Jargon Buster - F

Confused by DIY terms? We’ve got you covered from A-Z with our Jargon Buster!

Feed and expansion tank

A cistern or tank for supplying cold water to a hot water system without a separate expansion cistern, which also incorporates accommodation for the expansion of water when heated such as in heating and hot water systems.


A strip of impervious material, usually flexible metal (lead) that stops water from entering the junction between a roof covering and another material.

Flemish Bond

Flemish bond is a style of bricklaying which consists of alternating the long face and the ends of the bricks when laying them. The alternating brickwork gives a pleasing appearance but the internal bonding arrangement produces continuous, narrow, vertical joints parallel to the wall surface which may weaken the bond slightly.


A device fitted along with a water valve / ballcock to automatically maintain a desired water level in a water tank.

Flue Duct

A duct that contains the flue of a chimney configuration.

Flue (Open flue)

A flue or chimney structure that removes the products of combustion to the outside air, with the air for combustion, being drawn directly from the room, space or enclosure containing the gas fired appliance.

Flue (room sealed)

A flue or chimney structure that removes the products of combustion to the outside air, with the air for combustion being drawn directly from the outside.

Flue Liner

This is the wall of a chimney structure consisting of components the surface of which is in contact with the products of combustion, this includes a rigid or flexible liner inserted into a chimney to form the flue and the inner wall of a metal or masonry chimney construction.

Flue outlet (terminal)

A fitting on the outlet of the flue where the products of combustion discharges to the atmosphere.


A device which, by the melting of one or more of its specifically designed and proportional components, opens the circuit in which it is inserted by breaking the current when this exceeds a given value for a sufficient time. The fuse comprises all the parts that form the complete device.


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