Paint peeling off internally

This is a problem to do with breathability of the walls. Housing built before the second world war used lime as a mortar, rather than the cement that we conventionally use now. Lime has different properties to cement and one of the main ones here, is that it breathes, i.e. it lets water vapour through. This breathability means that the moisture content of the wall changes slowly as the atmospheric conditions change and as the humidity of the room changes. This is most noticeable in rooms like bathrooms, bedrooms and kitchens.

Modern conventional paints are not breathable, neither is cement based render, so over time we have effectively sealed in moisture, or made it so that it can only travel in one direction. For example. If you have cement rendered the outside of your home, or painted it with conventional masonry paint, then you will have effectively sealed this side of the wall. The moisture in the walls has to go somewhere. If it migrates to the inside of house then it will need to pass through the layers of paint / wallpaper in order to evaporate. This is where the problem lies because conventional paints do not breathe either. The hydraulic pressure of the moisture will 'blow' the paint off of the walls and you are left with bubbled paintwork, or paint that just falls off of the walls.

Remedy

If you use lime render on your building it will allow the moisture to disperse naturally into the atmosphere. You will need to use a breathable finish if you wish to paint the walls, earthBorn have a silicate paint , or you could use limewash.

On the inside of the house use breathable paints, these will allow any moisture to escape without 'blowing' it off. Natural paints from companies like Auro and earthBorn produce paint finishes that are fully breathable.

If you are also repairing the plaster / render at the same time we would recommend using a natural and breathable filler . Auro produce such a product and it is wonderful to work with. 

Note

Water based emulsions from conventional paint manufacturers are not breathable.