COLA construction

What COLA structure types work best for schools?

The three main COLA structure types for schools are steel-framed metal roof (Colorbond), steel-framed fabric membrane (PVC or PTFE), and shade sail (HDPE mesh). Metal and fabric membrane provide full weatherproofing for year-round timetabled use. Shade sails provide UV protection and suit spaces where wet-weather use is not required.

• Steel Colorbond: Hot-dip galvanised columns and beams with metal sheet cladding in gable, curved barrel vault, skillion, or cantilever profiles. Gable is the most common and cost-efficient layout. Fully waterproof with a 50-year-plus frame design life. Skylights typically cover 5 to 10% of roof area, supplemented by electrical lighting.
• Fabric membrane (PVC or PTFE): Architectural-grade PVC or PTFE stretched over a steel frame. PVC delivers 100% UV protection, full waterproofing, and 9 to 13% natural light transmission, so electrical lighting is usually unnecessary during school hours. Curved and non-rectangular shapes are standard, and the membrane absorbs more rain sound than metal.
• HDPE shade cloth (shade sail): Starts at 84% UV protection and blocks 60 to 70% of rain, making it a permeable cover. Suits applications where UV protection is the main requirement and the structure can be replaced over its working life.

For schools specifying a reliable, timetabled space, the choice between metal and fabric typically comes down to acoustic needs, natural light priorities, and shape flexibility.

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Steel vs fabric COLA: what's the difference?

Steel (Colorbond) and fabric membrane (PVC) COLAs both provide full weatherproofing on a steel frame, and they differ in natural light, rain acoustics, installation speed, shape flexibility, and lifecycle cost. Steel roofs use metal cladding with skylights; fabric roofs transmit natural light through the membrane and absorb more rain sound.

Steel Colorbond A steel Colorbond COLA uses hot-dip galvanised columns and beams with metal sheet cladding. Skylights covering 5 to 10% of roof area supplement natural light, with electrical lighting used alongside during the day. Metal roofing transmits rain sound, which matters for acoustic planning when the space hosts assemblies or teaching during wet weather. Rectangular and square layouts suit steel best; curved or angled steel requires additional fabrication.

PVC fabric membrane A PVC fabric membrane COLA stretches architectural-grade PVC over the same steel frame. The membrane transmits 9 to 13% of natural light, so the space stays bright on overcast days without electrical lighting during school hours. PVC absorbs substantially more rain sound than metal. Membrane installation takes roughly three days regardless of structure size, because the crew scales up with the structure. Curved and non-rectangular shapes are standard.

Lifecycle and cost The steel frame under a PVC COLA has a 50-year design life; the membrane lasts 30-plus years. Membrane replacement runs about 20 to 30% of the original build cost because the frame stays. For an equivalent outcome including bird-proofing, lighting, and acoustic treatment, steel and fabric are comparable in price.

Prefab vs custom COLA: what's the difference?

A prefab COLA is a pre-engineered kit structure in set sizes, while a custom COLA is designed from scratch around a school's specific site, timetable, and programming needs. Prefab is faster to quote and often cheaper per square metre. Custom typically delivers a better-fitting outcome for varied programming because the design follows how the school will actually use the area.

When prefab fits The prefab approach works from a product catalogue: a school picks a span width, a length, and a roof profile, and the supplier delivers a standard kit (usually a gable steel shed). This suits simple shade-only applications like basic weather coverage over a lunch area or walkway.

When custom fits A multi-use sports court or assembly space benefits from purpose-designed dimensions. A custom COLA accounts for sport-specific clearance heights, court orientation relative to sun path, acoustic treatment for assemblies, and run-back safety zones around court edges. The design defines span, height, orientation, roof material, acoustic provisions, lighting, and integrations (retractable hoops, AV, community-hire access) before any steel member is specified.

Trade-offs Custom projects require more upfront planning, a Development Application (DA), and engineering sign-off, and the timeline is longer than for prefab. At Blackburn High School, court orientation was adjusted during consultation to achieve a better build within budget, which shows how purpose-designed work absorbs site-specific variables.

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How long does a school COLA installation take?

A school COLA project typically takes several weeks to a few months from design through completion, depending on structure size, council approval timelines, and site complexity. On-site construction is the shortest phase when off-site fabrication is used, because steel components arrive ready to assemble rather than being built from raw materials on campus.

Project phases and installation speed The overall timeline covers consultation and brief definition, design and engineering, council approval or Development Application (DA), off-site fabrication, and on-site construction. PVC membrane installation takes roughly three days on site regardless of structure size, because the crew scales up as the structure grows.

Council approval variability The DA phase is often the least predictable, because council processing times vary by jurisdiction and project scope. A Complying Development Certificate (CDC) fast-track approval can take 5 to 15 business days with correct documentation, while a full DA typically takes 6 to 12 weeks. Blackburn High School's 38-metre by 61-metre multi-court COLA started construction in August 2018 and was completed in early 2019, covering two full basketball courts, four volleyball courts, tiered seating, and integrated sports equipment.

How to compress the overall timeline Schools can reduce project duration by defining the brief clearly before engaging a builder, scheduling construction during holiday or term-break periods, and using an integrated design-and-construct provider to avoid handoff delays between separate architects, engineers, and builders.