Fireplaces, chimneys and flues


Flue terminals shall be suitable for their purpose and assist the functioning of the flue. Issues to be taken into account include:

  1. draught improvement
  2. chimney capping.

Relevant standards for flue terminals

BS EN 13502‘Chimneys. Requirements and test methods for clay/ceramic flue terminals’.
BS EN 1858‘Chimneys. Components. Concrete flue blocks.’
BS EN 1856‘Chimneys. Requirements for metal chimneys’.

Terminals should be:

  • purpose-made or formed by extending the flue lining a minimum of 20mm above the head of the chimney
  • embedded a minimum of 125mm into the chimney, excluding any flaunching, or 0.25x the length of the terminal, whichever is the greater
  • the same cross-sectional area as the flue (solid fuel has a minimum requirement of a 200mm diameter).

The terminal of a masonry flue should be jointed to the flue lining with cement mortar to form a seal.

Draught improvement

Where downdraughts may occur, terminals designed to increase updraught should be fitted. However, a terminal will not overcome problems caused by high pressure zones. Where relevant, the Solid Fuel Association or other authoritative body should be consulted.

Chimney capping

Where a chimney is to be capped:

  • a single unjointed concrete or stone capping should be used
  • it should project and be throated to cast water away from the face of the chimney
  • the slab should project 50mm beyond the sides of the chimney, and the withes between flues should be carried to the underside of the slab.

Decorative brick cappings should be carefully constructed to avoid rain penetration and frost damage. The use of frost-resistant bricks may be required.

In Scotland, bricks used for facing brickwork should be frost-resistant.