If it’s a potentially damp wall, then don’t fill with bonding plaster as it’s very hygroscopic. Use a cement mortar mix which will probably be fine, or add a little damp proofing agent if it really has an ongoing damp problem. Build it up in layers if it’s over say 30mm deep, and leave the top to be finished with finishing plaster.
If it’s a potentially damp wall, then don’t fill with bonding plaster as it’s very hygroscopic. Use a cement mortar mix which will probably be fine, or add a little damp proofing agent if it really has an ongoing damp problem. Build it up in layers if it’s over say 30mm deep, and leave the top to be finished with finishing plaster.