Lime plastering

[pandora]

We had our house plastered 18 months ago, and I was never really satisfied with the finish in a couple of the rooms. The builders claimed to know about lime plastering but were clueless, and unfortunately managed to time their most rubbish work with my week in hospital. Quel surprise :roll:

Now I would like to finish off some of the rooms to a better standard of plastering. I will be doing to work with a friend who can plaster but is not experienced with lime techniques. My question is this - can you put a top coat of lime plaster on the top of plaster that is already there, is sound just not nicely finished? If so, what is the best way of going about it - would I just have to make sure the existing lime plaster is well dampened down, or would I be looking at removing it and starting again? I hope I'm not!

 

[chippy]

Good question I have got a similar problem, hope someone will answer this.

 

[Ian Bond]

I've managed to skim over small areas of old lime plaster finish by scoring the surface to provide a key, and damping down well with a limewash solution (just lime putty mixed with water and brushed on).

It's stuck well and once limewashed over blended in reasonably, however my walls are supposed to be fairly rough as it's a cottage, and the original plaster follows the contours of the rubble masonry.

If the work was that bad, the plaster should be given the chance to put things right at his own expense - he's lost the chance for repeat business and recommendations otherwise.

NB: Thanks to Gervase for the limewash tip to help the finish adhere - I just used plain water previously but liked Gervase's suggestion so tried it.

 

[Gervase]

Ian's pretty well covered it - scarify the surface well beforehand to provide a key, wet it well to kill any suction and apply some limewash as a tack coat to help adhesion. If the surface has been painted with a non-porous paint you may have problems, so make sure the surface is well scratched. One good way is to knock some masonry nails through a wooden float so they stick out a couple of millimetres. A pal of mine swears by bottle tops (the crown tops from beer bottles) nailed onto an old float. Either way, you want to scratch the surface well without gouging off great lumps of existing plaster.

 

[Ian Bond]

What a great excuse to purchase beer!

I wonder if your pal's found a way we can claim tax relief for bottles of beer as capital expenditure?

:lol: :lol:

 

[chippy]

Is it possible to achieve a good flat finish, my walls are level but I would like to skim over the entire surface as they are a quite battered in places, what mix would I use, should this be put on in the same way as board finish and polished up?

 

[Ian Bond]

You can achieve a perfectly flat and smooth finish using dots and screeds, and steel floats to polish the finished surface [not that I've ever managed to achieve anywhere near this level of perfection!]

Mike Wye has published a traditional building maintenance guide, which includes a section on lime plastering - well worth a read. It includes advice on the mix required for finishing different surfaces.

Over-polishing the finish to a hard surface will reduce breathability which may not be desirable.


Practical Guide :

http://www.mikewye.co.uk/faqs.htm