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Posted By Topic: Bonding concrete slab without a bath or shower

Aug 13 2019 17:56

Hello there.

I'm prewiring 5 units all sharing the same concrete slab.

All the units have their baths and showers upstairs with a wooden floor separating top from bottom. There is a kitchen on the ground floor however...

I'm guessing that I don't need to bond the concrete reinforcing steel in this case? I've tried to interpret the book, just looking for some confirmation.



Aug 13 2019 19:32

That's correct. It only applies to floors or walls in a room containing a shower or bath.

It does say concrete wall, so I'm not sure if that includes concrete blocks which may then be concrete filled? They would usually also have reinforcing.
Probably, they should be included.

Aug 14 2019 08:33

If the slab is in direct contact with ground(no DPL); then using it as the earth electrode (one connection for each installation) not only provides a better contact with mass of ground than driven / laid electrode(s), but future-proofs the bonding issue.


Aug 14 2019 14:23

But if the slab is constructed as per the spec then it would have dpc so wouldn't provide a very good earth at all?

Aug 14 2019 14:51

Not all foundations have a DPC. Slabs with "edge thickening" generally have full DPC; others have a full edge foundation that's in direct contact with ground.