Steel Beam Sizes In Australia: A Sydney Guide To UB, UC, PFC, SHS And RHS
By Highlander Metals
Steel beam sizes on Australian engineering drawings identify the type, dimensions and nominal mass of structural steel sections. For example, 310UB40.4 means a Universal Beam with a nominal depth of 310 mm and mass of 40.4 kilograms per metre. Understanding these designations helps homeowners and builders discuss structural steel fabrication Sydney projects accurately. Whether you're removing a wall, extending your home or building a staircase, this guide explains the common steel sections specified on Sydney construction drawings.
What Do Steel Beam Sizes Mean on Your Engineer's Drawings?
Australian steel section designations identify a member's profile and key measurements. The designation 310UB40.4 describes a Universal Beam with a nominal depth of 310 millimetres and a mass of 40.4 kilograms per metre. Engineers use these designations to specify sections, while fabricators reference manufacturer tables to confirm their actual dimensions.
The designation breaks down as follows:
- 310: Nominal depth in millimetres.
- UB: Universal Beam.
- 40.4: Nominal mass in kilograms per metre.
Nominal and actual dimensions can differ. InfraBuild's published specifications confirm that 310UB40.4 measures 304 mm deep and 165 mm wide across its flanges.
These distinctions matter when checking available space, connections and fabrication requirements.
Universal Beams (UB): The Go-To Section for Sydney Extensions and Wall Removals
A Universal Beam (UB) is an I-shaped steel section commonly specified to support structural loads across openings. UBs frequently appear in Sydney renovation plans involving extensions, floor supports and load-bearing wall removals.
For example, a Sutherland Shire homeowner opening up a kitchen and living area may require a steel beam to support loads previously carried by a wall. Common steel I beam sizes include 200UB18.2, 250UB25.7 and 310UB40.4.
These examples illustrate Australian section naming conventions, not recommended sizes for particular openings. When comparing universal steel beam sizes, remember that beams with similar nominal depths can have different flange dimensions, thicknesses and structural properties.
The engineer determines the appropriate member. Highlander Metals then fabricates the specified beam and connections according to approved drawings.
Universal Columns (UC): When Your Build Needs Heavier Support
A Universal Column (UC) is an H-shaped structural section with relatively wide flanges. Engineers commonly specify UCs for supporting columns and structural frames, although their suitability depends on the design.
For example, 200UC46.2 identifies a Universal Column with a nominal depth of 200 mm and mass of 46.2 kg/m. A Sydney extension might require a UC beneath a beam, with engineered base plates and connections transferring loads into the supporting structure.
UCs and UBs are not interchangeable simply because their nominal depths appear similar. Their geometry and structural behaviour differ.
What Is a PFC in Structural Steel?
A Parallel Flange Channel (PFC) is a C-shaped structural steel section with a flat web and two parallel flanges extending in the same direction. Engineers specify PFCs for framing, edge supports, stair components and other applications where a channel profile suits the design. Unlike Universal Beams, PFCs have an open, asymmetrical cross-section.
A designation such as 150PFC identifies the nominal channel size. Because its shape differs from a UB, a PFC cannot be substituted for another section without engineering approval.
SHS, RHS and CHS: Hollow Sections for Posts, Frames and Stairs
Structural steel also includes hollow sections used for posts, frames and architectural features.
The main types are:
- SHS — Square Hollow Section: Equal external width and depth.
- RHS — Rectangular Hollow Section: Different external width and depth.
- CHS — Circular Hollow Section: Round hollow steel.
Hollow sections are generally designated by external dimensions and nominal wall thickness. For example, 100 × 100 × 5 SHS identifies a square section with 100 mm external sides and a 5 mm nominal wall thickness.
An RHS might be specified as
150 × 100 × 5 RHS. These sections commonly appear in engineered posts, architectural frames and components for
custom staircases. Their suitability depends on loading, connection details, appearance and the engineer's specification.
Common Steel Beam Sizes in Australia at a Glance
The following table provides examples of
structural steel section sizes found on Australian construction drawings.
| Section type | Drawing designation | Typical residential application |
|---|---|---|
| Universal Beam | 200UB18.2 | Engineered opening supports |
| Universal Beam | 250UB25.7 | Floor and roof support |
| Universal Beam | 310UB40.4 | Load-bearing beams |
| Universal Column | 200UC46.2 | Columns and supporting frames |
| Parallel Flange Channel | 150PFC | Edge framing and channels |
| Square Hollow Section | 100 × 100 × 5 SHS | Posts and frames |
| Rectangular Hollow Section | 150 × 100 × 5 RHS | Frames and stair components |
| Circular Hollow Section | 114.3 × 4.5 CHS | Round posts and supports |
These are identification examples, not structural sizing recommendations.
