The shape of a roof influences far more than the appearance of a building. It affects ceiling height, usable roof space, drainage, spans, load paths and how the roof connects to the walls below.
Understanding the main types of steel roof trusses can help homeowners, builders and designers make better decisions before engineering and manufacturing begin.
Steel roof trusses are used in homes, extensions, garages, multi-unit developments and some commercial buildings. The appropriate system depends on the architectural plans, roof pitch, span, roof covering, wind classification, support locations and required loads.
A truss should therefore be selected for its structural and practical requirements—not simply because its shape looks appealing.
Understanding the Different Types of Steel Roof Trusses
A roof truss is an engineered framework that supports the roof and transfers loads to the supporting structure below.
The top chords generally follow the roof slope, while the bottom chord may support a ceiling or form part of the internal structure. Diagonal and vertical webs connect the chords and help distribute structural forces.
The term used to describe a truss can refer to the overall roof shape, the ceiling profile or the structural role it performs. For example, a hip roof is a roof system that may contain several different truss configurations rather than one single “hip truss”.
Every project requires engineering appropriate to the building and site, with approved drawings used for manufacture and installation.
1. Gable or Common Trusses
A gable roof has two sloping sides that meet at a central ridge. The ends of the building typically form triangular gable walls.
Common trusses are repeated at designed centres along the main roof area and provide a relatively straightforward way to create this roof form.
Gable roofs are widely used in residential construction because they are relatively simple to plan and can accommodate a range of roof pitches and coverings.
They can also provide useful roof space for insulation, electrical services and other building requirements.
However, the simplicity of the roof shape does not remove the need for engineering. Bracing, tie-downs, connections and support points must be designed for the specific span, loads and site wind conditions.
Common applications: Houses, garages, extensions and straightforward residential roof designs.
2. Hip Roof Truss Systems
A hip roof slopes down towards the walls on all sides rather than ending with a vertical gable.
This creates a balanced roof profile that is common across many traditional and contemporary Australian homes.
A steel hip roof can incorporate several truss and framing components, including common trusses, truncated trusses, girder trusses and smaller jack or creeper members. The exact arrangement depends on the building’s geometry.
Hip roofs require careful coordination because loads can be concentrated around girder trusses, valleys and other junctions.
Accurate architectural and structural drawings allow each component to be engineered, manufactured, labelled and positioned correctly.
Common applications: Residential homes, extensions and buildings where a balanced roof profile is preferred.
3. Skillion or Mono-Pitch Trusses
A skillion roof, also called a mono-pitch roof, has a single continuous slope rather than two opposing roof planes.
Its clean, modern appearance makes it popular for contemporary homes, extensions, studios, garages and outdoor structures.
One advantage is the opportunity to create a higher ceiling or clerestory windows along the raised side. The single roof fall can also simplify the direction of rainwater drainage.
However, the roof pitch, guttering, downpipes and stormwater strategy need to be considered together.
Because the two sides of the roof are structurally different, the high and low supports can experience different forces. Engineering must account for the roof span, wind uplift, roof covering, ceiling loads and connections to the supporting walls.
Common applications: Modern homes, extensions, studios, garages and outdoor areas.
4. Scissor Trusses
Scissor trusses are designed to create a sloping internal ceiling rather than a conventional flat ceiling.
The lower chords rise towards the centre of the truss, creating the characteristic shape that gives the system its name.
This configuration can create a cathedral-style or vaulted ceiling in areas such as living rooms, bedrooms and entrances without requiring conventional flat ceiling framing.
The roof pitch and internal ceiling pitch are different, so the truss must be engineered specifically for the required geometry.
Designers also need to consider insulation, lighting, ducted services, ceiling finishes and the forces transferred to the supporting walls.
Common applications: Open-plan living areas, feature ceilings, bedrooms and entry spaces.
5. Parallel Chord or Flat Trusses
Parallel chord trusses have top and bottom chords that run approximately parallel to each other.
They can be useful where a low-pitch roof, flat ceiling or additional depth for services is required. They are also used in some commercial structures, awnings and unusual roof configurations.
A roof described as “flat” still requires appropriate falls and drainage. Water management must be considered as part of the overall roof design.
Parallel chord configurations can also be useful for certain longer or unusual spans, but their depth, web arrangement, bearings and connections must be engineered for the actual loads.
One important rule applies to all engineered trusses: members must not be cut, drilled, removed or altered on site without approval from the relevant engineer or truss designer.
Common applications: Low-pitch roofs, flat-ceiling areas, commercial structures, awnings and specialised spans.
6. Cantilever Trusses
A cantilever truss extends beyond its supporting point without requiring a post directly beneath the outer end.
