Best way to fill this - Lime plaster ?

[PJ_]

Hello, first time poster here.

What's the best way to fill this gap?

It's between a circa 1960s gypsum plastered stud wall, and the inside of the original late victorian external brick wall which has lime mortar throughout – and is also lime rendered externally.

The internal face of the brick wall was once covered in 3 course lime plaster I presume, but this is long gone, it had batons / plasterboard over it.

I'm keeping this part of the wall exposed for now, I just want the right material to fill the vertical gap. It's about 40 - 70mm in places.

A plasterer I know suggested flinging in hardwall, and then scrimming it with easifill, but I'm keen to use lime because the external wall is breathable and I think any gypsum used there could potentially soak up moisture from outside over time. It's a small area though, so maybe hardwall would be ok........

I have plenty of unused lime plaster left over from some other recent renovation work I'm doing elsewhere in the property. I thought that could work well and not trap any moisture / create staining.

Don't want it to fail though, so asking for advice about what materials and procedures would be best to use.

Thanks

 

[aockenden]

Because of the different materials on either side of the joint, and the 90 degree angle of the join, there’s liable to be a good amount of movement due to fluctuations in internal temperature and moisture levels. So if it were me I would use a fiber-reinforced lime plaster which should help it weather this movement. It would be 1-2 parts fine-cut hemp fiber, 1-2 parts fine washed sand, 1 part lime putty for me. Then pack it deeply into the joint and smooth it off with a trowel and brush it in with an old paintbrush.

 

[PJ_]

Thanks for the info. That makes sense and sounds sensible.
I've got some LimeCote plaster here which has fibres added, but I don't think the aggregate in it is sand - it's chalk I believe. It's been good stuff to work with so far over old lath. Think I'll use that.