Hi @caitlyndiy,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
Rendering over limestone is difficult but not impossible. The main issue is that limestone is a soft, porous stone that absorbs moisture, which can make it hard for the render to stick properly. If the surface isn’t prepared correctly, or if the wrong materials are used, the render can crack, blister, or peel away over time. Because of this, it’s not a straightforward DIY project and often ends up costing more to fix if it’s not done right the first time. I've spoken with our suppliers, and they could not tell me what products or techniques would be suitable.
If you are inexperienced, I wouldn't recommend this as a learning project. The materials can be expensive, and small mistakes, such as trapping moisture or using the wrong primer, can cause long-term issues.
If you were sure you wanted a rendered finish, I would contact a professional renderer who has experience with limestone or other natural stone surfaces. They will know which products and techniques to use. They will also be able to give you the smooth, durable finish you want without the risk of future problems.
The only rendered alternative I can think of is to attach fibre cement sheets to the blocks and then render over that. To do this, you would need to attach some timber framing to the blocks and then attach the fibre cement sheeting to the framing as direct contact between the sheets and the stone can also cause issues.
Alternatively, you could clad the blocks with something like merbau decking or ekodeck. You wouldn't have a rendered finish, but it will still look nice if done well.
Let me know what you think.
Jacob