This can be used to create deeper eaves, covered entries, architectural projections and other overhangs.
The cantilevered section relies on the structure behind the support to resist the resulting forces. Its projection, loads, wind uplift and connections therefore need to be incorporated into the engineering from the beginning.
Cantilevers should be clearly shown on the architectural and structural drawings. Adding a larger overhang after the trusses have already been designed or manufactured can significantly change the loads and may require redesign.
Common applications: Deep eaves, covered entrances, architectural projections and selected verandah designs.
7. Attic or Room-in-Roof Trusses
Attic trusses are designed to leave usable space within the roof structure.
Depending on the design and applicable approvals, this space may be used for storage, a loft or an additional room.
Unlike a standard roof truss, an attic configuration must account for the additional loads and requirements associated with usable floor space.
The design may need to accommodate:
- Floor loads
- Stairs or access
- Insulation
- Windows
- Electrical and plumbing services
- Ventilation
- Fire and building requirements
Standard trusses must never have webs removed simply to create additional room.
Where an attic space is required, specialist trusses, separate floor framing or a combined structural solution may be necessary.
Common applications: Lofts, storage areas and buildings requiring additional usable roof space.
Can One Building Use More Than One Truss Type?
Yes. In fact, many buildings use several truss configurations within the same roof system.
For example, a home may have:
- A hip roof over the main living areas
- A skillion roof over an extension
- Scissor trusses over a feature living room
- Cantilevered sections for deep eaves
- Girder trusses supporting roof junctions
Combining different types of steel roof trusses requires careful coordination.
Valleys, ridges, support walls, ceiling transitions and changes in roof pitch must all align. Loads from one section may be transferred through another truss, beam or supporting wall.
The final truss layout should show where each component belongs and how the complete roof structure works together.
Architectural and structural drawings should be coordinated before manufacture, particularly where ceiling heights, roof pitches or support locations change.
Which Steel Roof Truss Type Is Best for a House?
There is no single “best” truss type for every house.
Gable and hip systems suit many conventional residential designs, while skillion and scissor configurations can create distinctive rooflines or higher ceilings. Parallel chord, cantilever and attic systems can address more specialised requirements.
When comparing the types of steel roof trusses, consider:
- Overall roof shape and architectural design
- Required ceiling profile and height
- Clear spans and support locations
- Roof pitch
- Roof covering and associated loads
- Solar panel and other additional loads
- Site wind classification and exposure
- Eaves, verandahs and cantilevers
- Ducted air conditioning and other services
- Insulation and ventilation requirements
- Roof access
- Delivery and installation access
A change to a supporting wall, ceiling height or heavy service after engineering has been completed may require the truss design to be reviewed.
Why Use Steel for Roof Trusses?
Steel framing offers several advantages for engineered roof systems.
Light-gauge steel components can be digitally designed, accurately manufactured and prefabricated before arriving on site. Components can also be labelled to match the approved layout, helping installers identify where each truss belongs.
Steel is dimensionally consistent and is not susceptible to termite or borer damage in the same way as untreated timber.
Steel is also non-combustible. However, the fire performance of a complete roof system depends on all components and construction details, not the truss material alone.
Prefabrication can also help reduce site cutting and modification, provided the plans are coordinated before manufacturing begins.
What Information Is Needed Before Manufacturing?
Accurate information is essential before steel roof trusses are manufactured.
Depending on the project, the manufacturer may require current:
- Architectural plans
- Structural engineering
- Roof plans
- Sections and elevations
- Roof pitches
- Ceiling heights
- Eaves and overhang dimensions
- Support locations
- Roof covering specifications
- Wind classification
- Solar or other additional loads
- Service requirements
- Special structural details
Having coordinated information early helps identify the appropriate truss configurations, connections and manufacturing requirements.
It can also reduce the risk of redesign, manufacturing delays or costly modifications on site.
Choose the Roof System Early
Gable, hip, skillion, scissor, parallel chord, cantilever and attic configurations each solve different structural and architectural requirements.
The right choice should consider the complete roof system—including drainage, ceiling design, spans, supports, services, wind loads and construction requirements.
Early coordination between the builder, designer, engineer and steel manufacturer can make a complex roof much easier to manufacture and install.
About Prime Steel Frames & Trusses
Prime Steel Frames & Trusses is a 100% Australian-owned manufacturer and supplier serving Sydney and regional NSW.
The company provides custom steel wall frames, roof trusses, joists and structural steel solutions for homes, extensions and other building projects, with installation support available for selected projects.
Using quality framing systems, including TRUECORE®️ steel where specified, Prime Steel Frames & Trusses focuses on accurate prefabrication, design coordination, dependable delivery and practical support from quotation through to installation.