Adaptive Reuse Test-Fit: Program Area, Records Load, and a Second Stair
A county client asks you to test-fit a 38,000 nsf office program into a vacant 1955 department store. Each of the three floors is 45,000 gsf, with a 22 ft column grid. The building has one central enclosed stair, one open stair at the rear, one freight elevator, 13 ft floor-to-floor, and no sprinklers. The program: 185 workstations at 150 nsf each (including departmental circulation), 12 enclosed offices at 150 nsf, four conference rooms totaling 3,200 nsf, a 2,500 nsf records room, and a public counter sized for 60 visitors at once. The 1955 structural drawings show a 100 psf live load rating on the upper floors and slab-on-grade at the ground floor. Your code consultant reports that the locally amended code requires two remote exits per floor and limits travel distance to 250 ft; the longest path from the northeast corner measures 310 ft. The client wants to sign a lease in 30 days.
1. Does the program fit? Show the area math and identify the assumptions the client must confirm before signing.
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Start by reconciling the numbers. The listed components total 35,250 nsf: 185 x 150 = 27,750 for workstations, 12 x 150 = 1,800 for offices, 3,200 for conference, 2,500 for records. That leaves only 2,750 nsf for print, break, IT, reception, and storage, which is thin for 185 people. Confirm whether the client's 38,000 nsf is net assignable or already includes support.
Gross up. At 80 percent efficiency, 38,000 / 0.80 = 47,500 gsf. At 85 percent, 38,000 / 0.85 = 44,700 gsf. Two floors provide 90,000 gsf, so raw area is not the constraint.
The constraint is contiguity. One floor of 45,000 gsf fits only at the top of the efficiency range and leaves no room for the second exit the egress analysis will require, so plan on two floors with the public counter and records room at grade.
Check the bay: 150 nsf per workstation is roughly a 12 x 12.5 ft module, comfortable in a 22 ft grid. A 150 nsf office fits a 10 x 15 ft room, but 12 perimeter offices will fight the window rhythm and the 22 ft bays; model it before promising a layout.
Finally, test growth: a 15 percent headcount increase raises workstations alone to about 31,900 nsf. Show the client that scenario before the lease is signed, not after.
2. The records room is programmed at 2,500 nsf with a 150 psf live load. What are the structural implications and your recommendation?
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The records room is the item most likely to sink the deal. At 2,500 nsf and 150 psf, the total live load is about 375,000 pounds, and file shelving usually delivers that load as concentrated leg loads rather than the uniform load the 1955 rating assumes. High-density mobile shelving can reach 250 to 300 psf. Two things need verification: what the original drawings actually rate, and what the shelving layout produces.
Options, in order of cost:
- Put the records room on the ground floor over slab-on-grade. At 150 psf a slab on grade is almost always adequate; confirm with a geotechnical report that the subgrade is not fill.
- If it must be above grade, have the structural engineer evaluate the existing beams, columns, and footings, and design supplemental framing between existing columns or a raised floor that distributes load. This is a real cost and schedule item, and it affects floor-to-floor strategy.
- Reduce the load by changing shelving type or digitizing part of the archive, which may shrink the room but not necessarily the area required.
Do not accept 'it held files before' as evidence. Get the engineer's letter before lease signing, because the answer changes the rentable area, the budget, and possibly the floor assignment.
3. Address the egress and sprinkler strategy. What must be resolved before the client signs the lease?
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Two separate code issues are hiding here and should not be conflated.
Means of egress: with any realistic occupant load, each floor needs at least two remote exits. The building has one central enclosed stair and one open stair. An open stair in a 1955 building is very unlikely to be a legal exit for a business occupancy; it must be enclosed or replaced. The baseline, therefore, is a second enclosed stair remote from the first with an exit discharge. That is a shaft through three floors, a real cost and schedule item that must be priced before lease signing.
Travel distance: 310 ft exceeds the 250 ft your code consultant cites. A second stair placed at the northeast corner can bring the path within the limit, but measure from the worst point in the tenant space, not from the stair door.
Sprinklers: the building has none. Sprinklers will not substitute for the second exit, but they may buy additional travel distance under the locally amended code, and they may be needed anyway depending on occupancy and area. Get the AHJ's written position rather than an unofficial opinion.
Before lease: obtain a signed code summary from the code consultant and a structural letter covering the records room and the new stair penetrations, and put a cost range in front of the client with the lease decision.