A liquid membrane allows a wall to be waterproof. You will typically find liquid membrane applied to the outside concrete wall. A waterproof liquid membrane can also be applied to plaster walls. Though this process is not very common, many mistakes can occur. The article below will highlight the most common mistakes when applying a liquid membrane to a plaster wall.
Less is More
If you use too much liquid membrane the plaster can begin to soften and become damaged. Apply thin coats of liquid membrane. Once the first coat is dry, you can add another coat until you have 3 coats.
Clean the Wall
A plaster wall that is not clean will not be good for liquid membrane. You can get areas where the liquid membrane will not properly set. Wipe down the plaster wall with a damp sponge and mild oil-free soap.
Start with a flat and smooth surface. Use plaster and a putty knife to fill in any cracks or holes. Smooth and feather the plaster and then sand it down flush when it is dry.
Apply waterproof tape in the corners of plaster walls. This will allow the liquid membrane to be more effective.