Hello. Thank you for such a helpful website – your advice is fantastic. We would be very grateful for your assistance on a matter we have concerning new plaster in a 300 year old, mid terrace properly. We recently had the old plaster removed in two of our middle floor rooms as it was loose, and the builder repaired the old stone walls with lime render. We thought he was then going to plaster with lime, but after cracks appeared in the new plaster shortly after it was applied and after questioning him, it turns out gypsum plaster was used. We presume the cracks have appeared because of the old stone walls moving, and the plaster being rigid and unable to accommodate the movement? We are reluctant to remove the new plaster due to the potential damage it may cause to the stonework underneath, so are looking to have the builder repair the cracks. Our questions are, is this the most sensible course of action, and if so, is there a product you can recommend for repairing the cracks that may offer the flexibility to cope with the movement old stone walls naturally have and minimise further cracking? Any further advice or suggestions you could offer would be greatly appreciated. Many thanks in anticipation.
Thank you for getting in touch. It’s a little difficult for us to give you an answer without seeing the issues but generally speaking lime fillers wont work with gypsum and even if they can, movement can occur through the entire surface so you can find that the issue occurs elsewhere. Ideally the coating should be carefully removed and then replaced with a more appropriate product if that is possible. Please let us know if we can be of further help.