Install Shaver Point in Wall below Lintel

[Traveller]

I have to install a shaver point in the breeze blocks of an outside cavity wall, so would use a 47mm plaster box. The problem is that the only practical location is about two feet below the end of a window lintel (and about 4 or 5 inches in from the edge of the window recess (so under the end of the lintel assuming a 6-inch lintel/wall overlap.
Is it permissable or sensible to remove 47mm of a breeze block in such a position?
Comments appreciated.

 

[Dartlec]

I have to install a shaver point in the breeze blocks of an outside cavity wall, so would use a 47mm plaster box. The problem is that the only practical location is about two feet below the end of a window lintel (and about 4 or 5 inches in from the edge of the window recess (so under the end of the lintel assuming a 6-inch lintel/wall overlap.
Is it permissable or sensible to remove 47mm of a breeze block in such a position?
Comments appreciated.

Not sure on specific regulations (Part A of the building regs may have something), but 2 feet sounds like enough leeway to me - presumably the cable is coming up to it or from the side?

IIRC chases are only supposed to go 1/3 through a wall, but you won't need to go a full 47mm into the wall anyway I imagine once allowing for plaster or finish on top of the breeze. I did once many years ago try to put a deep back box in and end up in the cavity between houses but that was pre modern breeze block.

I assume you mean a metal back box rather than plaster board one?

 

[Traveller]

Thanks for the reply. The cable could come in from behind the back box through the cavity wall or from a chase to the side. The back box would be a steel one.
I know there are recommendations about wires in cavities but it is difficult to see a problem regarding the breaching of a cavity when the breach would only be one metre or so from the open top of the cavity anyway (this is an upstairs bathroom).

 

[Dartlec]

Thanks for the reply. The cable could come in from behind the back box through the cavity wall or from a chase to the side. The back box would be a steel one.
I know there are recommendations about wires in cavities but it is difficult to see a problem regarding the breaching of a cavity when the breach would only be one metre or so from the open top of the cavity anyway (this is an upstairs bathroom).

There are (at least) two issues with the cavity -
1. the possible addition of insulation - those polystyrene beads can react with pvc cable
2. The possibility of bridging the gap between cavities and allowing damp etc through.

If you have good access from above you could consider putting the cable in oval trunking or conduit to mitigate potential issues.

Having said that, quite a lot of local houses of a certain vintage have consumer units in Mantel cupboards, which nicely bridge the cavity, and then the cables running at least partly within it.

 

[Traveller]

Thanks again. No poly beads in the cavity or elsewhere although there is some sort of fibreglass roof-insulation type of material in the cavities. However, over a short distance a rod will push through this. If I go that way I will take your advice and use some oval conduit.

 

[telectrix]

Thanks again. No poly beads in the cavity or elsewhere although there is some sort of fibreglass roof-insulation type of material in the cavities. However, over a short distance a rod will push through this. If I go that way I will take your advice and use some oval conduit.

or flexible conduit. reasier to fit.