Plasterers - what's your mix for bonding coat on new build aerated blocks?

plasterer_paul_ne

General Builder

1y ago

Cheers Simon, never used SBR on blocks before only on floors. Makes sense with the suction. Will give it a go on Monday.

drylining_brian_subby

SubbHubb member

1y ago

Thistle Bond-It is also specifically designed for high suction backgrounds like Thermalite. Bit pricey but it's the proper tool for the job on spec work. Main contractors love it because it's a named BG product they can put in the O&M.

skimmersimon

SubbHubb member

1y ago

Don't PVA Thermalite, it's too absorbent and the PVA skins over before you can coat it properly. Use SBR diluted 1:4 with water, brush it on, let it go tacky not dry, then apply your bonding. Plenty of suction in those blocks so shouldn't have adhesion problems.

tradefinisher_trev

Painter & Decorator

1y ago

Mix wise I go 4:1 sharp sand and multi finish to build up the bonding thickness. Give it a firm key scratch with a devil float before it sets properly. Don't rush the skim onto it same day.