I'm Having a pair of patio doors fitted next week in my dinning room, its the classic window out, cut the brick work down and fit doors. i have a modern ish perssimon home built in about 1985. My concern is that the cavity isn't bridged thus reducing insallation and allowing damp in. I can get my head around cavity closers for the reveals on the sides but not the floor I don't want a threashold board and have asked the window company to screed up to the doors. what should they put in the open floor cavity to do the job properly ie dpm, insallation, etc. I'm scared they'll just fill the void with concrete so would like to know what to look out for.