Warehouse column spacing in a steel portal-frame building usually runs 6–9 m between frames along the length, the range China’s GB 51022 recommends for light portal frames. Across the width, the same code recommends single spans of 12–48 m, whether the frame clear-spans or splits at interior column lines. The 50–60 ft grids common in newer US distribution buildings are a leasing-market convention, and they need translating before they reach a portal-frame quote. The workable grid comes from four inputs: the dock wall, the rack module, seismic rack clearance, and the frame spacing at which the roof gets heavier.
| Grid dimension | Typical figure and source |
|---|---|
| Frame spacing along the length, light portal frame | 6–9 m recommended by GB 51022-2015, China’s code for single-storey solid-web portal frames with light roofs, up to 18 m high, a height-to-width ratio below 1 and bridge cranes up to 20 t (A1–A5 duty) |
| Single span across the width, same frame type | 12–48 m, with longer spans allowed where the design justifies them (same code) |
| Purlin span beyond which trussed purlins are recommended | Over 9 m for simply supported purlins (same code) |
| Column spacing in newer US distribution buildings | About 50–60 ft (15.2–18.3 m) in one or both directions, a leasing-market convention (Janover’s industrial property guide) |
| Speed bay depth behind US dock doors | Typically at least 60 ft (about 18.3 m), with deeper bays increasingly common (same guide) |
| Common grid in modern UK warehouses | About 32 × 16 m (Panattoni UK) |
| Rack-to-column separation, Seismic Design Categories D–F | 5% of the top loaded level height down-aisle and 2% cross-aisle, unless a displacement analysis supports less (ANSI MH16.1-2023, RMI’s rack design standard, as summarised in Steel King’s seismic design note) |
GB 51022-2015 remains China’s specialist code for light portal frames. Since 1 January 2022, the mandatory GB 55006-2021 General Code for Steel Structures prevails wherever the two differ.
Why Doesn’t US Warehouse Column Spacing Transfer Directly to a Portal Frame?
US warehouse column spacing of 50–60 ft cannot be copied onto a portal frame unchanged, because portal frames typically stand 6–9 m apart. Each interior line also carries a column at every frame, and a column comes out only by design. That difference is where a grid copied from a US spec sheet starts changing the steel quote.
Stretch the frames to 50 ft (15.24 m) and the purlins pass the 9 m point where GB 51022 recommends trussed purlins for simple spans. They also pass the 12 m the code advises for solid-web purlins, so the roof system usually changes too. Keeping the frames at 7.62 m and omitting every second interior column gives the same 15.24 m between interior columns. The frame above each omitted column then sits on a transfer beam or truss, the arrangement the code recommends where interior columns are left out.
A 60 ft grid (18.29 m) works the same way. Frames go to 9.14 m, just past the band, or drop to 6.10 m with two interior columns in three omitted.
The arithmetic leaves at least two routes: wider frames with a heavier roof, or standard frames with transfer beams. A third is a different roof system altogether. Which costs less depends on span, roof load and whether a crane runs on those column lines. Price the options side by side before the grid is frozen.
Metric projects meet the same question. The 60,000 m² logistics and cold storage centre in Dushanbe runs one 12 × 24 m grid across all four buildings. Whichever way that grid is oriented, its lengthwise dimension is at least 12 m, beyond the 6–9 m band. When a grid arrives in feet, we clarify which direction each figure runs and whether interior columns may sit on transfer beams before pricing it.
How Wide Should the Spans Between Interior Column Lines Be?
The spans between interior column lines of a portal-frame warehouse are sized by what has to cross the floor. Each extra line trades rafter depth for more footings and more obstructions. Every frame carries that split, so it decides where racks, loaders and cranes can run for the life of the building.
Footings grow in whole frame lines. A 120 m building with frames at 7.5 m has 16 bays and 17 frame lines. A clear-span frame then stands on 34 main-frame footings and a three-span frame on 68, before counting endwall posts. Shorter spans return that cost as shallower rafters and lighter frames, which is why designers usually split very wide buildings.
The Kumasi timber plant took a 50 m single span, which sets its rafter depth and haunch sizing. The clear floor won because forklifts and drying racks lose time around columns. The Arequipa pipe plant went the other way with four 25 m spans. The column lines on either side of its extrusion bay carry a 10 t overhead crane runway.
Where racks run along the length, each span should hold a whole number of rack modules plus the width the column line itself needs. The explainer on what a warehouse bay is sets out the module arithmetic. A span that misses by half a module loses a rack row or pushes a column into an aisle.
| Operation | Width layout that usually fits | Condition that has to hold |
|---|---|---|
| Bulk or floor-stacked goods worked by loaders | Clear span | Building width inside the span the frame can carry at an acceptable steel weight |
| Selective racks in rows along the length | Interior column lines inside rack flues | Each span equals whole rack modules plus the flue the column needs |
| Racks in rows across the width | Clear span, or interior lines on cross-aisles | Column lines land on a cross-aisle or a row end, not mid-row |
| Overhead crane bays | Interior lines as runway supports | Crane span and hook height fixed before the frames are designed |
| Very wide halls in high-wind regions | Several spans | A single clear span would need sections too heavy to ship or erect economically |
How Far Should the First Column Line Sit From the Dock Wall?
