Exterior masonry filler.

[tabbypurr]

Well powder is much less weight than putty.

Freegle if you're in town, or on the garden if you're not.

NT

[Dave Plowman (News)]

Bit of Googling produced a ready mixed lime mortar with fine sand. At an affordable price. How long would it need to dry before being painted?

[tabbypurr]

For builder's lime in 3 days it's firm, in 2 maybe. Keep it damp if possible. But if you use putty of different hydraulicity the time to set might be different.

NT

[Roger Hayter]

Lime putty is non-hydraulic. Otherwise it would set before use. I think it takes weeks to set as it absorbs CO2. OTOH if you are using it to fill a narrow crack it may not matter. It will probably never set under impervious paint.

[tabbypurr]

No-one suggested using impervious paint. Builder's lime is mildly hydraulic, making it far quicker to set & thus easier to work with.

NT

[Dave Plowman (News)]

I'm intending painting it with ordinary masonry paint. As I said in my first post. Are you saying you can't do this with a lime based mortar?

[tabbypurr]

You can do that if you want. I'd let the filler dry out first.

NT

[Roger Hayter]

If you don't require it to become particularly strong or hard then it doesn't seem to matter. That's assuming the masonry is happy being sealed. If you want the joints to be ventilated and the lime mortar to harden then, no, it would be better to use a breathable paint. Such as limewash or one the plastic-based variants.

[newshound]

And it always seems to me to have slightly better plasticity than something you have just mixed up from dry lime.

[Dave Plowman (News)]

I ordered up some lime mortar and it's arrived. Any treatment needed to the 'stone' before doing the repair? Give it a good soak with a PVA solution?

[tabbypurr]

NT

[Roger Hayter]

Well the soak is good, just not the PVA!