Chimney for gas fire

[stobear]

Neighbours of my parents are building an extension and have erected a chimney at the side of the extension which they say is to be used with a gas fire. Can someone clarify of the chimney height needs to go beyond the tallest point of the roof? I think I heard it did for a real fire , but not so sure for a gas fire

Thanks

 

[Betsy Og]

If the flue is straight then probably only the usual 2 to 3 ft above crest of roof (if some weird bit of the roof above the main crest then maybe not obliged to be above that).

If the flue is drawn up at an angle then for every ft sideways you need to go something like 2 ft above crest - so obviously if dragging flue sideways much could well end up with a ridiculous chimney.

With gas fires you can get balanced flues which means you just pipe horizontally out through the wall - the fireplace would need to be on an external wall for this to work