Does anybody know what this is?

[Jakewilk91]

Behind the plaster on a stud wall in a 1950s house. Seems to be made of an almost ceramic like material.

 

[noseall]

Is it some sort of backing plaster key?

 

[Tigercubrider]

It looks like a ceramic block that is hollow, and came with a surface ready to be plastered, they were more like tiles than bricks

 

[ajstoneservices]

Looks to be a clay ribbed block.

 

[Jakewilk91]

After googling structurl clay tiles, if say that' what they are. I take it I wouldn' be able to chisel into them to flush mount my sockets as they are hollow?

 

[misterhelpful]

Certainly looks like a typical 'hollow' brick/block. If so, it will have a variant of a honeycomb pattern, which may well still have some scope for chiseling out and still offer some fixing spots. Try googling 'honeycomb bricks' to see what I mean, and you might find something similar to what you have.

 

[Tigercubrider]

You might be able to fill a hole with quick set mortar and push a back box in

 

[JohnD]

it is easily smashed. Drill rows of holes in a shape that your backbox will easily fit in. In the past I have used sand and cement to pack enough of the cavity to set the box, but I might consider pink (fire grade) expanding foam. If you stuff the hollow brick around the hole with mineral wool insulation first it gives you something to press the mortar against. you have to lay a bed of mortar underneath the box first, then you can press it into the gaps at the side and above with your fingers or a dowel-like tool. It is easier if you shove it in off a plasterers trowel. A soft mix will bulge upwards and sideways when pressed to give a tight fit. Spray the brick with water first to prevent it sucking the mortar dry.

Mortar sticks well to galvanised backboxes.

 

[^woody^]

Hollow clay block/tile which were tried on various estates post WW2 for the inner skins of cavity walls and internal partitions.

 

[securespark]

I have heard it called Salamander.
They are brittle, hollow and thin!