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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).
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:
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.
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.
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.
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.
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.
Spiral ducting is supplied in the industry-standard 3-metre length. For shorter sections or tight spaces, spiral duct can be cut to any length on site with a metal cutting disc or reciprocating saw u2014 mark the cut with masking tape for a square edge and deburr before assembly.
Gauge increases with diameter. Ducts from 80mm to 250mm are typically 0.5mm galvanised steel; 275mm to 450mm are 0.7mm; 500mm to 800mm are 0.8mm; and 900mm to 1000mm are 1.0mm. These gauges comply with DW/144 standards.
Standard galvanised spiral duct can be used externally for short runs, but the zinc coating will weather over time. For permanent external installations or corrosive environments, we recommend stainless steel spiral duct or applying a protective coating. Contact us on 0116 246 0031 to discuss your requirements.
We stock spiral ducting up to 1000mm diameter as standard. Larger diameters can be manufactured to order. Call our team on 0116 246 0031 for lead times and pricing on non-standard sizes.
