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Topic Title: Routing cables in a kitchen with obstacles and complications
Topic Summary: RSJ, Vaulted ceiling and Island work surface
Created On: 17 November 2012 09:22 PM
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 17 November 2012 09:22 PM
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sparkiemike

Posts: 1549
Joined: 24 January 2008

I am looking for some suggestions or ideas for routing cables.

I am working on a large-ish domestic self-build. In one of the rooms (family room/kitchen) there is a very large steel RSJ that spans the whole room.

On the other side of the RSJ is the kitchen, so usual kitchen requirements for power (incl ranger cooker with induction hob) and some more.

In addition part of the kitchen has a vaulted ceiling and there is an island with a few power requirements (microwave, sockets, waste disposal & boiling water tap)

So the RSJ, vaulted ceiling and island make it difficult/impossible to route cables in the traditional method i.e. from the ceiling down.

So next option is from the floor up. The floor construction is going to be as follows, concrete slab, rigid insulation (150mm), DPM, wet under floor heating, then sand and cement (pumped) screed on top of and around underfloor heating with final floor finish wood / ceramic tiles on top of screed.

What have others used to mechanically protect cables in this situation?

I am thinking towards some kind of underfloor trunking designed for placing on the concrete slab. If I did this would be acceptable to cut the rigid insulation to accommodate the trunking thereby making is thinner?

Any other suggestions would be welcome.
 17 November 2012 09:46 PM
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Davesparx

Posts: 262
Joined: 30 October 2009

Its either that or running a big ol bit of box trunking round the outside of the building and drilling through. The island may still be a problem though. Not a nice one. Are they adverse to metal conduit ;-)
 18 November 2012 07:14 AM
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Fm

Posts: 725
Joined: 24 August 2011

I would run metal conduit in the slab.
I wuld not cut the insulation, as it will affec the thermal properties of the slab.
When it all starts to go wrongnit will be the sparks fault for cutting the insulation, thats why all the heating doesnt work.

Get a signed disclaimer, or instruct the builder to do it, as you excluded this from your original scope of works
 18 November 2012 08:48 AM
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ebee

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What provision did the project designer (coordinator ) make for services such as cables and pipes etc?

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Edited: 18 November 2012 at 09:05 AM by ebee
 18 November 2012 08:54 AM
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aligarjon

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Starting with the island i would be tempted to run a 4mm swa radial under the screed and maybe under the rigid insulation as well to keep it away from the under floor heating. The swa only need run from an isolator at low level on the wall or from a kitchen base unit round the side if thats easier. There must be away across for pipework and wastes etc.


I would probably wire the rest in the usual safe zones round the base of the vaulted ceiling. Not too difficult to do if the walls are being dabbed ?

once above the kitchen worktops going directly between sockets in safe zones.

If you can't go over the rsj go around it, you still have 150mm.


Gary

i can't see how you can do it from below because of the under floor heating . there are bound to be cross over points.

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 18 November 2012 09:11 AM
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Grumpy

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I've hole drilled an RSJ, in fact a double RSJ, to get 32mm and 40mm wastes through. Ask the steel designer.
 18 November 2012 11:01 AM
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sparkiemike

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Thanks for all the replies


Originally posted by: Fm
I would run metal conduit in the slab.


Slab is already down, I hear you about contractual issues

Originally posted by: ebee
What provision did the project designer (coordinator ) make for services such as cables and pipes etc?


It is a self build so there is a lot of "build and then design", the only provision that has been made is for the waste pipes.

Originally posted by: aligarjon

Starting with the island i would be tempted to run a 4mm swa radial under the screed and maybe under the rigid insulation as well to keep it away from the under floor heating. The swa only need run from an isolator at low level on the wall or from a kitchen base unit round the side if thats easier. There must be away across for pipework and wastes etc.

The 4mm is an idea, the other pipework is not in the design yet

I would probably wire the rest in the usual safe zones round the base of the vaulted ceiling. Not too difficult to do if the walls are being dabbed ?

Nope, it is being plastered

once above the kitchen worktops going directly between sockets in safe zones.

This is an option - just a few windows to contend with

If you can't go over the rsj go around it, you still have 150mm.

Again I am considering it, just where the RSJ is there is a "reveal" so there would be quiet a few tight bends

i can't see how you can do it from below because of the under floor heating . there are bound to be cross over points.

The willl not be heating under the kitchen units, if the trunking went to the far wall and then around the inside wall the cables could then pop up were necessary, with one section of trunking for the island


Originally posted by: Grumpy

I've hole drilled an RSJ, in fact a double RSJ, to get 32mm and 40mm wastes through. Ask the steel designer.


How thick was it, the only part I can see is the bottom flange and it is at least an 25mm thick.
 18 November 2012 06:31 PM
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Grumpy

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25mm thick? What kind of steel is it and what's it holding up? The Blackpool tower? Are you sure?
The ones I drilled were probably 10 - 12mm and I used cheapo Screwfix holesaws and lots of WD40 and slow ahead. I was amazed at how easy it was (especially as I delegated the job to my oppo!).
 18 November 2012 06:59 PM
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sparkiemike

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Yep, sure. It spans about 8 meters and is holding up cavity wall for the 1st floor and roof.
 18 November 2012 08:04 PM
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peteTLM

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MT 4 trunking around the base perimeter behind where the cabinets are going to go, drops up and down to sockets etc.

If your going to the island the only way is across the floor. Id use pvc conduit, rigid or flexi, but with the cables put in before the screed goes down.
Just extend the ring into it.

Strap the conduit to the slab as the insulation will keep the heat away from the conduits.

8m is a big span for a conventional built house, so dims seem right.
Id be interested as to what they put the rsj down onto support wise!

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 18 November 2012 08:34 PM
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sparkiemike

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Originally posted by: peteTLM
8m is a big span for a conventional built house, so dims seem right.

Id be interested as to what they put the rsj down onto support wise!


Vertical steels - so its like a goal post
 19 November 2012 12:17 PM
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stateit

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This morning I've just pulled in my cables in a similar set up...

25mm Flexi plastic conduit set in the slab supplying the start of the 4mm radials to either side of the kitchen, 6 mm to the island.

The conduits were fixed to the base of the block-and-beam floor base in the under-unit area along the perimeter of the floor. The island one pokes up above floor level in the island area. They don't interfere with the wet floor heating.

The cable runs along the units are to be clipped to the wall a few inches above the finished floor level. Visible when unit kick-boards are removed. The vertical runs up to accessories bury into the wall from about 700mm from FFL.

You could pull cables in before pouring... I find my cable tails poking up tend to get mangled by builders / labourers in the week or so they're left in there.
["Phone call: We need that cable in today - it's getting poured tomorrow" Two weeks later it's still not poured].
If cables aren't put in before pouring put in a drawer string and securely tape the ends of the conduit so they don't get poured into / carp falling down them..

For getting cable across an RSJ - on a steel that long you usually will find a hole drilled somehwere. If not an HSS bit in a drill does the work in no time. You'll be surprised how easily it drills.

-------------------------
S George
http://www.sg-electrical.com
 19 November 2012 09:32 PM
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peteTLM

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For getting cable across an RSJ - on a steel that long you usually will find a hole drilled somehwere. If not an HSS bit in a drill does the work in no time. You'll be surprised how easily it drills.



Get someone like the surveyor etc to agree with this first otherwise you will be paying for a plate to be welded in and made good, and your cables chopped off

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 19 November 2012 09:33 PM
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sparkiemike

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absolutely agree with that
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