All Promat boards tend to have a high suction and therefore it is generally difficult to apply gypsum plaster. Traditionally PVA has been used, apply a number of sealing coats of diluted universal primer/PVA (e.g. 1 part PVA and 5 parts water). Sealing coats should be allowed to dry thoroughly (approximately 24 hours). Then apply a bonding coat (3 parts PVA and 1 part water). Apply the plaster skim (5mm thick maximum) while the bonding coat is wet and tacky.

Alternatively, PVA has been replaced by proprietary preparation coats, which can be applied in a single application (depending on drying conditions), such as Parex Microgobetis 3000, often known to the contractors as ‘pink grit’.

It is recommended that a small test area is plastered initially to ensure that the boards have been adequately sealed. It is advisable that self-adhesive or hessian scrim is applied over joints and internal angles. Paper scrim is not recommended.

NOTE: The bonding agent and plaster manufacturers’ recommendations should be followed at all times.