Lime Plaster on Internal walls

[L1zzy]

Hi all - its awhile since I last posted as i have been busy on the lifework that is my listed rubble stone cottage in Dorset. However as usual I'm after some thoughts and guidance on a recent 'development'. At the time of writing an exposed gable wall (I'm part of a terrace but 1 of my gable walls juts out in front of the other cottages) has had all the old concrete render(s) removed revealing lots of ..rubblestone and lime mortar in very poor state after many years of water ingress. The wall has been left to dry out and this morning the traditional builder is raking out and repointing it - he will later render the wall with Lime mortar and Limewash it.

Having nothing better to do at the weekend and after sitting in bed drinking coffee looking at the peeling paint on the inside of this wall on Saturday morning I decided to begin to peel off all the old paint. I've now stripped 3 of the walls to the room back to the original lime plaster. This effort has exposed large areas of 'friable' lime plaster that even after drying remains very 'sandy' and brushes away the moment you touch the area or sneeze , also two large cracks in the plaster either side of the chimney breast which juts into the room (I can see through the the rubble stone and even get a soft breeze coming through the cracks!) there are a few patches of very very soft pale brown hair in sort of occasional isolated lumps - feels almost spaniel like or even human certainly not goat or horse hair) In some places the render has parted company with the rubblestone on teh other side and sounds 'blown'

My question is what would you suggest next steps should be - options I'm considering are

1. Fill and repair all the cracks and holes with Lime mortar 3.5 sand to 1 Lime putty and live with the fact that much of whats there has parted company with the rubblestone.But given its being repointed on the outside the wall should stay up!
Limewash or distemper the walls once the repairs are dry.

2. Get the builder to quote on replastering the entire room. (Question does this mean he has to remove all the current blown sections of render)

3. Do something else...sell the cottage get a life?!!

Clearly option 1 is appealing as its less expensive (any ideas on cost of replastering in Lime ?) but perhaps there are more than 2 options? your views and opinions are welcome. (I would show a photo but being techno phobe have no digital camera )

 

[kevmiles1]

I would remove all the blown plaster wether it is a few patches or the whole room and then put a top coat where the original base coat is sound and used haired lime where it needs dobbing out. If you have taken the trouble of having the exterior done properly then the inside should be done to. If it is mainly just a skim it should cost much.

 

[DaveBrigg]

I wouldn't be too hasty in removing 'blown' plaster. From our experience, on ceilings it is difficult to prevent it falling off, but on walls, especially if well bonded by hair, it may stay there without much effort. Some of our walls have patches of lime which give a hollow sound when tapped, but I cured this by not tapping them any more.
From my limited experience of repairs, your first option sounds spot on. The two cracks need to be properly filled since this is a structural weakness, but a couple of coats of limewash may be enough to stop the render brushing away.
The small clumps of hair you have found are 'rat tails' (at least that's what they are called around here) and come from the previous builder's work-experience boy not putting enough effort into pulling the clumps of hair apart before dropping them into the mix. Now if only you could find the original receipt...

 

[Gervase]

Dave's right - don't rush into removing plaster just because it sounds hollow.
Press it gently - does it flex noticeably? If it does and there are cracks around the flexing areas, then it's a candidate for removal. Otherwise, just patch the missing parts with a coarse haired mix, lay on a tack coat of diluted limewash and put a lime skim over the whole wall. Even the skim might not be necessary - you may be able to get away with just skimming the replacement patches and feathering the new to the old with a damp sponge and them limewashing the whole wall with three coats to consolidate everything.
It's a lot less messy, less work and retains as much of the original as possible, which is always desirable. Option 1 is your best approach.

 

[L1zzy]

Hi all - many thanks for your views and experience. I spoke to the builder last night (he's now put the scratch coat on the exterior of the Gable wall) he had had a look at interior of the wall and his view was that just the two sections on either side of the Chimney breast need the plaster removing preparatory to his Lime plasterer perhaps putting a 'mesh' in place then replastering in Lime next week. Whereas last night I was ok with this - I think Gervase I'm going to try your 'flexibility ' test tonite to see what actually needs to be removed before I start to wield my bolster. If there are patches that don't flex I think I will leave those till I meet with the plasterer and discuss with him.

Regarding the very friable sandy eroded patches of mortar how does one stabilise these enough to apply haired mortar - do you just keep brushing away till you reach stability if you know what I mean?

By the way any ideas what this 'mesh' is?

 

[Carol]

I think your option 1 would be a good starting point. If the areas of 'dodginess' are patchy and there are some parts quite sound you might consider a bit of patching. I did this last year after knocking a hole (accidentally with a vacuum cleaner) with extensive advice from the good PPUK folk. While my first interior lime plaster is not perfectly flat, it has not fallen off.

The estimated cost of a complete re-plaster was eyewatering and we found that the new work helped the older stuff to become more stable on the wall. Something to do with lime's healing properties I think!

 

[FamilyWiggs]

I expect the mesh is a metal mesh that ;provides a substrate for the plaster to stick to. Whilst not exactly "traditional", it not exactly devil-spawned. We used a little bit of it for awkward or to cover pipes without the risk of plast cracking as they heat up/cool down.

Can't quite see why he'd need it if only repairing some small patches though...

 

[L1zzy]

Hi - last night I managed to hack off the most 'moveing bits' after following Gervase's 'flexibility test' I have now reached an area which is tightly adhereing to the rubblestone so will leave this as is. Any thoughts about whether I need to square off the edges to the now 3ft x 2ft exposed rubblestone preparatory to the Plasterer re rendering or can I leave it with an uneven edge? After proabbly at least 50 years of being suffocated by concrete and damp its so lovely to see rubblestone drier this morning and the gradual reverting to proper functioning of the pointing - Lime is such an excellent thing - its like magic.Mind you my bedroom looks like a builders yard!

Last question (for today) one of the 3 walls just has a large crack in the Lime render running almost the entire width but this crack is not very wide (less than an inch) can this be filled or do I need to make it a bit bigger the render isn't otherwise too bad on this stretch and I'm loathe to start banging it if I don't need to but the crack will need filling.

Thankyou all for your support - sometimes one feels rather alone doing the restoration work - I get alot of comments from family and complete strangers about how 'its not a very femine thing to be doing is it ?' and 'you should have bought a little modern house nearer work' theres very little 'WOW it is begining to look so PRETTY and Well Done or most needed at times ' do you need a hand with anything?'

 

[FamilyWiggs]

L1zzy - post us a pic or two and we will coo, enthuse, praise and motivate you a-plenty! 8)

Keep up the good work.