How to skim coat a rendered wall?

[Jayden67]

Hi I'm trying to skim coat a bedroom wall some of the old skim coat had fallen off all that's left is the old render in good condition I've been trying to find a pva to use for plaster but can't find one I've heard that people also use sbr but the only ones I could find is for tiles and I'm not if I can use it or not 

[MitchellMc]

Welcome to the Bunnings Workshop community @Jayden67. It's terrific to have you join us, and many thanks for your question about plastering.

You generally do not need to add PVA, SBR or any other bonding additive when skim coating over render that is in good condition. A gypsum skim coat will bond perfectly well to sound, stable render on its own. The key thing, especially given the previous skim coat has fallen off, is surface preparation. Make sure all loose material is removed, the render is solid, and the surface is thoroughly dust-free. If the wall is very dry or porous, lightly dampening it with clean water just before skimming is usually enough to control suction and help the plaster adhere properly. Using PVA or SBR is often misunderstood and can actually cause problems if misused, particularly if it dries glossy and creates a barrier rather than a bond. If the render is firm, clean and not chalky, you can confidently skim coat straight over the top without any additives, and you should get a good, long-lasting result.

Here's a helpful guide: How to hard plaster a brick wall.

Please let me know if you have any questions.

Mitchell