Chimney Question for New Construction

[Prof]

I'm about to start the construction process for a 1600 sq ft cape cod in Western PA. I'm acting as my own general contractor, but subing out much of the work. I have a question about the chimney. We are going to have a masonry heater on the 1st floor and a wood stove in the basement (will eventually be a finished family room). I'm going to run 2 class A chimneys up a chase (we will observe a 2+ inch clearances within the chase). The masonry heater will be an 8 inch and the wood stove will have a 6 inch. My question is this: I've read that the chimneys should be offset at the top. I've seen 4 in and 9 in offsets in different places. Does anyone know if there is anything in the building code about this? Any guidance would be much appreciated. I've attached a couple of rough floor plans (the architectural drawings are too large to upload).

 

[webby3650]

I usually stagger the 2 flues by a foot not including the cap. Will you need to offset with elbows? Or are is there enough space between the 2 already? You need 10"-12" between the them.

 

[Prof]

There should be enough space between them to avoid elbows.

 

[webby3650]

There should be enough space between them to avoid elbows.

Just make the upstairs flue taller by a foot or so. The basement flue is most likely to pull smoke down when not in use. But since it's a masonry heater, it's unlikely it will give you troubles.
That's the beauty of using class A, if there is an issue it's easy to add a section to it.

 

[bholler]

We rarely see issues with 2 flues side by side but it absolutely can happen. like webby said class a is very forgiving you can always add a section.

 

[velvetfoot]

Is this staggering about downdrafting smoke down a cold flue, because that's what my issue has been. I would have the most used flue be the highest and upwind of the usual prevailing winds. For me, I have an oil flue in the same chase and also put on an automatic damper to help. I think this arrangement has helped, some. Not sure if this is optimum from an aesthetics point of view, or whatever, but here's my chase:

Edit: And there were sections added.