Which kind of mortar for chimney?

[Jeppes96]

Don't know if I have posted in the right thread, please move my thread otherwise. Hi, I have a chimney that needs tiling, the problem is that there's a difference of about 45mm that needs to be plastered first, what kind of mortar can I use for this? Is it even possible? I have looked at plaster mortar type c but this is recommended for a layer thickness of only about 12mm. The chimney is about 150 years old, I don't know what kind of mortar "they" used when they built the chimney. Regards, Jesper

 

[Stefan1972]

If it is that old, it is guaranteed to be lime mortar which is soft, but building 45mm sounds drastic. Can't it be solved in another way or skip the tiles just there? A chimney gets warm and moves, so it might not even be suitable to have any covering tiles there that go over to other walls if they crack.

 

[Jeppes96]

There is conduit in the chimney today, so the heat is probably not an issue, the thing is we have opened up to the ridge, and in the attic, the chimney is 45mm wider and has a plastered surface compared to the lower floor, and this is only on one side of the chimney where it is wider.