6.8 Fireplaces, chimneys and flues

6.8 - Appendix 6.8A
	Provision of combustion air
6.8 - Appendix 6.8B
	Minimum sizes for flues contained in chimneys
6.8 - Appendix 6.8C
	Typical construction details
6.8 - Appendix 6.8D
	Flue outlet positions for solid fuel appliances
6.8 - Appendix 6.8E
	Flue outlet position for gas appliances
6.8 - Appendix 6.8F
	Flue outlet positions for oil appliances

Appendix 6.8-A

Provision of combustion air

	Solid fuel up to 45kW output		Gas *	Oil
	Open	Closed appliance **	Up to 70kW input	Up to 45kW output
England, Wales and Isle of Man	50% of throat area***	550mm2/kW above 5kW rating	500mm2/kW above 7kW input for an appliance in a room or space	550mm2/kW above 5kW rating for an appliance in a room or space
Scotland	1500mm2 for fireplaces up to 450mm wide (measured between firebricks), for fireplaces exceeding 450mm width manufacturers' details should be followed	As England and Wales	As BS 5440: Part 2 (as England and Wales)	As England and Wales
Northern Ireland	As England and Wales	550mm2 up to 6kW rating. Over 6kW add 550mm2 for each kW above 6kW.	450mm2 up to 8kW. Over 8kW add 450mm2 for each kW above 8kW	As solid fuel closed appliance

Notes:

Full details of ventilation requirements for all types of appliances are contained in the relevant building regulations.

* Decorative fuel effect gas appliances should have a provision for combustion air complying with the relevant part of BS 5871.

Normally a minimum of 10,000mm² of purpose provided ventilation is required. Air vents should be direct to the external air or to an adjacent room or internal space which has an air vent or vents to the external air of at least the same free area. Air vents should have aperture dimensions no smaller than 5mm.

** Where closed appliances use a flue fitted with a draught stabiliser the total free area should be increased to 300mm²/kW for the first 5kw plus 850mm²/kW for the balance of appliance output.

***In the case of a fire with a canopy the open air vents should be 50% of the flue area.

Appendix 6.8-B

Minimum sizes for flues contained in chimneys

Solid fuel burning appliance up to 45kW output
Serving	Minimum flue size [mm]
Fireplace recess with an opening up to 500mm x 550mm	200 diameter or square section of equivalent area
Fireplace with larger opening	See approved Document J
Closed appliance up to 20kW rated output burning smokeless fuel	125 diameter or square section of equivalent area
Closed appliance up to 30kW rated output burning any fuel	150 diameter or square section of equivalent area
Closed appliance above 30kW and up to 50kW rated output burning any fuel	175 diameter or square section of equivalent area

Non fan-assisted individually flued gas burning appliances up to 70kW input excluding balanced flue
Serving	Minimum flue size
Gas fire	Round flue with a cross-sectional area of at least 12,000mm2 (125mm diameter) or rectangular flue with a cross-sectional area of at least 16,500mm2 with minimum dimension of 90mm
Any other	At least the cross-sectional area of the outlet from the appliance

Inset live or decorative gas fuel effect appliances
Serving	Minimum flue size
Open fire within a fireplace opening up to 500mm x 550mm	Circular or rectangular minimum flue dimension 175mm

Oil burning appliances up to 45kW output

Not less than the size of the appliance outlet

Appendix 6.8-C

Typical construction details

KEY TO TERMS

For weathering detail see Detail C

DETAILS OF EXTERNAL CHIMNEY BREAST WITH MASONRY INNER LEAF

Other alternatives may be suitable provided they meet the appropriate Performance Standards.

DETAIL A

DETAIL B

DETAIL C

Weatherproofing details recommended for use in Very Severe and Severe exposure zones.

In other exposure zones the dpc tray can be dressed up the outside of the flue liner. All other details are the same.

Note: All flashings and trays in chimneys to be metal (see Clause M11).

TYPICAL EXTERNAL FIREPLACE RECESS AND CHIMNEY-TIMBER FRAME CONSTRUCTION

Appendix 6.8-D

Flue outlet positions for solid fuel appliances

	Point where flue passes through weather surface (Notes 1,2)	Clearance to flue outlet
A	at or within 600m of the ridge.	at least 600mm above the ridge.
B	elsewhere on a roof (whether pitched or flat)	at least 2300mm horizontally from the nearest point on the weather surface and: a) at least 1000mm above the highest point of intersection of the chimney and the weather surface: or b) at least as high as the ridge.
C	below (on a pitched roof) or within 2300mm horizontally to an openable rooflight, dormer window or other opening, (Note 3)	at least 1000mm above the top of the opening.
D	within 2300mm of an adjoining or adjacent building, whether or not beyond the boundary, (Note 3)	at least 600mm above the adjacent building.

