Plumbing Lines through RC Slabs 1

[KCRatnayake]

Hello all,
Usually, our slab thicknesses are 125mm to 225mm depending on the size of panels and in most domestic construction we use 150mm tk (6") slabs for toilet areas. Most of plumbing consultants are producing drawings showing 63mm outer diameter pipes (with some small ones) to go through RC slabs; you folks, as structural engineering consultants, allow this? If yes, what is the criteria? (I.e. distance between two pipes, location (top, bottom or mid depth), any specific pipe material etc.) Also, is there any guideline for electrical conduits in slabs?

Any comment would be appreciated.

clefcon

 

[jike]

Piping thru structural slabs is quite common but there might be areas that we need to avoid or provide extrra reinforcement. These are things that should be coordinated between the plumbing designer and the structural engineer. PT slabs will require special consideration. You need to be very careful of lining up a whole bunch of holes perpendicular to the span of a one way slab (I call this the swiss cheese effect).

It is always prefered to place penetrations before the slab is poured.

Guidelines should be provided by the Structural Engineer of record as this will varying depending upon the design and type of RC slab. ACI 318-02, 6.3 has some very general guidelines for conduit and pipes but the most restrictive provisions should control.

 

[hokie66]

I agree with jike's comments, but somehow by your question I think you are asking about horizontal runs of pipe rather than pipe penetrations.

Plumbing horizontal runs should always be under the slab, not in it. There would be some exceptions where plumbing is concealed in beams or heavy slabs, but not in the 125 to 225 slabs you mentioned.

Conduit is commonly run in slabs, in the middle between the reinforcing layers. 1/4 thickness of slab should be the maximum, and you need to watch out for concentrations of conduit where they all come together. Minimum spacing between conduits as for reinforcing steel, to allow for placement of concrete. Absolutely do not allow tying of conduit to parallel reinforcing bars. No aluminium conduit should be embedded.

 

[msquared48]

Fully agree with Hokie.

Mike McCann
MMC Engineering

 

[KCRatnayake]

Thanks all for valuable comments!

Clefcon