Chasing hollow clay bricks

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I’m renovating the kitchen and bathroom on a 1950s semi-detached house, the inner leaf of the bricks are made of hollow clay bricks (see images attached) - I found they are very fragile and ductile, the ‘web’ section is easily fractured due to the hollow design.

images
images


Now I will need to add new sockets as there is only one double socket in the entire kitchen,
  • Does the 1/3 vertical 1/6 horizontal chasing rule for normal bricks still apply for the hollow clay bricks?
  • The existing wall are covered with sand & cement plaster (approx 10mm thickness), is it enough to bury the cable (with or without capping?) if I just chisel a channel of the old plaster off the wall and not touching the bricks? I already bought a cheap wall chaser for this job, so depth can be maintained. The ring final circuit is RCD protected.
  • I guess for the back box the damage is unavoidable due to the depth required?
Many thanks for your help in advance.
 
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No point wrecking the first layer on those hollow blocks on long horizontal runs, or even vertical ones if you can avoid it.

Usually in a kitchen, most cables can be run surface behind the kitchen base units, with a short vertical chase between the worktop and the socket above the worktop.

It wouldn't be an issue to chase out those short bits, generally.

If using oval conduit is going to tip the balance as regards to long chasing runs, avoid using conduit.

You may have a corner where pipes are, which will be boxed in. IF you do, take advantage of it and use it.



You will find the back boxes will almost certainly need to be cemented in.
 
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Chasing out blocks like those is a fail, and will have structural implications.

The much easier alternative:
Fix 20mm battens to the wall, clip the wiring directly to the wall between the battens and use 35mm metal boxes fixed to the wall surface. No chasing or recessing required.
12.5mm plasterboard over the top, which will leave the edge of the metal boxes slightly proud of the surface, the usual 3mm plaster skim will make up that difference.
 
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