Lime plaster coats

[Anne]

All the lime suppliers say to use three coats or at least two coats when plastering. First coat is haired and the second is mortar with a finish coat if desired.

Question: Is there any reason at all I can't just use a haired coat? The house is medieval and everywhere that I've found old plaster there is only one coat of haired. it seems to me that to be accurate to the house I'd only be using one coat of haired. Anything I'm missing here?

I have tried this and come back the next day to put on the first coat of limewash the brushing in of the limewash gives a really nice finish to the plaster. I know they also say to wait 3 weeks before painting but for anyone who's limewashed directly onto stone walls that have just been pointed it's so much easier when the mortar is still slightly wet this also just seems to make sense, and I doubt medieval people would be saying no we have to wait for the lime to cure instead of doing what was easier and what worked.

 

[Gervase]

There's no reason why you can't use what's called 'coat and a half' plastering - you put on a coat of haired coarse stuff and knock it back well with a wooden float to close up any cracks, and then - while it's still 'green hard'; soft enough to dent with a fingernail - you put on another thin layer of the same stuff which you work over with a float to get the smooth finish you want. Ideally that coat is unhaired, but if you work it well enough you'll get enough free lime and fine aggregate to the surface to cover any loose hairs - just don't be tempted to pull them out of the plaster once you've smoothed it over!
Coat-and-a-half works best on a fairly even surface - if you have big dips and high points on the wall underneath your plaster will have to accommodate too great a range of thicknesses and will certainly crack.

 

[Anne]

Well giving this a try as I can always knock it all off and start again if it's a mess but I'm pretty confident. The wall in question at the moment is stone and no where near even so forget the wooden float I'm not after flat so I followed the contours of the wall with a wet sponge, it's kinda flat but don't bring a level. I'll limewash it tomorrow and finish my floating with the paint brush. I'll keep checking for cracks that's my biggest worry really there were a few before I floated it but none 6 hours after, we'll see what tomorrow brings. Thanks Gervase always good to hear others thoughts and at least here you know you aren't the only crazy one. =)