Measure interior floor area

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?
Thanks,
John
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That's about a 3% difference. Without knowing any details, that could be attrbuted to a number of things, the most likely one being a bit of embellishment in the listing. "Spacious 1800 sg ft colonial" sounds better than "Spacious 1745 sg ft colonial".
BTW, why would you measure the living area floor space to get an estimate for attic insulation? Why not just measure the attic floor space?
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In my area, "finished square feet" is measured on the outside of the house. That doesn't make sense since inside the walls is not livable space. It's probably done that way to make the tax assessor's life easier.
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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
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