What is on this wall?

[curium]

View media item 106608
This is the interior of an external wall in my 3rd bedroom. The property is a 1934 semi-detached that we've recently moved into.

The walls do not have a cavity so i was investigating removing the 'plaster' back to brick and installing dot-and-dab insulated plasterboard. The walls felt reasonably solid but hollow in places.

The exterior of this wall has a pebbledash render.

The previous owner had installed lining paper. I removed the skirtings and saw what looked like a plaster skim. Underneath the skim is a very powdery substance that comes away very easily.

I'm wondering if it is a type of render that was also used as a mortar in between the bricks as I can see what looks like bricks in the picture below.

Advice on what I'm looking at and how best to proceed gratefully received.

Cheers.

 

[stuart45]

Probably lime.

 

[curium]

Is lime normally this powdery? I've never lived in such an old house so this is all new to me.

It looks like the mortar in between the visible bricks is the same same stuff used to render over the top of the bricks.

Is there likely to be any issue with going back to the brick and then boarding with insulated plaster board?

I'm worried that with mortar this friable that removing the render will cause bricks to come loose.

 

[opps]

The plaster finish doesn't look that thick, can you not dob and dab over it without removing the old plaster? If you are concerned about weight loading, then perhaps drive some screws through to support the dot and dab