Sterling and Ashburn sit next to each other on the map and ask different questions of a racking system. Sterling is the corridor's deepest concentration of true flex-industrial space — shallow bays, modest clear heights, multi-tenant buildings that filled through the 1980s and 1990s. Ashburn grew up around the data center industry and stores things that industry needs. Both are served by Loudoun County Building & Development, both sit on the Route 28 and Route 7 spine, and a system designed for one will frequently underperform in the other.
Sterling: A Flex Market First
The single most useful thing to understand about Sterling is that most of its industrial stock was not built for distribution. The Route 28 and Sully Road corridor is flex: 18-to-26-foot clear, shallow bays, one or two docks per unit, built for contractors, light assembly and local distribution rather than for regional throughput.
That geometry, not budget, is usually what limits the system. In a shallow bay you run out of depth before you run out of money, and the constraint is frequently the turning radius at the end of an aisle rather than the clear height. We lay out around the real column grid and the equipment actually in use, which in a lot of these buildings is a walkie or a small counterbalance rather than a reach truck.
Older Sterling Park and Shaw Road stock drops further, to 16-to-22-foot clear, and brings the additional question of what the floor will carry. Slab thickness in buildings of that vintage is frequently undocumented. We core before anchor design rather than assuming a number.
Ashburn: Access Beats Density
Ashburn's storage demand is dominated by what sits around the data centers rather than by distribution. Spare parts rooms, cable and consumables, contractor laydown and construction staging.
The design logic inverts there. In distribution, a pallet position is a cost to minimise. In data center support storage, the system exists to guarantee a specific part is in hand within minutes, because the cost of not finding it dwarfs any saving from denser storage. That means shallow selective, wire decking, every SKU on a pick face, carton flow for fast-moving consumables, and no deep lanes burying anything.
Along Route 7 and Loudoun County Parkway there is newer, taller product — 24-to-32-foot clear with better dock ratios — where conventional distribution logic does apply. Both exist in Ashburn, a few minutes apart, and the right question is which one you are actually running.
Clear Height: Measure the Obstruction, Not the Deck
This matters more in low-clear buildings than anywhere else, and most of this market is low-clear.
The usable height is set by the lowest sprinkler head and the lowest obstruction in the bay — ductwork, lighting, conduit, structural bracing — not by the structural deck the drawings show. In a 20-foot building, misjudging that by 18 inches can cost you a full beam level, which is a large share of your capacity. In a 36-foot building the same error is an annoyance. Here it is the difference between the system paying for itself and not.
NFPA 13 sets the minimum clearance between the top of storage and the sprinkler deflector, and that requirement does not negotiate. We measure bay by bay rather than taking one reading and applying it across the building, because in multi-tenant flex the mechanical runs are rarely uniform.
What Actually Gets Specified Here
- Selective at 14-to-22 feet — the workhorse for both markets. Directly accessible, simple to permit and modify, and forgiving when the operation changes.
- Wire decking as standard — keeps sightlines clear, satisfies sprinkler water penetration, and in parts storage makes the difference between finding something and hunting for it.
- Carton flow at the pick face — for consumables and case picking, gravity-fed lanes beat static shelving on speed and rotation.
- Cantilever — conduit, pipe, cable reels and long stock. Common in both contractor space and data center support.
- Industrial shelving — where inventory never sees a pallet, which is a larger share of this market than most people expect. We would rather specify shelving that suits the work than pallet rack that does not.
- Push-back or pallet flow — genuinely useful in the taller Route 7 product where a single SKU justifies lane depth, and rarely the right answer in a shallow flex bay.
Permitting Through Loudoun County
Sterling, Ashburn and Dulles are all unincorporated, so there is no separate town building department and Loudoun County Building & Development is the authority for the whole area. That is simpler than the position a few miles south, where Fairfax County, the City of Fairfax, and the towns of Herndon and Leesburg are all separate authorities.
Virginia enforces the Uniform Statewide Building Code, written at state level and administered locally. Rack systems require a building permit with drawings sealed by a Virginia-licensed design professional above threshold height and load. Where commodity is stored above 12 feet — 6 feet for high-hazard — a high-piled combustible storage review under IFC Chapter 32 runs concurrently, adopted through the Virginia Statewide Fire Prevention Code.
Submit both packages together. Sequential submittal is the most common avoidable delay on these projects, and it costs weeks for no benefit.
Working in Occupied Buildings
Almost every job in this market happens in a building that is running. In multi-tenant flex that adds a wrinkle beyond the tenant's own operation: shared loading areas, neighbouring tenants, and landlord rules about noise, hours and access.
We establish those constraints before the schedule is set rather than discovering them on day one — building hours, dock access, whether the freight elevator is usable, whether there is anywhere to stage material. In data center support space, phasing around live operations is the default and the aisles the facility depends on stay reachable throughout.
Practical Steps
- Measure to the lowest obstruction in each bay. In a low-clear building this is the single most consequential number in the project.
- Say what equipment you actually run. Aisle width follows the truck. Speccing for a reach truck you do not own wastes floor.
- Core the slab in older buildings. Sterling Park and Shaw Road stock rarely has documented thickness.
- Decide honestly whether you are a parts operation or a distribution operation. The answer changes the whole design, and plenty of buildings here are the former while being described as the latter.
- Submit the building permit and high-piled storage review the same day. They run concurrently if you let them.