What size chimney flue do I need?

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KNOTSANE

New Member
Jan 1, 2012
2
New Orleans, Louisiana
I have an outdoor fireplace that is close to the flue installation phase. The interior dimensions of my fire box is 16.5 inches deep and 24 inches wide. The height to the center of the arch is around 24 inches. The fire brick will extend about 10 inches above the visible box up to the base of the chimney. What would be the correct size flue for this size fireplace. This is an exterior masonry fireplace with no damper. I will be using the square masonry flues.
 
IIRC, the flu should be no larger than 15% of the
cross-sectional area of the opening...

Your rough dimensions are 24 x 24, but you can be more
accurate if you care to...

24 in x 24 in = 576 Sq in

576 x 15% = 86. 4 Sq in

Sq Rt of 86.4 = 9.295 Sq in

So a 9x 9 flue should do ya fine...

HTH
 
Thank you so much for the information DASKY. I picked up some 13 X 13 and it just looks way to big for my application. I am enjoying doing this project and naturally I want the fireplace to look great and be functional for my needs as an outdoor fireplace. Thanks again and Happy New Year.
 
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