Office Conversion with High-Piled Storage
A four-story, 90,000 ft² office building in Reno was built in 1986 with a wet-pipe system designed for light hazard: 0.10 gpm/ft² over 1,500 ft², a 6-in. riser, 1.5-in. branch lines, and K=5.6 pendent sprinklers at a 10-ft ceiling. A new tenant leases 18,000 ft² on the first floor and proposes open-aisle rack storage of boxed furniture and plastic-wrapped components. Storage will be 12 ft high in 10-ft aisles; the ceiling is 12 ft. The owner argues that the building is fully sprinklered and no changes are needed. The hydraulic calculation placard shows a system demand of 1,050 gpm at 55 psi. A recent flow test gives 1,300 gpm at 40 psi residual, 60 psi static. The tenant wants occupancy in six weeks. The local fire marshal has not yet reviewed the storage arrangement. You are asked to advise the owner before the tenant signs the lease.
1. What hazard and design basis should govern the proposed storage, and why is the existing light-hazard design not automatically acceptable?
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The starting point is not the existing light-hazard label; it is the commodity and storage arrangement. Boxed furniture with plastic-wrapped components is likely Class IV or a Group A plastic depending on the plastic content, and 12-ft storage under a 12-ft ceiling leaves no clearance below the existing 10-ft deflectors. That alone makes the arrangement noncompliant. The storage also changes the design basis from 0.10 gpm/ft² over 1,500 ft² to a storage density and remote area determined from commodity classification, storage height, aisle width, and ceiling height; in-rack sprinklers may be required if the plastic content is significant. A quick hydraulic check shows the existing placard demand of 1,050 gpm at 55 psi leaves only 170 gpm of margin against a 1,300-gpm/40-psi supply, and a storage design will usually push demand higher. The correct response is a new commodity classification and hydraulic analysis, not a verbal assurance.
2. Evaluate the physical and hydraulic adequacy of the existing sprinkler system for the proposed storage. What specific deficiencies would you expect to find?
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I would expect at least four issues. First, clearance: the top of storage cannot intrude into the required clearance below sprinkler deflectors, so either storage height must come down or sprinklers must be raised and the entire layout recalculated. Second, sprinkler spacing and K-factor: light-hazard spacing with K=5.6 heads is unlikely to satisfy a storage density at the required pressure, especially if the ceiling is only 12 ft and the deflectors are close to the storage. Third, branch-line capacity: 1.5-in. branch lines and the existing 6-in. riser may not deliver the higher storage demand at an acceptable residual pressure. Fourth, the water supply: a 1,300-gpm at 40-psi test is not a large margin once the storage demand and hose allowance are added. I would not accept the system based on 'fully sprinklered'; I would require a hydraulic calculation using the classified commodity and the actual storage geometry, and I would verify that the supply curve supports the new demand at the base of the riser.
3. Outline the compliance path you would require before the tenant occupies the space.
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The owner should treat the lease as contingent on a sprinkler redesign. The sequence: classify the commodity and storage arrangement with the tenant's actual packaging and plastic content; have a licensed fire protection engineer or contractor prepare a storage design and hydraulic calculation; submit plans and calculations to the fire marshal, including a high-piled storage permit if applicable; install the required modifications, which may include raising sprinklers, adding in-rack sprinklers, changing heads, or increasing supply capacity; and perform acceptance testing. If the six-week schedule cannot accommodate design review, permitting, fabrication, and installation, the tenant should delay occupancy or reduce storage height and commodity loading until the work is complete. The owner should not rely on the existing light-hazard placard or on the fire marshal's silence as approval.