repairing lime plaster over lath - help!

[tycarregydwr]

Haven't been on here in ages as we've been busy with the outdoor aspects of country life and getting the smallholding and business going, and not had time to do anything on the house. Having also a lack of funds, we've decided to take a leap of faith and attempt lime plaster repairs ourself. We haven't done any before, and have some limited plastering experience with modern plaster.
The area we want to start on is in two sections, lime plaster over slate which is not too bad, and lime plaster over lath which is not great - we're excavating under the wallpaper and discovering some holes and lots of old patches, some in lime and some in gypsum. I think that in most areas the plaster still has its key but I'm not 100% sure. I'm hoping we can get away with just repairing the holes and possibly skimming, but I supposed worst-case scenario it all comes off and we have to start from scratch.

We bought haired lime ready mixed but haven't tried yet.

Does anyone have any must-read links or better yet videos of lime plastering over lath, and/or patching holes?

Thank you!

 

[Zebra]

Here's a link:
http://www.ekmpowershop25.com/ekmps/shops/ekm_tiger/bb147996-96ac-4037-8ad2-066739685492/files/New%20PDF_s/Rendering%20&%20Plastering%20Lime.pdf
Also very much recommend the one-day lime plastering course at Ty-Mawr in Brecon.
But if you've got the stuff, I reckon get your marigolds on and give it a go! Put a tarpaulin on the floor, that way if it all falls on the floor, you can pick it up and stick it back on again! What have you got to lose? Remember to wet the background well so that the plaster sticks, and to push hard so that the nibs push through the laths.
I've used Lime Hemp plaster as a base coat on laths rather than haired lime, just because I tried it on the Lime Plastering course and found it easy to use. The tricky part is when the laths flex while you're trying to do it, or when the nibs break off the back before you've finished applying the plaster.
When you say "repairing holes and possibly skimming" do you mean that you're hoping to apply a layer of gypsum over the repaired wall? I think this would be a shame.
If you do have to do the whole lot, don't despair though, lime plastering is immensely satisfying!

 

[skier-hughes]

And if you mean skimming over with lime, I wouldn't bother, the character of the not so good looking lime is what makes old houses so nice. You can tell which sections we've had to repair as the plaster is smooth, but I wouldn't have skimmed over the rest to make them all look the same, soon enough, the smooth will become rough as everyday life batters it into submission!!!!!

Mixing the ready mixed (to prepare it for use) is the hard bit, as you can end up catching all the hair.

 

[tycarregydwr]

Sorry to be unclear, I certainly do not intend to skim it with gypsum! The original stuff is under a LOT of wallpaper, and we won't be replacing that, so the whole wall, once the holes are filled, is going to need something. I was going to attempt a thin lime finishing coat over it all - I'm certain my shoddy patching attempts (as well as the older ones) will still show through so there will be plenty of character. But I can't just leave it as it is, horible, patchy, after decades of wallpaper and general mistreatment.

Not got time to do any courses, and anyway I apparently only have a few more weeks before the hair dissolves (!) so I need to get on with it.

 

[tycarregydwr]

Oh and just to make it more interesting, I have found one hole with broken lath it's about 5" in diameter, looks like something or someone punched through it. Any ideas? I take it this is going to be a gigantic pain in the proverbial to deal with?

 

[Zebra]

Some sort of repair could be undertaken through the hole. If you don't want to enlarge the hole, which would allow you to get to the studs where the broken lath is attached, and replace it with another, then you could try to bridge the gap in another way, and make something for the new plaster to hold onto. If you had a piece of lath - make one if need be - you could insert it into the hole, behind the existing laths, and hold it vertically so that it bridges the gap. Then you could screw it on to the laths above and below. Piloting the laths above and below beforehand would be a good idea so that they don't split. You could do more than one if necessary. That's what I'd do I reckon, anyway.

 

[tycarregydwr]

Some sort of repair could be undertaken through the hole. If you don't want to enlarge the hole, which would allow you to get to the studs where the broken lath is attached, and replace it with another, then you could try to bridge the gap in another way, and make something for the new plaster to hold onto. If you had a piece of lath - make one if need be - you could insert it into the hole, behind the existing laths, and hold it vertically so that it bridges the gap. Then you could screw it on to the laths above and below. Piloting the laths above and below beforehand would be a good idea so that they don't split. You could do more than one if necessary. That's what I'd do I reckon, anyway.

thanks! that's what i was thinking, hope i can wing something. i just need to get the courage up to dive in and make an attempt, i am so nervous but keep telling myself NOTHING could be worse than it is right now...

 

[MatthewC]

I was going to attempt a thin lime finishing coat over it all

If you mean to do this coat over old lime, you can get some stuff called DG27 from Mike Wye (other suppliers are available) which is a special (=expensive) sandy paint which you put on the old plaster and just skim over it. We certainly can't see the joins!

 

[Zebra]

Roll your sleeves up and dive in - you'll feel better once you get going!

 

[DJH]

You could slip in a piece of plasterboard or even stiff card or hardboard into the hole with some adhesive such as gypsum or plaster of Paris on it to stick it on the back of the good lathes and pull it tight with a screw extended through a piece of batten that straddles the hole and screws into the backing piece. Leave it to set, remove the screw and batten and fill the hole at your leisure. It's best to wet everything first so the plaster grips to the back of the lathes.

Doug

 

[tycarregydwr]

So we had a bash at it yesterday. Finished stripping wallpaper and god only knows what else off the walls and then got to patching. There were 4 holes of diameter 4" to about 12", we used pre-mixed haired coarse lime. It seemed to go on well. The major problem was that I tried to get the holes to the point where the edges were firm, but well, I could have taken the whole wall off. Two of the new patches are on the edge of a huge area (at least 1 square meter) which is just patch upon patch upon patch of various vintages. The other two, the edges looked like they were still keyed - the little lumps of plaster were between the laths, but the plaster is moving, and is so dry and crumbly that I could have just pulled it all off. So I pulled off the worst, brushed the edges, and we just tried. I guess it might not work, but we'll have to see.
The other area that I tried to work on is a long crack - the lathed wall abuts an exterior wall which is plaster over stone and it looks like there was some historical movement. I tried to fill the crack but most of it is very narrow so we'll just have to see what happens. We're going to let the patches dry (any idea on how long? the plaster is roughly 1" thick I think) and then attempt to put on a fine lime plaster top coat over the whole thing.
Oh one more question, most of the wall has stuff on it - it might be very old paint, or limewash, or a combination (there are multiple layers). Some of it has flaked off with the wallpaper but not all. Is it enough to rub down any loose bits and then try to coat over it, or am I going to need to get it all off first?

The opposite wall is still covered in its 'structural wallpaper' because I suspect that the plaster is in a much wrose state and once uncovered, might all need to come off. Based on our very brief experience yesterday, I have more confidence that we *could* do it, but I'm still nervous, and need to set aside a chunk of time for it. And figure out how to cantilever myself as it's over a U staircase... (has anyone learned how to levitate yet)?