Pre-Engineered Buildings (PEB) for Factories and Warehouses

Thirty metres without a single column, a roof nine metres up, and a frame that arrives on trucks as numbered pieces and is standing within a few weeks: that is the promise that has made the pre-engineered building, or PEB, the default shell for new factories and warehouses across India. Drive along any industrial road around Surat, Vapi, Sanand or Chakan and most of the new sheds are PEB — tapered steel portal frames, light cold-formed purlins, and colour-coated metal sheets on the roof and walls.

The speed is real, but so are the failures. Owners buy a shed by the square foot, compare three quotations on price alone, and discover later that one supplier designed for a lower wind speed, another left out the crane, and none of them included the floor slab that the forklifts will run on for the next thirty years. Roofs drum in the rain and turn the shed into an oven in May. Anchor bolts are cast a few millimetres out and the frames go up forced into place. None of these are failures of the PEB system; they are failures of the brief.

This guide explains how a PEB works, what the structural engineer and supplier must be told, how spans, bays and heights are chosen, what happens at the foundation, how to make a metal shed comfortable in a Gujarat summer, and what the whole package costs. It is general guidance for owners and planners: every PEB must be designed, checked and supervised by qualified structural engineers to the applicable Indian Standards.

What "pre-engineered" actually means

A conventional steel shed is built from standard hot-rolled sections — I-beams, channels and angles in fixed sizes — fabricated in a local workshop or on site, often with trusses for the roof. The section is the same size along its whole length, even where the bending is small. A pre-engineered building inverts that logic. Each primary frame is designed for the project's span, height and loads, and the column and rafter are built up from steel plates welded into an I-shape whose depth varies along the length: deep at the knee where the bending is greatest, shallower towards the base and the ridge where it is less. Steel goes only where the forces need it.

The second half of the system is the secondary steel: purlins on the roof and girts on the walls, cold-rolled from thin galvanised or painted strip into Z or C shapes. They are light, they lap over the frames to act continuously, and they carry the sheeting. Everything — frames, purlins, bracing, sheeting, flashings, gutters and bolts — is designed, detailed, cut, punched and painted in the supplier's plant, then shipped as a kit with erection drawings. On site there is no welding of primary members, only bolting.

How PEB arrived in Indian industry

The metal building system grew up in the United States in the twentieth century, where manufacturers standardised the design of tapered frames and cold-formed secondaries and published common practice through the Metal Building Manufacturers Association. In India, industrial sheds were long built of RCC, of steel trusses on brick or RCC columns, or of asbestos-cement sheets on steel trusses. From the 1990s, and especially through the 2000s, Indian and international PEB manufacturers set up plants, and the system spread quickly through warehousing, logistics parks, engineering units, textile processing and food plants. Today most new single-storey industrial sheds are PEB or conventional steel, while RCC remains common for multi-storey units, heavy process buildings and the office and welfare blocks in front of them.

Anatomy of a PEB frame

A single-span PEB is a series of identical portal frames standing at regular intervals — the bays — tied together by purlins, girts and bracing. The portal frame is the main structure: two tapered columns and two tapered rafters, joined by bolted end-plate connections at the knee (the haunch) and at the ridge. The frame resists vertical loads by bending and resists wind across the building by acting as a rigid portal. Wind and earthquake forces along the length of the building are taken by diagonal bracing — rods, cables or angles — in at least one bay of the roof and walls, usually the end bays or a bay near the middle.

Two details in Fig. 1 matter for planning. First, clear height is measured to the underside of the deepest part of the rafter at the haunch, not to the eave line on the drawing, and the difference can be 600–1200 mm. Racking, crane hooks, sprinklers and light fittings all need the clear figure. Second, most PEB column bases are designed as pinned: the base plate and anchor bolts hold the column in place but are not designed to resist large bending. That keeps foundations smaller, but the frame relies on the haunch connection for its stiffness, so those bolts must be the specified grade, fully tightened and inspected.

Spans, bays and heights: sizing the shed to the process

A shed should be drawn around the work that will happen inside it, not around a round number. Start with the process line or racking layout, the largest machine and its maintenance space, the truck dock positions, and any overhead crane. Then test two or three structural grids against that layout. Every internal column removed makes the floor more flexible but adds steel to the frame; every extra metre of height adds steel to the columns and wall area to the cladding. The structural engineer and the PEB supplier can price these options quickly, and the comparison usually pays for itself.

Span is the biggest decision. A single clear span of 20–40 m is routine for PEB, and wider spans are built, but beyond the low thirties many owners find that a multi-span frame with one or two lines of internal columns is lighter and cheaper, provided the columns fall in the gaps between racks or along aisles. Bay spacing — the distance between frames — commonly ranges from about 6 to 9 m; longer bays need deeper purlins, and the bay should suit dock doors, rack runs and the position of skylights. Clear height follows the use: about 6 m for light assembly, 7.5–9 m for general manufacturing, and more for high-bay warehouses or sheds with cranes.

