Joining cable under floorboards

[Graham Jones]

Hello,

My plan to add a socket to an existing ring circuit is turning out to be a major worry for me. This really should be something a competent diy-er could do. But in order to do it correctly, therefore following the regs, is turning into a nightmare.

I will need to extend an existing ring, so initally I just thought a junction box under the floorboards is the easiest way. But then I find that junction boxes are not recommended for use in non-accessible places. I would say that under floorboards is non-accessible. So I found that you could get maintenance free junction boxes. But then after doing some more reasearch it seems that whether these comply with the regs is debatable and who knows if these will do the test of time. I don't really want to be the guinea pig!

So now I would like to attempt the "proper" way of crimping and then heat-sheiding. But as I have never done this I would like some advice on how difficult this actually is. Is this easy to get right first time? Or is it somewhat of a skill that needs to be learned. I don't mind buying the proper tools.

All this leads me to wonder about the existing junction boxes in my house, all the lighting circuit is done with junction boxes, a few other existing sockets also use junction boxes. Some are under floorboards some are in the loft.

Should I worry about these? Has anyone ever found a junction box where one of the screws has worked loose. Maybe I should replace them all? The ones in the loft I can easily inspect and I would say these could be classed as accessible. Other people here must have junction boxes under floorboards, do you inspect them regularly, say once every 10 years?

Thanks for any replies that might set my mind at ease! (very difficult actually)

Graham

[Nightjar]

On 22/10/2010 12:55, Graham Jones wrote: ...

Yes I have an no I don't. When I have had to add connections to junction boxes, I've never found any screws that have worked loose. Indeed, if there was a problem, it was loosening them off after a decade or two. However, I was pleased that there were no junction boxes under the ground floor of one house I lived in when the river overflowed its banks and filled the under-floor void.

Colin Bignell

[Dave Plowman (News)]

You say wrong. Under floorboards is ok for a JB - inaccessible means plastered in etc.

[David Robinson]

Running it from an existing socket, via existing trunking, is the easiest way! ;)

What do the regs say about new sockets on existing circuits? Is anyone interpreting them as requiring new cable runs to be RCD protected?

If you're doing minor work on an existing installation, I think you have to use a bit of common sense IMO. I'm not saying that's necessarily _right_ or _legal_, but if what you have is acceptable (albeit not in accordance with latest regs), than extension should be at least as good, and not make anything less safe, but I'm not sure I'd worry about making the little extra bit _better_ than all the rest.

e.g. ...

...so one extra one is going to make not-a-lot of difference.

Do you like to worry about things?

Yes, in our old house all screws in all light switches, socket backs, and junction boxes were "lose" in that they could be tightened easily, but not so lose that the wires would fall out. The wires could move a little. All wires had been twisted together anyway, so it made no practical difference at junction boxes. At light switches and sockets backs, you would imagine that there could be a problem - but until they were disturbed (by me) I saw none.

You could. There must be millions of houses wired just the same though. While thinking about it might cause you to lose sleep (a good enough reason to do it maybe), has anyone heard of a junction box causing a fire?

No. Also, if you're paranoid and you keep tightening them up really tight every year, then after a few years the wires will snap under the screws.

Oh dear!

I've re-wired my house to have no junction boxes under floor boards. A few in the loft, but very easily accessible - fixed to joists, above floorboards.

btw, if you search on here, you'll find a debate as to whether under floorboards is "accessible" - i.e. if putting a JB there meets the regs.

Cheers, David.

[Tim Streater]

In this instance "loose" was correct.

[js.b1]

The problem is not 10yrs, it is 40-60yrs when junction box (JB) screws can work loose.

The best way of extending a ring is to break the existing ring and run new legs to the new socket(s) - thereby integrating the sockets so as to maintain a ring topology.

An easy way of having accessible JB, particularly for a central lighting centre such as upstairs & downstairs lights, is to use a 1G or 2G box with blank-plate just below the ceiling somewhere. That is how I will migrate our 19 junction boxes (!), many of which are broken, sheath terminated outside, not actually necessary (*) and all those I found had loose terminals. The occasional flickering lights which the UPS did not confirm were actually from bad connections flashing over and old red polythene insulation actually turning brown.

• By not actually necessary I mean there is a JB above every ceiling rose for loop-in wiring with just 1 cable dropping to the ceiling rose; said JB are buried under 280mm of loft insulation now and (from the stench) something else too.

