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Spiral Ducting

What is Spiral ducting? 

Ducting, ducts or ductwork are pipes or tubes, that typically form part of a ventilation system.

Spiral ducting is a circular (round), spirally wound length of duct.This type of ductwork is generally cost-effective as it can be made with 32% less sheet metal than rectangular ducting. It is also less likely to leak due to it having fewer transverse & longitudinal joints when run in long, straight sections.

Spiral duct materials

This product can be fabricated from various different materials, some of these are:

  • Galvanised steel
  • Stainless steel 

Spiral duct is most commonly made from galvanised steel due to the zinc coating which prevents rust from forming. This is generally the most cost-effective option.

For special requirements, for example within the food industry, spiral can also be made in stainless steel upon request. Please contact us to get a quote for stainless steel spiral. 

Spiral duct sizes

A common question we often get asked is "Is the sizing of ducting the inside or outside diameter?" To answer this simply, spiral ducting is sized on the inside diameter of the duct. All corresponding fittings are made to fit this size.

Ducting Express can supply ductwork in 3 meter lengths from 80mm-900mm in diameter. Larger sizes are also available upon request. Please contact us to get a quote for 1000mm diameter spiral duct sizes and above. 

But what if I don’t need a 3 meter length? Ducting can be easily cut to your required size using a hacksaw.

Installing spiral ductwork

Spiral ducting has large ends, we refer to these large ends as “female” and duct fittings have small (“male”) end spigots. By fittings, we mean any bends, t-pieces, concentric reducers, weather cowls etc. The male end of the fittings fit inside of the female end of the duct. 

If you need to join two lengths of spiral or two fittings together i.e two parts with the same end, you’ll require a connection piece. When joining two female ends you’ll need a male connector, or a female connector to join two male ends. As long as your coupler has the same diameter as your duct, they’ll connect up to create part of your duct system.

Of course, you will need a way to hang you ducting. An extremely important part of your ductwork installation is bracketry. An inadequately bracketed system can be extremely dangerous. We recommend having at least one bracket every 3 metres. Split clips or Suspension Clips (single hangers) are the products you would use to for this. These both fulfil the same purpose, and can be used to attach your duct to the ceiling or wall. 

Split Clips have two suspension points: one on each side of the duct, offering a more secure fitting. These brackets require the use of either M8 or M10 threaded rod. Split clips are necessary with larger duct sizes, but should also be used on smaller ducts in certain circumstances. 

Single Hangers can also be used for the suspension of circular ducting. These products have one point of suspension and can use a hanger bolt or, like it’s split clip counterpart, can fit M8 or M10 threaded rod.

Spiral ducting accessories 

Ducting Express are not just spiral ducting suppliers, we are a one stop shop for all your ducting accessories too. 

Need to fix your duct system together? No problem. Check out our ducting accessories category for all your fasteners and fixings.

For fastening without the need for any pre-drilled holes, we advise our customers to use self-drill screws. These products really do save time.

Once you’ve decided on a method of fastening your duct work together, you’ll want to choose a sealant. Our preferred choice is LD410 Duct Sealant. This water-based sealant will provide a permanent seal whilst withstanding a reasonable amount of vibration. Of course, there are other options too; Cloth Tape or Foil Duct Tape to name a few.

Still have further questions? Contact our team of spiral ducting UK experts. A member of our knowledgeable team will be able to assist you.