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"Gauge" is the thickness of the steel a stud is made from — 1.2mm, 1.5mm or 2.0mm are the common SFS sizes. Gauge doesn't get much attention on site, but it has a significant effect on how tall a wall can be, how much wind load it can take, how much it costs, and how it's fixed. This guide explains what gauge means, how the common gauges differ, and how to choose.

What does "gauge" actually mean?

Gauge is the thickness of the steel sheet the stud is roll-formed from. A 1.2mm gauge stud is made from a 1.2mm thick strip of steel. A 2.0mm gauge stud is made from a 2.0mm thick strip.

When the steel strip passes through the roll-forming machine, it's folded into the C or I profile. The gauge of the input strip becomes the wall thickness of the finished stud — the web thickness, the flange thickness, all the same.

Gauge is measured in millimetres. Common SFS gauges are 1.2mm, 1.5mm, and 2.0mm. Occasionally 1.0mm or 2.5mm are used, but they're rare in standard drylining.

The common SFS gauges

1.2mm gauge

The standard gauge for most SFS applications. Suitable for:

• Standard internal partitions in domestic and light commercial buildings
• Standard SFS infill walls up to around 6m height (with the right stud width)
• Most drylining and wall lining applications
• Anywhere the loads are moderate and deflection is not critical

1.2mm is the default. If the manufacturer's span table shows a 1.2mm stud can do the job, use it. It's the cheapest gauge per metre.

1.5mm gauge

The "middle" gauge, used where 1.2mm isn't enough but 2.0mm is overkill. Suitable for:

• Taller walls (over 6m with standard stud widths)
• Higher wind loading (exposed sites, mid-rise buildings)
• Higher acoustic performance walls
• Some loadbearing applications
• Where deflection limits are tighter than standard

1.5mm costs more than 1.2mm (typically 20–30% more per metre) but gives noticeably better stiffness. It's often specified where 1.2mm would technically work but the engineer wants more margin.

2.0mm gauge

The heaviest standard gauge. Used where performance demands it. Suitable for:

• High-rise infill walls (over 10m)
• Loadbearing walls carrying significant structural loads
• High wind loading (coastal, exposed, tall buildings)
• Heavy-duty applications (sports halls, industrial)
• Where studs will be subject to impact or abuse

2.0mm costs significantly more than 1.2mm (typically 40–60% more per metre) and is heavier to handle. But it delivers maximum stiffness and load capacity at a given width.

How gauge affects strength

Strength of a stud scales roughly with the square of the gauge. So:

• Doubling gauge from 1.0mm to 2.0mm gives roughly 4× the strength
• Going from 1.2mm to 1.5mm gives roughly 1.5× the strength
• Going from 1.2mm to 2.0mm gives roughly 2.8× the strength

The exact relationship depends on the stud profile, but the principle holds — heavier gauge is meaningfully stronger, not just marginally.

For an SFS wall, "strength" in practice means:

• Resistance to bending under wind load
• Resistance to axial compression (for loadbearing walls)
• Resistance to lateral buckling (for tall studs)
• Ability to hold fixings and transfer loads to tracks

All of these improve with heavier gauge.

How gauge affects span

The span of a stud — how tall a wall it can support without excessive deflection — depends on both width and gauge. Increasing gauge is one way to increase span without increasing wall thickness.

For example, approximate maximum span of a 70mm stud at 600mm centres with normal wind loading:

These are approximate. Always check the manufacturer's span table for the specific conditions — wind loading, deflection limit, stud centres, and fire rating all affect the answer.

Gauge vs width — which matters more?

Both matter, but they affect different things.

Width primarily affects:

• Acoustic performance (bigger cavity = better isolation)
• Service void size (more space for pipes and cables)
• Wall thickness (bigger width = thicker wall)

Gauge primarily affects:

• Strength and stiffness
• Span capability
• Deflection under wind load
• Weight (heavier gauge is heavier to handle)

If you need more span, you can either increase width or increase gauge. Increasing width also gains you acoustic and service void benefits, but costs you floor space. Increasing gauge preserves wall thickness but doesn't add acoustic performance.

In practice:

• Standard partitions — 70mm × 1.2mm is fine
• Acoustic partitions — go wide first (90mm, 100mm), then add gauge if needed
• Tall walls — go up in gauge first, then width, depending on the deflection limit
• Loadbearing walls — engineer specifies both, usually starting with heavier gauge

Gauge and fire/acoustic performance

Fire

Gauge has very little effect on fire performance. Fire rating is dominated by the board layers, insulation, and (at longer ratings) the stud profile in the tested system. If a 90-minute test was carried out with a 1.2mm stud, you can use 1.2mm. If it used 2.0mm, you must use 2.0mm.

Some building regulations require heavier gauge for higher fire ratings, but that's usually because the tested system was heavier gauge, not because gauge itself creates fire resistance.

Acoustics

Gauge has a small effect on acoustics — heavier gauge studs are slightly stiffer, which marginally improves the acoustic performance of the wall. But this is a minor factor compared to board mass, insulation and isolation. Don't choose heavier gauge for acoustics alone; choose it for strength or span.

Gauge and fixings

Heavier gauge studs need different fixings:

• 1.2mm — standard 25mm self-drilling tek screws are fine
• 1.5mm — standard tek screws work but may need slightly longer (32mm)
• 2.0mm — need longer screws (38mm+) and sometimes pre-drilling for harder grades of steel

Base and head track fixings also need to be appropriate for the gauge of the track (which is usually the same as the stud) and the substrate (concrete, steel, timber).

Cost impact of upgrading gauge

Gauge upgrades cost money — and the cost scales faster than you might think. Rough per-metre cost uplift:

• 1.2mm → 1.5mm: roughly +20–30%
• 1.5mm → 2.0mm: roughly +25–35%
• 1.2mm → 2.0mm: roughly +50–70%

For a typical house extension with 30 linear metres of SFS wall, upgrading from 1.2mm to 2.0mm might add £50–£100 to the metal cost. For a large commercial project with 500 linear metres, the same upgrade could add £1,000 or more.

Every upgrade is worth weighing against the performance gain. If 1.2mm meets the span requirement, don't upgrade "just to be safe" — it's wasted cost that doesn't improve any other performance metric.

How to choose

Start with 1.2mm. Then check:

1. Does 1.2mm span the wall height? Check the span table against the wall height, wind loading, and deflection limit. If yes, use 1.2mm.
2. Is the wall loadbearing? If yes, engineer will specify the gauge — usually 1.5mm or 2.0mm.
3. Is the acoustic target high? If Rw 55+, go up in width first (90mm or 100mm), then add gauge only if needed.
4. Is the fire rating 90+ minutes? Check the tested build-up — the gauge required is whatever the test used.
5. Is the wall exposed to high wind? Engineer may specify heavier gauge rather than wider stud. Follow the design.

If you're unsure, get a quote for both 1.2mm and 1.5mm at the required stud width and compare cost vs performance. If the difference is small, 1.5mm gives you more margin. If the difference is large, and 1.2mm meets the requirement, stick with 1.2mm.

Summary

Gauge is the thickness of the steel a stud is made from. The common SFS gauges are 1.2mm, 1.5mm, and 2.0mm. Heavier gauge means:

• More strength
• More span
• Less deflection under wind load
• Higher cost
• Heavier to handle

For most applications, 1.2mm is sufficient. Upgrade to 1.5mm or 2.0mm only when the span, load, or performance requirements demand it. Always check the manufacturer's span table for the specific conditions, and get quotes for the alternatives before committing.