I know the span & pitch of my roof (28'+16"[overhang back]+40"[overhang front] @ 4/12 pitch) but am having a wee bit of problems figuring the math out. We are going to place it approx. 60" in from the front. The height for the chimney must be 3' above the highest point where it passes throught the roof and at least 2' above anything within a 10' horiznal radius of it.
2007-03-19 16:44:02 · 2 answers · asked by Jonas W 2 in Home & Garden ➔ Maintenance & Repairs
Since your roof is a 4/12 pitch(rise of 4 inches per foot) any point 10 feet from the chimney going up the roof would be 40" higher than the roof at the chimney. You then need to add 24" additional height above that. So your height for your chimney will be a minimum of 64". If you are 10 feet or less from the peak you only have to be 24" above the peak.
2007-03-19 17:40:07 · answer #1 · answered by stedyedy 5 · 0⤊ 0⤋
With that slope, and the side of the chimney 4'above the roof at that point, the nearest point of roof up slope would be 12' away. If you went up 3' instead of 4, the nearest point would b 3/4 of 12 or 9 '. So you want to be at least 3'-4'' above the highest point of chimney penetration. Unless there are seismic considerations, a higher chimney might be best. It improves draft, and helps avoid downdraft. Don't forget to include a chimney screen. I like the diamond mesh ones. They are thicker, and last longer.
2007-03-20 00:38:51 · answer #2 · answered by Ed 6 · 0⤊ 0⤋