Bay window corner - (making flush and vertical)

[Koomorph]

I need to bring a section of an external corner of my bay window out (build it up) so that it’s flush with the other walls and so that the corner line runs vertically in a straight line matching the rest of the corner.

See pictures below – the lower part of the wall was plastered/rendered really badly.... and I need to make it flush again. The light coming through at the bottom shows how “concave” the wall is. It’s over an inch or more deep at the deepest part.
The other picture shows the straight pencil line (faintly) of how the corner should run so that is in line with the rest of the corner above it.

I’m wondering what’s the best process to do this..... run string top to bottom and build it up?
And what’s the best stuff to use for the job? Bonding....? Hardwall? Or something else? Should I PVA it before?
The grey wall is a totally waterproof old damp course I think – really tough!

Many thanks everyone!

(Oh... and I understand that the new straight corner probably won’t meet the corner of the skirting right at the bottom.... I think I’ll need a bit of creativity at that point.... )

 

[Micilin]

First of all is it sound ?

If so then I would think about your key . That's a lot of plaster to use with just PVA. A pVA, bonding slurry would be better. Bondit or WBA too.

I'm not sure about the pencil line?


I would fix a timber pofile up on one side (the worst), in line with where you want the wall but alowing 3mm for a bead. Build it up in 3 coats, filling out heaviest areas first.Let then firm up and scrath them. Don't be tempted to horse on an inch of stuff in one go.

When one side is bult out then reverse your timber profile, and fill out . THen remove the profile, tidy up and fix a 3mm stop bead (or 5mm if thats what you have)


I'm not sure how you will sort out the skirting though

 

[Koomorph]

Thanks for the advice Micilin

The wall is very sound – and tough as nails! Not sure what it is - some sort of damp proof course that runs about a meter up from the skirting that was applied sometime after the house was built – and that’s why that corner is so poorly done as it was “shaped” after the original build when they put this course on. It’s totally waterproof any doesn’t absorb any water... so I need to use something that won’t take days to go off if possible.

By PVA bonding slurry do you mean something like Bonding or Multi mixed in with PVA? Could you advise a ratio?