Installation Guidelines for Clay Flue Liners
Ensure that the flue liner to be installed suits the intended appliance or open fire dimensions.

All flue linings and components should be examined before installation and any damaged items should not be used.

Flue linings are to be installed with the rebate / socket uppermost and jointed with the appropriate Lagan Chimney Systems fireproof mortar/sealant.

Joints should be fully sealed and pointed; any surplus sealant protruding into the flue should be removed during construction (wipe using damp sponge).

When using clay flue liners the gap between the flue linings and the surrounding masonry should be at least 15mm. These gaps should be filled with insulating material such as a weak lime mortar mix or lightweight insulating concrete (vermiculite). Backfill each flue as each liner is constructed.

Only factory made components should be used to form bends or offsets. All offsets must be adequately supported.

Flue construction should be protected against exposure to rain and at the end of each day until the mortar / sealant has fully hardened.

Perform checks to ensure that the internal flueway is clear of any protrusions or obstructions and remove any excess fireproof mortar / sealant, cement mortar and debris.

Smoke testing during construction
The purpose of smoke testing is to check that the flue gases will rise freely up the flue and to identify any possible faults, such as incorrectly sealed joints, damaged components and/or obstructions in the flue.

If the flue components have been inspected and the installation checked as work proceeds it may not be necessary to carry out the smoke test. However if there are any doubts as to the integrity of the flue carry out the following smoke test.

Smoke Test Procedure
Close all doors and windows in the room served by the flue. Warm the flue for up to 10 minutes using a blowlamp or similar to establish a flue draw. A longer warming up period may be required when testing larger flue sizes and in the case of wet or cold flues.

Place two or more smoke pellets on a masonry block stood on end within the fire opening or recess and ignite.

When the smoke is seen to steadily exit from the top of the flue or terminal, seal off the top using an inflatable bladder or a plastic bag placed over the terminal and sealed around the edges.

Check the full length of the flue/chimney construction for any significant leakage. This includes checking for smoke leakage around window openings and cavities when the chimney is built in as part of a cavity wall.

The test should be allowed to continue for at least 5 minutes and is considered satisfactory if there is no significant leakage of smoke through the walls of the flue. If significant leakage does occur the cause should be investigated and rectified, followed by repeating the test. A strong plume of smoke escaping through a joint or defect would be considered as a major leakage.

Always follow the manufacturer’s safety instructions when using smoke pellets and take the necessary protection to avoid inhalation of the smoke. Once the flue has satisfied the test, ensure the closures at the top and bottom of the flue are removed.

Installation Guide for Terminals (Pots)
The chimney terminalis is an important component of a chimney system. It takes the flue gas outlet away from the turbulence created by the bulk of the chimney stack and can reduce the likelihood of water ingress. Also, it can put the flue outlet above the high pressure zone, which causes down draught problems.

The terminal should be embedded into the top of the stack by 125mm or one quarter of the height of the terminal, whichever is the greater. A straight-sided terminal should be butted against the top of the last liner.

A tapered terminal should be fitted over the last liner. Note that the top of the last liner lies within the corralled brickwork in this case.

A flue terminal should always be used to obtain a satisfactory chimney performance. The chimney should not be terminated with just a mortar flaunching or exposed flue liner.

General Maintenance
Chimneys should be swept at least twice a year, once before the heating season, once after.