Dealing with hygroscopic salt contamination

The salts come from some form of moisture , either rising or penetrating damp . So solving the damp in turn will solve the salt issue . Exposing the brick will mean once the damp issue is solved it will aid drying out so it will be fine to paint over but during drying salts will keep reappearing. Otherwise you can re render with a salt retardant additive .

Hi, This can be remedied by the removal of all plaster and renders back to brick. Allow the wall to dry for a few days then brush off residual dust with a medium coarse brush. Apply (for internal walls) a 3x coat (non hydraulic) mature lime plaster system. The lime putty in the mix should have been hydrated for at least 3 months prior to application. Allow to dry naturally without additional heat sources. For exterior walls: All of the above, a 2x coat lime plaster system is usually sufficient. This is a long lasting solution for your problem provided that the walls are made of brick and there are no other continuous sources of water ingress. Best wishes, Sibylle

You could strip the walls back to brick and apply a permeable damp proof paint but this depends on the condition of the mortar which may need repointing. The other alternative we use is to treat the wall with a salt neutraliser. And board over with plasterboard using a salt retardant water proof adhesive. Not the conventional board adhesive as this will pull the moisture through into the new plaster.

If you have salt contamination of your walls (Hygroscopic just means it absorbs water) then these salts are certainly attributable to what is commonly called rising damp. The correct term is Hydrostatic damp - and this is water pressure from underneath the property - as a result of a high water table - This pressure forces water into the mortar - which allows water to rise through it, Mortar will absorb 20% of its weight - and as soon as this moisture reaches internal plaster it acts like a wick - and hence the tide mark on the walls. The presence of these salts also means you do not have mould on the wet surface of the wall because those salts kill the spores that form the mould. The ground salts are actually Nitrates and there is no way I know of for walls to be contaminated with ground salts other than rising damp.

Yes as long as the cavity’s are clear and not being a solid wall

stripping the plaster back to the brick will not solve the problem on its own. Hydraulic salt contamination without any obvious dampness is a real problem. Source of contamination must be identified before remedial work undertaken.