Why Some Pleated Filters Use Expanded Metal Support and Others Don’t

Pleated filters may look similar from the outside, but the way they are supported inside can make a real difference to how they perform in service. Some use expanded metal on one or both faces, while others rely on different internal support structures or are built with media that can hold its shape without it. For mechanical contractors and technical buyers, the key question is not which construction looks stronger, but which one suits the airflow, dust load and installation conditions.

What the support layer is doing in a pleated filter

The support component in a pleated filter exists to keep the media stable while air moves through it. Pleated media provides more surface area than a flat sheet, but it also creates more exposed edges and deeper folds that can flex under load.

In practice, support helps with:

• •resisting bowing or collapse when pressure drop rises
• •keeping pleats evenly spaced so airflow is distributed across the full face
• •protecting the media from handling damage during installation and service
• •maintaining shape in systems with variable airflow or vibration

Expanded metal is one common way to do this, but it is not the only way. Depending on the filter design, the support may be on the air leaving side, the air entering side, or integrated into the frame and pleat geometry.

Why some filters use expanded metal support

Expanded metal is popular because it adds stiffness without blocking too much of the filter face. It gives the pleated pack a firm backing, which can be useful where the filter is expected to stay structurally stable under changing operating conditions.

Where expanded metal is often a good fit

Expanded metal support is commonly suited to:

• •higher face-velocity applications where the media is under more stress
• •filters installed in systems with vibration or movement
• •rougher handling conditions during transport or changeout
• •applications where the filter may see variable loading between inspections

For contractors, a supported pleated filter can be a practical choice when the system has limited room for deformation or when the filter is mounted in a position that makes handling more difficult. It can also help reduce the risk of pleat distortion if the unit is in a service environment that is prone to dust surges.

That said, expanded metal is not automatically the better option for every job. It adds material, and in some designs that can increase resistance slightly compared with a lighter construction. The right answer depends on the full filter build, not just the support face.

Why some pleated filters do not use expanded metal

Some pleated filters are designed to work well without expanded metal because the media, pleat spacing and frame provide enough structural support for the intended duty. These products can be suitable where the airflow is steady, the dust load is moderate, and the installation conditions are controlled.

Common non-metal support approaches

Depending on the product, support may come from:

• •a synthetic or reinforced media structure
• •a rigid card or moisture-resistant frame design
• •pleat separators or bonded pleat geometry
• •internal support members that are built into the filter construction rather than added as a face layer

This can be useful in compact systems where weight matters, or where the manufacturer has engineered the media to hold shape without extra reinforcement. In some applications, removing the expanded metal also makes the filter easier to handle and dispose of.

There are also systems where the filter is only lightly loaded and the support requirement is modest. In those cases, a simpler design can be perfectly appropriate if it is matched to the duty.

How to choose the right construction for the job

The best support method depends on how the filter will actually be used. A pleated filter that performs well in one installation may be a poor fit in another if the airflow profile, dust type or service access is different.

Points to assess before specifying a filter

• •the operating airflow and available face area
• •whether the system sees regular vibration or movement
• •how much dust the site typically generates
• •whether the filter is installed horizontally, vertically or in a tight access location
• •the depth of the filter and how much room there is for pleat stability
• •whether the housing or equipment manufacturer specifies a particular construction

Where the site is dusty or the system has a tendency to load up quickly, a more rigid construction may be worthwhile. Where access is easy and the duty is lighter, a simpler pleated filter may be all that is needed.

If the filter is part of a ventilation system that needs to align with AS 1668.2:2024, site requirements should be confirmed with the mechanical services engineer or building owner. The correct filter format is only one part of the overall system design.

Support method is only one part of filter performance

It is easy to focus on whether a pleated filter has expanded metal, but support alone does not define performance. Media quality, pleat depth, frame integrity and sealing all matter as well.

A technically suitable filter should also consider:

• •how the media captures particles at the intended stage of filtration
• •whether the frame fits properly and seals against bypass
• •whether the pleats are stable enough to maintain usable surface area over time
• •how the filter will be inspected in service

If pressure drop gauges are fitted, monitor them as part of your maintenance routine. Inspection frequency depends on the system, site conditions and dust load, and it should follow the filter and equipment manufacturer instructions rather than a fixed calendar schedule.

For projects where standard sizes do not suit the housing, how to measure an air filter is a useful starting point. If the application needs a non-standard build, custom air filters may be the better option.

When to specify a simpler filter and when to step up the construction

A simpler pleated filter can be a good fit when you want straightforward maintenance, controlled airflow and a moderate dust load. These filters are common in many commercial and light industrial applications where the housing is stable and access is easy.

A more heavily supported construction is worth considering when:

• •the filter is exposed to vibration or frequent handling
• •the system has variable operating conditions
• •the installation space is tight and the filter needs to hold its form
• •the dust load is more demanding and the filter may be inspected less often between checks

If you are comparing products across different rating systems, keep in mind that MERV, EN 779 and ISO 16890 do not convert directly. If the specification calls for EN 779 classes such as G3/G4 or F5-F9, those are still widely used in Australia, even though ISO 16890 has superseded EN 779 in many contexts.

Washability is also something to confirm on the specific product. Some filters are designed to be washable - check the product instructions rather than assuming a pleated filter can be reused.

Choosing the right filter for the site

The support construction should match the environment, not just the drawing. Expanded metal support can improve rigidity in demanding conditions, while other pleated filter designs are perfectly suitable where the load is lighter or the media and frame already provide enough structure.

For mechanical contractors and technical buyers, the most practical approach is to weigh airflow, housing design, access, dust load and manufacturer guidance together. If you are unsure which construction suits a specific system, it is worth comparing options before ordering so the filter fits the application the first time.

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, and we can help match the right filter construction to the job. Call 07 3800 3448 or request a quote. You can also contact us or browse our products.