How to repair render on a cinder block wall

[Nanne]

 

The rendering on my external cinder block wall is slowly coming off. I’m not aiming to restore the rendered look right now — I just want to waterproof it before the next wet season. In the long run, repairing the entire wall will be Body Corporate responsibility. Should I check the wall’s moisture level before sealing it? Kill the heavy lichen / mould first?  My understanding is that the sealer needs to be breathable. Is it normal for a rendered surface to peel or flake easily?

What would be the best product to use?

[JacobZ]

Hi @Nanne,

I'm aware of breathable brick and block sealers, like this Crommelin Natural Finish Penetrating Sealer and Water Repellent, but not paintable waterproofing products. 

Render falling off your wall could be due to a number of things, with moisture in the wall being one of them. If moisture is the reason for the damage, then our focus should be on eliminating the source of the moisture. Narrowing down the source of the moisture is going to be the key to fixing the issue long-term.

If you are just looking to protect those patches from external moisture, such as rain or condensation in the short term, I would just paint over them with 2-3 coats of an exterior paint. 

This will offer you protection in the short term, so a more thorough repair can be carried out by the Body Corporate in the future.

If there is moisture in the wall, then the paint may fail prematurely, but without identifying the source of the moisture and rectifying that issue first, it would be your best option for a short-term repair.

To give your paint the best chance of staying on long term, I would suggest you remove the lichen and mould first. You can use a product like 30 Seconds 2L Mould Off Spray Nozzle to kill it, then scrub it off with clean water.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[Nanne]

Hi Jacob

There are a few reasons why the wall has lichen, mould, and the render is peeling. The previous A/C unit had its condensation pipe running along that wall (it’s since been removed). The building is also around 20 years old and, as far as I know, may not have been repainted since then. On top of that, the complex has gone through two major floods.

I also need to paint the outdoor wooden patio beams — would I be able to use the same paint for those as well?

Thank you
Marianne

[MitchellMc]

Hi @Nanne,

Yes, the same exterior paint can be used in both areas. Most exterior paints are suitable for both masonry and timber.

Mitchell