Advice needed: repairing walls behind skirting

Hi - sorry if this has been covered before - I’m a newbie here

so I’ve removed all the skirting in my hall - for the most part the plaster is in tact on the internal walks (brick) but on the external walls (stone) the old plaster behind the skirting has completely crumbled away - in one area it has exposed a very very rotten block of wood that seems to have ‘replaced a stone’ it has no structural load in that part of the wall it seems.

so my question is what on earth can I use to patch up such large areas (especially as on corners) doesn’t need to be pretty as covering with tall skirting. Or is this something best left to a professional (I’m just trying to keep all costs right down)
Thanks guys

Hi,

If your house is like mine, the wooden blocks were built into the stone walls during construction, specifically to allow the skirting boards to be nailed into them.

Some might disagree, but as a DIY'er, I wouldn't do anything to patch the walls - the gaps will be covered by the skirting anyway!
That is as long as the the plaster further up the wall is sound, otherwise it is a lot bigger job.

Personally, I would use this stuff to fix the new skirting:
https://www.toolstation.com/soudal-genius-gun-plasterboard-adhesive-foam/p99304

It is a low expansion expanding foam.
For really big gaps, it can be built up in layers.
It should be fine to fix the skirting and fill the gaps in your photos.

For best results, follow the instructions!
Clear up any loose stones and grit/dust from the wall.
Mask off your floor to stop drips damaging it.
Dampening the wall first with a mist of water will decrease curing time.
Hold the skirting in place with weights while the foam cures, to stop any excess expansion pushing the board off of the wall.
...and wear the gloves provided!

As I say, some might call this a bodge, but it's cheap and it works!

youve got rising damp and rotting nailing blocks. completely remove the blocks ad knock off the plaster to 300mm above signs of damaged plaster.have a look at the other sides of the walls for similar damage.

Thanks for the replies - it’s an old stone cottage so there is no damp proof course.
It just appears to be this side of the door where there is wood - the other side is stone.
Wondering why there is wood just there?

nailing blocks were used for fixing skirtings,railsand door frames.the floor looks to be damp under the flooring boards.