Loads, codes and the design brief

The most important document in a PEB purchase is not the quotation but the design basis — a short statement of the codes, loads and assumptions on which the supplier has designed the building. Two quotations can differ by a large amount simply because one has assumed a lower wind speed, a lighter roof live load or no collateral load for services. Ask every supplier to submit the same design basis, and have it reviewed by an independent structural engineer appointed by the owner before comparing prices.

In India, steel design is generally to IS 800:2007, the general code for construction in steel, and cold-formed purlins and girts are commonly checked to IS 801 or to the international cold-formed codes the supplier uses. Loads come from IS 875: Part 1 for dead loads, Part 2 for imposed loads, and Part 3 for wind. Earthquake forces come from IS 1893 Part 1, and steel for frames is generally to IS 2062. Many PEB suppliers also refer to the Metal Building Manufacturers Association manual or American steel codes for some checks; that is common, but the owner's engineer should confirm that the design meets the Indian Standards and local approvals. The National Building Code of India 2016, Part 6 (Structural Design) and Part 4 (Fire and Life Safety) set the wider framework.

Wind decides most PEB designs

A light steel shed weighs little, so wind — not gravity — often governs its design. IS 875 Part 3 gives basic wind speeds that range from 33 m/s to 55 m/s across India, and coastal Gujarat sits towards the higher end. The design wind pressure then depends on terrain, height, the shape of the building and, crucially, whether large openings such as dock doors could be open in a storm, which raises internal pressure and the uplift on the roof. Many shed failures in cyclones begin at the edges and corners of the roof, at canopies, or where sheet fasteners pull through. The wind assumptions, the treatment of openings and the fastener spacing at roof edges are worth checking line by line.

Foundations, anchor bolts and the floor slab

The PEB supplier designs the steel; the foundations are usually designed by the owner's structural engineer from the support reactions the supplier provides, together with a soil investigation. Because the columns are light and the roof is light, uplift and horizontal thrust can matter as much as downward load, so the foundation must hold the column down and stop it sliding as well as hold it up. In black cotton soils, common across parts of Gujarat and Maharashtra, foundations and plinth beams need particular attention to swelling and shrinkage.

Anchor bolts are where site and factory meet. They are cast into the pedestals weeks before the steel arrives, and if they are a few millimetres out of position, out of level or at the wrong projection, the base plates will not fit. The usual practice is to fix the bolts with a steel template, check them with a total station or careful taping against the grid, record the as-built positions, and send that record to the supplier before dispatch. The gap under the base plate is filled with a non-shrink grout after the frame is aligned.

The floor slab deserves as much engineering as the frame, because it carries the heaviest and most repeated loads in the building: rack legs, forklift wheels and stacked goods. Industrial floors are commonly 150–250 mm reinforced or fibre-reinforced concrete on a well-compacted sub-base, with joints planned so that cracks form where they are intended. The design depends on rack leg loads, forklift axle loads and the soil, so the racking supplier's leg loads should reach the engineer before the slab is designed. Machine foundations for presses, looms or compressors are usually separate blocks isolated from the slab.

Heat, light and air under a metal roof

A bare metal roof absorbs a great deal of sun, and the underside can become much hotter than the outside air on a still afternoon. Workers below feel that heat as radiation from overhead, even when the air temperature is tolerable. In a Surat or Ahmedabad summer this is the single biggest complaint about PEB sheds, and it is cheaper to solve at design stage than after the shed is full of people and stock. The Factories Act, 1948, and state factory rules also set requirements for ventilation, space per worker and reasonable temperatures in workrooms, which the factory's consultant should check.

Four measures do most of the work. Insulation under or within the roof — a glass-wool or rock-wool blanket with a reflective facing, or a sandwich panel with a PUF or PIR core — cuts the radiant heat reaching the floor. A light, reflective roof colour lowers the sheet temperature. Ventilation lets the hot air that collects under the ridge escape: continuous ridge ventilators or turbo ventilators at the top, with low-level louvres or openings on the walls to draw fresh air in. And daylight panels — polycarbonate or fibreglass sheets that match the roof profile — reduce daytime electric lighting, but should be limited and spread out, because too many skylights let in heat and glare as well as light.

What a PEB shed costs and how long it takes

PEB quotations are usually given as a lump sum for the steel building, often explained as a rate per kilogram of steel or per square metre of floor. Steel consumption for a simple shed without cranes is often quoted in the region of 20–40 kg per square metre of floor for primary and secondary steel together, rising with span, height, wind speed, crane loads and mezzanines; that range is indicative and the design decides the real figure. This blog's steel structure guide uses about ₹90–150 per kg for fabricated, painted and erected structural steel, and PEB packages fall within a similar band depending on steel prices, paint systems and site access.

