Tiling onto plaster

• 1.1 Plaster is a relatively weak material (in comparison to wood, brickwork, concrete etc). The maximum weight of tiling which can be supported by a dry, well-adhered plaster background, is 20 kg/m2.
• 1.2 New plasterwork should have been completed at least 4 weeks prior to tiling commencing. Even if the surface appears to be dry in less than 4 weeks, the layers underneath will not be.

When plaster comes into contact with cement it forms a weak layer of ettringite that can cause the adhesive and plaster to not adhere to one another. Careful preparation is needed to stop this happening.

Plaster finishes, when prepared for tiling, should be finished in accordance with the recommendations given in BS 5385-1:1995 section 3.4.

Very often the finished surface of plaster can be very variable, depending on the conditions and the plasterer. The surface can be very dusty or, if overtrowelled, it can be very dense and shiny.

Plaster is water sensitive and is therefore not an ideal substrate in areas subject to wetting such as showers or wet rooms.

Correctly preparing the surface

Plaster finishes, when prepared for tiling, should be prepared as recommended in BS 5385-1:1995 section 3.4. Quite often though, the finished surface can be very shiny or dusty and this needs to be prepared correctly prior to tiling, otherwise failures could occur.