How to repaint outdoor concrete slab?

[torabora851]

Hi, I'm going to repaint the concrete slab in my backyard. The slab is around 5x13m in size. Do I need to completely remove the old paint (I’m not sure how to do that), or would it be okay to just clean it with a high-pressure washer? Also, could you please recommend a paint? Please check the photos:

[JacobZ]

Hi @torabora851,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.

There's no need to remove all of the existing paint, however you should remove as much of the flaking paint as possible, such as the paint shown in your second image.

I'd suggest grabbing a Masterfinish 150mm Floor Scraper and giving the flaking paint a good scrape to remove anything that is not well adhered to the concrete beneath.

You can then give the concrete a good clean with the pressure cleaner to remove any other loose materials.

My suggestion in terms of paint, is the Concrete & Paving Range from Dulux. It is a 3-step system consisting of a cleaner, primer and paint coating. Your situation is somewhat complex because you have areas that are still coated, and areas that are bare concrete. This system has a different cleaner and primer that are dependent on the conditions of the concrete, whether it is bare, or previously sealed.

I have spoken with Dulux's weekend assistance team who have said that it would be hard to determine the better method without knowing what kind of paint was used to coat the concrete before. Unfortunately, their technical team, who are the ones who will be able to provide more definitive advice, are unavailable on the weekends. 

Please allow me to get in touch with them when they are back in the office tomorrow and I will be back with a more firm answer.

In the meantime, let me know if you have any further questions that I can assist with.

Jacob

[torabora851]

Hi Jacob, 

Thank you for the information. How do you think, it is worth trying some paint stripper? https://www.bunnings.com.au/poly-1l-polystrippa-paint-stripper-1l_p1715074 Or the paint strippers only for metal and wood paint?

[JacobZ]

Hi @torabora851,

Apologies for the delay in responding.

I have spoken with the technical team at Dulux who have looked over your photos for me.

Unfortunately, their advice is that the only way to have a warrantable coating considering the state of the existing paint, is to have the concrete ground back to bare concrete so you can use the bare concrete system. 

Unfortunately, paint stripper will not remove the paint that has seeped into the concrete over time, the only way to remove this is to grind back the concrete.

They've said you could try the sealed concrete system, however there are no guarantees it would last, and it is likely you would have to recoat the concrete in a few years. If you were happy to do this, it might be a good option for you.

If you wanted to have the concrete ground back, I'd suggest using a service such as HiPages or True Local to find concrete grinding businesses that operate in your area.

Let me know if you have any further questions.

Jacob

[Dave-1]

Good Afternoon @torabora851 

I had a similar issue with old flaky paint on my patio.

Remove all you think you can and then remove more is about what it comes down to. Mechanicaly removal is the best way I found, I did consider paint stripper but put it in the "too high a cost money wise (I had just redone my front door with it) and also enviromentaly having it around the garden type deal.

I didnt go with the paint that @JacobZ has mentioned but it is good paint. I explained why in my project Patio renovation using paving paint 

I did run into a few small issues and had to go over and touch it up. Having paint on some areas and no paint on others does add to the bonding problems. Solvable but extra elbow grease is probarly where you will end up.

Dave