some advice please: I'm refurbishing some sash windows in a house just bought. I have removed the frames to effect repair and the glass is very thin and noticed a plastic covering over it too. I think to ensure it doesn't shatter as it was used as an office so probably had some health and safety reason for being installed. My question is, what replacement glass thickness must I use (4/6mm?) and what are the rules for safety glass heights? 6mm wound poss provide better sound insulation but the weight is a possible problem . Currently looking for a recommended two part export resin and fillet too