Lime Plaster - how?

[Bayliss]

I have removed an area of plaster which was falling off the wall through decay and previous dampness damage. I now wish to re-plaster this small area (4' x 2') using lime plaster. I have an quantity of premixed lime purchased from local merchant but am unsure of additional 'ingredients'.I thought add some chopped straw but should I also add soft sand? Thanks for your comment/suggestions.

 

[robgil]

when you say premixed lime do you mean putty? what is the rest of the plaster like? does it have straw in it or hair perhaps?
a few pics might help.

 

[Bayliss]

Yes its lime putty I purchased in an very large tub. The wall had previously been plastered over with modern gypsum which I have removed, under this is remains of daub with some straw showing. Looks like over the decades bits have been added/removed and now its multi material. Can't do pics I'm afraid

 

[robgil]

do you know for sure it was plastered originally?

 

[Bayliss]

I am making an assumption TBH, however the cottage is about 300 years old and has suffered alterations and admendments over the years. I want to use lime plaster as this seems to me to be the least harmful approach and will at least allow any dampness that rises to evaporate out of the plaster I hope.

 

[Flyfisher]

Straw is a common ingredient of daub, but I've not heard of it being used in lime plaster (but I'm no expert). Hair is the usual additive in lime plaster, as well as sand of course, but I've not yet tried it myself so can't be too precise.

While we're waiting for a real expert to arrive, this thread describes the process quite well: http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=11156

 

[robgil]

are you looking to be historically accurate or do you just want to patch the wall up?
if it is just a hole in cement plaster then i would probably mend it with cement , this is on the assumption that you have a cement plastered wall and a chunk of cement has blown.
did you find out and repair/remedy the cause of the damp?

 

[Fizzer]

Hiya, I'm not an expert, but have been laboring for the plasterer who is replacing some cement render with lime on several walls in our house.
I can't comment on addatives because he's not using any on our brick and stone walls, however he was quite insistant that patching with lime is very tricky and prone to crack, especially when patching next to a different material.

As a result he made sure that every last scrap of concrete render was gone before starting a wall, all the way up to the edges.

Mind your eyes with the lime stuff too.

 

[fjpdesigns]

You can use straw in render instead of hair, it's a well tried and tested procedure and quite commonly used. I have often used it. They do say that barley is better than wheat as it's stronger, but never having used wheat straw I can't verify this thoery. Whilst on the subject, I have never used cow muck in my render either, and don't think I will try either.

 

[Bitstreams]

I have patched with moderate hydraulic lime (a dry mix from The Old House Store) to bring the repair up to the surrounding surface and then use lime putty (premixed smooth stuff also from OHS) to complete the repair.

Simon