Breathable Ceilings?

[MissChaucer]

Hi All
Sorry if it sounds a silly question ... i have just bought a period property (1820) which is a composition of brick, stone & cob.
I realise the walls need to be rendered/plastered with a breathable material but how about the ceilngs and internal walls? I say this as i realise that the lime based compounds have a certain type of fluidity thus they may expand at different rates and crack the adjoining internal walls or ceilngs
thanks for your help
M

 

[MatthewC]

What are your internal walls and ceilings made of? And the floors?

I'd never thought of possibility of lime products causing cracking by differential expansion. Far more likely is cracking caused by rigidity of modern materials vs the movement of limestone etc!

Matthew

 

[MissChaucer]

Hi and thanks for your reply
They are Lathe and plaster ceilings with floorboards above
thanks
M

 

[MatthewC]

The expansion/contraction of limestone and the accompanying flexibility of lime products means that you are far better off to only use lime products, even for internal walls and ceilings. Anything containing cement is rigid in comparison and thus will most likely crack (as in my new modern extension). I would reckon that if you have lath then lime is almost mandatory as modern plaster would surely crack on lath even as you apply it in adjacent areas.

 

[MissChaucer]

Thanks a lot Matthew .... thats made my mind up
good wishes

 

[bennoa1]

Assume its listed in which case you'll need Listed Building Consent for many repairs and alternations so you're best speaking to the local planning dept. to check if you will need LBC. Lath & plaster is standard so I'd stick with that - if its loose then you'll need to patch it up. Never use gypsum or cement as it will create long term issues and will damage the building fabric. Any contractor who tells you to use this run a mile and find someone who knows about old buildings.
If you want to add wall insulation then I have used a wooden frame infilled with sheeps wool insulation, covered with a wood wool board and finished with lime hemp plaster. Final coat of clay paint. All breathable but adds some insulation to cold walls. You will need LBC for this.
bennoa1

 

[Penners]

MissChaucer - I agree with what Matthew says about the relative "plasticity" of lime by comparison with gypsum or cement plasters. However, I felt it worth preparing you for the fact that almost any structure that contains a variety of materials (eg: plaster, wood, masonry, etc.) risks a certain amount of differential movement with normal changes in temperature and/or humidity. So be prepared for the fact that you may still experience some mild cracking, particularly where different surfaces meet - ceilings and walls, plaster and beams... and so on. Bear in mind also that ceilings tend to flex slightly with upstairs loadings, so this can also cause some cracking.

None of this is any kind of cause for worry, and presents only a mild inconvenience (unless you are super-fussy!). A bit of modest filling every few years sorts it out.

 

[MatthewC]

And to illustrate what Penners says above, the worst cracking in my house is in the new extension. This was where we had to completely rebuild a Victorian brick box on the back, exactly as it was. And guess what, there is a crack the whole way round between the plasterboard ceiling and the walls! Elsewhere, where we have used lime in the old structure, there are only three cracks in walls even though we plastered eight rooms. Curiously those cracks are all in lath walls and I must say I don't know what caused them.

 

[Penners]

cracks are all in lath walls and I must say I don't know what caused them.

It's quite common for vibrations elsewhere in the building (walking on suspended floors, hammering, children running around, even nearby road traffic, etc.) to cause laths to move a bit, which can cause cracking in plaster. Were the laths new? If so, some shrinkage/warping in the wood could also be the culprit.