How to fill concrete holes before applying full cover exterior paint?

[BC2]

Hi 

I am looking to make the concrete surface in the attached picture even so I can apply a full cover exterior paint to achieve a rendered look, please advise which product should i use?

Thank you

[EricL]

Hello @BC2 

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

Is this a free-standing wall or is it a retaining wall? If it is a retaining wall, unless it has been sealed from the other side anything placed on its surface will eventually peel off due to moisture passing through the wall. But if it is free standing with nothing on the other side, please have a look at my recommendations below. 

In regards to rendering, I suggest thoroughly cleaning the wall with a pressure washer and then treating it with 30 Seconds 2L Outdoor Cleaner Concentrate in combination with an Oates Long Handle Grout Brush. 

I recommend roughing up the surface of the unfinished area with a Trojan 5x15 Row Stainless Steel Wire Brush. Please make sure to wash away the concrete dust that will be generated by the steel brush. Once the surface is dry and clean, you can then begin planning on rendering the surface. 

Here is a handy step-by-step guide: How to render

Depending on the weather, the render must be allowed to totally cure and be absolutely dry before you make any plans on painting it. It could take anywhere from 4 to 6 weeks for the render to be absolutely moisture free. Painting too early will result in the paint peeling off.

I propose having a look at Dulux Weathersheild or Taubmans Sunproof external paint for your masonry wall. They are self-priming and can go onto a variety of surfaces.

Please make sure to wear personal protection such as gloves, goggles and a mask when working on your project.

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

Eric

[BC2]

Hi Eric

Thank you so much for the insight unfortunately it is a retaining wall and I doubt it has been sealed from the other side , so I guess rendering is not an option :(.

Do you have any other suggestions on what could be done to improve the overall appearance of the wall ? I was thinking maybe cladding it with fibre cement or some other sort of panels , if that s a viable option can you provide some guidance please.

There s around 50 sqm of retaining wall with the highest one being 2.2m high

Thank you

[JacobZ]

Hi @BC2,

Just to keep you posted, I've contacted Sika Australia to see if they have a suitable repair mortar for this job. I'm currently awaiting a response and will let you know when they've responded.

Fibre cement sheet products would certainly be a suitable option that you can consider. 

A basic product such as HardieFlex could be attached to the concrete using masonry screws. This could then be painted or rendered depending on your preference.

Some other fibre cement options that come pre-textured to resemble render are James Hardie Brushed Concrete Cladding and James Hardie Hardie Fine Texture Cladding. 

You might also like to look through the full range of External Fibre Cement Panels & Cladding Solutions that James Hardie have on offer.

I will update you once I have a response from Sika Australia

In the meantime, feel free to let me know what you think and ask any other questions you might have.

Jacob

[EricL]

Hello @BC2 

I was thinking about your concrete retaining wall last night and thought about using Merbau Screening panels like in this discussion - Merbau panel screening by @WendyL. It's an excellent method of covering up your masonry wall and giving it a bit of character. 

I also suggest having a look at these alternatives - Pergola privacy screen by @Bankzee and D.I.Y. Merbau slat fence for courtyard screening by @CagsMac. These can all be adapted to be standalone features that can cover your masonry wall.   

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

Eric

[BC2]

Thank you Jacob appreciate your help in finding a suitable mortar product.

Thank you also for providing list of fibre cement product , if these are attached straight to the concrete is there a risk that the mold and moisture will pass through the panels? 

[BC2]

Thank you Eric for sharing these , i have been scratching my head on what to do do with these walls for quite some time now and these are great ideas,

[EricL]

Hi @BC2 

Please remember to post an update, once you've decided on how you would like to move forward with your masonry wall. 

If you need further assistance, please let us know.

Eric

[JacobZ]

Hi @BC2,

Moisture may be present, but these fibre cement products are fine to handle moisture. Mould is always going to be a possibility where moisture is present, but the vertical nature of the sheets would allow for moisture to drain, so the risk is not massive.

Just to update you, Sika has gotten back to me and recommended Sika 20kg Sika MonoTop-352NFG Structural Repair Mortar with some information to consider.

"Sika MonoTop®-352 NFG light weight, high build repair mortar would be our most suitable stocked product for this repair application however if there is movement between slabs this mortar, installed into cavities to 50mm depth, may fracture which needs to be considered."

Let me know what you think.

Jacob