Choosing the right roofing material for your COLA

Fabric membrane

Pros:

• Flexibility: Fabric membrane roofs can be made to fit any roof shape or size, making them ideal for sports spaces that require a unique design.
• Lightweight: Fabric membrane roofs are lightweight, making them easy to install and reducing the need for heavy equipment.
• Cost-effective: The larger a fabric membrane roof, the most cost-effective it is. This means they’re a great value option for bigger COLAs.

Cons:

• Colour selection: Fabric membrane is currently available in a limited range of colours, including white, off white and grey.
• Fire resistance: Some bushfire zoning requires metal roofing so may not be suitable for fabric membrane.

Steel roofing

Pros:

• Durability: Steel roofs are known for their strength and durability, making them ideal for high traffic areas like school sports spaces.
• Aesthetics: Steel roofs are available in a wide range of colours and finishes that can complement the aesthetics of the school building.
• Energy efficiency: Steel roofs can be used to support solar panels as they have a sturdy, stable surface.

Cons:

• Requires birdproofing: Steel roof structures naturally have more spaces for birds to roost due to the beams. Additional birdproofing is required to prevent this.
• Design options: Steel roofs typically need to be built in a traditional shape, like gable, hip or skillion as the material is less flexible than PVC.

Light transmission

Fabric membrane offers more light transmission than steel roofing. It naturally allows some light to pass through the material while still offering a high amount of UV protection. These structures allow you to feel like you’re outdoors while still being protected from the elements as the light diffuses evenly, just like you’re outside. This is a great way to get the benefits of the outdoors while minimising risk of sun damage.

Steel structures have little light transmission, creating a more bordered experience that can feel like an indoor space. To maximise lighting for a steel roof, we typically add skylight panels or electrical lighting. Sometimes the placement of a steel structure can impact buildings nearby. For example, if a COLA is built directly next to classrooms, it can block sunlight from shining through these windows. In these cases, fabric membrane can be best as it lets light through.

Despite the difference in light transmission, both types of structures provide UV protection from the sun’s damaging rays. If you want to experience the difference, stand under each and see!

Maintenance

It’s a common misconception that metal COLAs don’t require maintenance. To keep the structure in optimum condition, it’s recommended to have it checked every 12 months by a professional for rusting and other structural issues. Additionally, there’s ongoing maintenance. If there are trees nearby dropping leaves, you may need gutter guards as well as regular cleaning of gutters, and skylights need to be cleaned to maintain light transmission.

You may have to follow specific maintenance requirements. For example, NSW government schools must have their roof anchors inspected and re-certified every 12 months for metal COLAs. Fabric structures need to be cleaned regularly (at least once a year) to get the benefits of your warranty and keep them looking fresh.
While a structure may stay standing without much maintenance, to maximise its lifespan it’s important to undergo routine maintenance and keep track of any work performed. 

Warranty

Both steel roofing and fabric membrane structures can come with a warranty of up to 20-25 years, although it depends on the specific type of fabric membrane used. These cover against defects in the material and workmanship. When planning a structure, it’s useful to take a closer look at the warranties for the products you’re interested in to check how they compare.

Lifespan

A number of factors can impact the lifespan of a structure. Taking proper care to maintain the structure, with regular checks and cleaning, will not only keep it looking fresh but keep it in great shape. For steel roofs, the choice of member can play into longevity. An open truss provides more little spaces for cobwebs or birds to roost while one large beam minimises this.

It’s vital the material selection considers where the site is located. For example, structures close to the coast may be in a high corrosion region. This means they’re more likely to develop rust over time without the right finishes, like hot dip galvanising.

Some parts of a structure are more susceptible to wear and tear than others. Down pipes can be easily kicked and dented so adding guards is a simple step to protect them – in fact, this is required in NSW for government-funded projects. Lights should be fixed, back resistant and waterproof so they don’t move or break. And with connection points, like bolts and welding, most susceptible to corrosion, they should be checked every six months. It’s not hard to ensure your structure can reach its full lifespan with basic care.

Cost

Cost varies depending on the size of the structure and a range of other factors, including surface material, add-ons and timing. However, generally the larger a fabric membrane structure, the more cost effective it is. On a very small scale metal structures are more cost effective but the larger a project is the more value fabric membrane will offer.

Project duration

Fabric membrane and steel roof structures both take a similar amount of time to plan and complete. While the on-site construction time for a fabric structure is slightly shorter, this has a minimal impact on the overall project

Additional features

Features like lighting and sound can be supported by both types of structures. It’s even possible to add large fans (up to 7m) to cool the underneath of a large COLA, however the main limitations for these add-ons may be size or service availability (eg. electrical connection).