Steel Tonnage Estimator

Sizing the frame before drawings exist · industrial buildings for Africa and South America

Preliminary estimate · not a quotation

An engineering calculator and an unfolded portal frame drawing side by side on a dark workbench

Design by Johnny Export engineer at Hebei Hongji Shunda, writing on steel buildings for Africa and South America.

Building parameters

Clear span m

Length m

Eave height m

Bay spacing m

Door width m

Door height m

Overhead crane t

Hook height m

Walls and roof cladding

Seismic / snow governing hazard

Result

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— – —kg/m²

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Floor area

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Total steel

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Main frame weight

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Component	kg/m²	Tonnes

Send the site and what it will hold. We confirm the frame.

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How this number is built

Not settled by this estimate

Seismic and snow loads — the selector above carries a coarse band, not a calculation. Our archive does contain such jobs: a 7,392 m² high-seismic building at 113.7 kg/m² overall, and an 800 m² mountain job under heavy snow at 102.7. Both are archive jobs; the 800 m² one predates the current 1,000 m² minimum and is shown as record only. What the band cannot tell you is the shape a seismic frame takes — moment connections and bracing change, not just member size. The local code decides, and it must be read before this figure is quoted.
Wind is not modelled at all. No wind factor is applied above. The site's maximum wind speed over the past 50 years is one of the most important inputs to steel weight, and in an exposed location it moves the tonnage more than span does. It has to come from the local code and the site record, not from this page.
Crane duty class — a 10 t crane on light duty and a 10 t crane on continuous duty are different structures.
Mezzanines, platforms, stairs and embedded items — priced by scope and deliberately left out of this figure.
Open-sided or part-clad buildings — the selector above covers single skin and insulated panels. A building with no wall cladding at all carries still less wall purlin than either, and this page has no separate band for it.

Read this before you use the number Maximum wind speed at the build site over the past 50 years is one of the most important parameters for steel weight. No wind factor is applied in this model. The figures above are a rough estimate for reference only — not a design basis.

Cladding is the second input that moves this figure most Single skin and insulated panels do not carry the same steel — the insulated buildings we have delivered run heavier purlins, an extra liner and more wall purlin. Two 2,000 m² jobs sat about 21 kg/m² apart for this reason: 50.1 overall for an insulated warehouse on a 40 m clear span, 29.1 for a single-skin job on a 25 m clear span with a mid-column line. Part of that gap is the frame (31.7 against 19.0 main), part is the cladding. Check that the selector matches what the customer is actually buying.

Geometry check — can it be built this way?

does not change the tonnage

What this panel does and does not do It answers one question only: does the door and the crane physically fit inside the frame you described? It never changes the tonnage above. Column depth and haunch depth are estimated from the span, so the real limits come from the structural design — treat a pass here as "no obvious clash", not as a clearance drawing.

Bay spacing and the tonnage figure Steel weight per m² barely moves between 5 m and 9 m bays — more frames per metre, but each frame carries proportionally less, so it very nearly cancels out. No bay-spacing factor is applied to the number above, and none should be inferred. The 38 projects behind Table 1 all sit at 6–9 m bays, so a 5 m bay is outside that record — it changes nothing in the tonnage, but read Table 1 with that in mind. Bay spacing does something far more concrete: it sets the widest door you can have, because the opening has to fit between two columns.

Reference — measured on delivered projects

Table 1 · Total steel by floor area, ordinary conditions, no crane, **all cladding types mixed** (38 delivered projects) — the row matching your input is highlighted
Floor area	Projects	Range kg/m²	Median	Why it reads that way
Below 200 m²Not taken	—	73 – 196	—	Sections hit minimum sizes; weight per m² stops responding to area
200 – 500 m²Not taken	6	56 – 107	67.6	Still partly minimum-section driven
500 – 1,000 m²Not taken	11	29 – 103	58.7	Transition band
1,000 – 2,000 m²	8	42 – 100	51.1	Smallest size we take; the stable band starts here
2,000 – 4,000 m²	10	37 – 109	51.2	Stable
Above 4,000 m²	3	24 – 56	52.9	Stable; the top of the range is a hurricane-zone job