[John Rumm]

You are probably worrying too much!

Depends on your interpretation of "non accessible". Under a floor where all you need to is take out a couple of screws to re-lift a floorboard is not really non accessible. Plenty of places have JBs installed under the floor like this.

Under a floor where its going to have underfloor heating pipes installed all over it and then a fully bonded hardwood floor installed on top - might be more non-accessible. (although even then you are still often only a stanly knife and a bit of new plasterboard away from access to those from the other side!)

So in your situation, I would look to see if I can run a cable from an existing socket first, rather than having an under floor joint. If you can't then I would use a good quality junction box - make the screw off well, and cable clip the cables in and out of the box for a few inches to make sure they are supported and can't pull on the box.

Crimping and heatshrink is ideal for joining two cables that you are going to plaster over etc, its not a good substitute for a junction box.

For a wire to wire joint, yup easy. Even with no experience. one practice on some spare wire and you should be able to do it first time every time.

As long as you have a ratchet action crimper, its fairly straight forward.

Quite common - not much to worry about.

I have found old ones where the screws are not that tight - probably just due to the copper creeping a little over time. They were still making a decent electrical connection though. The worst ones tend to be where they are in circuits that frequently run near to their max load, and are subject to repeated heating / cooling cycles. Here is the cables are not well supported they can work loose.

I don't even know what is in this house yet, but have had JBs under the floor in other properties. I have never formally inspected any of them, apart from when needing to access one for some other reason.

[Andy Dingley]

"Inaccessible" is relative. My usual approach is to try and make the inaccessible accessible, by putting in a decent floorboard trap that I can re-open in the future without major grief. For floorboards this usually means a short trap near a corner, so that I can roll a corner of carpet back and unscrew something, rather than needing to move furniture and then lift a whole floorboard.

I'm considering one at the moment (wall penetration to outside lights) where I'm going to sink a large galvanised box into the wall and make a short trap in the skirting board over it. We're hoping to sand the floor in there in a couple of years time and I don't want any chopping of the boards if I can avoid it.

[A Plumber]

Don't think you should do it unless you have part P certificate m8

[ARWadsworth]

The socket is in a bedroom.

[ARWadsworth]

I agree.

If you are really worried about a junction box then take the cable to the nearest socket that is on the ring instead.

Cheers

[Dave Plowman (News)]

I doubt the regs are written for DIY types - most home owners wouldn't have a clue where a JB might be under the floor - and that would apply to an electrician brought in to sort any fault too. But do you really need to make it easy to get to your own work? I've never had connections in a JB fail.

[Andy Dingley]

RTFM. My house(s) have one. One copy is paper, the other is labelled (where possible) on the wall or floor itself. There's a lot of stuff pencilled under the wallpaper.

[Bob Eager]

Same here. The paper gives measurements from specified walls (X and Y). The floorboards (not decorative) have large indelible circles/crosses with the relevant junction box type and number beside them.

[John Rumm]

Part P does not apply since this is a non notifiable activity.

[Dave Plowman (News)]

Very laudable. I've done much the same. But as I said the regs ain't written with the likes of us in mind.

[Fred]

Can you run cable behind skirting? I thought you weren't supposed to in case someone nails the skirting through it but perhaps that's a recommendation rather than a rule? I'm not suggesting you would because you would know where you have fitted the box but a future owner might not. OTOH it's not as if you are running it the length of the skirting board, which increases the chances of a nail finding it.

[Fred]

When I first learned of this, I worried like the OP too. There seemed to be conflicting advice here whether under the floor was accessible or not but it seems this time round, pretty much everyone is happy that it is accessible. I understand that many lights are wired from JBs under the floor above (though I've never had any like this), so if there was a problem nationwide, I think it would have been found by now. This thread has reassured me too.

Part of our kitchen has the tiled bathroom above. I'm wondering when the time comes, would it be easy to rewire the kitchen by pulling the ceiling off, rather than the tiles up!

[John Rumm]

The inventive sparky may be able to avoid either!

[Fred]

I was wondering about this. The advice with JBs is that the cables must be clipped so that the weight of the cable isn't trying to pull the wires out. If you are using the "keyhole surgery" method of rewiring where you lift a board/make a hole in the floor the other side of the room and use rods to lay the cable, how can you clip the cable along its length?

I guess the important thing is to clip around the JB and you will have access to that but don't the regs require clipping along the length of the cable?

Thanks