Many older houses in the United Kingdom have unlined chimneys. Installing a chimney liner is essential to prevent combustion gases rising from the fire from corroding the mortar of the chimney brickwork. If left unlined, the chimney could weaken and pose a dangerous structural problem to the entire property. The easiest way to install a chimney liner is to use a flexible, one-piece stainless steel flue liner that you feed into the chimney from the top.
Choose the correct size of flexible chimney liner. This is usually a minimum of 150mm diameter but if fitting a wood-burning stove or specific appliance with a flue outlet, select the correct size to match the flue outlet.
Arrange for a scaffolding company to erect scaffolding so that you can access your rooftop and chimney. In the United Kingdom, by law you must use scaffolding for any rooftop work or maintenance.
Chop away the flaunching surrounding the base of the chimney pot with a hammer and chisel. Lower the chimney pot to the ground on a rope.
Attach a weighted line to the conical end piece of the one-piece flexible flue liner. Use a builder's weight or small sandbag. Carefully lower the weighted line to the bottom of the chimney.
Feed the one-piece flexible flue liner through the top of the chimney. Get a friend to pull on the weighted line below to draw the liner to the bottom of the chimney.
Unscrew or unclamp the conical end piece of the flue liner.
Bolt the closure plate in place across the base of the chimney, above the fireplace.
Clamp the flue liner to the closure plate or, if using a heating appliance with a flue outlet, clamp the liner to the outlet using the supplied fixings.
Seal the joint with fire cement, using the supplied dispenser or a trowel.
Feed the one-piece, flexible flue liner through the top of the chimney.
Replace the chimney pot, using ready-mixed mortar to secure it in place. Shape the mortar to match the original flaunching.
Installing a chimney liner requires considerable DIY or construction experience and knowledge. If in any doubt, hire a builder to install the liner. Chimney liner installations must meet UK building regulations (see Resources). Houses built in the UK after 1965 will have chimney liners already installed.
Flue liners connected to gas fires or oil heaters must be fixed to a closure plate at the top of the chimney. This plate should be bedded on mortar laid at the top of the chimney. Ensure your scaffold provider meets current British health and safety standards by asking for their safety certificate.