Painting new concrete gravel boards

[DIYedboy]

I've built a retaining wall using 12" gravel boards and 9" hollow concrete blocks behind those and now want to paint them with white sandtex, should I prime with something first?

 

[DIYedboy]

anyone out there?

 

[misterhelpful]

I can't ever recall painting gravel boards myself but would imagine the majority could be painted with masonry paint. If they are the absorbent concrete type then you could water the first coat down a little (same goes for the blocks) but the smooth brick patterned type may require a grip primer first like one of the Zinsser products.

Paint on retaining walls often suffer from peeling/flaking due to the constant moisture in the ground they hold back. If you do not have drainage holes or some form of waterproofing on the rear of the wall, this might happen in your case even if you use the primer. I'm no expert in retaining walls and don't know exactly what yours is retaining but excessive moisture can cause problems - hopefully someone else can advise you on that aspect of it.

 

[JohnD]

masonry paint, water based. The concrete can be very dry and hungry so instead of the usual 10% water thinning, thin 20% and apply two mist coats. You will know when you have satisfied the suction, because the concrete will no longer pull the moisture from your brush. Keep applying mist coats until it's satisfied. Then it will be quicker and easier to apply the finish coats.

herre's one I did earlier.
View media item 975
p.s. White will quickly get dirty, and will show the mould, algae and mud splashes.

 

[DIYedboy]

Thanks John D, mist coats it is then. In actual fact, the retaining wall I built is made from 4" concrete blocks, a 2" cavity filled with gravel, then 9" hollow concrete blocks then 12" high concrete gravel boards in front of those!