Mixing different insulation and plaster types

[Sam333]

Hello - I am about to completely strip out an old stone cottage and I have a question about internal insulation.

The living room has 3 external walls which I intend to insulate with wood fiber and lime plaster.

As I’m doing the majority this work myself and I have never plastered before I feel relatively comfortable with the process and doing the walls, but I really don’t want to attempt the ceiling - I want to get a plasterer in to do that - so my question is could I have regular plasterboard/ gypsum plaster for the ceiling and 1 internal wall , or does the whole room need to be done in wood fiber and lime?

Thanks!

 

[jamest]

I can see no reason not to use gypsum on ceilings (unless they're original or the space above is cold) or internal walls (unless there's a damp problem). As the ceiling and internal wall surfaces should be relatively warm, there should be no condensation issues. I have used lime plaster and vapour permeable internal wall insulation on external walls and left internal walls and ceilings as is (mostly gypsum) with no ill effects (the only effects have been beneficial both regarding heat retention and moisture management).

 

[Sam333]

Thank you for your reply , that’s a great help!
How did you deal with the meeting/ connecting point between the newly plastered lime wall and the existing ceilings/ internal walls?

 

[jamest]

I was lucky, my walls are timber framed with brick infill. So the different plasters doesn't actually meet. If you have stone interior walls, then you should probably insulate them as well, to about 30 - 40 cm inwards from where they meet the external wall (if you don't, there will be cold spots where the walls meet). If you do that, then you'll probably want to lime plaster the whole internal wall as well. If they are timber partition walls, then that's not needed (as you can insulate between the studs). If you're worried about the boundary between the ceiling and the wall, you could always stick a bead of something or a cornice along it. I've not had a problem though with lime meeting gypsum along the edges of the ceiling (fingers crossed).

I'm not too worried about what my plaster looks like though, so I've got NHL lime meeting lime putty, NHL meeting gypsum and none of the meets are creating anything I'd call a problem.

 

[jamest]

Just to clarify - the plasters mainly meet at ceiling level (though not exclusively) because the meets between walls don't happen very often because of the frame posts.

 

[Sam333]

I was thinking Cornice would be a good solution! Thanks a lot, appreciate your replies

 

[Lacan07]

Hello - I am about to completely strip out an old stone cottage and I have a question about internal insulation.

The living room has 3 external walls which I intend to insulate with wood fiber and lime plaster.

As I’m doing the majority this work myself and I have never plastered before I feel relatively comfortable with the process and doing the walls, but I really don’t want to attempt the ceiling - I want to get a plasterer in to do that - so my question is could I have regular plasterboard/ gypsum plaster for the ceiling and 1 internal wall , or does the whole room need to be done in wood fiber and lime?

Thanks!

Yes, this is fine.

And yes its wise to avoid plastering ceilings with lime. Most of my ceilings are gypsum for that reason.

 

[Sam333]

Thanks for your reply. As everything is being stripped out , new ceilings etc, would you do the external walls (wood fiber/lime) first and then the ceilings later?

 

[Lacan07]

Thanks for your reply. As everything is being stripped out , new ceilings etc, would you do the external walls (wood fiber/lime) first and then the ceilings later?

Yes I would as you'd avoid a thermal bridge if the wood fibre can extend into the joist area / void. The ceiling then comes into contact with the wood fibre, rather than vice versa, if that makes sense. I would have the gypsum plasterer skim the ceiling first however before the wood fibre skim.

install wood fibre

install ceiling / plasterboard

skim ceiling

skim fibre board

 

[Sam333]

Thank you so much!