Beadboard on exterior wall of Siporex/lightweight concrete

[Nil-Åke]

We have a vacation home where we are planning to renovate the kitchen. The exterior walls are made of 200mm siporex from the 1930s or so, which are plastered both inside and outside.

Currently, there is a masonite board placed directly against the exterior wall on the inside, which we want to replace with beadboard. I'm thinking a horizontal batten is screwed directly into the exterior wall with lightweight concrete screws, and then vertical beadboard is nailed onto this.

Does anyone have any input on this solution? Could the batten be moisture damaged with this proposal? Should a vapor barrier be used even though there hasn't been one before?

Thanks in advance

 

[Testarn]

If the masonite hasn't been damaged by moisture, then a nail batten shouldn't be either.
You can place the batten on the masonite and let it remain there.