Drawing

[Jim GM4DHJ ...]

Do you need a offset in a coal fire chimney flue to make it draw or is it just an old wives tale? ..

[newshound]

Never heard it. Can't see any physical reason. My woodburner one just goes straight up.

[Chris Hogg]

+1 In my last property, SWMBO wanted to replace the existing open fireplace with one raised up about 12", which meant the whole fireplace and flue had to be moved a similar distance to one side (don't ask!), which in turn meant altering the flue from dog-leg to straight up. No obvious disadvantages, and with the advantage that with the aid if a suitable mirror and torch you could look all the way up the inside and see whether it needed sweeping.

[The Natural Philosopher]

old wives tale.

Thr critical thing is that the cross sectional area of the flue immedaitely above the fire should be no less than 1/4 andf preferably

1/3rd of the aperture that feeds the fire...

[Jim GM4DHJ ...]

fairy nuff .....

[Jim GM4DHJ ...]

was thinking that ......

[spuorgelgoog]

Seems to be completely incorrect, rather than an old wives' tale

I suppose an offset would help reduce rain coming down the chimney, which might have some benefit as a damp chimney is a cold chimney.

Owain

[Peter Parry]

See :-

For more information than you could possibly need. (Americans seem to get a bit carried away with chimneys for some odd reason).

Search for "Smoke Shelf" if it isn't enough.

Most these days seem to consider them to be unnecessary as others have said.

.

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[Jim GM4DHJ ...]

very true...I once thought that if the offset was smaller in cross section the flow would increase .....

[Brian Gaff]

Cue Frank Sinatra singing There's a Flaw in my flue? Brian

[Dave Plowman (News)]

I'd guess it's more to stop rain etc getting direct access?