Plastering
PLASTERING AFTER DAMP PROOFING WORKS
PLASTERING
Re-plastering often involves the use of a dense sand and cement render as a backing coat that incorporates a waterproof additive. A gypsum skim coat is then applied for a smooth finish.
We recommend that when damp proofing works are carried out that the wall plaster is removed from the floor level up to at minimum height of 1 meter, or just past the last signs of dampness. This is to eliminate the hygroscopic action of salts within the old original wall plaster.
Hygroscopic salts have the ability to absorb moisture from the surrounding environment and the amount of moisture absorbed is dependent on the type and quantity of the particular salt and the humidity of the surrounding environment. Hygroscopic salts can cause masonry to remain damp even though there is no source of water ingress; wallpaper, especially, can become very damp solely due to contamination with hygroscopic salts.
DECORATION
After a re-plastering is completed, all areas must be visibly dry before the new plaster can be decorated; this is usually around 14 days. This should only be done with a water-based emulsion, without the use of vinyl paints, and do not wallpaper the treated areas for a minimum of 1 year.
When applying the emulsion, apply 1 mist-coat to the walls before applying a full coat of emulsion. To make a mist coat, mix three parts of water with one part of the emulsion. You should always check the paint tin for the manufacturer's instructions as ratios can vary. You don't have to use the exact same paint you've chosen for the final topcoat but you should use a similar colour for an even finish.