Steel building cost per square metre
A budget guide of £150–£300+ per m² plus VAT, supplied and erected, for South Wales. Below is what sits inside that figure, what moves it from one end of the range to the other, and the cost it does not include — which on a sloping site is the one that catches people out.
- Budget guide
- £150–£300+
- Per m² of frame footprint, plus VAT.
- Basis
- Erected
- Quoted supplied and erected, not frame delivered on a lorry.
- Base included
- No
- Site strip, stone, slab and drainage are a separate trade.
- Measured on
- Span × length
- The frame footprint, not the slab — the slab is bigger.
The range is a budget guide published with the agreement of South West Steel Buildings, our building partner, who design, supply and erect the buildings. It is a guide and not a quote, and no building has ever been priced by multiplying two numbers together.
What the rate covers
Steel, purlins, side rails, cladding, roof lights, doors, and erection — the figure here is quoted supplied and erected rather than as a frame delivered on a lorry for your own team to put up. Supply-only is a normal way to buy a steel building and it is cheaper, so if that is what you are comparing against, you are not comparing like with like.
It is measured on the footprint of the frame — span multiplied by length. Not the slab area, which is larger once the oversail is added, and not the working platform, which is larger again. A 15 by 24 metre building is 360 square metres for the purposes of this rate whatever the concrete ends up measuring.
What it assumes is a level, prepared, cured base waiting when the erectors arrive. That assumption is doing an enormous amount of work, and it is the subject of the rest of this site.
Why one building is £150 and another is £300
The spread is not vagueness. It is five decisions you have not made yet, each of which moves the rate on its own.
Eaves height adds steel to every frame in the building and gives you no extra floor to divide it by, so it pushes the rate up faster than almost anything else. Span does the same: a wide clear span needs heavier sections the whole way through. How much of it is clad separates an open hay barn from a fully sheeted, insulated workshop — the same frame, a very different envelope. Doors are expensive, and roller shutters more so than sliding doors. And access decides the erection half of the figure: a site a lorry and a telehandler can work on comfortably is cheaper to build on than one they cannot.
The bottom of the range is a modest-height, open-sided, simple building on a good site. The top is tall, wide, fully clad and full of doors — and the supplier's own figure is open-ended at that end for a reason.
Why other guides say £250–£350
Search for this and the first figure is usually £250–£350 per square metre, from Checkatrade's cost guide. It is a fair figure for what it measures, which is not quite what this page measures.
It is a UK-wide average for steel framed buildings of every kind, houses included, and the guide itself says London and the South East run higher. It prices the frame erected with cladding and leaves the groundworks out, as ours does, but does not say whether VAT is in. Ours is agricultural, industrial and commercial portal frames only, in South Wales, supplied and erected, plus VAT, from South West Steel Buildings, who build them.
The two ranges overlap at the top. A simple farm building sits below theirs; a tall, fully clad unit with doors can sit inside it. Neither is a price for your building.
Costs in Wales that are not in either figure
Beyond the base, two Welsh costs catch people out because English guides never mention them. Construction of 100 m² or more needs its surface water drainage approved by the council's SuDS Approval Body, which means an application fee and, usually, drainage works — a soakaway, an attenuation pond or a tank for the roof water. And any building needs either a prior notification or a planning application, each with its own fee and drawings.
Both are set out on the planning guide for farm buildings in Wales. If the building is a roof over an existing yard, the yard roofing grant calculator shows what the Welsh Government would pay towards it.