Minimum project size · 1,000 m² of floor area

Below 1,000 m² we do not take the project. The first three rows of Table 1 are still shown because they are the evidence for that rule, not because those sizes are in scope.
Why the line sits there: under 1,000 m² the rafters, columns and purlins are already at the smallest sections we can specify, so weight per m² stops falling and turns back up. The first row of Table 1 reads 73 – 196 kg/m² — the highest figure in the table — on the smallest buildings. Steel is being wasted per m² at that size, and the owner pays for that waste with no structural return.
Archive jobs under that size are record only. Projects below 1,000 m² in our files predate the current minimum. They are history, not an offer to build at that size.
Ancillary units are taken with the main project, not on their own. A pump house, a switchgear room or a weighbridge office inside a plant we are already building is taken as part of that contract, and the 1,000 m² line is not applied to it in isolation. A small building that arrives as a standalone enquiry is below the minimum and is not quoted.

Table 1 · read this before quoting it Maximum wind speed at the build site over the past 50 years is one of the most important parameters for steel weight. These ranges carry no wind factor — a site in a hurricane belt will sit above them. Rough estimate only.

Table 1B · **Single skin, no insulation** — total steel by floor area (3 delivered projects) — the row matching your input is highlighted when single skin is selected
Floor area	Projects	Range kg/m²	What the record is
Below 200 m²Not taken	—	by tonnage floor	No single-skin job this small; the minimum-section floor is applied instead
200 – 500 m²Not taken	1	34.7	One job at 468 m², 3 m brick wall below the sheeting
500 – 1,000 m²Not taken	0	—	No measured job in this band; the figure is interpolated
1,000 – 2,000 m²	1	29.5	One job at 1,275 m²
2,000 – 4,000 m²	1	29.1	One job at 2,000 m², mid-column line at 25 m clear span
Above 4,000 m²	0	—	No measured job in this band; the figure is carried over

Table 1B · this one rests on three jobs only Maximum wind speed at the build site over the past 50 years is one of the most important parameters for steel weight, and no wind factor is applied here either. Three delivered jobs is a thin record: read the top of the range as the safer number, and treat the 500–1,000 m² band as interpolated rather than measured.

Table 2 · Three delivered buildings, taken apart line by line
Building	Width	Area	Configuration	Main frame	Total kg/m²
Sawmill shed, Paramaribo	35 m clear	1,750 m²	5 t crane, open sided, 6 m eave	20.6	48.0
Plant building, Brazil	70 m total	6,860 m²	7 m bays, internal columns, single storey	29.9	52.9
Warehouse, 60.35 × 40.8	40 m clear	2,462 m²	Single storey, no crane	34.7	44.1

Table 2 · what these three buildings had in common Maximum wind speed at the build site over the past 50 years is one of the most important parameters for steel weight, and these three were all built below hurricane exposure. Read them as a starting point, not a target.

Two things these tables show

70 m of total width does not cost more steel than 40 m of clear span. The Brazilian building spans 70 m across with internal columns and lands at 52.9 kg/m². A true 40 m clear span lands at 44.1 — but its main frame alone is 34.7, heavier than the Brazilian building's 29.9. The premium for going column-free sits in the frame, not in the roof.
Area matters more than span, up to about 1,000 m². Below that the members hit minimum sections and the weight per m² rises for reasons that have nothing to do with the design being heavy.
Cladding type is worth more than a whole area band. Two jobs of the same 2,000 m² came in at 50.1 and 29.1 kg/m² — an insulated warehouse and a single-skin job. Cladding and frame span together account for that gap, which is why the estimator asks for the cladding type before it answers.

Widths 8–120 m · bays 6–9 m · no prices appear on this page by design · no wind factor is applied, so confirm the site's 50-year maximum wind speed · every figure is an estimate until drawings and a site-specific load set exist.
Steel structures for mining, oil & gas, energy, logistics and EPC — Africa and South America.