How to render this wall?

[christinaa16]

Is it possible to render this wall? I would love a flat smooth surface/finish on this wall. Is it possible to render it to achieve a flush surface finish? 

 

[EricL]

Hello @christinaa16 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about rendering your wall.

Can I please request a little bit more information about your wall? Is it a retaining wall or is it self-standing with nothing behind it? Is it made of limestone or is it aerated masonry blocks? I only ask these questions as some wall materials can't be rendered due to moisture passing through it. 

When moisture passes through a porous surface from one side to the other it is referred to as hydrostatic pressure. Any cover, paint or render placed over the that surface will get pushed off thereby rendering the render as useless.

One quick giveaway is when mould and mildew grow in patches over the entire surface of the wall. It is a sure sign that moisture is passing through this wall. You'll often see rivulets of water making their way through the joints of the wall during a heavy downpour. Another sign that water is being held back behind the wall. 

Generally, the wall should have been sealed from behind with a waterproof membrane and thereby preventing water from passing through. 

If you have any other questions we can help with, please let us know.

Eric

[christinaa16]

Hi Eric,

Thank you for the warm welcome to the Bunnings Workshop community. I appreciate your detailed response regarding rendering walls.

To answer your questions, the wall in question is self-standing with nothing directly behind it, except for my in-ground pool. The wall is made of aerated masonry blocks.

I understand the importance of addressing potential moisture issues to prevent the render from becoming ineffective. Given the proximity to the pool, I'm particularly concerned about moisture passing through the wall.

Could you please advise on the best type of waterproof membrane to use before rendering, considering the wall’s material and its location next to the pool? Additionally, are there any specific products or techniques you recommend for sealing the wall to ensure a long-lasting render?

Thank you for your assistance.

[EricL]

Hello @christinaa16 

This is exactly what I was referring to and I'm glad that you're aware of it. Unfortunately, I'm currently unaware of a product that you can use on the surface of your aerated blocks to prevent moisture from passing through. As I mentioned before sealing the wall at the back should have been addressed before the wall was sealed off. 

I propose engaging the services of an experienced masonry/rendering specialist. They will be able to address the moisture issue and perhaps offer a way to seal the aerated blocks.

One other option that comes to mind is to build a treated timber frame and place cement sheet over it then render the cement sheet.

Let me call on our experienced members @Dave-1, @Nailbag and @homeinmelbourne for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

[Nailbag]

Hi @christinaa16 my first thought was as @EricL has suggested which is to build a treated pine timber frame which can be secured to both the concrete ground and to the stone blocks. Then cladded with blue-board cement sheeting on the face and on the top returning back to wall. The joins will need to be taped or use a jointing compound. You will also have to consider some form of water drainage from behind the rendered wall. Such as 20mm holes spaced along the bottom.

Regards, Nailbag