Installing a Flue Lining

To install the lining, remove the chimneypot and cement flaunching which supports it. After the flue has been swept, test for internal obstructions by passing the tapered plug through the chimney on the end of the rope.

A nose cone with a rope is usually provided to enable the lining to be pulled down by a rope; this is later detached.

Connect the tapered plug to the lining and lower the lining down from the top of the chimney. Get help at the bottom to pull the rope, easing the lining round bends. Alternatively, the lining may be fitted by pulling it up from the bottom of the flue.

The bottom end of the lining should seat on the shoulder of the socket on the appliance primary flue. Flexible lining is expensive, so calculate carefully; allow for bends a little more generously than the actual bend, so that the curve can be as gentle as possible. Leave also sufficient liner for connection to the flue outlet at the appliance.

Avoid stretching or otherwise distending the liner as this may pull the steel lamination apart. Steel flue lining is easily cut with a hacksaw, but take similar care to avoid unravelling.

Another way to avoid unravelling of the lining is to wrap a piece of sticky tape around it before cutting.

Sections of stainless-steel lining can be joined with a special connector.

At the chimney top, remove all flaunching and seat a clamp plate and ring firmly on the centre of the chimney opening and clamp the flue pipe. Trim off excess. Remake the flaunching, using a 1:5 high-alumina cement mix. Neatly slope the new flaunching to take away rainwater. Make sure that the connections and flaunching are not disturbed until this sets.

Fit a cowl of suitable pattern. Usually, a ‘straight’ cowl is used for gas appliances, and a coned type for appliances using oil.

Terminal point

The outlet from a Class II gas appliance must allow free discharge, prevent down draughts and entry of any matter which might restrict the flue.

The terminal must be positioned so that a current of free air may pass over it at all times: it must be at least 610mm from any opening window, skylight, ventilator or inlet to a ventilating system.

It is very important to seal the space between the lining and the chimney at the top and bottom. If necessary, add loose infill, such as mineral wool, for insulation and seal the seating of inspection and soot doors.

Vitreous enamel

This is similarly supplied in various lengths, with a socket at one end. Vitreous pipe can be cut with a sharp saw but care should be taken to cut cleanly and avoid splintering the enamelled surface.

A flexible carborundum wheel can also be used on a power drill to cut vitreous-enamel pipe. Wear protective goggles as a safeguard against splinters when cutting.

The bends

Angled bends, usually of 135° radius, are made in vitreous enamelled pipe. Bends have a socket at one end and a spigot at the other. Enamelled pipe bends may be supplied with an inspection plate.


Another method of lining an existing chimney, developed by Rentokil Laboratories, uses an inflatable rubber tube which is placed in the flue.

Each end of the flue is then sealed and the tube inflated until its diameter corresponds to the size of the flue required. Metal spacers are attached to the tube where a bend occurs to keep the tube in the centre of the flue.

10. November 2011 by admin
Categories: Featured, Handyman Tips | Tags: , , , , , , , , , | Comments Off on Installing a Flue Lining


Get every new post delivered to your Inbox

Join other followers: