roughcasting

[godsjob]

HI does any body know if it is possible to roughcast over painted smooth render. Had a local firm look at the house and they have said it would be posible by applying a coat of waterproof pva? then scratch coat then final coat and stones. Any help would be much apreciated as i havent a clue about plastering or any job in the building trade and dont want to be tricked into payiny for a botch job.
Thanks to all who help

 

[trowelmonkey1]

sounds plausible to me but wait to see what a rendering expert says, it's certainly the process i'd use internally on painted surfaces, not a waterproof PVA though as that would be unnecessary indoors

 

[Alastairreid]

if the existing smooth render is sound it can be pressure washed, lines scored into it with a grinder or stihl saw. depending on the type of paint i would use a skutch hammer to get all the loose material off.
i would remove the window ingoes and soffits, treat with fungicidal wash and finally stabalising solution.
all text book stuff really.

 

[trowelmonkey1]

see now that didn't take long did it!?

thanks Alastair! question though, why the stabilising solution? not doubting you i just want to know the science behind it, i find i remember things better when i understand reasons

 

[Alastairreid]

hi trowelmonkey.
we use stabilising solution the same reason pva or sbr is used for preparation of substrates prior to the application of scratchcoat.

as the products we use are polymers, bonding agents are not advised as they can react with the polymers causing discolouration.

stabilising solution, fungicidal wash as well as pressure washing are necessary procedures and always good practise when casting or rendering over previously painted substrates.

clicky

 

[trowelmonkey1]

thanks for that reply Alastair!

so the solution is really for suction control then by the sound of it.