That will depend on humidity and porousness of the concrete

Really dry. Tape a square of clear plastic on them (gladwrap is okay) and leave it at least a couple of hours. If any moisture is under the plastic they're not dry enough yet.

I'm not sure I'd use ordinary acrylic undercoat on bare concrete though. You normally need to seal anything porous first - see, for e.g. https://www.resene.co.nz/archspec/datasheets/d409-ConcreteSeal3in1.pdf 

More instructions for painting concrete here: https://www.resene.co.nz/archspec/datasheets/d322-Walk-on-flooring-and-paving-paint.pdf. I've used this waterborne paving paint (i.e. clean up in water) before and it is pretty good.

mdf:

 

Really dry. Tape a square of clear plastic on them (gladwrap is okay) and leave it at least a couple of hours. If any moisture is under the plastic they're not dry enough yet.

 

I'm not sure I'd use ordinary acrylic undercoat on bare concrete though. You normally need to seal anything porous first - see, for e.g. https://www.resene.co.nz/archspec/datasheets/d409-ConcreteSeal3in1.pdf 

 

More instructions for painting concrete here: https://www.resene.co.nz/archspec/datasheets/d322-Walk-on-flooring-and-paving-paint.pdf. I've used this waterborne paving paint (i.e. clean up in water) before and it is pretty good.

 

yep I used this and it’s well worth it. Lots of mess about but it does work well. Have more to do this summer :-)

Hey those are great tips, thanks. I'll check out the undercoat too.

Resene Paint store lady says the 3in1 is a tough product to use and is recommending Sure Seal instead even though they sell both.https://www.resene.co.nz/archspec/datasheets/d42-Sureseal-Sealer.pdf why is the 3in1 hard to use?

Also, I have enough resene Sonyx 101 cool colour acrylic in the right colour left over for top coating. You reckon it will be too slippery? I've used it successfully on threshold wood, just touch it up as it wears off.

JayADee:

 

Resene Paint store lady says the 3in1 is a tough product to use and is recommending Sure Seal instead even though they sell both.https://www.resene.co.nz/archspec/datasheets/d42-Sureseal-Sealer.pdf why is the 3in1 hard to use?

 

Also, I have enough resene Sonyx 101 cool colour acrylic in the right colour left over for top coating. You reckon it will be too slippery? I've used it successfully on threshold wood, just touch it up as it wears off.

 

Not sure what she is referring to exactly but 3 in 1 does dry really quickly so you can get lag marks if you're not careful. Maybe its that? Sureseal is a really good product and is recommended for concrete too. It can also be used for other things too (e.g. gib). I also think (?) it is available in a wider range of sizes. Sureseal is easier to clean up afterwards too, though the last time I used 3 in 1 I just used an old brush and threw it away when I was done.

I wouldn't use sonyx personally. Being walked on is much more strenuous than looking nice on a weatherboard. Weatherboard paint is designed to be relatively flexible to deal with expansion and contraction in the sun, but flexibility in something you walk on isn't ideal. You might find it is a bit tacky if you stand on it after its been in the sun, and it certainly won't last as long. You might want to paint a test patch somewhere hidden (or even on a board) and see what it is like to walk on. 

Sonyx is shinier than paving paint but if the concrete it is going on is even vaguely rough it will probably be okay. If you're worried about slipping, you can get a grit additive that you stir in to one of your coats to make it more abrasive / less slippery. 

i used weatherboad paint on some old stairs, its lasted about 6 years with morning sun on it. now its starting to bubble.

i don't know what she meant either. I'm a pretty experienced DIYer and it's going onto mostly a flat, horizontal surface, how hard can it be? I'm planning on throwing the brush out after as well. It'll be in pretty rough shape after doing that job anyway!

 6 years is pretty darn good. :)

Hmmm, I'll spring for the walk on then if they can do it in shuttle Grey to match the rest because being soft and flexible is a very valid point. It's going on a fairly sunny spot too. If it goes well I'll also do the other set of concrete entrance steps.

The concrete was laid in 1950 and despite the old paint it's pretty gritty. Good point, probably be fine without grit added.

I am going to use a water based walk on.

These comments have been incredibly helpful, thanks!!

We had a house (mid 70's) with long "verandah" made of concrete - half was just the concrete, the other half covered in a bitumen-based type membrane. When we took it over from my parents around 1990, we looked into repainting it.  Spoke to Resene at the time about paving paint and the guy said just to use Lumbersider - might need more frequent coating but much easier in the long run.  Over the next 30 years we repainted in Lumbersider maybe four or five times - so matching Jase's experience as noted above.  Worked great in my opinion.

Lumersider is low sheen, less reflective. It absorbs more sun and peals more quickly than higher sheen paints, though this is mostly about painting wood particularly oily wood.

Regarding how long to leave concrete to dry, with no real knowledge of painting concrete but kiwi bloke level knowledge of painting, I'd try to give the concrete a week to dry before painting it. If there's a way for any water to drain / evaporate out another way I might reduce that. I might be being too generous there but generally patience helps with regard to painting.

Cool. Seems like another good choice. I'm going to go paint shopping Monday. I'll grab the concrete seal 3in1 and walk on paint but if they haven’t got that then lumbersider looks like a good alternative. Thanks for the info.

Handsomedan:

 

That will depend on humidity

 

So about a month if you are in Auckland. ;-)

Does concrete dry, or cure?  I thought that the moisture does a chemical magic trick internally, so to speak.  I'd be happy after two days if it was me.

[EDIT] Read post properly before replying.  I'll get my coat.

TLD:

 

Handsomedan:

 

That will depend on humidity

 

 

So about a month if you are in Auckland. ;-)

 

Does concrete dry, or cure?  I thought that the moisture does a chemical magic trick internally, so to speak.  I'd be happy after two days if it was me.

 

[EDIT] Read post properly before replying.  I'll get my coat.

 

Lol. I might post a before and after eventually. It's raining out. 

Update: bought a litre of the 3in1 and 4 litres of walk on in Shuttle Grey from resene plus a couple ok brushes from Bunnings. Just waiting for the steps to dry out enough now. :)

It's going to make a very big difference looks wise.

Update: after doing the plastic test overnight to make sure the concrete was dry I used a litre of Resene concrete seal 3 in 1 to undercoat both sets of steps. I had less than half a step to go when it ran out (the coverage estimate must be for really smooth concrete. I should have listened to my inner scepticism). My local shop, a Mitre10, of course did not have any but by dumb luck they had my second choice, a couple of 500ml tins of Resene Sure Seal. So I finished off the step with a tin of that. 

Sure Seal has a 3 hour recoat time vs 1hr for the 3 in 1 which is likely why tradies like it.

Anyway, had breakfast and took the dog for a walk etc then did a topcoat of Resene walk on.

Next morning did another coat of walk on.

Looks absolutely brilliant. Looked great even after the first walk on coat.

I'm not letting anybody on it for 48 hours.

Neither undercoat product was hard to use but the sure seal flows on nicer.

Next up I'm doing the bricks that make up a garden edging right next to the steps so the grey continues along the house.

By the time I get the front door painted, the bricks painted and the security screen doors on the front of the house will have had a nice little make over.

Thanks again for the great advice I'm stoked with the result. 

PS the half round roof is getting roofer attention in February.