patching a strange internal concrete plaster wall

[SteWood]

Hi folks

I'm adding a new downstairs toilet to my house and need to add 2 doors into an internal wall that at present has just one (one of the new door openings will overlap some of the existing door opening). Because one of the doors will need to be where part of the present door opening I cannot just cut a hole for a new door frame. The thing is the construction of this internal wall is a new one on me. It's neither block work nor a stud wall. It's a kind of concrete plaster that seems pretty solid. It's also pretty thin so building a section of the wall in standard stud work might prove to be difficult as plasterboard added on whould be thicker than the existing wall. So my question is does anyone know what this concrete plaster is, where I can get some and what the best solution would be for this.

Photo to come once I get back to my place..

Regards
Steve

 

[SteWood]

Pics as discussed..

 

[vinn]

Stand back and take photos showing the context of the wall surfaces and the opening.
Was this ever an outside wall?

 

[SteWood]

Hi Vinn

OK see below. Am certain this was never an external wall as it's too thin and there's a fireplace about 4ft beyond it. The building is a Victorian extension to a 1600s house and all the walls even in the newer section thicker than this. BTW the below photos look like they're one, they're not they're photos of the same door frame from either side.

 

[vinn]

Whatever the finish is can be by-passed by thickening the wall on both sides with plaster board after cutting out whatever you want to remove with an angle grinder.
You could use a sub-frame for the door lining.

The wall surface looks like a sand & cement slurry finish.

 

[SteWood]

OK thanks. I actually quite like it as it feels a lot more solid then a stud wall. Would they have done it but attaching additional boards to the wall then pouring the slurry into the gap made or by making a mixture stiff enough to trowel on and stick?

 

[vinn]

It may have been dashed on. You could trowel on a very tight coat of slurry to take up suction and give a scratch coat, and then hurl the slurry at the wall.

 

[SteWood]

OK thanks will go with your first suggestion but it's good to know.