I'm not an architect, but a simple google of "how to calculate living square footage" tells me your designer is correct.

Such things are well established by industry standards.

The term "living square footage" doesn't appear in any area calculation standard commonly used for single family houses. What you and your designer should be using is ""Finished Area" as defined by ANSI Z765-1996 which is essentially the gross area measured to the outside face of the structure with some exceptions.

SQUARE FOOTAGE–METHOD FOR CALCULATING: ANSI Z765-2003

Since it is time consuming to calculate the room areas and add them up you should probably do that yourself rather than paying your designer to do it.

There are other standards like these:

• Gross internal area (GIA) - The floor area contained within the building measured to the internal face of the external walls.
• Net internal area (NIA) (or usable floor area UFA) - The NIA is the GIA less the floor areas taken up by lobbies, enclosed machinery rooms on the roof, stairs and escalators, mechanical and electrical services, lifts, columns, toilet areas (other than in domestic property), ducts, and risers.

I can't speak to the residential world, but in the commercial world It is common practice to measure to the outside of the exterior wall framing unless otherwise specified. Also keep in mind if you are measuring and adding up rooms, you are not accounting for interior wall thickness, and if they are schematic dimensions they are also likely rounded.

As JDS describes, "gross" area is measured to the outside face of the studs or structure, and includes everything inside that imaginary line. There's little point in simply calculating "clear" interior areas, except to figure out if one has enough room for one's existing couch or bed (which is important). You aren't being ripped off!

When it comes time to sell your house (if ever) you're going to thank your designer :)

In what way would you be ripped off? Does the designer charge by the square foot?

Thank you everyone.. Jds- yes the designer does charge by the square foot and thats not the problem. It's the builders that charge by the square foot and I just wanted to make sure that what I was being told was right.t Now that you all clarified that this is indeed correct I won't bother with it anymore. So again thank you all for the clarification.

Also to clarify before I was educated by the architects, what I mean about feeling ripped off had to do with the square footage difference I was coming up with. But now that you've showed me I was wrong. It's not a big deal anymore. thanks again