Would you include or exclude corridors in a mage's mansion's measurements?

[Senko]

A mage's magnificant mansion (below) is 3 10 foot cubes per level. Would you say corridors should be included or excluded in that measurement. For example you have a short corridor with 3 bedrooms leading off it. One to the left, one to the right and one at the end. Each bedroom is a 10 foot cube for a total of 3 10 foot cubes. Would you use a fourth cube to simulate the corridor giving it a 10 x 10 size same as the bedrooms and requiring 4 10 foot cubes. Alternatively would you exclude if from the measurements? I'm thinking the former but it feels a bit harsh to need to use some of your mansions size to create corridors between rooms.

Mage's Magnificent Mansion
Source PRPG Core Rulebook pg. 307
School conjuration (creation); Level arcanist 7, psychic 7, sorcerer 7, wizard 7
Casting
Casting Time 1 standard action
Components V, S, F (a miniature ivory door, a piece of polished marble, and a silver spoon, each worth 5 gp)
Effect
Range close (25 ft. + 5 ft./2 levels)
Effect extradimensional mansion, up to three 10-ft. cubes/level (S)
Duration 2 hours/level (D)
Saving Throw none; Spell Resistance no
Description
You conjure up an extradimensional dwelling that has a single entrance on the plane from which the spell was cast. The entry point looks like a faint shimmering in the air that is 4 feet wide and 8 feet high. Only those you designate may enter the mansion, and the portal is shut and made invisible behind you when you enter. You may open it again from your own side at will. Once observers have passed beyond the entrance, they are in a magnificent foyer with numerous chambers beyond. The atmosphere is clean, fresh, and warm.

You can create any floor plan you desire to the limit of the spell's effect. The place is furnished and contains sufficient foodstuffs to serve a nine-course banquet to a dozen people per caster level. A staff of near-transparent servants (as many as two per caster level), liveried and obedient, wait upon all who enter. The servants function as unseen servant spells except that they are visible and can go anywhere in the mansion.

Since the place can be entered only through its special portal, outside conditions do not affect the mansion, nor do conditions inside it pass to the plane beyond.

[Bjørn Røyrvik]

We don't worry about exact measurements. AS long as we don't try to fill it beyond reasonable capacity (generally no more people than can be fed) the exact size and shape isn't an issue.

[Northern Spotted Owl]

Since it’s a 7th level spell, the caster is at least 13th level. Hence you have 13*3 = 39 cubes. With 8-9’ ceilings, that’s 3900 sq ft.

You should be able to fit in hallways, stairs, and such.

[Phoebus Alexandros]

“You can create any floor plan you desire to the limit of the spell's effect.”

A floor plan includes corridors, hallways, etc. Even at its general maximum of 6,000 square feet this spell doesn’t create a proper mansion in the modern sense, but do a quick perusal of a 3,900 square foot home—the number and types of rooms, etc. I doubt the average adventuring party would feel cramped inside the confines of a Magnificent Mansion spell.

[Mysterious Stranger]

Corridors are part of a building so should be included. Nothing prevents you from using the space of the corridor for other things. You can put some shelves on the wall of a staircase, or a chest in the hallway. Not counting the corridor can easily be abused. For example, you could have a hallway between two rooms that was 10 feet wide and 30 feet long. How is this any different than having a 30 foot by 10 foot room?

When you buy a house in the real world, they count the hallways and staircases in the total square footage.

[Taja the Barbarian]

The real question is: Does it really matter? The actual floor plan is largely irrelevant unless one or more occupants are actively plotting against others...

That being said: Yes, hallways would count against total area if not specifically stated otherwise (I believe the D&D3.0 Stronghold Guide had a 'pay by room, but no cost for hallways' rule but also included a 'no 100ft wide hallways filled with furniture allowed' caveat).

[Mark Hoover 330]

Foyer and kitchen form the north and south ends of the house, each made up of 6 10'x10' cubes making each space 20'x30. The dining hall is the entire west side of the house, being 13 cubes or 10'x130'. The entire East side of the house is 13 fully enclosed 10'x10' cubes, either for sleeping, study or bathrooms. Finally, a single 10'x10' cube is under the kitchen, connected by a trapdoor and acts as a root cellar or storage.

The entire mansion is on one level and sleeps, say, 14 people, 2 to a sleeping cell. Among the enclosed cells on the east side then that leaves 6 of those cells for latrines or garderobes or what not, an actual BATH room and library space for the wizard types. The dining room is the "hallway" of the house conducting traffic from the foyer to the south back to the kitchen in the north. The whole building, then, is a big cube.

All the walls are beige. Every sleeping cell features a dormitory style bunk beds a wardrobe and a single table, all exactly the same and uniform in dimension. The 9 course meal is the most balanced, yet palate neutral food imaginable. All drinks are clean artisanal spring water. This "mansion" is the most efficient use of space and resources on the entire prime material plane.

[VoodistMonk]

Yes, corridors are included in the measurements. Not that it actually matters, at all, but yes they are absolutely counted as part of the area.