Internal wall finish - dry lining/lime plaster

[mm289]

Weighing up which approach to take to finishing a couple of walls upstairs so after some opinions which I know you lovely people will have

To jog the memory as I tend not to post much, its a C18 farmhouse that was obliterated with cement and uPVC in the '80s. We have spent 10 years as and when able removing said cement and uPVC and replacing with lime and timber :lol: Doing so has gradually restored the building removing damp, repairing decaying brickwork etc - you all know the story.

Anyway, we are now doing some work upstairs and have removed yet more cement render (1" thick) which was then covered with plaster and plasterboard to reveal the original brick smothered in bituminous paint :roll:

The walls are 9" solid brick and I have to decide how to finish them. They are both outside walls, and the other two walls are cement render/plaster (internal solid wall) and plasterboard (internal partition) (Tried to add a pic but not been succesfull so far )

As I see it I have two options which I would like some opinions on:
1. Lime plaster as I have downstairs. Issues being will the lime plaster take to the bitumen covered bricks? I will try to remove this but not hopeful. If I do lime plaster I will have two walls in lime and two not so paint match is going to be interesting..... The lime plaster won't insulate much but will breath although being first floor these walls have no damp issues. Also, the ceilings were quite low so the wall plate is at the height the bricks stop in this pic. Above that has been covered by plasterboard infil to the ceiling so lime wouldn't work there unless i lay it on some wood wool board or similar.
2.Dry line wall with 25mm batten followed by space blanket type insulation similar to this http://www.ybsinsulation.com/roof-insulation/pitched-roof-insulation/superquilt-pitch-roof/ followed by 25mm batten with plasterboard fixed to it. Advantages are it gives me some insulation and a consistent finish to the inside of the room. Disadvantage is the risk of the external wall not breathing and interstatial condensation. My thought process is the Superquilt will act as a vapour barrier if taped properly so I can minimise air leaks into the external cavity and I could leave gaps for air flow from this cavity into the roof space. As this wall is quite dry anyway I am not concerned with it having to dry out etc but I don't want to create any new problems.

So there ya go, thats todays essay - any thoughts?

Cheers,

MM

 

[Abi Cott]

It's coated in bitumen. It's not going to breathe. Insulation might help reduce condensation. But it's coated in bitumen so it's not going to breathe.

It's late and I'm feeling staccato (or should that be sarcastic?), but it's coated in bitumen so it's not going to breathe.

 

[Feltwell]

The bitumen will kill any breathability but presumably was applied because the wall was damp. You say it's dry now, are you sure? What's changed on the outside of the wall to make it now be dry? I'd be tempted to scrape a square of bitumen off, tape some clear plastic to the wall and leave for a few days to see if you get condensation forming behind the plastic.

To make the wall breathable you wouldn't need to remove all the bitumen. Is it possible to scrape it enough just to get say half of it off? I'd then be tempted to speak to someone like Mike Wye or Ty-Mawr and see if they think some kind of primer would be needed prior to lime plastering. You could go for one of the insulating plasters if you wanted - not as effective as modern insulation I know but somehow insulation and plasterboard just doesn't seem right!

 

[Nannynags]

MM, it sounds as if we had the same builders. I am only into my second year though and struggling with the 4-5 inches of cement render on the downstairs. I understand what you mean about the using dry lining for upstairs. Its easier and does provide you with some warmth within the walls. I have the same issues and think that although its going to take me forever (im very slow at plastering) I'll do it with lime. We've already have the gypsum pop off the wall with damp behind it and have batten and plasterboarded as a temporary measure. Or until we finally finish downstairs Will be very interested in watching your progress though.

 

[mm289]

Thanks for the feedback. @Feltwell I am pretty happy the wall is dry, we have been here quite a few years and never had any issues upstairs, also we took of the render about 3 months ago and have been keeping an eye on the wall. The brickwork and historic lime mortar is very dry unlike when we removed the tonnes of render on the ground floor to reveal soaking walls and dissolving bricks :shock: .

