Chimneys

• The chimney may be constructed of
  • Gas flue blocks to BS1289
  • Chimney blocks to BS6461
  • Factory-made insulated chimneys to BS4543

Unlined Chimney

• High level connection:
  • Seal the break chimney between 250mm and 1000mm
  • Provide a means to clear debris from the catchment area
• Base/recess level connection:
  • MIN 75mm clearance between the outlet and chimney wall
  • MIN projection of an appliance into the chimney is 250mm

Solid Fuel Chimneys

• Suitable for gas and oil fired appliances
  • Restrictors or damper plates should be removed or secured in the open position
• Recess
  • 200mm - minimum back thickenss (jamb)
    • Could be reduced to 100mm if serves two recesses
  • 690mm - 840mm - with of the recess, adequate for all gas appliances
  • 350mm - depth of the recess
• Hearth
  • Constructed of a concrete
  • 125mm - minimum thickness
  • Must extent fully into the fire recess
  • 500mm - minimum projection in front of the jambs
  • 150mm - minimum projection on each side
  • 'Baxi overnight hearth'
    • Has a duct which comunicates a ventilated floor void
    • Must be sealed prior to the installation of a gas fire
• Lintels and Throat Units
  • Triangular in cross section to avoid obstructing the flow of smoke
• Fireback
  • Heat-resistant fire clay is built into the rear of the fire
• Flue Systems New Installations
  • Flue must contain a clear circular space of minimum 175mm
  • 45° - maximum offset angle
  • Flue must be lined
    • Clay lining BS EN 1457
    • Rebated and socketed kiln-burnt aggregate and high alumina cement lining
    • Rebated and socketed clay pipes and fittins to BS65
    • Flexible stainless steel linings are not recommended
• Flue Systems Existing Installations
  • An existing 225x225mm brick chimney - suitable for new appliances
  • Chimney built befor 1965 may not be lined