Lagging in a small roof space

May 24, 2007 3 Replies
B

We're having the kitchen done and the ceiling's been taken down.



2/3rds of the kitchen is in the house proper (i.e. bathroom above it) with 1/3 being an "extension" (35* roof) built at the time of construction of the house in 1984.

There was some insulation in that roof space laid over the wires/ pipes. There is access to the roof void, but you'd have to be pretty skinny to work up there.



I've taken that insulation out as it was *really* crappy. Having read this group, I see that insulation (in lofts anyway) should be laid under wires. However, as I said, you're not going to have much work done up in the roof space without taking the ceiling down as part of a total kitchen refit.



Is it alright to lay over the wires/pipes in this situation? Certainly it has been appreciated by our electrician/plumber, but that's because we've had the ceiling down. Of course I will leave the ~9" clearance over the light fittings per our electrician's instructions (not sure how I'll do that, but I'll muddle through :) ).



As the ceiling's going up again tomorrow, any advice would be appreciated.



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T

wrote

Make sure power and particularly cooker cables are routed over the top of insulation. If the cables are threaded though holes in joists, it is likely that you will be able to squeeze one layer of insulation under the cabling. Additional layers should be broken and gaps left to allow air circulation around cables. For cables completely surrounded by insulation, the regs state a de-rating factor of upto half the full rated capacity.

Phil

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B

Many thanks. Looks like, even though that's the way it was, I really shouldn't be laying on top of the cables then.

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D

On 24 May 2007 04:10:02 -0700 someone who may be " snipped-for-privacy@googlemail.com" wrote this:-

A rule of thumb is that insulation laid over the cables of lighting circuits will probably be alright. However, insulation laid over the cables of power circuits is likely to mean that the protective device rating should be reduced.

However, this is a rule of thumb. In all cases this must be verified by the appropriate calculations.

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