A friend is tired of having snow/ice slide down the metal roof on his barn taking out the metal flue stack for his oil furnace. He asked if I could construct a block chimney on the back wall of the barn. I’ve done masonry work but never built a chimney. I’ve planned on using the square chimney blocks built off a cement pad. But here are my unknowns. I told him we need a flue liner and typical application is the clay liners, the chimney will stand about 11′ and the furnace flue will enter the chimney about 6′ off the ground would it be acceptable to just use the metal flue all the way up and just fab a metal cap? What are you thoughts on the cement pad size, thickness etc.
Any other chimney construction tips would be helpful.
Thanks
Scott R.
Replies
What the heck nobody has any input for chimney construction????
Throw me something even if it' a half-a$$ed-guess.
Another question, do you think it should extend below frost or will it be fine sitting on a pad?
Hi Scott,
It's best to get a footing below freeze/thaw level. Shouldn't be too hard if you're going to use chimney blocks. Just dig a hole 6" oversize (of the block) and 42" deep and fill with concrete. Yeah, I know. Easier said than done, but if you wanna do it right...........
Of course, I wouldn't use chimney block outside. They are like sponges, they suck up water, freeze/thaw etc. you know. Brick is better. (yes people, I know, they suck up water too)
Ya gotta be careful Scott. Some people in here will analize the flow of water thru brick versus concrete block, yada yada yada
I would use the clay tiles (not knowing what metal pipe you have and if it would even fit in the concrete chimney blocks) .
To me, 11' just doesn't seem enough for a good draw. A little higher would be better.
Cap it off with a good stainless steel chimney cap.
And for god sakes, build a cricket to shed rain and snow away from the chimney.
Good luck to ya. Rod
Didn't see the first post.
My understanding is that clay flue liners are permitted solely because they've been around forever, but wou;dn't qualify for venting wood fire places and (I <i>think</i>) oil fired furnaces.
Go with a frame chase, properly fireblocked and an appropriate metal vent (L-vent of class A chimney vent)
Can you just run a chimney pipe out the gable end of the barn instead of thru the roof? That would cure the snow problem. A block chimney would have to set on a foundation below frost line and would need a cleanout at the bottom, and also would require a flue liner. This should not be too hard to build, but would be more expensive. Is this for a gas, propane, oil, wood, coal burner? Wood requires a larger flue than gas, coal is probably not used, but I think it does not require as large a flue as wood due to it's higher temperature.
Thanks guys. It is for an oil furnace. As for moving to a gable end... let's just say a chimney would be easer, avoiding any long winded explanation how this barn is built and divided up. Eleven ft. from the ground measures fine for roof clearance due to a low eave and moderate pitch (Does the 2' above the highest point within 10' still apply or has that changed in recent years?)
Scott R.
If this is just a 'B' pipe in a barn, farmers are making more money than they let on to want to spend it like that.
There are 'L' shaped snow stops made to add to the roof itself to stop major slides while it melts. Imagine a heavy duty Lexan 4" angle iron. about six inches long.
But if building the masonry chimney, use the clay liner and keep it separate from the concrete lifts. Use refractory cement for the flues and regular mortar for the block lifts. You can put a parge coat on the lifts to make it look stuccoed instead of cheap and it will help shed moisture a little.Excellence is its own reward!
Piffin, just a nit: he mentioned oil fired, so B-vent would not be an approved vent, tha's only for gas fired stuff. L-vent or masonry is needed for oil fired.
I recommend against masonry: the clay flue liners are, at least in my neck of the woods, rarely installed properly. (I look down 5-10 a week.)
Heck, use masonry for the struture if it makes sense cosemtically, but use L-vent for the flue itself - cheaper and safer.