Painting outside wall blocks

sillysocks

Hoping to get the back walls of our garden painted over the next few days. They are heavy concrete blocks that have never been painted (just in the original grey state!).

Does anyone know should we use some kind of primer/undercoat on them before we start with the paint? If we should any recommendations for what to buy? We've quite a lot of wall to paint so don't want to mess it up !

Wertz

Thinned down masonry paint is fine. About 20% water in the first coat, let it soak into the blocks. Then 2 straight coats to finish. Pig of a job...one for a sprayer really if you have a big area to cover.

sillysocks

Had thought about the sprayers but read somewhere that they aren't great?
Anyone used them and thought they were good? At the moment the grass is being killed off and will be replanted so not worried about paint getting on that.

Would definitely be easier with one of those! There's two walls to paint, one is 20m long and other is 12m long, and I'd say about 2.5/3 metres tall.

Wertz

Depends what kind of sprayer you're talking about...not the Ronseal Fencelife backpack sprayer type affair or the 20 quid plug in bottle sprayer...those aren't suitable in this case (and aren't great for much else either). I'm talking about the kind you hire out for the day, preferrably the airless type.
Seriously with those kind of sqM to cover, it's going to be a back breaking process with a roller. You've almost 100sqM of a raw porous surface to paint.

sillysocks

Oh didn't know you could hire them out..... any ideas how much they'd cost?

dh0661

Wertz wrote: »

let it soak into the blocks.

There is not much chance of anything soaking into the blocks after all the rain and dampness we've had in the last while, and no signs of an improvement in the near feature by all accounts.
I would have thought that walls should be reasonably dry before priming ?.

sillysocks

Yeah looking outside now at the rain (again!) I guess we won't be doing it for a while yet.

dh0661

Thought so - but I do think that blocks would have to be at least some way dry before you'd start painting.
I'm sure there are some more expert people reading this who will give some advice.

Wertz

dh0661 wrote: »

There is not much chance of anything soaking into the blocks after all the rain and dampness we've had in the last while, and no signs of an improvement in the near feature by all accounts.
I would have thought that walls should be reasonably dry before priming ?.

Reasonably dry yes, no-one's going to paint something that's visibly wet, or with imminent rain, unless they're an idiot.
A few hours of sunshine/wind combined with the effect of gravity is enough for raw blocks to loose any excess moisture, it doesn't have to cure like render or plaster. The paint you're putting on to the blocks is water based acyrlic emulsion; it's not like oil paint where you would have a reaction due to underlying moisture...with water base, the rest of the water evaporates as the paint gradually dries (or gets washed off in a freak downpour )

As for the hire of a sprayer? Last time I got one it was about €90 for the day, that's a while back though.