How to bag or render a concrete block retaining wall?

[JustTryinMyBest]

I’d really love to give our garden retaining wall a refresh. At first I was just going to paint but then someone suggested that I might be able to bag or render it. I’m leaning towards bagging as I’m not after a perfectly smooth finish. I’ve looked up bagging techniques online and found plenty of information regarding bagging flat brickwork but I’m just wondering if anyone has any advice on how I can approach bagging the retaining wall

given it’s not a flush surface (please refer to attached photo; I’m not sure what you call

it but the edges of each block are angled back in). There is also the added complexity of a set of steps in the middle (see attached photo).
Any advice on approaches or products would be greatly appreciated; thank you in advance! 

[Jewelleryrescue]

Hi @JustTryinMyBest 

You  have some long wall to do . So I dont recommend  bagging it is it would be so hard to do neatly with all the wall ins and outs.

I would  use your same bagging colour mix as you wanted , and  use a  renders  straw  paint brush designed to paint cement like  products and it will be much  faster and eaiser to get into the corners.

Like any paint job do 2 or 3 coat to make and even  finish.

https://www.bunnings.com.au/dunlop-160mm-renderers-brush_p0960322

Dunlop 160mm Renderers Brush  I/N: 0960322 $28

Your wall needs  pressure washing first to get most of that algea off before painting just in case you didnt know.

[EricL]

Hello @JustTryinMyBest 

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

One of the things you'll need to investigate on your retaining wall is moisture. Is it coming out of the front of the retaining blocks. If it is, it means that water is getting trapped at the back of the retaining wall and any of it not getting drained away is passing through the front of the retaining wall.    

This means that any paint you put on the surface of the blocks will get pushed off by the hydrostatic pressure coming from the back of the block. Usually when retaining walls are built a waterproofing membrane is placed at the back of the retaining wall. This stops water from accumulating in the back of the blocks.

However, if the surface of the wall is dry and it appears that there is no water condensing on the block surface it's possible that your retaining wall was sealed properly. If it is sealed properly, I suggest giving it a good clean with a pressure washer and scrubbing the surface with a bristle brush and regular detergent. This will remove any oil or grease on the surface of the block.

I agree with @Jewelleryrescue's recommendation and that is to paint the surface rather than bagging it. Reaching the deep portions of the retaining wall will be very difficult and it's easier to use a brush. In regards to rendering it, it is possible, but if the retaining wall moves cracks will appear on the render.

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

Eric