Thistle over Lime

[limelime]

Hello.

I have a 1930's terraced house in England. The internal walls have a black base coat with a thin white top coat. I understand this is black ash mortar ('orrible stuff!) with a lime finish.

I wanted to rapair blown areas etc and then get the lot skimmed (using modern thistle finishing coat), but I've had conflicting information about whether this is a bad idea or not.

Numerous plasterers have said "yeah it's fine, no worries, I've been doing it for decades", but I've also read that many people have had problems, and British Gypsum say they don't advise it as it will 'delaminate' (fall off after time) due to the differing hardness of lime and gypsum.

My only other option is to remove all plaster, dot-and-dab, then skim, which is more time-consumng and costly.

Does anyone have a definitive answer?

Many thanks in advance.

 

[jamesthefirst]

Hi, you can prime with Mike wyes lime primer Dg27 then give it a skim over with their Regency lime finish at 1-2 mm If you need a slightly thicker coat then fill out with a 3-2 finish followed by the Regency.

 

[limelime]

Hi, and thanks for the response.

I've had a look at Mike Wye's web site.

The surface is already lime, so would DG27 be necessary?

 

[jamesthefirst]

Hi, and thanks for the response.

I've had a look at Mike Wye's web site.

The surface is already lime, so would DG27 be necessary?

If you want to use thistle plasters then prime with stabilising solution, Betakontakt or Bondit or Plasprime. Board over lathe ceilings for a pukka job and yes use the Dg27 or similar if you want to use a lime skim. Just wetting lime backgrounds is acceptable before skimming over with lime but normally only on new work.Your walls will have too much suction and the above products will consolidate the background as well as provide a key.

 

[Gazmonster]

You could leave all the messy old plaster on the wall and fix battons to it spaced at 400 centres if its reasonably flat, if not then pack them out with window packers then board and skim? you wont have to cover the house in plastic this way.