One of the most common reasons for carrying out plastering work in old houses during renovation is to complete a course of damp proof treatment. Whether one is treating rising damp or waterproofing basement walls the direct bonding of plasterboard on walls prone to dampness should be avoided unless an air-gap membrane is used to create a physical barrier between the wall and the plasterboard.

When plastering after the insertion of a new damp course it is important to use either a renovating plaster mix that has been specially formulated for the purpose or, if using backing render with a skim coat, a waterproofing admixture that permits evaporation of water vapour but inhibits the movement of salts.

Waterproof plastering, used for example to hold back dampness in below ground areas, basements and cellars, is more commonly referred to as tanking.  Tanking slurry is generally sandwiched between a dense render coat and top coat of renovating plaster.

Tips for plastering damp proofed walls above ground

• Use renovating plaster or two coats of backing plaster with waterproof additive topped with a skim coat or
• Use a mesh faced damp proof membrane having an air gap and either plaster or dot and dab plasterboard on top

Tips for plastering basement, cellar or below ground walls

• Use tanking slurry sandwiched between a dense render coat and top coat of renovating plaster or
• Use a fully sealed cavity drain membrane system and either plaster, dot and dab or dry line on top (drainage may be required).

Plastering requires a great deal of skill to get a pleasing finish.  Dry lining with plasterboards require less skill, though the final coat or top coat of plaster, or skim, can still be tricky for DIY enthusiasts