Basically the muppets who "renovated" the farmhouse in the '80's consistently applied the following steps to the entire house:
1. pain all brickwork with bitumen
2. Apply between 1 and 3" of extremely strong cement render
3. Plaster in gypsum
4. Fit uPVC windows by hacking out the brickwork for the smaller original windows to fit a standard size uPVC frame, including destroying keystone arches over
5. Don't bother fitting any lintels to support nor infill gaps around frame so windows warp/crack/leak
6. Fit uPVC guttering badly
7. Pour concrete plinth all round house to a distance of 3ft
8. Cement render the entire front of house in rock hard render
9. Point entire house in cement
10. and my personal favourite, when disconnecting the pipe from the rainwater well that used to feed the kitchen sink, don't block of the exit from the well and then pur a cement path over. So for the next 30 years every time the rainwater well fills (from the gutters) it pours out an invisible hole in the side and soaks the ground under the kitchen/wall :twisted:

All of which we have been gradually remedying

.....and back on topic...... @Nannynags I have today experimented with scraping the bitumen off with a carbide scraper. Had a fair bit of success although it is quite hard work :roll: Current thinking is if we can do this successfully over the two walls then I will lime plaster, although we will be left with some walls upstairs in lime and some not.

Another thought, is I would really like to have at least one exposed brick wall in the place. The problem I have is the original lime is very powdery and the bricks are quite soft as well so I think we will just get continual shedding of dust. ANyone had any experience of stopping this - without applying a sealant like PVA obviously :shock:

Cheers,

MM

 

[a twig]

On our house, upstairs I've hacked off gypsum and replastered the external walls with lime plaster, but left internal/partition walls, as frankly life is too short, and I now have a child related deadline. For each room I've done, sorting the external walls out has resolved any damp/humidity issues.

Re:colour match in this scenario, I've used earthborn clay paint, and had no problems, matches perfectly after two coats.

Re: dust, limewash the bricks. Won't quite be the finish you're after but will hold it all together, and still look good.

Can't help on the bitumen I'm afraid!

 

[TheForge]

Earthborn do a breathable wall glaze to stabilise dusting surfaces. Might help.

 

[mm289]

@theforge great spot thanks, that looks quite interesting.

If i could upload pics I would show progress but the site won't let me attach small jpeg's

cheers,

MM

 

[skier-hughes]

Check strippers of sudbury to see if they do a bitumen remover.

 

[steveb]

We must have had the same builders in too... A busy bunch it would seem

Anyhow - not tried it myself on bitumen but an oscillating tool (fein multimaster or equivalent) with a scraping blade may well save the manual work. Not sure if you can hire one to try it, but I bought one and it's the best tool I ever owned.

Re bricks, our builder rubbed down the wall with wetted similar other old bricks which removed enough of the lime, a brush and a re-point was all that was then needed.

 

[Zebra]

Regarding very old soft bricks left exposed, it's not very authentic. However, I have done it on the stairs. I replaced any loose pointing, which was most of it. I didn't seal it but it really doesn't crumble or emit dust much at all. I just brush it over with a soft brush to dust it, and not much comes away. The bricks are approximately 300 years old.

 

[mm289]

Agreed, it isn't really very authentic for a house, although the barns next door are like that , but it is quite a nice feature :lol:

 

[Zebra]

Another option is woodfibre boards screwed to the brickwork, which replace the plasterboard but are also insulating. Lime render on top. Of course, internal wall insulation is not as good as external wall insulation, because of interstitial condensation, and having a breathable internal finish does nothing to prevent moisture getting into the wall.
So perhaps the foil and plasterboard method is best, or celotex-type insulation boards, as long as you can truly make it airtight. It's no good having the best insulation in the world if gaps and holes are left in it where the wind whistles through. You can buy tapes to ensure airtightness. Then the wall can still breathe to the outside, can it not?

 

[Tony.]

What’s the external finish off the wall?
Never removed bitumen before but can’t imagine it will be easy and not leave a residue that prevents breathability.

Will the wall breathe from the other side of that makes sense?