We've found that the % of common space can really vary depending on the context of the project. For what it is worth though, in our newest project (30 apartments, wood framed 3 story double loaded corridor building) we had:
Apartments:
19500 SF
Common:
2740 SF
Onsite mgmt: 435 SF
Circulation:
4895 SF
Utility:
1800 SF
This is all net - we assume about 12% add'l SF to include uninhabitable square footage.
My experience is that more is usually better - clustered near entry to ensure that common space is used. Common rooms on upper floors tend to not get used unless they are a clear destination (like a work out space).
Best of luck. You can email me if you have follow up questions.
beall@cathedralsquare.org -------------------------------------------
Samuel Beall AIA
Architect
Cathedral Square Corporation
Burlington VT
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