Custom Filter Frames: Choosing Cardboard, Plastic, Galvanised or Aluminium

Custom filter frames are not one-size-fits-all. The frame material affects how the filter handles moisture, how it sits in the rack, how easily it can be serviced, and whether it suits a dry plant room, a humid coastal site or a washdown-prone environment.

For facility managers, contractors and industrial buyers, the best choice is usually the one that matches the environment and the maintenance access available, while still fitting the equipment and filtration stage you need. If you are planning replacements or custom sizes, it helps to compare the frame options before you order custom air filters.

Why frame material matters

The media does the filtering, but the frame determines how the filter survives in service and how well it seals in the equipment.

A good frame should:

• •hold its shape under airflow and handling
• •fit cleanly into the filter track or holding frame
• •suit the site environment, including humidity and dust loading
• •support safe removal and replacement during servicing
• •avoid unnecessary corrosion, swelling or damage over time

In many Australian sites, the right material depends less on the filter type itself and more on where it is installed. A rooftop unit exposed to weather, for example, has very different needs to a dry indoor air handling unit or a dusty workshop extraction point.

Cardboard frames: simple, light and suitable for dry areas

Cardboard frames are commonly used where the environment is dry and the filter is not exposed to water, heavy condensation or aggressive cleaning. They are light, easy to handle and often suitable for general ventilation applications where service access is straightforward.

They can be a practical choice when:

• •the unit is indoors and protected from moisture
• •the filter is changed from a clean access panel or filter door
• •the application does not involve washdown, spraying or high humidity
• •cost and ease of handling are important considerations

Cardboard is not usually the best option where there is regular condensation, damp air, or a risk of the frame softening during service. If the site has moisture issues, it is worth discussing a more durable frame material with your supplier or mechanical services engineer.

Plastic frames: useful where moisture resistance is important

Plastic frames are often chosen when the site has humidity, occasional condensation or a need for better resistance to moisture than cardboard can provide. They are also useful where the frame may be handled more often and you want something less likely to deform in damp conditions.

Plastic may suit:

• •commercial HVAC systems in humid spaces
• •indoor plant rooms where condensation is possible
• •locations where the filter may be exposed to intermittent moisture
• •applications where a non-metal frame is preferred

Some plastic-framed filters are also easier to manage in service because they do not corrode in the same way as metal. That said, plastic is not automatically the right answer for every site. In higher temperature areas, or where the frame needs more rigidity, another material may be better.

If you are unsure which frame to specify, it can help to review the whole filter assembly, not just the media. Our our products page is a useful starting point when comparing standard and custom options.

Galvanised frames: a strong option for many general industrial applications

Galvanised steel frames are widely used where a stronger frame is needed and the environment is not excessively corrosive. They provide good rigidity and can work well in many industrial and commercial settings, particularly where the filter must stay flat in a secure holding frame.

They are often selected for:

• •plant rooms and mechanical equipment rooms
• •industrial sites with moderate dust loading
• •filters that need a sturdier frame for repeated handling
• •applications where a metal frame is preferred for support and fit

Galvanised frames can be suitable in many situations, but moisture and corrosion need to be considered carefully. If the air stream is damp, or if the filter is near coastal exposure, chemical vapours or regular cleaning with water, galvanised steel may not offer the best long-term result.

For sites with changing operating conditions, inspection frequency depends on the system, site conditions and dust load. Follow the filter and equipment manufacturer instructions, and monitor pressure drop where gauges are fitted.

Aluminium frames: light, durable and well suited to corrosive environments

Aluminium is often chosen where corrosion resistance matters more than the lowest upfront cost. It is also light, which can help during servicing, especially where filters are accessed at height or in tight plant rooms.

Aluminium frames can be a strong choice for:

• •coastal or marine-adjacent sites
• •humid environments
• •applications where corrosion resistance is a priority
• •installations where lighter handling is helpful during servicing

Because aluminium resists rust, it is commonly considered for environments where galvanised steel may deteriorate more quickly. It is also a sensible option where repeated removal and refitting are expected and the frame needs to remain stable and easy to handle.

Where access is awkward, lighter frames can make servicing simpler and reduce the chance of damage during installation. That can matter in systems with limited clearance, ceiling plenums or high-level access panels.

Matching the frame to the environment and access conditions

A practical way to choose is to think about three questions: what is the environment like, how often will the filter be accessed, and what kind of airflow and containment does the equipment need?

Dry indoor environments

For clean, dry indoor locations, cardboard may be perfectly suitable if the filter is not exposed to moisture and the access arrangement is simple. Plastic, galvanised or aluminium may still be chosen if the site wants a more durable frame or the filters are handled frequently.

Humid or condensation-prone environments

If moisture is likely, avoid specifying cardboard unless the product is clearly intended for that setting. Plastic or aluminium will often be better choices, with galvanised steel considered where the environment is not corrosive and the frame strength is important.

Coastal or corrosive environments

Salt-laden air, chemical exposure and repeated damp conditions can shorten the life of some frame materials. Aluminium is often worth considering first, while galvanised steel may still be used in protected indoor locations if conditions are controlled.

Restricted service access

When filters are changed through narrow doors, ceiling spaces or awkward access panels, frame rigidity and weight become important. A lighter frame can be easier to manage, but it still needs to hold its shape and seal properly in the unit.

If you are measuring a replacement filter, the size and frame depth need to be correct for the housing. Our guide on how to measure an air filter can help avoid ordering issues.

Other details to check before ordering

Frame material is only one part of the specification. Before ordering, confirm the following:

• •the exact dimensions, including depth and any lip or flange details
• •whether the filter needs a rigid frame or a disposable style
• •whether the site has moisture, condensation or corrosion concerns
• •whether access requires a lighter filter for easier handling
• •whether the equipment manufacturer has specific sizing or fit requirements
• •whether the site should be reviewed under AS 1668.2:2024, with requirements confirmed by the mechanical services engineer or building owner

If you are dealing with multiple sites, it may make sense to standardise where possible, but not at the expense of the environment. A frame material that works in one building may not be the right fit in another.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, established 2009. We can help supply or make the right custom filter frame for your site, including cardboard, plastic, galvanised or aluminium options.

If you need help choosing the best frame material for your environment or access conditions, call 07 3800 3448 or request a quote. You can also contact us to discuss your requirements or review filter servicing and commercial filter servicing support options.