how do i stop bonding from cracking

[vodka10]

have just put bonding on an upstairs wall and before applying gave the brick wall a coat of pva bonding then later on put the bonding coat on which was fine until it started to dry out when it cracked what is the cause of this and how do i stop it happening again

 

[Richard C]

Bonding is primarily for low suction backgrounds & blockwork isn’t; the moisture is being sucked out too quickly. PVA the wall once, let dry; liberally PVA again & plaster while still tacky. Bonding can be used up to around 10mm or so thick in one hit but if I’m using as a base coat on crumbly walls, I always apply it in 2 successive coats rather than 1 thick one. A little water spray as it's going off can also help if it starts to craze. If the blockwork is in good condition, Hardwall plaster may be a better choice as a base.

 

[clout stench]

hardwall or browning undercoat but skim same day. no pva necessary, just damp down lightly before applying undercoat.