Spiral Ducting

Spiral Duct Lengths

We supply straight spiral ducting in the industry-standard 3-metre length — the choice for main duct runs, offering fewer joints and faster installation. For shorter sections, tight plant rooms, or awkward site access, spiral duct cuts cleanly to any length on site (see below).

Material and Construction

All our spiral duct is manufactured from galvanised mild steel strip, spirally wound and locked-seamed to produce a rigid, round tube with an inherently airtight joint. The galvanised zinc coating provides long-lasting corrosion resistance for indoor ventilation systems. Material gauges increase with diameter to maintain structural rigidity:

• 80 mm – 250 mm — 0.5 mm gauge
• 275 mm – 450 mm — 0.7 mm gauge
• 500 mm – 800 mm — 0.8 mm gauge
• 900 mm – 1000 mm — 1.0 mm gauge

Every length is manufactured to DW/144, the UK sheet-metal ductwork specification, guaranteeing dimensional accuracy and full compatibility with standard fittings from any DW/144-compliant supplier.

Stainless Steel and Special Materials

For aggressive environments such as swimming pool halls, coastal sites, pharmaceutical clean rooms, or chemical extraction, we can supply spiral duct in 304 or 316 grade stainless steel to order. Contact us for pricing and lead times.

How Spiral Duct Connects

Spiral duct has a female (plain) end at both sides. To join two lengths together you need a male coupler (also called a connector or joiner) that inserts into each duct end. Fittings such as bends, T-pieces, and reducers already have a male (crimped) spigot, so they push directly into the female duct end. Joints should be sealed with duct sealant and foil tape and secured with self-tapping screws or split clips.

Cutting Spiral Duct on Site

Spiral ducting can be cut to any required length on site using a metal cutting disc, reciprocating saw, or tin snips. Mark the cut line with masking tape wrapped around the circumference for a clean, square cut. Deburr cut edges with a flat file to remove sharp burrs before assembly.

Applications

• Commercial supply and extract ventilation
• Kitchen and canteen extraction
• Dust and fume extraction in workshops
• Air conditioning distribution
• Warehouse and factory general ventilation
• Residential MVHR and bathroom extract runs

Why Choose Alpha Air for Spiral Duct?

Alpha Air holds one of the largest stocks of spiral ducting in the Midlands, covering every standard diameter in 3 m lengths. Over 90% of orders placed before 3 pm are dispatched the same working day. Delivery is free on orders over £400, and our technical sales team is available on 0116 246 0031 to help with sizing, specification, and bulk-order pricing.