Paint removal - masonary

[mo]

The paint on my shed is flaking - some of it comes off quite easily with a scraper but some is more stubborn.

As far as I know the 2 paint removal methods are a heat gun or somesort of chemical that you paint on

What is the ebst to use outside?

The shed is made of breezeblock I think but the external bit is smooth so I guess it must be rendered or something....

When I repaint it I will be using masonary paint of course which can be bought textured or smooht - will textured cover up bumps/cracks better?

[Clot]

First question - wire brush.

Re second - I've not tried them so cannot comment.

[Spamlet]

I've never managed to get paint off masonry with a blowtorch/heatgun. Not entirely sure why: suspect that the surface is too rough and porous, so the solvent/wood resin vapours cannot build up to form the blisters that lift the paint.

Not a job that I would want to be lumbered with, and I would imagine the pros would bead blast. You might be able to clean it up with a power washer, before repainting. Wire brushing a whole wall by hand would wear you out in no time, and using a powered brush would leave metal over the masonry which would make rust marks.

Powerwash would be my bet. (Watch out for any woodwork though, as a fully focused jet will drill it.)

S

[Clot]

B Tenders, wire brushing will sort it out.

[NT]

A quick wire brush to remove anything loose, and just paint over. Its one case whre it simply isnt worth making the job 4x harder for the sake of 25% longer paint life.

If you want white, lime paint fills cracks, can be used to smooth breeze blocks, is as cheap as paint gets and lasts ages.

[Andy Dingley]

I use a flat paintscraper, with a little touching up from a wire brush (mostly to shift algae). I don't use any power tools, as the flat scraper is the most effective. As I have far too much wall to contemplate stripping all of it (for that I'd have someone sand blast it) I'm just taking off the flakey stuff.

Another trick is to hose the wall down afterwards (or let it rain) and leave it for a day or two. It's surprising how much more of the previous "stable" paint then decides to start flaking around the edge. A particularly effective source of moisture for doing this is fresh paint, so don't be surprised if you've got some rework to do with a bit of scraping and re-painting after your first coat.

[Spamlet]

A quick wire brush to remove anything loose, and just paint over. Its one case whre it simply isnt worth making the job 4x harder for the sake of 25% longer paint life.

If you want white, lime paint fills cracks, can be used to smooth breeze blocks, is as cheap as paint gets and lasts ages.

Phew, what a big wiki! The lime section seems to be the most expansive: plenty of room for additions elsewhere, but remarkable scope. Is 'builder's lime' slaked lime or 'quick' lime? Does a limewash have to be aged before use (lime putty I seem to recall, taking 6 months, on the restoration TV progs)

S

[NT]

Maybe you've got a few minutes to add some?

Its slaked lime, quicklime is a higher risk item. Aged before use? No. There's been a lot of promotion of aged putties, but imho theyre a bit of an emperor's clothes product. =A36 Builders lime does fine, albeit not as fine a texture as dulux etc.

Simple lime paint doesnt handle as well during painting, it needs a regular quick stir, and I rotate the brush going from bucket to wall to stop it running off, but its very quick to use, and once its painted I've been surprised by how well it lasts. I've been using it outdoors for what... most of a decade now, and no sign of deterioration anywhere. And I wouldnt whine if it had, as a) a new coat is so quick & easy to do (drips on the floor just rinse off after theyre dry) and b) a new coat re-binds the old paint, which modern masonry paints dont do effectively.

NT

[Dave Liquorice]

Or you just can't get the paint hot enough for long enough when on a great big masonary heatsink? At least not without a BFO "line burner" type blow lamp.

See another recent thread. Small domestic pressure washer and "dirtblaster" lance certainly got a lot of the flaking paint of our walls on a test run. A lot quicker and with far less effort than scraping or wire brush. Leaving it for a few days after the initial going over then having another may be benificial. Some of the paint that didn't come off in the test run is now looser than it was.

[NT]

btw lime is also antibacterial, fungicidal, and acts as a mild stabilising solution.

NT

[stuart noble]

Heat doesn't work with water based paint. It bubbles and bakes on to the surface, but doesn't lift.

[Dave Liquorice]

So none of your exterior lime washed walls have been redone or touched up at all in ten years?

er so why doesn't the rain wash it off the walls? B-)

This is true but I was under the impression that if you get 5 years out of a limewashed wall before requiring being rewashed it's doing well. Sort of toying with limewash for here rather than a modern paint but not convinced we'd even get 5 years from limewash. We are very exposed and true gales (40mph sustained, gusting to 50mph) accompanied by heavy rain occur fairly often. There is something of the oder of 300 sq m of wall, the idea of having to rewash every few years doesn't appeal...

[Martin Bonner]

Agreed.

The nice man at

will sell you a chemical paint remover to remove practically any masonary paint. There is absolutely no point for a breeze-block shed, but I am glad to have removed the masonary paint from our Victorian house and replaced it with limewash. (and the nice man at Anglia Lime Company will be happy to sell you some; he may sound strangely familiar ...)

(I have no connection with the company, apart from as a satisfied customer.)

[stuart noble]

Not bad prices, but how come they can package methylene chloride strippers in plastic? The various brands I've used all come in metal containers.

[NT]

its been maybe 7ish years, no touchups or degradation so far.

If it rains hard enough soon enough after its painted that would happen, so just dont paint before its due to rain. I've found light rain doesnt seem to bother it. The lime takes longer to toughen up than it does to dry.

There are several lime paint formulations, and the naming isnt entirely consistent. What I used is just diluted lime putty. Mix builders lime with water to make putty, then dilute it 50/50. More well known is whitewash, which is chalk & water soluble glue, that doesnt last well.

If you've not used it before you might try a test patch and be prepared to hose it off, as if you put it on too thick it cracks as it dries, and if too thin it takes more coats. It does handle different to other paint types, but has worked fine for me. I'm done with dulux masonry.

NT

[Spamlet]

And you are still alive! My lungs hurt just thinking about it. Let alone my wallet!

S

[Spamlet]

btw lime is also antibacterial, fungicidal, and acts as a mild stabilising solution.

NT

All very enlightening thanks. Now would this be the same 'paint' that is used on all those miles of white picket fences in the US tv progs and films? And might this stick to our small picket fence that has been glossed but needs frequent redoing due to car splashes and algae?

Cheers, S

[Dave Liquorice]

Hum...

That might be a problem up here! Twice I've patched a bit of the render only to have my patch washed out by the rain over night. We had 4 or 5 mm of the stuff in an hour last night along with a F5/F6 wind, I wasn't really expecting any.

Ah, prehaps it is whitewash that I'm thinking of rather than limewash. Your builders lime and water actually absorbs CO2 from the air and turns back into calcium carbonate, that obviously wouldn't happen with chalk dust and glue...

[NT]

Checked it close up today, same as the day it was applied, other than dirtier.

uncured lime is certainly weaker than set cement. I just check the weather forecast, and if no rain forecast take my chance. I guess you could add some glue to it if you wanted.

The thing about lime that's hard to explain is its just much easier to apply, so if a bit gets washed off one day its no big deal.

whitewash is just chalk and water soluble glue, famous for not lasting long.

NT

[NT]

I've no idea whats used on US picket fences. If I were to paint such a fence I wouldnt choose simple lime putty though. There are a huge number of lime based paint recipes, varying from paints that have lasted centuries to temporary paints like whitewash. If you're interested I'll see if I can find more info.

Simple lime sticks to lots of surfaces but not everything. If it doesnt stick initially one can add 1% linseed oil.

NT