Render on painted block...can I

[Needy]

Hi all

We have a block shed that has been painted white,Can anybody tell me if it can be rendered over to be or do the masonry paint have to come off for the render to stick

Cheers

 

[Alastairreid]

score lines in the brickwork with an angle grinder/masonry cutting wheel
get as much paint off as you can first with a skutch hammer.
then mix up some sbr bonding agent with a hanfull of cement and water to make a slurry to paint onto the walls.
leave to dry then render away.

 

[Micilin]

score lines in the brickwork with an angle grinder/masonry cutting wheel
get as much paint off as you can first with a skutch hammer.
then mix up some sbr bonding agent with a hanfull of cement and water to make a slurry to paint onto the walls.
leave to dry then render away.

I'd do the same, but perhaps add some sand into the slurry to help give a key, brushing it on to give a rough texture. An OPC:SBR:SAND (1:1:1) is recommended, but a bit of water through it is no harm -perhaps up to equal volumes SBR and water. This is what I use in these cases.

As an aside I don't know if any of ye have come across 'Rendaid', you can trowel this on and then use a roller to give it a slight stipple for a key . We use it for preparing walls for monocouche when needed, and it is good gear but messy.