How to re-paint concrete paving?

Question

Hi, I want to repaint my previously painted rear concrete. It had been originally painted but I don't know what was used. I cleaned the surface with a high pressure washer then repainted it using White Knight water based paint but it didn't adhere properly, see attached photo.

EricL · Answer

Hello @GregoryC

Just to add to the recommendations made, I suggest removing both existing coatings on your concrete paving with a

https://www.bunnings.com.au/josco-75mm-twistknot-cup-brush_p6326282

in combination with a grinding tool. You can also look at using

https://www.bunnings.com.au/josco-125mm-purple-multi-strip-disc_p0413235

. Please remember to wear personal protection such as gloves, goggles and a heavy-duty dust mask.

Having a fresh clean surface means that the paving paint will have something to anchor onto. Compatibility issues sometimes arise between an existing coat and a new coat being put on. I often advise removing any old coating that is on the surface so that the new coat goes onto a properly prepared surface.

I also suggest looking at these guides - How To Paint Concrete Floors and How to Update Patio Pavers with Dulux Concrete & Paving.

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

Eric

GregoryC · Answer

Hi Mitchell,

Thanks for the reply. I don’t think the original paint was a gloss or semi-gloss. The White Knight paint was Ultra Pave paving & concrete paint and I only pressure cleaned the original painted surface.

MitchellMc · Answer

Welcome to the Bunnings Workshop community @GregoryC . It’s great to have you with us and many thanks for your question.

I'm sorry to see you've had this issue with the new coating.

For previously painted concrete, it's important to first clean the surface thoroughly, removing all dirt, dust, grease, and oil, and degreasing any contaminated areas. The next important preparation step is to sand glossy areas to remove the sheen before applying the new coating.

Do you happen to know whether the original coating had a gloss or semi-gloss finish? If it did, and the surface was only pressure-washed rather than sanded, that could explain why the new coating hasn't bonded adequately.

Unfortunately, the difficult part now is that the new coating is delaminating, so the surface is compromised and shouldn't simply be painted over. Any new coating would only be as well adhered as the failing layer underneath it.

You'll need to remove the poorly adhered coating back to a sound surface before starting again. This could be quite a substantial job, particularly if some areas have bonded better than others, and unfortunately it could be difficult to remove all the new coating without also affecting the original coating underneath.

Could you also let us know the exact White Knight product you used and whether you carried out any other preparation besides pressure washing? That will help us determine the best way forward.

Please let me know if you have any questions.

Mitchell