Small penetrations in existing concrete slabs 1

[jtstruct]

Do any of you know of "rules of thumb" available for small penetrations of existing concrete floor slabs? I have a condition where they would like to drill a small conduit (3/4&quot through an elevated cast-in-place floor slab (old building), or possibly drill a 3/4" groove in the top of the slab for a length of 3'. This got me thinking about wood design and typical requirements for joist penetrations - notching or drilling in relationship to the proximity of the bearing, depth of joist, length of span, etc.

Are there similar types of informal guidlines for concrete slab penetrations that you all are aware of? Any references would be greatly appreciated.

Thank you.

 

[JAE]

A 3/4" hole in the concrete isn't going to hurt anything to any significant degree.

The groove might be a bit more of a problem by creating a potential crack line. It could also reduce the load carrying capacity of the slab in that immediate area. I'd be more concerned about the groove...it depends on where the groove is relative to the slab span.

 

[dik]

JAE... have to watch out for those nasty prestressing cables <G>...

 

[JAE]

dik - right on with the prestress! - I agree that that would be real BAD to hit one of those.

He did say &quot;old buildling&quot; so I just assumed it was mild steel.