Conventional structural steel is a frame of standard rolled shapes, such as W-beams, HSS and channels, designed by the project's engineer and fabricated to that design. A pre-engineered metal building (PEMB) is a complete building system from one manufacturer, typically tapered frames built up from plate, cold-formed girts and purlins, and the roof and wall cladding, designed and supplied as a package. Pre-engineered systems suit simple rectangular, single-storey, clear-span buildings. Conventional steel suits multi-storey buildings, irregular layouts, heavy or changing loads, and buildings that mix steel with concrete, masonry or wood.
We cover the cost drivers of a beam and column frame in our guide to steel-framed building cost. This post goes further on how the two systems differ in design, responsibility, scope and future changes.
How each system is built
Conventional structural steel
- Primary frame: columns and beams from standard hot-rolled sections, with braced bays or moment frames for wind and seismic loads.
- Roof and floors: steel deck on open web joists or beams, or other systems chosen by the designer.
- Envelope: chosen separately: metal panels, masonry, precast, curtain wall or anything else the architect specifies.
- Connections: bolted and welded details designed for the project.
Pre-engineered metal building
- Primary frame: rigid frames made by welding plate into I-shaped members, often tapered so they are deep where bending is highest and shallow elsewhere.
- Secondary framing: cold-formed Z and C purlins on the roof and girts on the walls, which also brace the frames.
- Envelope: usually the manufacturer's own metal roof and wall panels, trims and accessories.
- Connections: standardized bolted end-plate connections, so the building goes together quickly.
The 2024 Ontario Building Code covers both routes. Structural steel is designed to CSA S16 (Article 4.3.4.1), cold-formed members such as girts and purlins to CSA S136 (Article 4.3.4.2), and steel building systems must be made by manufacturers certified under CSA A660 (Article 4.3.4.3).
Who designs it and who is responsible
This is the difference owners notice least and should understand most.
- Conventional steel: the project's structural engineer designs the frame and is the engineer of record. The fabricator prepares shop drawings, often designs the connections to the loads the engineer specifies, and the engineer reviews them. Changes are handled through the engineer.
- Pre-engineered building: the manufacturer's engineers design the building for the loads and codes it was ordered to. The manufacturer supplies sealed design drawings and the anchor rod layout with the column reactions. A separate engineer, usually retained by the owner or builder, designs the foundations for those reactions.
With a PEMB, the order is effectively the design. Snow loads (including drifts against adjacent buildings), collateral loads for sprinklers and ducts, future rooftop units, door openings and any future expansion all need to be in the order. Anything left out isn't in the frames.
Where each system fits best
A pre-engineered building is often the better fit when:
- The building is a single-storey rectangle: warehouse, shop, storage, agricultural or recreational building.
- A wide clear span with no interior columns is the priority.
- The owner wants one supplier for the frame and envelope.
- The design is unlikely to change during the project.
Conventional structural steel is often the better fit when:
- The building has more than one storey, an irregular footprint, setbacks or level changes.
- There are heavy or concentrated loads: mezzanines, cranes, heavy mechanical equipment, storage racks tied to the structure.
- The envelope is masonry, precast or glazing that needs a stiffer frame.
- Steel is mixed with concrete, masonry or wood, or connects to an existing building.
- Future changes are likely, such as new openings, added floors or new equipment.
Many projects end up as a mix: a pre-engineered shell with a conventionally framed office mezzanine, canopy, crane runway, equipment platform or stair inside.
What "installed" really includes
Searches for "steel building installed prices" and "steel buildings installation included" reflect a real problem: quotes for steel buildings cover very different scopes. Before comparing numbers, put every quote on the same footing. Check whether each one includes:
- Foundations, including the footings, piers, slab and anchor rods.
- Engineering: building design drawings, foundation design and any site-specific load checks.
- Erection: labour, crane and equipment, and who sets the anchor rods.
- Envelope: roof and wall panels, insulation, trims, gutters and downspouts.