What that looks like on real buildings
Frame figures are the guide range applied to the footprint, plus VAT and erected. The base figures are quantities from the calculator on this page, each at its own building's slab specification, on a level site with 200mm of topsoil. They are quantities rather than prices, because what a contractor charges you for them is a question for the contractor, not for us.
| Building | Footprint | Frame guide | Slab | Concrete | Type 1 |
|---|---|---|---|---|---|
| Double garage6 × 6 m | 36 m² | £5,400–£10,800 | 150 mm | 6.5 m³ | 12.1 t |
| Small machinery store12 × 18 m | 216 m² | £32,400–£64,800 | 200 mm | 47 m³ | 69.9 t |
| Mid-size farm building15 × 24 m | 360 m² | £54,000–£108,000 | 200 mm | 77.5 m³ | 115.9 t |
| Large machinery store18 × 30 m | 540 m² | £81,000–£162,000 | 200 mm | 115.5 m³ | 173.1 t |
Two things to take from that table. The frame range on a large building is wide enough to buy a second building, which is why a rate per square metre is a sense-check rather than a budget. And the concrete column is a real number with a real invoice behind it that appears in none of the frame figures.
The number that is not on the quote
A steel building quote is usually a fair price for what it covers. The problem is not the quote, it is the gap after it. Site strip, cut and fill, sub-base, slab, drainage and often an access track are a separate trade on a separate bill, and on a sloping Welsh field they can run to a third or more of what you end up spending.
A good supplier will hand you a foundation drawing, frequently free of charge, showing what the slab and the pads have to be. That is worth having and it is not a quantity. It does not tell you how many cubic metres of concrete you are ordering, how much stone, how much topsoil is coming off the field or how many lorries are taking it away — which is precisely the information you need to ask three contractors for a comparable price.
115.5 m³
Concrete for the slab alone under an 18 × 30 m building at 200 mm, plus around 173.1 tonnes of Type 1 beneath it. None of it is in the frame price.
The calculator below works that out for your own building, on your own slope, with your own depth of topsoil. It stops short of the pad foundations, which are sized by a structural engineer against your span, your height and what your ground will bear — anyone giving you a pad size without a design has guessed it.
Work out the base for your building
Pick the building type and the quantities follow. Change the fall across the site and the topsoil depth to your own field — those two move the earthworks more than the size of the building does.
What this does not work out: the pad foundations
The concrete pads the stanchions sit on are sized by a structural engineer, not by a formula. They change with the span, the eaves height, the wind loading on your particular site and what the ground will bear. Anyone quoting you a pad size without a design has guessed it.
Want this priced properly?
Send us the job and we'll get you engineered drawings and a quote for the frame — with the pad sizes this tool can't work out. The figures above go with your enquiry, so you don't have to type them again.
Every enquiry gets a reply the same day, and your figures go with it. The building itself is designed and priced by South West Steel Buildings, our building partner, so your details go to them too, and they will be in touch. How we handle your details.
Common questions
- How much does a steel building cost per square metre in the UK?
- As a budget guide, £150–£300+ per m² plus VAT, supplied and erected, for a steel frame building in South Wales. That is a range rather than a price because the things that move it are the things you have not decided yet: the span, the eaves height, how much of it is clad and how much is open, the doors, and whether a lorry can get to the site. The figure is measured on the footprint of the frame — span multiplied by length, and it does not include the base the building stands on — the site strip, sub-base, slab and drainage are a separate trade on a separate bill. Use it to sense-check a quote or to know whether a project is worth pursuing, not as a price.
- Does the price per square metre include the concrete base?
- No. A steel building rate covers the frame, purlins, side rails, cladding, roof lights, doors and — where it is quoted on that basis — erection. It assumes a level, prepared, cured base is waiting when the erectors arrive. Getting that base there is groundworks: site strip, cut and fill, sub-base, slab, drainage and often an access track, priced by a different trade at a different time. On a sloping site it is frequently a third or more of the total spend, and it is the part nobody gives you a quantity for. That is what the calculator on this site is for.
- Why do some guides say £250–£350 per square metre?
- That figure is from Checkatrade's national cost guide, and it is often the first number a search turns up. It is a UK average for steel framed buildings of all kinds — the same guide discusses steel framed houses — and it says costs in London and the South East run higher. It prices the frame erected with cladding, leaves out the groundworks as ours does, and does not say whether VAT is included. Ours is narrower on purpose: agricultural, industrial and commercial portal frames, in South Wales, supplied and erected, plus VAT, from the company that builds them. The two ranges overlap at the top. Neither is a price for your building.