The first column line behind a dock wall sets the staging depth, and in a portal frame that depth depends on which wall carries the docks. US industrial real-estate practice calls this zone the speed bay and usually puts it at 60 ft or more.
With docks on a sidewall of a multi-span frame, trucks unload across the width. The staging depth is then the outer span, measured from the dock wall to the first interior column line. A 60 ft speed bay therefore needs an outer span of about 18.3 m or more, while the spans further in can stay narrower for racking. A clear-span frame gives its whole width to staging.
With docks on an endwall, trucks unload along the length, and any interior column lines run with the traffic, one column at every frame. The first interior columns then stand only one frame spacing from the dock wall. With 9 m frames, omitting the first frame’s interior columns on a transfer beam gives about 18 m of clear depth, close to the 60 ft convention. With 7.5 m frames, one omitted frame line reaches only 15 m, and two reach 22.5 m.
Drive-in reception moves the staging zone inside the building. On a 10,000 m² port CFS warehouse in Buenos Aires, we aligned a 20 × 12 m column grid with the forklift lanes and cargo sorting zones. Trucks drive in at floor level through wide sliding doors. Decide which wall carries the docks, or whether trucks drive in, before anyone draws the span split, since moving either later means re-spanning the frames.
Where Should Interior Columns Sit Relative to the Rack Rows?
Interior columns in a racked warehouse sit best in the flue between back-to-back rows or at row ends, depending on column width, flue width and seismic rack clearance. A column in the wrong place costs positions on every rack level above it. That cost lands on storage capacity, a figure no steel quote itemises.
In Seismic Design Categories D to F, ANSI MH16.1 gives a default rack-to-column clearance for designs without a displacement analysis. Cross-aisle, that default keeps racks 2% of the top loaded level height away from a column. A 300 mm column centred between two rack rows loaded to 9 m therefore needs at least 300 + 180 + 180 = 660 mm between the two rack structures. Swap in your own column width and top-level height: that gap has to be at least the column width plus 4% of the height.
If the rack layout assumed a narrower gap, every row pair on that column line grows by the difference. The span then has to absorb it or give up a row. Down-aisle, the same method asks for 5% of the height, 450 mm at 9 m, between a column and the nearest upright. A column that breaks a row needs that gap on both sides: with a 300 mm column, the row gives up about 1.2 m at every level.
Outside those categories the default percentages no longer set the gap, although the column still has to clear the racks. Either way the figure is a seismic clearance check only; flue width, sprinkler layout and any column protection still follow the fire design under the adopted code.
What Sequence Settles the Grid When Docks, Racks, and Steel Pull Apart?
A warehouse column grid settles in a set order when docks, racking and steel weight pull in different directions. Each later input is sized inside the space the earlier one leaves, so the sequence shows which changes stay cheap late in design.
- Dock wall and staging depth: the truck court fixes the dock wall, which decides whether the speed bay comes from the outer span or omitted columns.
- Rack module and row direction: whole modules plus the flue each column line needs set the remaining spans.
- Frame spacing and roof system: frame spacing follows door widths and rack bays along the length, inside the 6–9 m band unless the roof changes.
- Seismic clearance: in Seismic Design Categories D to F the separation check can widen flues and push a span up by a module allowance.
Dock wall, rack module, frame spacing and seismic clearance have to converge together. The dock wall is locked first, because the site plan fixes it and the outer span derives from it. Frame spacing stays adjustable in design until shop drawings are released, which makes it the last dimension to settle. When the building clear-spans its width, holds floor stock or short rack runs and docks on one sidewall, standard frame spacing already works and a custom grid study adds little storage.
Which Columns Are Worth Paying to Move?
Two column positions weigh most on whether a warehouse column spacing plan pays off: the first interior line behind the docks and any column that breaks a rack row. Moving the first costs an outer span or a transfer beam. Moving the second costs a module allowance or a lost row.
Wider spacing is not automatically the better buy. On a 150 m wide church hall in Port Vila, five 30 m spans replaced a single clear span. Sections sized for cyclone wind across the full width would have pushed tonnage past what sea freight handles well. The final spans for any building still depend on local wind, snow and seismic loads confirmed by structural calculation.
Before proposing a span split, we verify two figures with the buyer: the staging depth behind the docks and the height of the top loaded rack level. With endwall docks and about 18 m of staging depth, ask for the omitted-column option to be priced alongside wider frames on your steel warehouse building quote. With sidewall docks, the outer span is the dimension to fix first.
FAQ
No single figure applies everywhere. Codes such as GB 51022 give recommended ranges for one frame type, and leasing markets advertise their own grids. Ask whether a quoted “standard” is a code range, a market grid or a supplier’s catalogue default.
Only as a structural modification. The frame it supported needs a transfer beam or truss spanning to the neighbouring columns. Those columns and their footings then need checking for the extra load. Designing the omission in before fabrication keeps the change on paper.
Wider spacing can reduce clear height when the eave height stays fixed. Longer spans and wider frame spacing usually raise rafter demand, which may mean deeper rafters or haunches. Check clear height under the lowest point of the frame, and raise the eave if the storage height needs it.
On column centrelines. GB 51022 measures span between column axes. The clear distance between two equal columns is therefore the grid dimension minus one column width.
Usually a stricter one. Stacker cranes and shuttles run in fixed aisles, and column lines have to stay outside them. Freeze the grid only once the aisle and rail layout is known.
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