Repairs to lime render and plaster

[diyjamesk]

Hi,
My house has got various cracked or crumbling bits of render both inside and out (mainly just cracks outside, a couple of crumbling bits inside). I can't afford to get builder to fix them so I'm going to have to attempt it myself. I've attached a couple of pictures of one bit that needs doing. The whole strip of plaster next to the window has crumbled with the worst bit being where I've pulled the paper back. I would like to repair it using lime since that's what it's currently made of. How exactly would I go about doing it? I think I'm a fairly competent DIYer but I've never worked with lime plaster before. Many thanks in advance!

James

 

[vinn]

Crumbling render like in the pics is typically caused by penetrating damp.

Hack off that panel of render back to masonry, and post a pic of the bare masonry surface.
Post pics showing the exterior render cracks and of any other internal crumbling patches.

Are your walls solid?
Do you have a wainscot panelling on the lower part of the external walls?


FWIW: you are missing a piece of the window frame staff bead - this will possibly make the lower sash unsafe.

 

[diyjamesk]

Hi,
Thanks for the reply. The walls are solid and there is 4' of hardboard panelling around the room. I'll get some pictures of the outside as soon as I can. Before I start hacking off render though, is it going to be possible to re plaster at this time of year? The house does have central heating.

That staff bead has been missing for a while now as I started renovating the windows and din't get round to finishing them before the winter. They're screwed in place though so don't pose any risk.

Thanks,
James

 

[vinn]

Yes, no problem with plaster or render in winter.

If penetrating damp is an issue you might have damp behind the hardboard panelling - who installed the panelling?

 

[diyjamesk]

I've now hacked off the render and it's revealed what seems like quite a bad problem. The render all came off just by poking with a screwdriver along with q few chunks of brick and mortar. Some brick is crumbling and has turned into what resembles wet clay and one whole brick seems to be missing. I haven't removed the panelling but I can feel that it's rotted behind. I lifted the carpet too and the boards in the corner are rotting. I've attached pictures of everything. What do you reckon?

The panelling was here when we moved in in 2004.

Thanks,
James

 

[StephenStephen]

I'm no expert at all, and never tried plastering with gypsum. To be honest I'm too nervous to try - leaving that to the professionals.
I'm in the last stages of replastering with lime putty plaster, and my experience is that it's great stuff to work with. I particularly like the way that I can take my time, and not worry about it going off really quickly. I also like the way that lime putty gets better (apparently) the longer you store it.
I've been experimenting with mixing it with hemp shiv, which seems to be working well.
I have also used NHL Hydraulic Lime - dry bagged, both premixed as consolidation mortar, and as powder to mix with sand - my experience is that it's pretty much the same to work with as cement, just takes a little longer to go off.
There's a lot of good info on Mike Wye's website, and they also have put some good videos on youtube.
The other good thing to read is 'Lime in Building' - a booklet by Jane Schofield http://theblackdogpress.bigcartel.com/product/lime-in-building-a-practical-guide-by-jane-schofield
I personally would use NHL for the outside and lime putty for the inside.
...and a couple of things I learnt along the way (apologies if you're way beyond this):
-Don't be tempted to mix in a bit of cement to lime render or plaster - the latest research suggests that it weakens it
-Don't use hydrated lime (sometimes called bag lime) - it's not intended to be used in this way
Go for it!

 

[vinn]

Thanks for the new photos.

Remove the immediate carpet grippers - lever them up - and roll the carpet back or remove it from the room. Clear all chattels from the work space.
Use a utility knife to cut paint bonds to release the wood trim work around the panelling.
Gently lever the panelling off - you might see fixings behind the trim.
I can see what looks like bubbled surfaces on the panels but perhaps thats how they are meant to be?

This damp pentration might extend across the front (window) wall - see what you find when you have removed the left and right panels in the pics.
Remove all damp "slush" & debris from the wall - is there any fungal damage to the wood thats been exposed?
Does the damp appear to be ongoing behind the door lining - what about inside the recess?

Crawl under the floor and examine the joist tails that are going into pockets in the front wall masonry - probe them for rot with a small screwdriver. Carefully examine the corner where the T&G is damaged.

What is the metal pipe used for - or has it been abandoned?

 

[diyjamesk]

I had a look at the cracks outside today and there are several places where damp could possibly be getting in. The mortar around the window frame was cracked, the bottom of the frame has rotted quite badly and there is a gap in the concrete window cill. I dug out any loose mortar and cleaned out all the dust and then filled the cracks and gap with mastic. I also bodged the rotted frame full of mastic as a temporary measure until I get round to fixing it properly. I'm going to keep checking the wall to see if it dries out or stays wet (it's already dried out a bit just since I removed all the plaster). There was also a chunk of render missing from near the drain so I filled it in with a load of mastic as a temporary measure.