- Openings: overhead doors, man doors, windows, framed openings and their framing.
- Interior steel: mezzanines, stairs, guards, equipment supports.
- Permits, delivery, and site work, such as grading, services and paving.
For a conventional frame, the structural steel quote usually covers the frame, connections, shop drawings, fabrication, finish and delivery, with erection either included or priced separately. Foundations and the envelope are other trades. The same rule applies: get a written scope with inclusions and exclusions. Our post on structural steel cost per square foot explains why floor-area budgets mislead when the scope isn't clear.
Foundations and anchor rods
Foundations are where the two systems most often get out of step. A pre-engineered rigid frame pushes outwards at its base as well as down, and the foundation and slab have to be designed to resist that thrust, often with tie rods or reinforcing that links the column bases. The manufacturer provides the reactions; the foundation engineer turns them into footings, piers and anchor rods.
The anchor rods have to match the manufacturer's base plate layout exactly, and they are usually cast in long before the building arrives. Confirm who supplies and sets them, and get the final anchor rod drawing before the concrete is poured. The same discipline applies to a conventional frame, where the fabricator's base plates and the engineer's anchor rod plan have to agree.
Adding mezzanines and loads later
The economy of a pre-engineered building comes from frames designed closely to the loads ordered. That is a strength until the owner wants to add something:
- Mezzanines. A mezzanine that hangs on, or braces against, the building frames puts load into members that may not have been designed for it. A common approach is a freestanding mezzanine on its own columns, but the building manufacturer or an engineer should confirm either way. Our steel mezzanine guide covers the options.
- Rooftop units and hanging loads. Purlins and frames have limited reserve capacity. New equipment needs a check.
- New openings. Cutting girts or bracing to add a door or window changes how the building is braced.
- Expansions. End walls can be designed for future expansion if that is specified at the time of order.
Conventional frames are easier to modify because standard sections are simple to reinforce, extend and connect to, but any added load still needs an engineer's review. See can you cut or weld steel beams before altering any existing member.
How to decide
Price both early, while the design is still flexible:
- Describe the building fully: size, height, use, loads, cranes, mezzanines, openings, future plans and the envelope you want.
- Get a pre-engineered quote and a conventional steel budget on the same scope.
- Compare not just the frame, but foundations, envelope, schedule and the cost of likely future changes.
- Have your engineer or designer confirm the chosen route for permit drawings.
Conventional steel for your building
We fabricate conventional structural steel to engineers' drawings: beams, columns, posts, lintels, plates, channels and miscellaneous steel, for new buildings and for work inside existing ones. We provide in-house shop drawings, CWB certified welding, engineering services where projects need them, and supply and installation across the GTA and Ontario.
Send your drawings for a free take-off and quote, or see our steel products.
Frequently asked questions
What is the difference between structural steel and a pre-engineered metal building?
A conventional structural steel building uses standard rolled shapes such as W-beams and HSS, designed by the project's engineer and fabricated from shop drawings. A pre-engineered metal building (PEMB) is a complete system from one manufacturer: frames built from plate, often tapered, plus cold-formed girts and purlins and usually the cladding, designed and supplied as a package.
Is a pre-engineered steel building cheaper than structural steel?
For a simple, rectangular, single-storey building with a clear span, a pre-engineered system is often economical because the manufacturer optimizes every frame. For multi-storey buildings, irregular plans, heavy loads, cranes or mixed materials, a conventional frame is often the better value. Pricing both on your actual building is the only reliable comparison.
Does the price of a steel building include installation?
Often not. Many steel building quotes cover the manufactured package delivered to site, with foundations, erection, insulation, doors, permits and site work priced separately by other trades. Always ask for a written scope that lists what is included and excluded.
Do pre-engineered buildings need special certification in Ontario?
Yes. The 2024 Ontario Building Code requires steel building systems to be manufactured by companies certified under CSA A660, the standard for certification of manufacturers of steel building systems.
