Electrical wiring along room floor perimeters?

[KevMusician]

Hello.

I appreciate that this is slightly unorthodox, but my Building Inspector and Electricians can't make their mind up. They equally say as long as the other person thinks it's okay...

Anyway, recently I have had wet UFH laid (pipes in screed) and as a result I have a lovely 1 inch perimeter around the whole of downstairs from where the perimeter insulation was/is.

I was wondering, to save a lot of hacking of plaster and to make the installation easier, if it was feasible to run the electrical wiring along the perimeter:

Untitled

• KevMusician
• 24 Oct 2011
• 1

I can obviously insert the wiring into conduit, but I can't really see this being necessary? The wiring sits well below the skirting fixing zone (apart from the rise to sockets).

What are your thoughts? Am I headed for a mental asylum?! Cheers!

 

[westie101]

Let me guess, it's not in BS7671, and neither one of them is prepared to actually make a decision for themselves!

Personal view would be that as long it runs in the bottom of the "trench" it is beneath the floor and safe from damage, the risers to the sockets are in recognised safe zones.

How deep will it be below floor level?

Are you contemplating putting insulation on top of the cable as this could affect it's rating?

 

[KevMusician]

Let me guess, it's not in BS7671, and neither one of them is prepared to actually make a decision for themselves!

Exactly!

How deep will it be below floor level?

About 125mm.

Are you contemplating putting insulation on top of the cable as this could affect it's rating?

I would PREFER to put the excavated 1inch polystyrene edge pieces back in to sit on top, so perhaps step up to 4mm T&E?

 

[westie101]

Seems to me that if it was a suspended floor and you clipped it to the underside of joist that would be OK and at a similar depth, so I can't see any reason why it should not comply with the safety requirements required.

On the basis it will be on top of concrete and have a brick(?) wall on one side I would think that heat dissipation would be enough to use 2.5 (I doubt there is a table in the guidelines that covers the installation method!)

 

[KevMusician]

Seems to me that if it was a suspended floor and you clipped it to the underside of joist that would be OK and at a similar depth, so I can't see any reason why it should not comply with the safety requirements required.

Good point there. Also, yeah, hollow cavity brick wall. Cheers for the advice westie. Hopefully the general consensus is as positive. It actually appears to be a great way to run wiring. Easier to install and repair. The only downside I can see is flood protection, but the house is slightly raised anyway.

 

[westie101]

The only downside I can see is flood protection

If there are no joints on the cabling any flooding will only affect sockets etc.

 

[mikhailfaradayski]

it seems like a reasonable solution, as already mentioned by Westie.

If the spark involved is a bit dubious about doing it that way simply because 'it is not written so in the book' then suggest to him that he could describe the installation in the deviations/special notes section of the EIC he will (probably) issue.

 

[electronicsuk]

If the building inspector is prepared to sign it off then there doesn't seem to be much worth worrying about. It sounds safer than the 150mm ceiling and corner safe zones that are in BS7671, and those are considered acceptable. Don't put polystyrene directly on top of the cables, though, as it can react with and eat away at PVC insulation.

 

[westie101]

Don't put polystyrene directly on top of the cables, though, as it can react with and eat away at PVC insulation.

Possibly bed it in a bit of sand

 

[KevMusician]

Cheers lads. All points taken on board. You've been a great help!

 

[ban-all-sheds]

Let me guess, it's not in BS7671, and neither one of them is prepared to actually make a decision for themselves!

Exactly!

If I were the electrician it would look enough like Installation Method 51 to satisfy me...

I would PREFER to put the excavated 1inch polystyrene edge pieces back in to sit on top, so perhaps step up to 4mm T&E?

Actually sitting on top of the cable?

Not a good idea, as the polystyrene will damage the cable.

Insulation in general - no worse than Method 3 on it's side?

If so 2.5mm² will be OK.

 

[KevMusician]

Not a good idea, as the polystyrene will damage the cable.

I can probably use the existing polythene membrane as a 'barrier' between the PVC and polystyrene, or just gaffa on the bottom of the polystyrene!