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Hello @JonS
Welcome to the Bunnings Workshop community. It's fantastic to have you join us, and thank you for sharing your question about rendering limestone.
Would it be possible for you to post a photo of your limestone wall? This will give our members a better idea of its condition. We can then offer you possible steps on how to render it. Is it a retaining wall or is it a wall connected to your house? Because limestone is so porous, special consideration will have to be taken as to what kind of render can be used on it. Let me speak to my hardware specialist and see if they can shed some light on rendering limestone.
Let me tag our experienced members @tom_builds and @ProjectPete for their recommendations.
We look forward to seeing your photos.
Eric
Hello @JonS
Thank you for posting those photos. The longer I look at your wall, the more I'm convinced it is a cement block wall. I suggest testing a hidden part of the block and scraping the paint off. If you run into light grey dust, it is a cement-based block. However, if it crumbles and is easy to penetrate, it could be a Hebel block. Either way, the paint must be removed from the wall before you render it. I suggest using a Grinder in combination with a Multipurpose strip disc. Make sure to use a Pressure washer to clean the wall after grinding it.
Limestone by its nature is soft and easy to scratch. A cement surface on the other hand is hard and is difficult to damage. Once you've determined which one you have, you can then decide if you want to render it.
If you decide to render it, I recommend adding Bondall BondCrete Cement Additive to your render mix. Make sure to remove all the loose masonry and debris before rendering the wall.
Here is a handy step-by-step guide: How to render
If you need further assistance, please let us know.
Eric
