painting concrete patio wall - seal and prime or just paint?

[lfnfan]

Hi

I'm trying to do my research for painting this wall.

I'm pretty sure the first step will be a power wash followed by fungicide and then another power wash.

Then I'm a bit confused if I need to seal it or prime it first or just get on and paint it!

For the paint I'm thinking something like Sandtex microseal (in whatever colour).

Many thanks for any advice!

 

[JohnD]

I'm guessing you mean an external wall.

If it is wet on one side, like a retaining wall, then water and minerals will come through it and push off the paint, so leave it bare.

If it is a dry wall, you can use masonry paint which is very durable. The first mist coat must be thinned with water as it soaks into the surface. If you are not charging your time by the hour, I find it an advantage to apply two heavily thinned coats to concrete, as it is very absorbent, and the first coat soaks in and disappears. It soaks in and dries so fast that by the time you have reached the end of the wall you can go back to the beginning and start again. You will know when you have misted it enough because it no longer sucks the moisture out of your brush. On new bare concrete I find a large brush quicker than a roller.

 

[lfnfan]

Hi @JohnD

Thanks very much for your reply. Yes - it's external - hopefully the picture gives an idea.

It's a patio retaining wall, and I have to say that we do have some cracks in the patio mortar between the pavers so there might be some moisture down behind the hidden side of the retaining wall from when it rains. I must say I don't see signs of minerals coming through though. The concrete retaining wall is about 1ft thick.

Leaving it bare is not really a great option as the 'customer' is quite determined the wall gets smartened up.

Is there anything I could treat it with before painting, for example?

I'm not charging my time - homeowner here.

 

[JohnD]

You could apply a porous render to smarten it.

 

[lfnfan]

OK. not quite what I was expecting but if paint is not the right product for the job... really appreciate your advice.

What sort of product would I be looking at for a porous render?

Depending on how thick it goes on I would need to figure out something for the overhang from the patio tiles to the render but one step at a time.

 

[JohnD]

I don't do it much. I believe a coarser sand is less prone to crack but soft sand is easier to apply. You can buy white cement, it costs a little more but you will not need much and it may look better. Ask on the Plastering and Rendering section.

BTW it needs a drip to prevent water running down the face. There are stainless steel beadings available that are used on outdoor render.