I have a large garage with workshop and storage above. I want to convert workshop and storage to living accomodation whilst keeping garage. At the moment the garage floor is same height as rest of floors. Building Regs say that garage floor must be 100mm lower than living accomodation, or alternatively it must slope from back to garage door. This would mean a lot of work either digging up and relaying concrete garage floor or raising floor height in rest of building. My question is, why can't I simply build a 100 mm threshold across the door from living part of building into garage. OK it would mean a step over and re-size door but this would be far less work and achieve the same end ie containing any spills in the garage. Do you think this would be acceptable to Building Control (I know why don't I ask them, but I just wanted some ideas first). Thanks in anticipation.