The steel is only part of the cost. The table below builds up an indicative October 2026 cost for a simple PEB warehouse or factory shed per square foot of floor area, excluding land, approvals, the admin block, electrical and fire-fighting systems, cranes, racking and GST. It is a planning band, not a quotation; real prices move with steel markets and the design brief.

A worked example: the 30 × 60 m warehouse in Fig. 2 has about 1,800 m², or roughly 19,400 sq ft, of floor. At the band above, the shell would cost roughly ₹1.3–2.7 crore before electrical work, fire protection, racking, the office block and GST. The low end assumes a modest wind zone, no crane, single-skin sheeting and a good soil; the high end reflects higher wind, insulated roofing, more doors and a heavier slab. The office in the front bay is priced separately — this blog's factory office guide uses about ₹800–2,000 per sq ft for office interiors.

These stages overlap, so a simple warehouse can often be handed over in roughly four to six months from a clear brief, depending on approvals, monsoon and steel supply. The time saved compared with an RCC shed is real, but it is lost quickly if the design basis is changed after fabrication starts.

Where PEB is heading

Three shifts are already visible on Indian industrial sites. Roofs are becoming power plants: rooftop solar is now a normal part of new sheds, and the purlins, sheet fixings and collateral load must be designed for it from the start rather than added later. Comfort is getting attention, with insulated panels, ridge ventilation and large fans increasingly specified so that workers can stay productive through the summer. And warehouses are getting taller and more automated, with very narrow aisle racking and higher clear heights that push frame design, floor flatness and fire protection together.

Green-building rating systems from IGBC and GRIHA include factory and warehouse categories, and steel's recyclability, daylighting, rainwater harvesting from large roofs and energy efficiency are scored. Some manufacturers are also experimenting with lower-carbon steel and with modular, demountable sheds for logistics tenants who may move after a lease. What will not change is the basic discipline: a clear brief, a checked design and careful erection.

Rules for buying a PEB building

• Draw the process, racking or crane layout first, and test two or three structural grids against it before asking for prices.
• Give every supplier the same written design basis — codes, wind speed, live and collateral loads, seismic zone, crane data, deflection limits — and compare like with like.
• Appoint an independent licensed structural engineer to review the supplier's calculations and drawings, design the foundations and inspect erection.
• Plan for solar panels, sprinkler pipes, ducts and lights as collateral load now; adding them later can overload purlins.
• Fix anchor bolts with templates, survey them, and send the as-built record to the supplier before dispatch.
• Insulate the roof, ventilate at the ridge and bring air in low; limit and spread skylights.
• Design the floor slab for real rack leg and forklift loads, with planned joints and isolated machine foundations.
• Keep braced bays free of future doors, and design one end wall as a future extension line.
• Ask for the paint system, sheet coating class and a maintenance schedule, especially in coastal or chemical environments.

Frequently asked questions

Is a PEB shed cheaper than an RCC building?

For single-storey sheds with wide spans, PEB is usually faster and often more economical, because the frames use steel only where it is needed and avoid formwork. For multi-storey buildings, heavy floor loads or small spans, RCC can be the better choice. Many factories use both: a PEB shed with an RCC admin and welfare block in front.

What is the maximum span of a PEB building?

Single clear spans of 20–40 m are routine, and wider spans are built for hangars and large warehouses. Beyond the low thirties, a multi-span frame with a line of internal columns is often lighter and cheaper if the columns can sit along aisles. The right span comes from the layout and a cost comparison by the structural engineer.

Which IS codes apply to pre-engineered buildings?

Steel design is generally to IS 800:2007, with loads from IS 875 Part 1 (dead), Part 2 (imposed) and Part 3 (wind), earthquake forces from IS 1893 Part 1, and structural steel to IS 2062. Cold-formed secondary members are checked to IS 801 or the supplier's international code. NBC 2016 Parts 4 and 6 and local building rules also apply. A licensed structural engineer should confirm the design basis.

How do you reduce heat in a PEB shed?

Insulate the roof with a reflective blanket or insulated panels, choose a light roof colour, fit ridge or turbo ventilators with low-level wall louvres so hot air can escape, spread a limited number of skylights, and add large slow-speed fans or evaporative cooling where work is heavy. These are cheapest when designed in from the start.

How long does a PEB building last?

A well-designed, well-painted PEB on good foundations can serve for decades. Its life depends mostly on corrosion protection, sheet coating, roof maintenance and keeping water away from column bases. Coastal and chemical environments need better paint systems or galvanising, and periodic inspection of bolts, sheets and gutters.