What are some methods for figuring out the slope of a floor?
I've always heard the slope referenced as, eg: "1/2inch over 6ft." - is this the normal way, and/or are there other common ways to say it?
One way is to take a long level (the longer the better : 6 and 8' levels work well).
Hold one end of the level on the higher point, and then once the level is level, measure the gap between the other end and the floor using a measuring tape. This will give you your height over your run (length of level), for that particular spot in the floor anyways.
Wow, a 1/2 inch over 6 inches is quite the floor, sure it is not a roof?!?! lol. I have never heard of a standard expression for floor level. I would simply express it over the span of the entire floor or from the crown spot. Example, 1 inch over 12 feet across joists, or maybe 1/2 inch over 8 feet with joists.
You are right saying that a long level can be used to measure the slope, however a laser is very useful in seeing all irregularities over the entire floor, side to side or any high spots in the field. Set the laser at maybe 6 inches above the floor as a nul reference, then take several measurement with a tape at several locations by setting the "0" on the floor and note where the laser hits the tape. Good Luck