Any masons who can give some pointers?

[SIERRADMAX]

The house I recently purchased was a typical cookie-cutter 2 story, full basement house constructed in early 2000's by a contractor who decided to use a fireplace insert and a double wall lined stainless steel flu. Additionally, he decided to install a powervent boiler thus eliminating the need for another flu. The one thing I hate about the house is these two setups.

What I WANT to do is install a 3 flu chimney. One flu for the boiler (In basement), one flu for a future wood boiler and another flu for a wood stove on the first floor (fireplace insert is going bye bye). I've been scratching my head with two options. Option One is running the chimney up the inside of the house, in the cavity where the stainless steel flu pipe is. I understand this will require additional structural work but I'm prepared to do so. The 2nd option is adding a 3 flu chimney on the outside of the house and coring through the foundation for the to the two flues for the oil boiler and future wood boiler. Then using a thru-wall thimble for the wood stove on the first floor.

The problem with Option 1 with a 9" wide flu, 1" airspace, 4" fireblock and 2" between combustibles, I would need a 23"-24" cavity. I've measured all the way up. I have those clearances until I get to the attic where there is 21-1/2" between the topplate of the 2nd floor wall framing and the bottom of the 2nd roof truss (24" O.C.). Is there a material I can place to protect the wood framing?Is there a slightly thinner brick?

The Problem I have with Option 2 is what kind of clearance is required between the chimney brick and the sheathing if I can go up the side of the house? And is there a good way of flashing the sides of the chimney to the sheathing? Does the chimney get anchored to the house framing?

 

[dvellone]

Although an outside chimney is better than one that is half out and half in, depending on what side of the house it's on (prevailing weather) the joints may weather a good bit over a short length of time and of course weather more than if the chimney is inside the house.

Though I'm a Mason by trade and advocate of masonry chimneys, why not just go with ss and a chase enclosure? Any after-the-fact masonry chimney (especially three flues and two floors) in a finished home is going to cost considerably more than if it were going up in new construction. It's a big undertaking, and unless you're particularly committed to the aesthetics of a full masonry chimney you can save a lot of money with ss and even veneer your chase in the living space for a nice look.

 

[Later]

Would building a chase that contains 3 class A, or the equivalent, appropriate flue for the oil or gas boiler, that extends from the basement to the attic be an option?

 

[gpcollen1]

So you want a fireplace that will suck all the heat out of your house? i don't get it...

 

[benjamin]

I'm not a mason but it sounds like you only need 1 1/2" cut out of the top plate and that's probably not a problem at all, especially if it's a 2x6 and not a bearing wall-parallel to the trusses. Step flashing is the way that the chimney is sealed at the roof, but I've never seen a good flashing for the chimey to siding.