Hi there we are having our loft converted by Billy the Kid and his band of builders, but I do have a serious question. How thick does the fire door seal have to be around the fire door? We live in an average sized end of terrace house. The doors we have are 30 inches wide and they are 44mm thick. Thanks for your help.

To be certain of doing the job properly you must ask for the door's fire test certification. Details will be contained in the data sheet attached to the certificate. Commonly for an FD30 or FD30s it is 15x4 but best to check.