- Is there a grant towards a steel building in Wales?
- For one kind of job, yes. The Welsh Government's Small Infrastructure grant pays £40 per square metre for a new roof over an existing livestock feeding area, gathering yard or solid manure store. It is a flat rate, not a share of the cost, and nothing can be ordered before the award letter. The yard roofing grant calculator on this site checks whether an area qualifies. New buildings and enclosed sheds are not covered by it.
- Why is the range so wide?
- Because a rate per square metre is an average of things that have not been decided yet. Eaves height adds steel to every frame in the building without adding a metre of floor. A wide clear span costs more per square metre than a narrow one. An open-sided hay barn and a fully clad insulated workshop are the same frame with very different envelopes. Doors are expensive and roller shutters more so. And a site a lorry and a telehandler cannot get to properly costs more to erect whatever is being put up. The bottom of the range is a simple, open, modest-height building on an easy site; the top is a tall, wide, fully clad one with doors, and it can go above that.
- Does a bigger building cost less per square metre?
- Usually yes, along the length rather than across the span. Frames sit at roughly 6 metre bay centres, and each bay you add reuses the same design, the same delivery and the same set-up on site, so the marginal bay is cheaper than the average one. Widening is the opposite: a bigger clear span needs heavier sections through the whole frame. That is why, when a budget is tight and more building is wanted, adding length is almost always better value than adding width. It applies to the base too — a longer slab is more concrete but the same site set-up.
- Is the price per square metre the same for a domestic garage?
- Not really, and small buildings tend to sit at or above the top of the range rather than the bottom. Delivery, erection and design are largely fixed costs, and on 36 square metres there is very little floor to spread them over. A double garage is a small job with the same overheads as a medium one. The guide range is still the right sense-check, but expect a domestic outbuilding to land at the expensive end of it per square metre while being a small number in total.
- How accurate is a per square metre figure for budgeting?
- It is good enough to decide whether to pursue a project and useless for committing to one. Treat it the way a builder treats a rate per square metre on a house: a way of establishing whether you are in the right order of magnitude before anyone spends time on drawings. The moment the building is specified — span, height, cladding, doors, access — the real number comes off a quote, and it can sit anywhere in the range or beyond it. What the rate is genuinely good for is catching a quote that is wildly out in either direction, and knowing to ask why.
Other buildings we cover
Same approach on each: what the building is, how it gets sized, where you stand on planning, and what the base underneath it comes to.
Machinery stores
Clear span, no posts in the way, and a floor that works harder than most. What it costs to put up and what it costs underneath.
Grain stores
Walls that get pushed from the inside, a floor that takes a loader, and a roof that rains on the crop if you get it wrong.
Livestock buildings
Housing that has to ventilate, drain and be scraped out. Falls, channels and the slurry rules — plus the 400 metre planning trap.
Farm workshops
Room to get a machine in and work all round it, with a floor specced for the jack rather than the tractor.
Hay barns
Open sides, air through it, and the lightest slab on the farm — if it needs one at all.
General purpose buildings
The shed that ends up doing everything. How to spec a building for a use you have not decided yet.
Stables and arenas
Stable blocks, American barns and indoor arenas. The same steel frame as a farm building — and a completely different planning position.
Garages and workshops
Steel framed garages, home workshops and man caves at the house. The eaves limit that decides whether you need planning permission, and the floor underneath.
Industrial units
Workshops, warehousing, trade counters and light manufacturing. Full planning, full Building Regs, and a yard that often costs more than the shed.
Get a real price for your building
A rate per square metre gets you to the right order of magnitude. Rough span and length is enough to start with, and you get engineered drawings and a price for the frame — including the pad foundation sizes no calculator can work out.