InfraBuild's
Universal Beam specifications confirm the listed UB designations and their dimensions. For complete section properties, consult the applicable current Australian manufacturer catalogue and approved engineering documentation. Availability and specifications should be checked before ordering.
Why Your Engineer Sets the Beam Size, Not a Size Chart
A steel section table identifies products; it cannot determine which beam is safe for your project. Engineers assess structural loads, support conditions, deflection, stability, connections and the building's overall load path.
AS 4100 — Steel Structures provides a relevant Australian structural design framework. Applying it requires engineering assessment rather than selecting a beam from a general sizing chart.
Two Sydney homes might have similarly sized wall openings but completely different roof structures, floor loads and foundations. Consequently, their required beams may differ.
Approved drawings may also specify steel grade, member orientation, base plates, bolts, welds and protective finishes. If a specified section is unavailable, any proposed substitution should return to the engineer for approval.
How Section Size Affects Fabrication, Finishing and Installation
Steel size influences fabrication, transport, lifting and installation planning. Longer or heavier members may require specialised handling. Restricted driveways, narrow access and established buildings can also complicate installation on Sydney renovation sites.
At Highlander Metals' Kirrawee workshop, projects begin with reviewing drawings, confirming measurements and understanding the required components. The fabrication process includes check measures and workshop drawings, with accredited partners preparing workshop drawings when required. Highlander Metals uses MIG (Metal Inert Gas), TIG (Tungsten Inert Gas) and stick welding methods according to project requirements.
Finishing is another consideration. Steel can be prepared for painting, powder coating or hot-dip galvanising, depending on the specified protective system.
For outdoor structures, including coastal Sydney projects, appropriate corrosion protection is particularly important. Galvanising can also affect fabrication details and scheduling.
Highlander Metals advises that smaller residential structural steel projects typically take one to three weeks from approved drawings, depending on complexity and material availability. Additional finishing requirements can extend the timeframe. Identifying access, lifting and finishing requirements early helps avoid unnecessary installation delays.
Getting Your Structural Steel Fabricated in Sydney
Once your engineer has specified the sections, accurate fabrication becomes the next priority. Highlander Metals provides structural steel fabrication in Sydney, manufacturing beams, columns, posts, brackets and complete frameworks from its Kirrawee workshop.
With more than 35 years of industry experience and a business trading since 2006, Highlander Metals supports residential and commercial construction throughout the Sutherland Shire, southern Sydney and surrounding areas.
Services include supply-only fabrication and supply-and-install arrangements, depending on project requirements. Buyers seeking standard steel products can also explore the Highlander Metals online shop.
For an accurate quotation, provide approved engineering drawings, project location, required finishes and relevant site-access details. Understanding
steel beam sizes helps you interpret your drawings, but the engineer's specification remains the foundation of a successful fabrication project.
Contact Highlander Metals on
(02) 9540 2508 or submit an enquiry through the
structural steel quote form to discuss your Sydney project.
Frequently Asked Questions
What does UB mean in structural steel?
UB means Universal Beam, an I-shaped structural section. Its Australian designation typically identifies nominal depth and mass per metre.
What is the difference between UB and UC steel?
Universal Beams generally have deeper, narrower profiles. Universal Columns have relatively wider flanges and are commonly specified for supporting columns.
What is PFC steel used for?
Parallel Flange Channels are used in engineered framing, edge supports and other structural applications. Their suitability depends on the design.
How do I read RHS and SHS sizes?
The designation generally identifies external dimensions followed by nominal wall thickness. For example, 100 × 100 × 5 SHS describes a square section with 100 mm sides and a 5 mm wall.
Can I choose a smaller steel beam to save money?
Not without engineering approval. Beam sizing depends on structural requirements, and substituting a section can compromise the design.
How long does structural steel fabrication take?
Highlander Metals indicates that smaller residential jobs typically take one to three weeks from approved drawings. Complexity, materials and finishing can affect delivery.
