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I own an old house in Touraine type longere. I have to redo the outer frames of all openings that are originally stone "tufa". I was advised to scratch the maximum stone (up to 1.5 or even 2 cm) which is aged on the surface and redo a thickness with a product type "stone mortar". This work does not repel me but my mortar will adhere correctly? Should we plant a few nails (as we did before, but rust!) Or put a fine fence to better adhere? Or do you have other recommendations?

The addition of 2 cm of mortar that you are considering seems very complicated to implement for a result that may not be very aesthetic. The application of a SIKALATEX bonding resin will be recommended to ensure the adhesion of the mortar on your stone, but the result may disappoint you. A much simpler solution to give a boost to your tufa stone would be to rent a sander / hydrogomeuse that will allow you to strip and smooth the surface at low pressure. The combination of water and sand allows to have an abrasive action on the support without damaging it. You will avoid the tedious job of cutting the stone and rebuilding the frames.

If the stone is too friable, consider the installation (by gluing) of reconstituted stone facing boards in harmony with your construction.

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