Help please with sandstone windowsill repair

25 Jul 2022
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United Kingdom
Hoping someone can give me some help and advice!

I’ll attach photos for reference. I’m attempting to repair my sandstone windowsill. The top of the sill is in pretty good condition and I’m in the process of getting all the old paint off and sanding it down to the stone.

However the underside of it is pretty badly damaged, I’m planning on ordering some colour matched sandstone mortar from Rowland Premix which seems to be the best product for the job and a reinforcement kit.

What I’m looking for is advice on how the best way to get the shape back, doesn’t have to be perfect.

My plan is to build a wood frame to run along the bottom to give the shape and screw the wood into the mortar joints of the brick below. Then use the mortar to start rebuilding the sill.

Am I best cutting out part of the sill to make straight edges or using a drill to kind of make key holes for the mortar to lock into.

Should I also use non ferrous screws and wire to build a frame for added support?

Really hope someone can guide me here!


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