80x100 Clear-Span Steel Building

Quantities, not prices, are publishable here: roof cladding runs 8,433 square feet — 5% above the 8,000-square-foot floor at a 4:12 pitch — with 148.1 cubic yards of nominal slab beneath it. The span is the commitment; everything inside it is rearrangeable later, and the 80-foot dimension is not.

Proportion drives cost here as much as size does: 360 ft of wall around 8,000 sq ft is 0.045 ft of wall per enclosed square foot, and a squarer plan of the same area would carry less. What moves the figure further on a an unfinished clear-span shell planned for a tenant or use that has not yet been decided is the fit-out flexible shell building planning implies, along with framed openings and the height chosen for the 80 ft span.

• the span itself, which sets the primary frame
• clear height maintained under a deeper frame
• bracing strategy in the walls and roof
• opening positions the span makes possible

This page is ordered around runway, because that is the decision this footprint settles first and every later choice follows from it.

The footprint holds 9 divisible bays — 3 across by 3 deep — and leaves 13 feet of depth for a demising line left unbuilt but planned for, so the shell can be split into separate leaseable bays without reworking the structure.

Read this footprint through its span. 80 feet across is the fixed constraint; 100 feet of length is the negotiable one, and at 1.25 to 1 the building is close to square, so movement runs in both directions. Rows that cannot be entered independently end up used as one long space.

A 80 by 100 footprint is a mildly directional plan: 8,000 sq ft enclosed by 360 ft of wall, at a 1.3:1 length-to-width proportion. Along its 100 ft dimension it takes 4 runs of divisible bays at 25 ft, leaving 0 ft over — the 0 ft is where the argument about this size actually happens. This mode treats the clear span as a blank the eventual occupant will divide, so the planning task is protecting future options rather than committing to one layout now. The building earns its value from how many different tenants or uses it could accommodate without structural rework, not from how well it fits any single one. A load-out lane, turning apron or service margin that is planned as permanent floor, not leftover space, is what keeps a wide floor usable years after it is filled.

This footprint is planned as an unfinished clear-span shell planned for a tenant or use that has not yet been decided. Spent as a square 89 by 89 instead, the same 8,000 sq ft would stand 3 divisible bays across rather than 2, and would trade this plan's length for parallel access. That is the width-against-depth decision this footprint has already made. Compared with a 80 by 80 of the same width, the extra depth here adds run rather than reach: it buys about 4 divisible bays in line, and every position past the second is retrieved by moving what stands in front of it. A building of this size behaves like a small yard under a roof: zones need to be defined, signed and left alone, or they migrate. There is no fixed workflow to design around, which is the point — the plan instead has to make sure common services (power, water, drainage) can be tapped independently at each notional bay without shared metering forcing tenants together. A clear span left undivided by plan, rather than by accident, keeps more future uses available than one filled in as needs arise.

One opening per position works on this gable: 3 across 80 feet, with 5 feet of wall to distribute as piers. Splitting that margin evenly is what keeps the elevation buildable. Security and after-hours access are easier to design in the door layout than to bolt on later.

Door placement is planned for whichever future division is most likely, generally one door per notional bay, so a later demising wall does not leave a bay without its own access.

At 25-foot nominal bays the structure works with the layout instead of against it: one divisible bay per bay line, walls free of awkward half-positions. The plan is only as good as the route into it, which is a site question rather than a building one.

With 3 rows deep, the rear row is behind the front one. Without a route past it, those divisible bays become storage positions rather than working ones — the real cost of depth at this width. Whoever operates the building daily should read the plan before it is frozen, because they know where the pinch points are.

Growth here usually means finishing more of the existing shell for a new tenant rather than adding structure, since the clear span was already sized for the largest plausible single occupant.

Configured as an unfinished clear-span shell planned for a tenant or use that has not yet been decided, 80x100 is judged on whether the 9 divisible bays it holds match the operation, and on whether the 5 feet of spare width leaves the route this mode depends on.

• Does the work need racking or work zones on both sides with a full vehicle lane down the middle, or does it need a second lane that this 80-foot span cannot give?
• Is the 100-foot length being bought for depth, or for the repeated bays — eight to ten repeated bays, which makes the layout a scheduling problem as much as a spatial one?
• What dimension genuinely has to be crossed without a column?
• Is the clear height measured under the frame, or at the eave?

Across a 80-foot span the 4:12 pitch adds 13.3 feet between eave and ridge. The centreline measures 33.3 feet; anything parked or stacked near a wall lives with the 20-foot eave. Daylight placement changes how a floor is used far more than its cost suggests.

Height on a 80 ft span is a separate decision from the 100 ft length, and it is the span that sets the frame's behavior. Raising the eave over 8,000 sq ft affects every bay along the 100 ft dimension, so the test is whether flexible shell building planning genuinely needs the extra clear height or only the floor area.

The use this column-free floor could equally be bought for is a clear-span floor organised around a line of stations that a product or unit moves through: there is no end-of-line buffer, so finished units back up into the last working station. Dividing the 8,000 sq ft by the 25 by 25 ft divisible bay gives roughly 8 positions before circulation is deducted a second time for cross movement. Whether the plan keeps 8 or drops to 4 comes back to the question this footprint is really answering: if this shell is split into two or three tenancies later, does each resulting bay still get its own door and utility access?

Because 13 feet clears the 12 feet this platform treats as usable, the end of the run is a room rather than a gap: 1,040 square feet for a demising line left unbuilt but planned for, so the shell can be split into separate leaseable bays without reworking the structure. Circulation width is the first thing surrendered under pressure and the first thing missed afterwards.

The 5 feet of spare width runs the whole 100-foot length — 500 square feet of wall strip. It earns its keep as shelving, staging or a walking route, not as another divisible bay. Two feet of spare width reads as nothing on a plan and as a great deal when a machine is being turned.

Spent as a square 89 by 89 instead, the same 8,000 sq ft would stand 3 divisible bays across rather than 2, and would trade this plan's length for parallel access. That is the width-against-depth decision this footprint has already made. Compared with a 80 by 80 of the same width, the extra depth here adds run rather than reach: it buys about 4 divisible bays in line, and every position past the second is retrieved by moving what stands in front of it. A building of this size behaves like a small yard under a roof: zones need to be defined, signed and left alone, or they migrate. There is no fixed workflow to design around, which is the point — the plan instead has to make sure common services (power, water, drainage) can be tapped independently at each notional bay without shared metering forcing tenants together. A clear span left undivided by plan, rather than by accident, keeps more future uses available than one filled in as needs arise. That movement pattern, not the 8,000-square-foot total, is what decides whether the leftover 13 feet is useful here.

• 40x80 moves the count from 9 to 2 divisible bays (1 across by 2 deep), which is the reason to choose between them.
• 60x60 moves the count from 9 to 4 divisible bays (4 across by 1 deep), which is the reason to choose between them.
• 50x80 moves the count from 9 to 4 divisible bays (2 across by 2 deep), which is the reason to choose between them.

Because this footprint is planned as an unfinished clear-span shell planned for a tenant or use that has not yet been decided, the useful next reads are different from the ones a differently shaped clear-span steel building suggests: flexible shell building planning, demising line planning, multi-tenant clear-span shell.