Existing holes in joists- use them or not?

[oldbutnotdead]

Project House needs (along with many other things) a full rewire. (If anyone wants some Edwardian pushfit conduit I've got some going spare). I've got a real electrician (Part P registered) on the job, he's quite happy for me to do some of the scut work (chases,cutting sockets in, floorboard lifts and joist drilling) to reduce his time on site but here's the problem;

Whoever did the last rewire (90s I suspect) drilled wherever the floorboards were easy to lift so some of the holes are outside the permitted zones. Is it acceptable to reuse those holes where they are useful and only drill new ones (in the permitted zones) where they're needed OR do I have to drill additional holes in the same joists in the permitted zones regardless.

And yes I'm going to have a chat with my real electrician but thought I'd gauge the general opinion first in case what I'm proposing is ludicrous.

Ta

 

[EFLImpudence]

Yes, of course, use the old holes - protecting for depth if necessary.

Other views are available.

 

[oldbutnotdead]

Should have mentioned- the existing holes aren't quite on joist centreline but they are more than 50mm below the top (nice chunky Victorian or earlier timber, smells lovely when you cut or drill it )

 

[JohnW2]

Yes, of course, use the old holes - protecting for depth if necessary. Other views are available.

They are - but I would seriously question any 'other views' which result in creating 'yet more' holes or notches in joists, most particularly if the reason the existing ones are not compliant with current regs is because they potentially (already!) compromise the structural integrity of the joist!

Kind Regards, John

 

[sparkwright]

By 'permitted zones', you mean things like the holes in the joists are too near the middle of the length of the joist, that kind of thing?

We're not talking electrical zones, I take it?

If so, the old holes should be ok, if they they aren't likely to get nailed through.

Just about every old house has holes in the joists where they shouldn't really be, but they don't fall down.

But if the hole is too near the top of the joist, there's plenty of houses with nailed through cables.

 

[oldbutnotdead]

Cheers chaps- the potential weakening of already drilled joists was where my logic was.
sparkwright yes the offending holes are outside 0.25-0.4 of the span (most in the middle of the span) but they are near centreline (60 odd mm below the top of the joist). And yes point taken re nailed through cables- usually by floor fitters putting hardboard down to flatten wobbly floorboards. Why are the floorboards wobbly? Because under the 6" floorboard is a 5" notch with every cable and pipe possible rammed into it (at least that's how restaurants in Swansea were wired)

 

[RF Lighting]

As long as they're ≥50mm deep then no problem. If they're less than 50mm deep then fit a safe plate to the joist.

If the existing holes are in the wrong place then drilling more holes in the right place is only going to make things worse. It's the lesser of two evils.

 

[PrenticeBoyofDerry]

As the above post by RFL, If you use existing holes that are in a zone that is not protected by the 50mm top/bottom rule, use safe plates to protect the cable. In other areas where the zone is one that the regs do not comply the span distances, the hole is already there, so would be daft not to consider using it, as that has already been compromised. Try to avoid routing the cable within the same area as the plumbing, give it it some separation.

http://www.screwfix.com/p/sabrefix-protecta-safe-plate-galvanised-45-x-90mm-pk20/30038

 

[oldbutnotdead]

I've never really liked those safe plates- never tried them on modern timber but on older stuff they tend to sit proud & give you wobbly floorboards. Unless you rout the top of the joist by 1mm which is technically notching it (or rout the underside of the floorboards which is more work but much neater finish). The other issue with them is they assume that whoever is spiking or screwing into the floor will only aim for the joists. Fortunately whoever did the original job did at least set the holes a decent depth below floor level. The Edwardian conduit notches are another matter.........

 

[ban-all-sheds]

If it's a Victorian house the joists are probably significantly oversized.

 

[riveralt]

Whoever did the last rewire (90s I suspect)

Seems a little soon and therefore a potential waste of money to be doing another rewire within 20 years or so of the last.
Are you sure you need one? or Are you being told you need a new one?
Extra sockets can easily be added; a new CU can easily be added; even new circuits can be added; but to go to the extreme of whole house rewire seems rather odd given the information you have supplied.

 

[oldbutnotdead]

Whoever did the last rewire (90s I suspect)

Seems a little soon and therefore a potential waste of money to be doing another rewire within 20 years or so of the last.
Are you sure you need one? or Are you being told you need a new one?
Extra sockets can easily be added; a new CU can easily be added; even new circuits can be added; but to go to the extreme of whole house rewire seems rather odd given the information you have supplied.

The current job is fairly pants. Each room is provided with 1 x 2 gang socket- circuits start as rings but then get spurred to hell (so several of the 2g sockets are spurred from the nearest convenient socket on the single ring. At least 1 socket has been moved by connecting T & E to some nasty rubber sheathed CCA (by the look of it) T & E and hiding the terminal block under the floor (the nasty rubber cable doesn't appear at the CU so somewhere there's another shoddy connection). Lighting is all central pendants (fine) but switches are where they could easily be placed rather than where I want them to be and there's a mixture of switch wiring (on some the switch pair comes back to the JB, on others the switch pair goes to the ceiling rose) which is irritating.

Given the rest of the work needed, it makes more sense to me to rip the lot and start again- certainly I'll sleep better. But thanks for making me think about it- in theory I suppose could do the work in the rooms other than the kitchen and bathrooms myself and call it additional sockets on existing circuits rather than new circuits..............

 

[JohnW2]

- in theory I suppose could do the work in the rooms other than the kitchen and bathrooms myself and call it additional sockets on existing circuits rather than new circuits..............

You could - provided that you are competent to do it safely, and to demonstrate that it has been done safely (by adequate testing etc.). Indeed, since April 2013 (in England, but not Wales), provided there were no 'new circuits' involved, you could also do any required work in the kitchen and anything in bathrooms which wasn't in prescribed 'zones' (which usually/often means only electric showers) without 'notification'.

Kind Regards, John

 

[PrenticeBoyofDerry]

I've never really liked those safe plates

It is a matter of safety, rather than what you like. It does not have to be safe plates providing you provide adequate mechanical protection, but they are the simplest option. You could consider earth shield cable but that could be a headache routing through existing holes.