Stabalising Flakey Surface

[DIYWell]

This sandstone lintel has had some long term water damage.



Structurally sound and dried out now but some of the stone surface is flakey.

What is the best method of stabalising the surface before plastering over?

 

[Deleted member 265726]

I would have removed the flaking paint from the lintel first. Don’t know about a suitable solution for sandstone.

 

[dontbelieveawordofit]

there are products availabe, never plastered sandstone internally .
my answer would be make a 2x1 frame and board the underside off the stone.

if I had to plaster it i’d source a stabiliser specifically for sandstone , then coat it with a lime render /plaster.

 

[DIYWell]

I would have removed the flaking paint from the lintel first. Don’t know about a suitable solution for sandstone.

The flakey paint is removed.

 

[DIYWell]

my answer would be make a 2x1 frame and board the underside off the stone.

I hadn't thought of that. I suppose I could skip the framing completely and just glue/screw thin ply directly over the surfaces.

 

[dontbelieveawordofit]

sandstone needs to breathe whatever.
a 6 or 9mm ply stuck up with adhesive would do and finish with a small quadrant or something around the edges.
9.5 mm plasterboard would be better if it’s bone dry plus you can plaster it all in.
stick it up with generous blobs of multistik adhesive and prop it up overnight.
you’ll still need to stabilise it first and/or blob it strategically where it’s most sound and/or least ropey.

 

[DIYWell]

Thankfully it is just that far corner that is sandy to the feel. The rest of the surface is good.

The more I think about it, covering with ply is becoming increasingly appealing.

 

[dontbelieveawordofit]

there you go.

 

[dontbelieveawordofit]

bond a 9mm ply to it and prop it overnight.