I have oak widow sills that have been weathered for 150 years. They are deeply crevassed and painting them is not a viable option.
I don't wish to replace them but would prefer to coat them in a layer of sand in a resin binding to give an imitation sandstone effect.
What would be the best adhesive and binding agent?

Would a pre-made material such as Sandtex not be suitable? They have outdoor, timber applicable sand based paint systems available from most good DIY stores.

Hello Rich,
Thank you for your answer. Yes I'm sure it would do, I have Sandtex over a rendered extension that dates back to the 30's, but it isn't what I'm wanting to do. I want an end product that looks as close to a sandstone slab as I can get, without stressing the existing masonry and foundations with massively heavy and expensive blocks.
Hence my question "what would be the best adhesive and binding agent" for a sandstone effect?