Chasing Concrete

[40 watt spark]

Hi all, anyone had any experience cutting chases in concrete walls in a domestic property ??

Nephews just bought his first 'fixer upper' house and unfortunately being family the rewires coming my way whether I want it or not........

The house is circa 1960s of concrete slab construction, ex council, re-wired in the early 80's by the council (lots of surface trunking, and accessories), theres still an old wood backed MK socket in the airing cupboard with VIR cables (thankfully disconnected) and the gas is bonded in 3 places.... the closest is 5m inside the house !

Now they obviously want everything replaced and flush mounted...... now I must of had a sheltered life as every house I've worked on has either been brick/skimmed or boarded/stud etc never had to chase concrete before !!

All I can think of is a diamond bladed wall chaser and dust extract and patience...... any advice most welcome..... apart 'from run a mile'

 

[jj4091]

I would have thought you may well cause problems with the structural integrity by cutting 50mm chases into the concrete & have all sorts of problems with re-inforcing bars. Like you, it is something I do not have experience of & it is probably why the council surface mounted everything. I think I would have a chat with the council or a structural engineer before I started this job.

 

[flameport]

The house is circa 1960s of concrete slab construction

Don't even bother chasing out. If you want concealed wiring, attach it to the existing wall surface and then plasterboard / skim over the whole lot.

Plasterboard might sound like lots of work and expense, but it will be much quicker and a lot less work than chasing into solid concrete. Bear in mind that even if you do chase in, you will still have to replaster the walls anyway.

 

[Chri5]

I agree, board it.

It will also add to the energy efficiency if you use a foam backed board or Kingspan lining.

 

[ban-all-sheds]

Yup - Kingspan and Celotex, and probably Gyproc, make composite boards which you just slap on the walls. Not as good, insulation-wise, as insulation and wallboards with a cavity between but still effective and the rooms don't get as small.

I would have thought you may well cause problems with the structural integrity by cutting 50mm chases into the concrete & have all sorts of problems with re-inforcing bars.

But you wouldn't go 50mm deep.....

 

[jj4091]

Yup - Kingspan and Celotex, and probably Gyproc, make composite boards which you just slap on the walls. Not as good, insulation-wise, as insulation and wallboards with a cavity between but still effective and the rooms don't get as small.

I would have thought you may well cause problems with the structural integrity by cutting 50mm chases into the concrete & have all sorts of problems with re-inforcing bars.

But you wouldn't go 50mm deep.....

You know quite well what I mean

 

[ban-all-sheds]

Well - no, actually, I don't.

Assuming the walls are plastered, the chases wouldn't need to be very deep at all, certainly not enough to cause structural problems or hit rebar.

Messy though, and 40-year old concrete will be hard...

 

[hairyben]

What's the original system?

I've rewired a few, most of these places are steel conduit which can normally be reused with extensions/spurs as necessary, sometimes following an original ring with spurs, sometimes 20A radials with just a ring for the kitchen, whatever the system lends itself to. Also worth considering is skirting trunking, D-line semi-circ trunking which can be run along a skirting and painted to blend in, coving trunking, hiding cables behind coving, etc etc.

the only real problematics are pyro or rubber conduit, cos then you really do have to start afresh.

Like said a structural engineer, especially if crossing ceilings is a good idea. I've found the plaster in some of these places to be about 1mm thick before now.

 

[RF Lighting]

the only real problematics are pyro

Just reuse it.

It'll be good for another 50 years

 

[ban-all-sheds]

I did think earlier of suggesting Plan C - convince nephew that the industrial look is the way to go, and use pyro and surface mount metalclad accessories...

 

[RF Lighting]

Phwoar

 

[hairyben]

the only real problematics are pyro

Just reuse it.

It'll be good for another 50 years

The biggest p*** take was that we were rewiring council flats that were cabled in pyro, chopping it off to install surface trunking. <bangs head on wall>

Whats old pyro typically like regarding earth leakage, RCD's etc?

oh, and how'd you do a R1R2 test on on ring wired in pyro?

 

[RF Lighting]

oh, and how'd you do a R1R2 test on on ring wired in pyro?

Funny you should say that

//www.diynot.com/forums/viewtopic.php?t=143390

 

[david_uk]

With a decent chaser and extractor it's possible, but I would suggest taking structural advice. Boarding it out might be an option.

The ceiling might be false though. The original construction of prefabs, the ceiling sections were precast and domed a bit like you see in car parks. Sometime people have boarded them to give a flat ceiling that you can run cables through, sometimes you see the original domed precast sections.

If you find one with tubes you can pull cables through that would be great, but I somehow suspect that won't be the case

 

[40 watt spark]

thanks for the advice, much appreciated.

The origional wiring was VIR in steel conduit, the conduit has been reused by the council rewire (looks like an 80's job, cream wylex with 1361's, 6mm bonding) they've used the origional conduit drops in each room(unfortunately looks like there was only 1 socket per room when it was built) the rest is all surface mounted conduit and accessories.

I'll try and guide him down the boarding out route, the house really does need some work all over, he's lucky he's got running water failing that D-line trunking and MK skirting, not seen coving trunking before, who makes it ??could be ideal

Pyro and metclads....woorrhhhh now were talking