1934 - Lime based walls? Inside leaf of exterior cavity walls - Can gypsum be used to skim old based walls - read shouldn't use cement based product?

Maxine

New Member
Totally new to all things 'plaster' wise. In a real dilemma! Re old painted woodchip wallpaper removed from (one of two) bedrooms in my 1934 bungalow, washed off most of the old blueish distemper, but can't tell if the walls are lime based, looks like they are (have attached two photos)? Need to know as thinking of a plaster skim so can decorate. Problem: patches of raised moisture readings at low level on internal side of the cavity walls. Old plaster falling off in two of these patches and sand like stuff oozing out. There is serious condensation prob and trying to deal with that, don't know if this has affected the walls. With best will in the the world can't find the cause of this, can't get anyone to help the cavity (already managed to grab some rubble out when insulation extracted but no one interested in helping with cavities. Also been told it's rising damp but offering no evidence for this other than raised moisture meter readings. . Don't want to go down the chemical injection route into the bricks just yet. And now the plaster question, sorry it took ages to get here:-
1. Wonderin if I should hack off old plaster one meter up, (with help) back to brick just to be rid of potential prob in the shortish term. BUT don't know if lime was used in the original walls? Can anyone tell from the photos - poor quality I know.
2 Don't know what type of plaster should be used, should it be breathable and keep salts at bay, anti condensation er all singing and dancing gulp! Spoke to a Plasterer recently (who didn't get back to me when I mentioned using a lime based plaster), they said gypsum will be fine but was a bit concerned as read that this isn't breathable plus that you ou shouldn't use cement plaster on lime based walls?
3 Have been looking at 'renovation' plaster, lots of different varieties out there e.g. Limelite seems to fit the bill as does Wykamol renovation plaster but not sure if this is entirely breathable, don't want plaster that will trap existing moisture behind. Can anyone please advise me on this, so many products available - very confused at the moment - gulp.

Would be grateful for any snippets of advice please, anything at all as can't move forward with decorating the rooms!

Thanks a lot for taking the time to read this.
 

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The pink plaster is gypsum. It look like there has been a problem in the past. Lime plaster is slow and expensive.
I would use Tarmac Limelite plaster with a limelite high impact finish. If back to brickwork.
What a surveyor would tell you is clean the black mould off the walls. The spores from black mould cause breathing problems. Dry the area out with a dehumidifier.
Turn the heat up and give the room plenty of ventilation. Keep furniture away from the walls to allow air flow.
 
You have removed some rubble from the cavity and you have removed the cavity wall insulation. This could be your problem.
Over the years cavity wall insulation sinks down the wall, it is common now to remove this. The cavity is then pumped with polystyrene beads which do not sink down the cavity.
 
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