Lime plaster on a daub panel, with pics

[Andys]

Hi All, Interestingly this isn't an old map I found, I've been rescuing a disintegrat-ey daub panel. Stainless screws (into the staves) and Big Washers seem to have stabilised it quite well and I've been keeping it damp and patching with new daub, which is wonderful stuff to use by the way.

I hope to keep the original lime plaster coating where it hasn't already been lost, it's only about 3mm thick and well haired, pretty tough and flexible but not too well stuck in places.

Any suggestions on the plaster mix for patching? - the old plaster doesn't seem to have any aggregate in it larger than dust.
I normally use a 2:1 sand: Lime Putty mix for general patching and repointing but for this thickness a fine sand+ lime putty + hair mix would seem to be in order, or maybe no sand at all(??) If the lime was originally slaked and the plaster mixed on site I'm wondering if there might have been enough misc roughage present to allow the plasterer to get away with just adding plenty of hair and hence putting it on thinly so it didn't crack up.
I don't really want to plaster overall and cover up the old plaster layer so I I thought I might recess the washers by careful use of a hole cutter, by hand maybe and fair over the hole with the haired plaster.
Any thoughts anyone?
Andy

Oh yes, this is how it looked earlier in the proceedings

 

[88v8]

That's a remarkable salvage job you've done there. The SPAB would approve!

The washers... plastic?

Perhaps silver sand for the patching plaster - fine but still angular.
Bit surprised there's hair in the finish coat, otoh the limewash would have eaten any hairs originally protruding from the surface.

Ivor

 

[Andys]

Thanks Ivor, to start with it was like making adjustments to a house of cards but it's firmed up as the repairs crept out from the starting point where the big hole was. Fortunately the staves are still ok or I think I'd have been sweeping the whole lot into a bin bag. The washers are stainless ones for fixing insulation panels, ebay is a wonderful thing...
I am intrigued by the thin haired plaster coat, you could peel it off and almost roll it up like a canvas painting - there's a lightweight but flexible haired plaster panel, which might be similar, on the way into the powder magazine in HMS Victory. SWMBO is used to finding me staring at walls and taking macro pictures of mortar joints:-/

Yes, silver sand seems like a good candidate. I should make up a test panel of daub and try a couple of recipes out on it...

 

[livias]

The thin rollupable coat will be made of lime putty, fine chalk and LOTS of hair. Well it would be in areas where chalk is readily available but good stone is not. Is it quite white in colour? that indicates chalk/lime rather than sand/lime. You can use synthetic hair if you want to replicate it

 

[livias]

Fat fingers ...

 

[Andys]

Thanks Livias, yes it's very white and not at all gritty. Fine chalk- is that the same as Whiting I wonder? We're not far from the South Downs so it looks feasible.
I have some hair, will get hold of some chalk and have a go.

 

[Andys]

Ok, I'm on the case. Found an article about chalky plaster, I'm certain this is the stuff I have- maybe it was a 'thing' in Hampshire as well as Suffolk...
Here it is, partly so I can find it later
http://www.suffolkbuildingconservation.co.uk/htdocs/chalk.html

 

[Kearn]

Looks almost identical to my Tudor skim coat in Sonning, Berkshire. Approx 2-3mm of haired chalk lime. Like you say, it is very flexible and workable even after 400 years! I have patch repaired up to the original with reasonable success. On the internal sides of my external walls, the skim coat is oddly straight into the daub, without an initial or secondary lime coat. Elsewhere in the same room on other panels I have two coats.

Good luck!