Is there an aqua-phobic render and plaster for bathroom wall subject to moisture/splashes?

1960’s besser block construction with assumed cement based render and plaster top coat. A small section become damaged due to a poorly positioned shower curtain resulting in constant water on the wall.

I’ll remove any damp/loose material (including larger area of flacking lead paint) however

what render and plaster product or additive would be ideal for repair? I’ll need to go back to the besser in at least a couple of spots.

The wall will be painted in a bathroom paint however I’m conscious this area will always be subject to higher moisture/splashes and a hydroponic plaster(top coat/render etc might be more ideal?

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R4addZ

Hi @broberts

You can add a waterproofing agent to the mortar/render like this one....

https://www.bunnings.com.au/bondall-silasec-4l-waterproofing-cement-additive_p0489176

MitchellMc

Welcome to the Bunnings Workshop community @broberts. It's wonderful to have you join us, and many thanks for your question about water-proofing render.

Great suggestion by @R4addZ. The only caveat is that it's only suitable for GP cement and not renders that have lime in them, which most do. Instead, it might be better to go with Gripset Betta 1L Prep Coat And Additive Waterproofing Primer, which can be applied as a primer coat and also mixed into your render/cement-based compounds. It doesn't have the issue with lime as Bonall Silasec does.

Please let me know if you have any questions.

Mitchell

broberts

Thank you.
Any chance you could recommend a render and plaster or suitable fine topcoat? The product suggested, Betta prep and prime recommends max 30% lime. I couldn’t locate a percentage for Davco render for example.

Would be great to have a shopping list for worse case scenario prepped and ready. I’m hoping I’ll be able to skim coat it or take it back enough to apply a single thick layer. Worse case is a rendered base and plaster top coat.much appreciated.

Im in Adelaide if that matters.

MitchellMc

Hi @broberts,

I haven't come across the 30% recommendation for the lime. Could you point me to the documentation containing that advice? I do see "Water proof render/screed (0–10 mm thick), use a solution of 1 part Prep Coat & Additive to 1.5 parts water, then add to sand/cement compound".

Unfortunately, the information on the percentage of lime in renders is not information that is made available.

Gyprock CSR 20kg Hardwall Plaster is generally used over render as a finishing coat.

If including the waterproofer within the products is a hassle, manufacturers have advised that you apply the coating over the cured products instead.

Mitchell

broberts

Sorry , a bit late. The 30% recommendation was listed on the Gripset Betta site however I gave their technical team a call and was advised that site is defunct and replaced by the Bondall site and the information is not accurate. Cheers

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