When a PEB quotation comes in higher than expected, the instinct is to blame the steel rate. Usually the steel rate is not the problem. Cost accumulates in the design decisions taken before anyone priced a kilogram of steel, and those are the ones still open to you.

The five decisions that set the price

1. Clear span. This is the dominant variable. A 30 m clear span does not cost 25% more than a 24 m span — it can cost 40% more, because rafter depth, plate thickness and tonnage per square metre all move non-linearly. Adding one internal column line at 24 m is often the single largest saving available on a project, and it is a layout decision, not a steel-buying one.

2. Bay spacing. Wider bays mean fewer frames and fewer foundations, but heavier individual members. There is a sweet spot — usually 6 to 8 metres for industrial sheds — and pushing past it to save on foundations usually costs more in steel.

3. Eave height. Height adds column length and wind exposure. It also adds wall area that carries no roof, so a tall narrow building costs more per square foot of covered area than its roof would suggest. Specify the height the operation needs, not the height that looks generous on a drawing.

4. Crane provision. A gantry runway is a moving point load travelling through the frame. It changes column design, bracing and foundations. If there is any chance a crane will be needed in five years, design for it now: retrofitting a runway into a frame that was never designed for one is expensive, and sometimes impossible.

5. Scope boundary. "Supply only", "supply and erection" and "turnkey including civil" are three different products with three different prices. Most of the gap between a suspiciously cheap quote and an expensive one is this line, not the steel.

Where the money hides in a "cheap" quote

A lower bottom line frequently carries one of these:

  • Thinner sheeting. 0.40 mm instead of 0.47 mm is a real cost cut and a real reduction in life, especially near the coast.
  • Lighter purlins or wider purlin spacing. Cheaper now, more deflection over time, and a roof that moves under wind load.
  • Excluded foundations or erection. Compare the scope list, not the total.
  • No bracing allowance. Secondary bracing is easy to omit from a drawing and hard to omit from a building.
  • A primer-only coating. Adequate inland, optimistic within 20 km of the coast.

None of these are necessarily dishonest — they are choices. The problem is when they are made silently.

What to ask for in writing

Before comparing two quotations, request the same four things from each bidder:

  1. Specified steel tonnage and the grade used.
  2. Sheet thickness (TCT, not just "colour coated") and the coating specification.
  3. A scope list stating explicitly what is included and what is excluded.
  4. The design basis — the codes followed and the basic wind speed assumed.

Two quotes for the same building with the same tonnage and the same scope should land within a few percent of each other. If they differ by 25%, one of them is a different building.

Levers that genuinely reduce cost

These are legitimate, in order of effect:

  • Add a column line to reduce the clear span, if the operation allows it.
  • Reduce eave height to what the process needs.
  • Standardise bays across the building rather than varying them.
  • Choose one cladding specification for the whole envelope instead of mixing.
  • Increase quantity. A schedule rate on 90,000 sq ft is genuinely better than on 15,000 — it is worth asking what the next price break is.
  • Build the crane provision in at design stage if you expect to need it, rather than retrofitting.

Levers that cost you more later

  • Thinning the sheet or the coating on a coastal site.
  • Skipping bracing or wind bracing to save a few tonnes.
  • Deferring foundations work to a separate contractor without coordinating the anchor bolt layout.
  • Buying the cheapest erection crew for a frame that was designed to tight tolerances.

The pattern is consistent: save on layout, not on specification. A building that is cheap because it was designed efficiently will perform. A building that is cheap because it was specified thinly will cost the difference back in maintenance, and it will do so in year five, when nobody is comparing quotations any more.

If you want an order-of-magnitude figure before starting the drawing work, the cost estimator on this site models the same variables described above.