Sometimes damaged brickwork and not cavity wall insulation can be the problem of damp and moisture getting into your property.
Here’s what to consider if you think this may be the case. Firstly, don’t rush in and plaster the external brickwork with waterproofing paint, check the surface first before you even start. Also make sure the damp proofing medium that you are going to use will actually let the brickwork breathe, you want the moisture within the cavity to evaporate naturally and not become trapped inside, otherwise this will lead to further problems like ‘spalling’ in the winter time, where moisture in the masonry freezes and expands causing more cracks in the brickwork.
Check your brickwork for any penetrating dampness, mould, moss and cracks etc a good indicator will be dampness on internal walls. Some patches can contain ‘salts’ from washed-out brickwork usually white, crystallised deposits which can blow out paint and plasterwork. Because these cold patches take 3 times as long to heat they produce more moisture and as a result erupt into black mould.
If the damp exists in the lower wall area of your wall it may be Rising Damp rather than External Damp again check the external walls first. If you have cavity walls, there will be wall ties in between securing both walls, these can become rusty, expand and crack brickwork. Use a metal detector to locate them, if you come across one that is also a damp blackspot chances are a faulty wall tie is to blame. Don’t try to attempt to remove more than two, contact a surveyor first. Once replaced or cleaned you can rebrick and repoint.
As with spalling, again replace bricks and repoint before any waterproofing paint is applied.
After waterproofing your outer walls you will need to treat any damp on your internal walls. If your plaster is good, and the walls have dried out you can treat them with a salt neutraliser or anti-mould cleaner before any redecoration. If the plaster is damaged, strip it back to 30cm above the highest damp point, let the wall fully dry and treat it with same salt neutraliser or anti-mould cleaner, then replaster and redecorate.