1st Floor hearth – typical construction?

[Roger H]

I’ve a groundfloor defunct range opening whose chimney stack at first and roof level was removed by a previous owner. Reinstatement will never be possible as an extension is accessed via the position of the old chimney at 1st floor. I want to run some wires down to serve downlighters in the old hearth but the retained slab of the first floor hearth is immovably insitu. Without dropping plasterboard, what is the typical construction detail of these? Building is 1840s stone cottage – hearth stone is black slate – depth undetermined. Looking into floor-void, joists run towards hearth – however, what I presume to be a trimmer runs at 90 degrees in front of hearth. Hearth projects 50cm forward from face of chimney breast below. What might I find on the other side of the trimmer? More trimmer? Rubble? Stone? Underneath is a plaster cieling that I am not keen on breaking into unless no other route. Any ideas appreciated.

 

[Roger H]

Ok, I should have googled more thoroughly. Could well look something like this:
https://environment7.uwe.ac.uk/resources/constructionsample/conweb/heating/chim_upperfloor.jpg

 

[stuart45]

Could be like this.

 

[Roger H]

Thanks - could be. Whichever, it does not look like an easy route to drill from the trimmer through to the chimney beneath!

 

[Lime]

Thanks - could be. Whichever, it does not look like an easy route to drill from the trimmer through to the chimney beneath!

There isn't an easy route for cable directly through the hearth.
You will have to investigate near where the edges of the hearth meet the wall to find a route down.

Don't assume the hearth is directly over the one below.
There is often some offset between hearths so you may find one side of the upstairs hearth is better to investigate/route the cables than the other.

 

[Zebra]

Where is it exactly you want to put the downlighters? There may be ways, even within the Regs, that you can come down in the wrong place, as it were, and then chase the cable in below ceiling height in the room below. But I'm not sure quite what it is you are trying to achieve.

 

[Roger H]

Hi Zebra.

I'm trying to insert downlighters to illuminate the opening of a defunct kitchen range style fireplace opening. I.e. Close it off with plasterboard above the opening and insert a couple of spots to illuminate the void.

As you say, I am now thinking about getting round via the sides. No easy wasy as immediately above the lintel the throat of the chimney narrows with masses of brickwork and stone on either side. May chase out a little bit of cieling to check going under the first floor hearth before I fully abandon that route.

Thanks,

R

 

[Zebra]

According to the Big Book of Regulations, you are allowed to chase cables along the very top of the wall, within the top 150mm below the ceiling, so this could be an option if you have to come through in the wrong place. ("Safe zones" marked in diagonal stripes on this diagram).

 

[plasticpigeon]

I've kind of done this. In my house the upstairs hearth was a very badly made trimmer arch made of bricks spanning from a joist to the front of the chimney breast with some lime concrete on top and quarries on that. As the range opening downstairs was quite a lot wider than the hearth upstairs i was able to rake out a mortar joint to the side of the trimmer arch on the front of the chimney breast between floors and poke the wires through and hang them down the flue. I don't know if it is within regs but it seemed sensible to me. I've put in a cooker hood with 2 lights (and made a bit of a hash of it) but it's a similar situation. In fact i ran the wires to a fused switched spur on the side of the chimney breast and then from that to the hood, but I'd have thought that if its just lights your after, then that wouldn't be necessary. I hope I don't that Zebra doesn't inform that this is a complete neigh neigh.

I realise after re reading this thread that I have just re stated what Lime said earlier. Anyway, it worked for me!!!

 

[Zebra]

I hope that Zebra doesn't inform that this is a complete neigh neigh.

Oh no, far be it from me to point the hoof.

 

[Mark R]

If all you need to do is route some wires properly, and these are for only a couple of lights there’s a solution I’ve occasionally used in my timber-frame house.

This is to use 12V LED lamps (good-quality ones are now OK), and site the transformer remotely. Then you have only to route thin 12V wires, which can be done much more easily as you don’t need to consider the onerous 17th Edition wiring regulations.

This only works with low-current LED lamps (NOT 12V halogens which draw high currents and need thick wiring for long runs.)

Switching might be a problem, but there are some reasonably reliable radio-switch plates available nowadays, or if you’re into electrics, you can rig up a remote low-voltage relay.

Cheers, Mark.