Limewash over 'Green' Lime Render

[malcolm]

Suppliers suggest not to paint limewash over newly applied render, presumably to allow the render to dry and carbonate etc. They don't seem to mention how long we should leave the render to dry before limewash.

Is the issue that the limewash would block the air supply required for the render to carbonate, or is it a moisture thing? I'm guessing carbonation in which case can I paint my well ventilated render as soon as the outside is dry and allow it to carbonate from the other side?

 

[livias]

Do they then! Nobody ever told me that and I have been limewashing new lime plaster for years with no issues. Of course it needs to be left for long enough that the limewash brush will not damage the surface. I expect that setting time will be slower after limewashing because the surface is less open but it should still happen. If you need to get your scaffold down then i would just go ahead and limewash. That is what I will be doing next week

Hm. I use pure limewash without any nasty additions like tallow. Perhaps that makes a difference

 

[Zebra]

But if plaster can breathe through limewash then surely it can carbonate through limewash. The mortar at the back of the mortar joint carbonates anyway...

 

[malcolm]

Thanks, I was thinking about using pozilime throughout as that's what I've got and the new lime is only a small area. The render is trying to dry very quickly and ought to be nice and dry by the time I finish all the other little patches.

It would be nice to get the scaffolding down but I still don't have the new gable frame in place (or even an indication of when it might turn up). I might end up boarding it up and doing it next year in a very organised fashion. I feel time is running out this year for anything involving lime.

 

[livias]

Pozilime is full of additives. I can let you have some white limewash if you want

 

[Keithj]

If the lime render is trying to dry very quickly, I'd be inclined to persuade it to slow down a bit so that it can carbonate properly.

Limewash (without additives) won't interfere with that.

 

[malcolm]

I still have a couple of days of water spraying on the new render. It is covered and I'm keeping it damp, but it is trying to dry and seems to soak up less water each day.

The Pozilime appears to contain PVA so is not the stuff for my lovely new render, and probably the reason why the render is supposed to be really dry before applying (good for my painted concrete though). I've ordered a bucket of lime putty to make proper limewash for the new render.

 

[formerly known as]

I always plaster over previous coats before 'dry' - this will prevent rapid drying and aid better adhesion - and limewash when the surface appears to be fairly, although not fully, dry. As already stated, if everything is permeable, so no problem.