme123]

I also think Don nailed it.

 

[infinity]

Yes, if you need a nice clean hole drilled really quickly use a wet core machine. No dust either.

 

[1793]

Norb 1793, If I understood correctly the reason going from the tennants panel on the third

floor was so that they were responsible for the electric bill ? So what is the new setup ?

This is a 3 story building with two tenant spaces, one per floor / story.
The ground level, is the garage area for each Unit. The two garages are separate from each other.
There are individual entries for each Unit. You enter on the ground floor into a Foyer with an elevator. When the elevator opens you are stranding in the hall of the Unit.
Down in the Foyer there is an In Wall AC/Heater that is 240V and on my customers panel, 3rd floor.
The stairwell I was thinking about using is the Emergency / walk up common to each Unit.
I hope this helps to clear up why the new approach is better.

 

[jeremysterling]

I'm glad the OP found an alternate route, but I'll weigh in on the coring discussion.

First, how is it possible to "blow out" the steel pan with a rotohammer?

Second, how is a dry 1" rotohammer bit going to jam in 4" of perlite concrete?

Third, how is subbing out skinny holes like this more cost-effective than a Harbor freight hammerdrill and a holesaw?

 

[hurk27]

Sometimes there are options of using existing conduits to get around from trying to find new routes, since there are most likely sub panels in the units one can use the feeder conduit if only adding an extra circuit and if the conduit has required extra fill space, other times like with the heater, you might be able to run a couple extra hots if the load doesn't need a neutral, and again there is sufficient fill space, many times derating only kicks in if the conduit is already over 6 circuits because of derating from the 90? column of table 310.16, as far as blowing out block while it happens it can be avoided by going real slow and turning off the hammering and just using just a rotating drill, I use the Bosch Blue Granite bits as they have a really sharp cutting edge and do a nice clean hole on both sides if you only use non-hammering through the last 1/2" of drilling, they are also great for drilling harden floor tile and Granite but cut through concrete like butter.

Like Don said, stairs and or elevator shafts can be off limits, and even if you were allowed fire sealing around the conduit would be required.

Another option is a feeder tap at the main service to a small two or 4 space panel, just keep in mind of not trespassing into the other owners space as that can be a problem.

 

[infinity]

Third, how is subbing out skinny holes like this more cost-effective than a Harbor freight hammerdrill and a holesaw?

I don't think that anyone was thinking that you would sub out 1" holes and that you would use your own coring machine.

 

[hurk27]

I don't think that anyone was thinking that you would sub out 1" holes and that you would use your own coring machine.

I kind of thought the samething like this isn't a $20k job subing out to do a 1" hole, or even using a coring machine, I have a 18 volt Dewalt hammer drill that will do 1" holes all day long even in 9k psi concrete if using the Bosch Blue Granite bits.

 

[jeremysterling]

I would just sub the drilling to a concrete coring guy...

I don't think that anyone was thinking that you would sub out 1" holes and that you would use your own coring machine.

At least one person thought it...

Yeah, the OP said there was an elevator to make it easier getting the coring rig up to the landings. I would carry the coring rig up the stairs, but that's how I roll.

I still think doing it dry would be better than trying to catch any runaway slurry running down the stairwell walls.

 

[plumb bob]

First, how is it possible to "blow out" the steel pan with a rotohammer?

In my area, the pan isn't usually that strong or thick, a hammer drill bit will puncture through it with sufficient pressure applied. The hole ain't too pretty.