Chimney Size?

[janetsflower]

Does anybody know if there are any guidelines we can follow for the size of a chimney in relation to the size of the fireplace in order to maximises the draw on it? We are building a new chimney and someone has mentioned to us that it needs to be built to a ratio of either 1:4 or 1:5 but we would appreciate some clarification on this. Many thanks in advance

[gasman]

This is a very difficult question to answer There are a variety of regs for different types of flue
BS 65 For clay pipes fittins and ducts
BS 715 For Metel
BS 1289-1 For Pre cast concrete
BS 1298-2 For Clay/Ceramic
Etc...etc And the list goes on and on and on. We need to know the intended use for the flue, Type of fule & applaince it is going to serve, Rated output of appliance, Its intended construction materials And the volume of the room, Is it going to be round, rectangular, square also if there is any purpose provided ventilation ???
Also the flue has to be registered by a corgi engineer and have a plaque attached to it stating the date it was commissioned the rating etc..etc...etc And also needs building regs approval aswell..REMEMBER people DIE because of faulty / inadequate flueing standards.

[janetsflower]

ok it sounds quite complicated then. Its a brick chimney with an open coal/woodburning real fire underneath. I thought corgi were just for gas applainces?

[gasman]

CORGI are also to do with Fluing Standards ( the safe evacuation of products of combustion ) wether Gas, Coal Wood or whatever...They all produce lethal fumes if incomplete combustion occour's.
A brick chinmey for a soild fuel fire must have no minor dimension of less than 175mm Regs require a brick chimney to be lined with :-
Clayflue liners to BS EN1457; or
Imperforate clay pipes (salt glazed ) to BS 65; or
High alumina cement and kiln burnt or pumice aggregate pipes; or
Metallic flue liners to BS 715.
The width of the recess is normally between 690mm and 840mm, with a depth of 350mm.
Hearths are constructed of concrete to the following dimensions:-
min thickness of 125mm
min 500mm forward of the front face of the opening
min 150mm on each side of the opening
and must extend fully into the fire recess.
The effectivness of a flue can be reduced by bad positioning of the terminal. If the prevaling wind cannot blow freely across the terminal at all times, high pressure can build up around it and easily overcome the flue's natural draught.

[janetsflower]

Thanks for all your advice, think i will contact the corgi man then!