Notes
1) The weather surface is the building external surface, such as its roof, tiles or external walls.
2) A flat roof has a pitch less than 10°.
3) The clearance given for A or B, as appropriate, will also apply.

Appendix 6.8-E

Location of outlets from flues servicing gas appliances

Location of outlets from flues serving gas appliances

Minimum separation distances for terminals in mm

Location		Balanced flue			Open flue
		Natural draught		Fanned draught	Natural draught	Fanned draught
A	Below an opening (1)	Appliance rated heat input (net)		300	(3)	300
		0-7kW >7-14kW >14-32kW >32kW	300 600 1500 2000
B	Above an opening (1)	0-32kW >32kW	300 600	300	(3)	300
C	Horizontally to an opening (1)	0-7kW >7-14kW >14kW	300 400 600	300	(3)	300
D	Below gutters, soil pipes or drain pipes	300		75	(3)	75
E	Below eaves	300		200	(3)	200
F	Below balcony or car port roof	600		200	(3)	200
G	From a vertical drainpipe or soil pipe	300		150 (4)	(3)	150
H	From an internal or external corner or to a boundary alongside the terminal (2)	600		300	(3)	200
I	Above ground, roof or balcony level	300		300	(3)	300
J	From a surface or a boundary facing the terminal (2)	600		600	(3)	600
K	From a terminal facing the terminal	600		1200	(3)	1200
L	From an opening in the car port into the building	1200		1200	(3)	1200
M	Vertically from a terminal on the same wall	1200		1500	(3)	1500
N	Horizontally from a terminal on the same wall	300		300	(3)	300
P	From a structure on the roof	N/A		N/A	1500mm if a ridge terminal. For any other terminal, as given in BS 5440-1:2000	N/A
Q	Above the highest point of intersection with the roof	N/A		Site in accordance with manufacturer's instructions	Site in accordance with BS 5440-1:2000	150

Notes:

1. An opening here means an openable element, such as an openable window, or a fixed opening such as an air vent. However, in addition, the outlet should not be nearer than 150mm (fanned draught) or 300mm (natural draught) to an opening into the building fabric formed for the purpose of accommodating a built in element, such as a window frame.
2. Boundary as defined in Paragraph 0.4. of Approved Document J: smaller separations to the boundary may be acceptable for appliances that have been shown to operate safely with such separations from surfaces adjacent to or opposite the flue outlet.
3. Should not be used.
4. This dimension may be reduced to 75mm for appliances of up to 5kW input (net).
5. N/A means not applicable.

Appendix 6.8-F

Location of outlets from flues serving oil-fired appliances

Minimum separation distances for terminals in mm

Location of outlet (1)		Appliance with pressure jet burner	Appliance with vaporising burner
A	Below an opening (2, 3)	600	should not be used
B	Horizontally to an opening (2, 3)	600	should not be used
C	Below a plastic/painted gutter, drainage pipe or eaves if combustible material protected (4)	75	should not be used
D	Below a balcony or a plastic/painted gutter, drainage pipe or eaves without protection to combustible material	600	should not be used
E	From vertical sanitary pipework	300	should not be used
F	From an external or internal corner or from a surface or boundary alongside the terminal	300	should not be used
G	Above ground or balcony level	300	should not be used
H	From a surface or boundary facing the terminal	600	should not be used
J	From a terminal facing the terminal	1200	should not be used
K	Vertically from a terminal on the same wall	1500	should not be used
L	Horizontally from a terminal on the same wall	750	should not be used
M	Above the highest point of an intersection with the roof	600 (6)	1000 (5)
N	From a vertical structure to the side of the terminal	750 (6)	2300
O	Above a vertical structure which is less than 750mm (pressure jet burner) or 2300mm (vaporising burner) horizontally from the side of the terminal	600 (6)	1000 (5)
P	From a ridge terminal to a vertical structure on the roof	1500	should not be used

Notes:

1. Terminals should only be positioned on walls where appliances have been approved for such configurations when tested in accordance with BS EN 303-1:1999 or OFTEC standards OFS A100 or OFS A101.
2. An opening means an openable element, such as an openable window, or a permanently open air vent.
3. Notwithstanding the dimensions above, a terminal should be at least 300mm from combustible material, e.g. a window frame.
4. A way of providing protection of combustible material would be to fit a heat shield at least 750mm wide.
5. Where a terminal is used with a vaporising burner, the terminal should be at least 2300mm horizontally from the roof.
6. Outlets for vertical balanced flues in locations M, N and O should be in accordance with manufacturer's instructions.