How deep does conduit have to buried?

[stevetogo]

Hi,

I have just finished chasing out the plasterboard for a new lightswitch - approx 1 meter long chase from the ceiling. (I've switched an internal door round, so I'm moving the light switch to the other side of the door)

I'm going to be running the cables down to the new switch in oval conduit. The conduit is 10mm deep and the plaster is about 13mm at its shallowest point. This would only cover the conduit with 3mm of plaster. Is that acceptable?
This is also assuming that the conduit is unsecured... saddles would obviously raise the conduit by several mm. Unless someone knows of a good way to secure the conduit without using saddles.
How much breeze block do I need to chase out to allow a decent covering of plaster?

The breeze blocks have several hollow cylinders running through the middle (is this normal? Sorry if thats a stupid question but I've never done any chases before) so when I dug out the recess for the switch back box, it just fell apart after I chiselled away the surface. This has left me with the dilemma about how to secure the back box too. I was going to drill and plug but the breeze block is only 10mm deep between the hollowest part of the block and the plasterboard for the other side of the wall!!
Any help would be appreciated.

 

[ban-all-sheds]

• http://www.voltimum.co.uk/files/gb/attachments/niu/l/attachments/c5-43.pdf
  
  
• http://web.archive.org/web/20061110111450/http://www.niceic.org.uk/downloads/concealedcables.pdf
  
  
• IEE article
  
  
• IEE Article on 17th Edition requirements for concealed cables.

 

[stevetogo]

Thanks for the reply but I was already aware of the regs.

The chase is run in a safe zone cos its going in a straight line from the switch to the ceiling.
Its an RCD protected circuit so it can be buried at a depth of less than 50mm.

Maybe this is in the wrong forum...

My question was more regarding how much clearance I need over the conduit for a good finish of plaster.
And suggestions for securing the conduit and box to the breezeblock

 

[holmslaw]

..

 

[stevetogo]

Cheers mate,

just what I needed to know.

 

[JohnW2]

Maybe this is in the wrong forum...

No, it's the right forum, but some people unfortunately get less-than-welcoming initial responses. In any event, I'm glad that you seem to have fairly quickly got the answers to the questions you actually asked.

Kind Regards, John.