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When a ground floor lobby and a stair, both serving multiple tenants, are combined (part of the same enclosure without vestibule), is the building common area calculated up to the first riser and the rest is considered major vertical penetration ?
Hi Leon,
Unfortunately, this scenario is not specifically addressed by the BOMA 96 Standard itself, leaving it somewhat open to interpretation.
If the stair is fully or mostly enclosed, we would usually classify the entire footprint of the stair as a Major Vertical Penetration. If the stair is open underneath, we might classify some of it as a Major Vertical Penetration, and the remainder as Building Common Area, or Floor Common Area, where the space becomes arguably Usable (usually between 5-8 feet in height, but this is also not defined).
As you can see, it's difficult to give a straight answer to your question. When in doubt, take what you believe is the most defensible position, so that you can justify your decision later if required.