Is this notifiable?

barrythegoldsmith · 26 Feb 2011

I'm planning to board out my loft space with chipboard, so I can store a load of crap up there, which means two slight alterations to the cabling up there. Since the house has had a rewire and new CU after the latest set of regs came in I have a full set of paperwork certifying it, which includes the cable installation method and I want to make sure it stays valid. I don't have any electrical test equipment except a multimeter and a neon, I'm just a standard DIYer.

First there is a cable that runs across the top of some joists, I would need to unhook it from the light fitting, reroute it through the joists and connect it back up. I'd use the same cable, and it would be the same length, just slightly rerouted.

Second there's a screw terminal junction box, I would replace it with a maintenance free one so I can board over the top and forget about it.

In both cases the cables/junction box are loose on top of plasterboard, and there's rockwool over the top.

TIA

ricicle · 26 Feb 2011

The work won't be notifiable but you must not notch roof joists.
I would not trust 'maintenance free' junction boxes to comply with regulations with regard to inspection. Can you not make an inspection hatch ?

barrythegoldsmith · 26 Feb 2011

ricicle said:
The work won't be notifiable but you must not notch roof joists.
I would not trust 'maintenance free' junction boxes to comply with regulations with regard to inspection. Can you not make an inspection hatch ?

Thanks, I wasn't planning to notch them, but drill a hole through dead centre. I thought the whole point of maintenance free JBs was so they could be placed where they wouldn't be inspected and still meet the 17th ed requirements? But I could certainly make an inspection hatch, it's only a storage space. That was my backup plan in case I couldn't swap the JB anyway. In that case I wouldn't need to swap it anyway, so it's just rerouting the cable on the electrical front.

PrenticeBoyofDerry · 26 Feb 2011

Go with the inspection hatch for JB, as the 'maintenance free' junction boxes have not been accredited with a BS (British Standards) number. So you find some sparks wont use nor recommend them.
If you are holing the joists, there are regulations that need to be complied to.
Link
//www.diynot.com/wiki/electrics:installation_techniques:route

barrythegoldsmith · 26 Feb 2011

Thanks. OK, so new plan on the reroute is to still go in the centre but to put a safeplate on top for some extra protection - these are only 3 inch joists.

PrenticeBoyofDerry · 26 Feb 2011

If the distance between joist top and outer edge of hole does exceed 50mm, there is no need to install safeplates.
But if you want to, nothing wrong with belt and braces.

flameport · 26 Feb 2011

barrythegoldsmith said:
I'm planning to board out my loft space with chipboard, so I can store a load of crap up there

Sell all of the crap on ebay, then use the money to have the loft properly insulated.

PrenticeBoyofDerry · 26 Feb 2011

Also remember when boarding your loft out ( after insulated properly that is

) , start boarding from the loft trap, schoolboy error if you don't!

seasickstevie · 26 Feb 2011

PrenticeBoyofDerry said:
If the distance between joist top and outer edge of hole does not exceed 50mm there is no need to install safeplates.

Or it could be the opposite

ban-all-sheds · 26 Feb 2011

Use composite insulating boards - no need reroute the cables at all then, assuming they are only lighting circuits.

barrythegoldsmith · 27 Feb 2011

ban-all-sheds said:
Use composite insulating boards - no need reroute the cables at all then, assuming they are only lighting circuits.

Thank you, hadn't heard of those - i've just looked them up and that looks like very good advice.

barrythegoldsmith · 27 Feb 2011

Could I get some clarification on the safeplates? Looks like different advice from different folks They're cheap enough but it is one more thing to track down and buy if not actually needed. The joists are not big enough to drill through the centre and still provide the required 50mm min from the top, this is in a loft that will be used very rarely for storage only, everything in the house has rcd protection.

PrenticeBoyofDerry · 27 Feb 2011

SNM said:
PrenticeBoyofDerry said:

If the distance between joist top and outer edge of hole does not exceed 50mm there is no need to install safeplates.

Click to expand...

Or it could be the opposite

Don't quite get what you mean

The hole must be at least 50mm from both underside of joist and top side of joist

Except you don't install safe plates at the underside of joist.
There should be a distance of at least 50mm from the hole to both underside and top side of joist.
In lofts that have not been boarded out the cables are often laid over the top of joists and insulation, when insulation is installed.
When someone decides to board the loft out consideration then need to be made regarding the correct and safe method of cable installation.

The normal practice is to at least achieve the 50mm distance between underside of joist, if this then does not allow for 50mm at top side, then additional protecting is needed, ie mechanical protection.

PrenticeBoyofDerry · 27 Feb 2011

barrythegoldsmith said:
Could I get some clarification on the safeplates? Looks like different advice from different folks They're cheap enough but it is one more thing to track down and buy if not actually needed. The joists are not big enough to drill through the centre and still provide the required 50mm min from the top, this is in a loft that will be used very rarely for storage only, everything in the house has rcd protection.

You don't need to use them if the distances between underside and top of joist are equal or exceed 50mm.
Just remember when you install your loft boards that you have
50mm on the joist and
18mm on your loft board, an amount for countersink say
minus 5mm on the safe side
So when you decide on screw length for fixing, take these measurements in to consideration.
So screw should be less than 50+18-5=63mm
This will prevent to screw damaging the cable, it is also advisable to try and avoid screwing in the areas where the cables are routed, so worth making a note of it. Then when fixing boards down just avoid those areas if possible. Belts/Braces

TicklyT · 27 Feb 2011

barrythegoldsmith said:
... these are only 3 inch joists.

Are they joists, or are they the bottom members of roof trusses?

If they are trusses, the loadings on them are different to joists, so the rules for notching / drilling joists cannot be applied. I doubt any drilling or notching would be permitted without the express permission of the truss manufacturer.

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Is this notifiable?

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