On Mar 12, 12:13 pm, "John61" wrote:
When I bought this 40-yr old 2-storey house (here in Canada) a couple of
years ago, was told the floor area is 1800 sq ft. Lately I measured from
inside wall-to-wall for getting estimate for attic insulation, it's smaller
than that (less than 1750). I think this is the "interior floor area" used
for "house for sale". Is there a standard way for the measurement?

Floor area can be interpreted a lot of different ways - none of them
are 'wrong', just a surprise if you assume one thing and the lister
meant another. In architecture and zoning circles a FAR - floor area
ratio - refers to the ratio of building area to lot area, and the
measurement is taken from the outside perimeter of the building. It
is no surprise that the seller or real estate agent used the largest
possible number.

R