lighting wires above or below acoustic mineral wool

[ajrobb]

I want to replace a 1978 Artex plasterboard ceiling with Soundbloc plasterboard on resilient bars and 100mm of acoustic mineral wool.

• Do I run the lighting cables next to the plasterboard or on top of the mineral wool?
  Do I need to increase the conductor size?

 

[ColJack]

what's above the rockwool? free air or floorboards?

 

[skenk]

In general and if possible cables should be run on top of insulation to avoid derating but if it's 1.5mm cable on a 6A MCB then they will be fine under 100mm glass wool.

 

[ajrobb]

what's above the rockwool? free air or floorboards?

50mm air then floorboards

 

[flameport]

Cables normally go above insulation where possible, but for a 6A lighting circuit it won't make any difference.

 

[ajrobb]

1.5mm cable on a 6A MCB

That reminds me - as an unqualified DIYer, I don't think I can modify the consumer unit (old fuse box). Is it normal to retrofit modern consumer units to 32 year old wiring?

 

[flameport]

In theory, anyone can replace a consumer unit, provided they notify building control first.
In reality, changing a consumer unit is not something the majority of DIY people could do or should be attempting.

A new consumer unit on old wiring is certainly possible. 32 year old wiring could be perfectly fine, totally ruined or anywhere in between.

 

[RF Lighting]

Assuuming it is 32 year old wiring in good condition, then I don't see why not.

 

[ajrobb]

I'll probably get the consumer unit replaced when I get the final safety check done (unless I find anything). It was last checked about 20 years ago when I had the plumbing strapped.

Also, are bathroom pull switches still used? My step-son's new build in Leeds has the bathroom switches on the wall out in the hall (very inconvenient). I shall be extending the small bathroom when I remove the airing cupboard and water cylinder. I'll need to move the pull switch.

 

[RF Lighting]

Yes, pull switches are fine. They seem to have gone out of vogue a bit these days, but nothing wrong with them.

 

[ajrobb]

[pull switches] seem to have gone out of vogue a bit these days

In Sweden, they've had bathroom switches out in the hall since the year dot. Seemed old fashioned and rustic to me 30 years ago.

 

[flameport]

For most bathrooms, the switch can be on the wall inside the bathroom.