How to render keystone blocks beside pool?

[XTW77]

Hi, we’re updating our dated pool area and have a low wall of keystone blocks edging the outer area. 

We would like to render the blocks making a smooth wall but wanted to know the best way to fill in the gaps  between each block and best materials to get a nice rendered finish.

Also, any suggestions to give the stencilled concrete a lift also welcomed.

Thank Tom

[JacobZ]

Hi Tom (@XTW77),

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

The majority of the problem here is creating a flat surface to render on. I can't say I'm aware of a product that you could apply to simply fill the large gaps created by the angles of the stones. A mortar product applied in a few layers might work, but I couldn't guarantee it would last because of the likelihood of the blocks shifting.

A few thoughts come to mind. The first is cutting the stones back so they are all flush with each other, the second is to remove the blocks and replace them with something flat, like a besser block and the third is to cut some blocks to slot into the angled notches and then use mortar to fix them to the stones.

The other option is to build some formwork around the blocks and pour concrete to fill in the gaps and create a flatter surface.

Ultimately, the biggest issue here is dealing with those angles. Once the surface is flat, rendering is relatively simple.

Allow me to tag @AlanM52, @Nailbag and @Dave-1 to see what they think.

For the stencilled concrete, a good clean with a Pressure Washer would be a good place to start. Once clean, you could use a concrete paint or sealer to freshen up the look and give it a bit of a lift.

Let me know what you think.

Jacob

[XTW77]

Thanks Jacob, I was thinking of creating a form and pour in concrete. I did wonder if I should add anything to key the concrete to the blocks, either vertical rebar or drill into each block and add rebar to project into the gaps between the blocks. 

After the basic form is created I thought a 4 to 1 concrete mix to render to get the final finish before painting? Unless there’s something better to use?

[JacobZ]

Hi @XTW77,

I'd be drilling into the blocks, inserting Reinforcing Dowels, then tying them with galvanised tie wire, to some Light Duty Reinforcing Trench Mesh. This would ensure the surfaces are well-connected and strong.

You could then use a 4 to 1 concrete and sand mix, or just use some premixed render like this Dunlop 20kg Multipurpose Acrylic Render. Either option would work well.

Let me know what you think.

Jacob

[Nailbag]

Hi @XTW77 

This might all be too much, but I would consider hiring a demolition saw to run a vertical cut from squared off edge of the top level paving as deep as it will go. Then use an SDS pneumatic chisel to finish the squaring off the face. Fitting an offset honing disc to your grinder will then allow you to smooth the face surface

I would then look at getting a few quotes to resurface the stencil-crete and the step face. I looked in to this many years ago and from memory it was quite affordable with many finish options available.

Nailbag

[Dave-1]

Good Evening @XTW77 

I am thinking of formwork and concrete to give you a flat surface to work with. I would even suggest to use some masonary screws into the blocks for the concrete to attach to (like short rebar) I do have a largish concern tho and that is you are relying upon the strength of the existing mortar/edging to hold things in place. I thought of concrete mate as the concrete but thinmk @JacobZ's suggestions of the ratios would be far better.

Dave

[XTW77]

Thanks all for the suggestions. Will give it a go after we lay an Ekodeck on the opposite side of the pool...