Patching patch plaster walls before painting

[Anonymous]

My house (a brick end terrace) was built around 1850. I'm just about finished stripping all the wallpaper from the interior walls, which I plan to paint with some sort of breathable paint. The plaster is in good overall condition but does need a bit of patching and I'm wondering what would be the best thing to use for that. A damp course was done last year and at that time the lower half of all the walls was replastered, presumably with gypsum plaster. The plaster on the upper half might be original but it could also have been replaced at a later date. There are also a few areas that have been filled in with plasterboard. Is there a lime equivalent to Polyfilla for minor patching? Or is there some other material that could be used to patch the old plaster as well as the newer bits? Thanks for any suggestions.

 

[Anonymous]

Pure lime putty or lime putty mixed with a little plaster of Paris can be used for this. The wall needs to be wetted first. The putty will shrink as it dries so to avoid cracking you will need to keep working it periodically.

Lime putty is slaked lime and comes in tubs, but needs searching out as most builders' merchants dont stock it. It can be kept almost for ever so long as it is kept wet. It looks rather like a very stiff, set yoghurt in covered by a thin whey-like liquid (limewash).

 

[Anonymous]

Your walls sound in common with most properties that have been around for 150 or so years, your old walls will have seen much patching up. Of course the best practice is to use breathable lime plaster for repare. But... you say the walls already have past patching in Gypsum polyfilla etc on the original surface, this is not uncommon. Fear not if you cannot afford or are unable to get or do patching in lime plaster, for small areas a little more pollyfilla will do. A few coats of limewash will finish the job beautifully, your walls will at least then have some breathabillity. remember also the importance of clean gutters, cleared air bricks, low outside ground levels, openfireplaces and original windows.

 

[Anonymous]

Given that a damp proof course has already been installed (and see Matt's post below about the usefulness of those - a waste of cash in too many cases) and therefore the walls presumably have had the original plaster hacked off for several feet and gypsum plaster or even cement with additives put in its place, the chances of the walls breathing are probably now very remote, and so frankly I'm not sure that anything you now repair small amounts with will make much difference. Large missing chunks can of course be repaired with lime plaster.

Also - it's doubtful that limewash will have much effect on the breathability here either.

It may not stick well to the gypsum without an additive, and if the walls are so patched it may not look too good either.

Possibly cover the lot with lining paper and casein distemper over that - or a simple emulsion.

Have a look at the site below - they sell both.


http://www.rose-of-jericho.demon.co.uk

 

[Anonymous]

I agree with Evelyn's post above. Given that your walls are plastered with gypsum, there's not much point in your ensuring that you use a breathable paint or patch-up filler. You could of course have all of this hacked off, and the wall replastered in lime, but as a dpc has been fitted (and assuming that it's working) even this would seem to be a bit superfluous.
If I were you, I would concentrate my efforts on ensuring that the pointing is in good order, and that the roof, gutters, flashing, etc. are all doing their job. Then I would fill and paint the interior of the wall with anything I fancied - breathable or not.

 

[Anonymous]

Thanks to all for your ideas. I think I have a better idea how to proceed now.