If you are looking for a general use exterior primer or stabiliser, a great option is Zinsser Bullseye 1-2-3. A highly penetrative, clear, solvent based stabiliser for use on most exterior masonry surfaces & exterior grade building boards. Use to treat chalky surfaces. Here are some photo's of the wall after all the paint has been taken off. The walls are not in bad condition apart from what I have snapped for you here, so if what appears in the image can be prepped without skimming, then I am confident I can go down that path, as the walls don't have alot of damage other than what I have shown here.

A fine polymer emulsion that deeply penetrate badly weathered surfaces suitable for use on chalky and dusty surfaces and areas were plaster and cement have started to become unstable. When you have removed as much loose material as possible, treat the worst affected areas with a stabilising solution which will bind any reaming loose martial, presenting you with a solid surface on which to paint. Only do this on the very worst affected areas though. Kingfisher “Weatherflex Stabilising Solution” is available in 5 litre plastic containers. It should be stored in a cool, dry area, AVOID frost and direct sunlight. Shelf life of the product in, unopened sealed containers is 12 months. This usually ensures that the walls have had sufficient time to dry-out in depth and that any loose material is washed away naturally when it rains.The builder has since sealed the outside but has advised using stabiliser on the render on the inside before painting to prevent anything coming through. I’ve read a lot of bad things about stabiliser so good idea or not? RD October last year I had the front of a Victorian house redecorated by a builder. It was in a bad state of repair as it had not...

New surfaces All surfaces must be sound, suitably dry and free from anything that will interfere with the With newly rendered surfaces, it is normal to have a certain level of dust and/or powder on the surface as a result of the drying-out process. Stabilises and hardens “friable” masonry or masonry surfaces which may have “gone soft” due to extreme weathering. This all costs a few quid (depending on area that needs skimming) but will give a great surface to then seal (mist coat) and paint ontoFriable surfaces are one such example. You can tell a surface is friable by rubbing it with your hand: if it rubs away, then that is a sign it might need stabilising solution.