I've removed most of the crumbling brick and soil-like dust but I ran out of hoover bags so I couldn't get it all out. A few of the bricks have turned into wet, crumbly clay but most seem solid still. The inside of the sash window box has also rotted but hopefully not enough to need replacing. There is no fungal damage that I can see and what looks like bubbling in the picture is just patterned wallpaper. I haven't got round to removing the panelling or floor boards yet but should be able to at some point this week; the panelling on the outside wall is going to be a problem though since there's a radiator attached to it.

I can only guess that the metal pipe is abandoned as there is no plumbing anywhere near it.

Thanks for all the advice,
James

 

[diyjamesk]

Stephen, had you worked with cement render before you did the lime plastering? I haven't got any experience with either.

Thanks for your reply!

 

[vinn]

All Wet Rot wood is fungal damaged. The whole window box will have to be removed for repair at some later date - its not difficult.
Dont cut the pipe or attempt to remove it unless you are certain its abandoned: it could be a dead-leg containing gas or water.

Forget about the lime plastering business - the best mix for your re-plastering will be a render of 3:1 sand and lime.
Lime putty plaster is not a DIY material, and can be dangerous in the eyes, and painful in cuts and scratches.

 

[diyjamesk]

I'll make sure to trace that pipe back to wherever it comes from, it's very badly corroded so it would be a liability if it is a dead-leg. Is that 3:1 sand and hydraulic lime that should be used? What about buying the plaster ready mixed like this? http://www.lime-mortars.co.uk/lime-plaster/non-hydraulic/base/25kg .

Thanks

 

[vinn]

Yes, you can use that for patching but for anything extensive its a bit expensive.

 

[StephenStephen]

Stephen, had you worked with cement render before you did the lime plastering? I haven't got any experience with either.

Thanks for your reply!

No - I'd not worked with any kind of render or plaster before

I'll make sure to trace that pipe back to wherever it comes from, it's very badly corroded so it would be a liability if it is a dead-leg. Is that 3:1 sand and hydraulic lime that should be used? What about buying the plaster ready mixed like this? http://www.lime-mortars.co.uk/lime-plaster/non-hydraulic/base/25kg .

Thanks

It's so confusing - that link is to non-hydraulic lime plaster which is the same as lime putty, also sometimes called air lime, premixed with sand, which yes, I personally would use indoors. It sets in air (carbonates), so will store if you keep the air out. Pure lime putty seems to be regarded as better (and more expensive) the longer it is stored.
What I'm not sure about is how fine a finish you'd get with that particular one - they seem to be suggesting you use finish plaster over the top.

Often it's the delivery which shoots the price up if you're using a smaller amount.

...and then for the outside, my personal preference would be 3:1 sand and hydraulic lime. Hydraulic lime is also confusingly called NHL (natural hydraulic lime) and comes with charming descriptions of how hydraulic it is, from feebly hydraulic - NHL 2, through moderately hydraulic NHL 3.5, up to eminently hydraulic lime NHL 5. It sets by hydration, and stores ok if kept dry, though I don't think it keeps forever. personally I'd use NHL 3.5 with sand for the outside.

...and then there's hydrated lime, which is something else again, and not what you want at all.

But (and it's a big but), almost all of what I've learnt is from books and videos, and I've only been using it for the last year, on one area in my home, and almost all internally, so take everything I say with a pinch of salt and listen to the guys on here who actually know what they're talking about.

 

[diyjamesk]

Stephen, how did you start out with the plastering? Did it take you a lot of attempts before you got something usable or were you able to take your time and get it right? I've been having a look at training days too as another option to getting into it. I'd like to be able to do it as there are a few bits around the house (including some lath and plaster walls that are crumbling) that need doing.

In terms of the wall repair, there are quite a few bricks that have turned to mush. Most bricks are okay but some have crumbled, why could this be? Could this be a structural problem too? I.e. How many crumbling bricks do I need to spot before it becomes a real problem?

The mastic outside is still not fully cured and I can't tell if it's solved the damp as it's been too cold for the bricks to dry out properly to start with. There's also a couple of bricks worth of mush that I'm worried about cleaning out.

I haven't managed to inspect under the floor yet. It's too narrow to crawl under at that point so I'm going to pull a few boards up tomorrow. There's a cellar under most of the room but it ends a few feet from the wall and then there is very little space under the boards.

Thanks again for all your replies so far,
James

 

[StephenStephen]

Stephen, how did you start out with the plastering? Did it take you a lot of attempts before you got something usable or were you able to take your time and get it right? I've been having a look at training days too as another option to getting into it. I'd like to be able to do it as there are a few bits around the house (including some lath and plaster walls that are crumbling) that need doing.

Thanks again for all your replies so far,
James

I planned to go on a training, but didn't manage to do so before starting. so I just looked at lots of videos and had a go!
If I was doing it again I would definitely go on a training day first.

In terms of getting something useable - it seems all pretty simple - just a matter of mixing lime and sand in the same way as you would mix cement and sand, but with less pressure to do it quickly. I would again recommend looking at Jane Schofield's booklet and look at on youtube (or buy the DVD) of Mike Wye's tutorials.
It all seems quite forgiving and flexible, which is why we ended up mixing in some hemp horse bedding from our local agricultural suppliers!