Lime Plaster Skim

[GRB]

Hi this is my first post, and I'm not quite sure how it all works....!

I've had to teach myself how to lime plaster, mostly because there are virtually no plasterers willing or able in the North East and I really wanted to have a go for my house's sake, and I've coped fine until now. In one room I'm about to skim over the existing lime plaster with two thin costs of 1:1 lime finishing plaster - I want to do this because the walls in the room had so many modern patches and repairs (in sand cement, plaster of paris etc) that I've hacked off and put scratch/floating coats back. There is so many of these patches that I think a re-skim would look much better. However, I have put a test panel of the finish lime plaster over the old lime plaster, which I cleaned, scratched slightly for a key and then damped thoroughly before applying the new, but as it has dried the surface has crazed / cracked.

Does anyone out there have any suggestions?

 

[Feltwell]

I'd be interested in any views on this too, as I was contemplating doing a skim over the walls in the attic room that is soon to be my daughter's bedroom. Lots of repairs need doing first, especially where different construction methods abut. I've some walls that are plaster on brick, some are lath & plaster, some are half of one and half of the other! Where the 2 building methods meet it's all pretty badly cracked. Generally the walls have seen better days - lining paper will help (esp. the extra heavy non-woven type), but a skim first then lining paper would be better still, if I can get a skim to stick.

 

[MatthewC]

It just so happens that I have been asking the very same question of my supplier of lime products***. In my house I have retained lots of large patches of old plaster (sometimes stained or painted) and need to be able to merge the old and the new so I can limewash over the whole thing.

My suppliers sell a product called DG27 which they describe as a gritty paint; its purpose is to provide a base on old plaster or other non-lime products (even plasterboard) so that you can put a lime plaster skim over the top. It also consolidates the surface if there is fine cracking etc. You paint this on and then do the skim the next day. They recommended a 3mm coat of 3:2 for the skim rather than 1:1, or even thin 3:2 followed by a thin Regency plaster (which probably is 1:1 or so).

Matthew
http://houseintheenchantedforest.blogspot.com/

*** I will name them as they have been so helpful - Mike Wye and Associates at http://www.mikewye.co.uk/

 

[GRB]

I appear to have solved my problem.... I left the crazed finishing coat on, went back to it 4-5 days later and put another thin coat over it (same mix) and that appears to have resolved the problem. This final coat has gone hard and has not crazed. I assume that the original plaster just sucked all of the water out of original skim that I put on.

Thanks for your advice MatthewC, I'm going to contact Mike Wye about DG27 as I would like to plaster skim over a modern plasterboard wall in another room (for another day!) so I hope it may come in useful for that.

 

[skier-hughes]

My plasterers just used white gypsum on the plasterboard we had to plaster. Can't tell the difference between those and the lime plastered ones.

 

[robgil]

I use a lime slurry coat first on a dampened back ground if i think the background will suck the plaster dry.