ive got some concrete walls to render. if i mix pva through my scudding and then give the walls a heavy scudding before applying my scratch and finish coats, should this be enough to prevent the render from blowing? has anyone got some feedback on this topic?
If by concrete you mean smooth precast follow below. If concrete blocks there is no need except some pva to kill suction if you think it needed.
The best bonding agent is SBR. Cementone Feb and others make it. If you mix it with dry cement to a wet slurry and apply it liberaly with stiff brush........ then apply scratch coat. Coat with slurry still tacky. scratch to key as normal.
The same thing can be done with PVA. The cement in the bonding agent makes it twice as effective. Another way is to mix bonding agent(pva or sbr) with cement and some sand and cast a rough spatter coat with harling trowel........messy but a good job. Next day scratch coat and proceed as normal. Maybe that is the scudding you referred to. You could do this to block if you wanted for a belt and braces job.
Water in small measure can be added to any of above methods.
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