Lagging and jacketing explained

Lagging is the insulation itself: the material wrapped round a pipe, duct or tank to keep heat in or out. On pipework it usually comes as pre-formed insulation sections, shells that clip round the pipe, in materials such as fibreglass, stone wool or phenolic foam.

A section is named for the pipe it fits and its thickness: pipe outside diameter × insulation thickness. A 76 × 25 section fits a 76 mm pipe and is 25 mm thick. That is the size on the box, on the supplier’s list and on the take-off, and it is the size we work in. The thickness itself usually comes from the specification, often worked out to BS 5422.

Cladding is the thin metal skin fitted over the lagging. In Ireland and the UK, fitters call it cladding, and you will also hear casing or pipe casing for the straight lengths. It protects the insulation from knocks, weather and water, and it gives the job a clean, finished look.

Because it goes over the lagging, it is always measured over the lagging, outside to outside. We add 0.3 cm so it slides on. Ours is aluminium as standard, 0.6 to 0.8 mm (up to 1.0 mm), plain, stucco embossed or colour-coated, with stainless steel 304 and 316 to order. See aluminium vs stainless steel.

Jacketing is the American word for the same metal cladding. It turns up in US manuals, in some manufacturers’ data sheets and in specifications written from them: “aluminium jacketing”, “metal jacket”, “stainless jacketing”. When a spec on an Irish job asks for jacketing, it means cladding, and that is what we make.

So: lagging is the insulation; cladding and jacketing are both the metal over it. On our site, our drawings and our cut lists we say cladding.

• Swaged ends: a formed step on the end of a piece, so one length slides into the next. Our straight pipe casing comes in 1 × MTR or 1/2 MTR lengths with swaged ends.
• Watershed lapping: the upper piece laps over the lower one, so water runs off, not in.
• Fixings: monel or stainless pop rivets and self-tapping screws, with joints strapped with aluminium bands. Fixings are not part of the cladding, but we can supply them on your quote.
• Fittings: every bend, tee, reducer and box is a shape of its own, like a radius bend, a tee or a D box (valve box).

The insulation contractor fits the lagging and the cladding on site. We are the workshop behind them: we fabricate the cladding to their measurements in Dublin 12 and they install it. We never install, and we never quote your client. A drawing, a schedule or a photo is enough to start, and the trade terms page has every other cladding word in one line each.