Rewire lighting circuits with limited access

[zippy]

Folks,

1950's 3-storey town house, flat roof with no roofspace access on top floor, laminate flooring throughout apart from a few bits in hall and landings ... and I need to run new lighting circuits to all 3 floors, CU on ground floor.

On quick inspection looks like it is riddled with metal conduit from switches and even to roses and using individual conduit wires with no earth. Had a quick look in one rose and only 3 conduit wires connected, so guessing there are a good few junction boxes up there too!

There is a small boxed void that runs top to bottom from CU on ground floor, through kitchen on first floor and up to bathroom on top floor, so I can get my runs up from CU to each floor easily, but beyond that I am struggling if I can't lift any floorboards.

Anyone out there dealt with anything remotely similar? Any tips on getting my runs out to existing switches and roses?

Is possible to do this from below via ceiling? I can probaby get runs started where they run parallel with the joists but at some point I have to cut across a whole load of joists before I can come back on myself parallel to joists again in a u-shape.

Is it allowable at all to notch the joists at ceiling edge and cross this way, or any other tips?

Guessing for switch-to-rose runs I will struggle to use old conduit to pull through new t+e so guessing I will just have to cut new channels as everything needs to be hidden?

Any help/advice/tips would be much appreciated ... and that's putting it lightly!

Thanks

Zippy

 

[uksparks]

I usually walk away from jobs like this as it's too much hassle!

 

[davesparks]

Why not just pull new singles in to the existing conduit? You would expect to only see 3 wires connected at most lights, a switch live and two neutrals, the feeds will just loop through the boxes.

And the reason you see no earth wires is that it is steel conduit!

 

[telectrix]

have to test the integrity of that conduit before quoting.

 

[baldsparkies]

Tell your customer exactly what you are faced with.
That you will keep disruption to a minimum, but may or may not need to disturb decor flooring ceilings ect.
All making good to be down to the customer. (Unless your up to plastering yourself and price for it)
And on the subject of price, cover your arse and don't short change yourself.

 

[R G]

Best way , and i have done a few like that is from the ceiling by making holes in the ceiling each side of the joists and drilling holes through the joists , I would run all new cables in parallel with the old in use to start with , at the switch drops you would need to make a hole in the ceiling at the top of any tubes , there may be some areas where the conduit can be used , but I should think theres going to be some boxes that are not accessible and a decision has to be made weather its singles or T&E , I would go with the latter if there are inaccessible boxes..

These are the sort of jobs that take some thought but you can find a way round it if you explain all to the customer before you start....

 

[Guest125]

Would have to agree with Dave here. Singles all the way and wire in 2 plate. Only thing is you would want to make sure the client is clear that your quote is based on the existing conduits being re-usable.

 

[SJD]

You say there is no access to the floor/ceiling void - this is a joists and floorboards construction, and not concrete floors?

If concrete, then can you not reuse the existing conduit for the lighting, as davesparks mentioned? There might well be access covers here and there in the ceiling & wall that can be used to help draw in new cables.

If joists and floorboards, then can't you cut 100mm holes in the ceiling, save the discs and refit them later. If needed allow for skimming the ceiling.

 

[Des 56]

Have you tried pulling on any of the existing wiring,if not this is your first job before quoting

Once you decide if they pull,the main problem may come with getting the supply from down below (if there is no pull)
You get the supply to a convenient light or switch,the landing being the only open area may very well be the best place to get that supply to lights/switches both above and below that floor

I would hazard a guess this is a simple singles rewiring through existing conduits,wall chasing and laminates destruction may end up being just an extreme solution
Take more care than normal before pricing,be sure exactly what you will be pricing for and any problems you uncover before the start


more
Had a quick look in one rose and only 3 conduit wires connected,
How many actual pipes are at the light positions and switches

 

[7029 dave]

Are we talking full conduit system.? It might be worth having a few switches 'off and roses and try the pull test. Singles will be your clue.

 

[davesparks]

From what he's said about individual wires and only 3 being connected suggests a proper conduit system

 

[7029 dave]

Some Electricians will just not spare the time, finding out, if cables pull, they would just tear the place apart, too time consuming in todays world of electrickary.

 

[Leesparkykent]

Or tell the customer your an electrician not a magician lol

 

[zippy]

You say there is no access to the floor/ceiling void - this is a joists and floorboards construction, and not concrete floors?

If concrete, then can you not reuse the existing conduit for the lighting, as davesparks mentioned? There might well be access covers here and there in the ceiling & wall that can be used to help draw in new cables.

If joists and floorboards, then can't you cut 100mm holes in the ceiling, save the discs and refit them later. If needed allow for skimming the ceiling.

Yep, its joists, plasterboard ceilings, floorboards with laminate on top.

 

[amlu]

cut holes in the ceiling, notch on the joist with a multicutter, patch up with bits of plasterboard and filler. if you have to.

 

[Leesparkykent]

Tell the customer to take the laminate up

 

[newtothis]

The OP mentioned he suspected numerous junction boxes ?
As a learner I'm trying to understand how you could pull Singles ?

 

[davesparks]

I don't think notches are allowed in the bottom of a joist.
But if you have an existing steel conduit system and aren't moving any points why would you need to?

Incidentally, why is this rewire necessary?

 

[davesparks]

The OP mentioned he suspected numerous junction boxes ?
As a learner I'm trying to understand how you could pull Singles ?

He is just guessing, and by the language used in the OP he is probably not familiar with the layout of such a conduit system.
Normally a buried conduit system like that will only have boxes at each light fitting with continuous conduits linking them and then a conduit from each light point to the switch.

 

[R G]

Thing is if theres any boxes that are below the floor boards , then he would have to decide which way is best , he should be able to use some of the conduit in places , usually in a wooden floor with proper conduit and singles system in use theres conduit boxes that are accessible only when the the boards are lifted, concrete is another matter ...