OK to have 2 sets of chimney pipe offsets?

[thisoldgoat]

I'm planning an installation which consists of a stove/stovepipe in the basement going straight up to the ceiling support into 6" ID double wall chimney passing thru a corner of a living area (enclosed in a chase), then into the attic and thru the roof. The house is a rectangle with a hip roof and a load bearing wall running down the center.

I will need to offset about 7" in the attic since the ceiling joists do not align with the roof joists.

Furthermore, it appears that I will also need to provide an offset of around 1" in that portion of chimney pipe that passes thru the chase in order to maintain 2" clearance to combustibles while keeping everything plumb. This is near the load bearing wall where both the floor joists and the ceiling joists overlap, leaving just enough room to install the components with little to no side to side adjustment possible. I'm not terribly interested in cutting/altering any framing members.

Q: Is it permissible to have 2 sets of offsets in an installation? Might there be enough wiggle room to fudge the ceiling support and/or the attic insulation barrier enough to gain that 1"?

I have not purchased any of the components yet; I am basing my calculations on diagrams/dimensions furnished by the manufacturer.

 

[Ludlow]

the ceiling joists do not align with the roof joists.

I framed houses in another life. That is very odd, unless you mean that the floor joists dont align with the ceiling joists. Roof rafters are spiked into the ceiling joists and equate to a 1.5" offset which would leave you an unobstructed 12" plumb.

 

[thisoldgoat]

Hi Ludlow, thanks for the reply. I'm probably causing confusion by calling stuff by the wrong name.

When I drop a plumb bob from the roof rafter, it points nearly dead center between the ceiling joists in the attic. Both are 16" OC.

The ends of the ceiling joists (attic floor) overlap side by side on the main load bearing wall presumably so that 14" joists could be used instead of 28". Essentially, these joists come from the sides and meet in the middle with side by side overlap on the top of the LB wall. It is this overlap that more or less dictates where my pipe supports will be. If I drop a plumb bob from the center of the ceiling joists it points a little off center between the floor joists. These joists are doubled, perhaps they are load bearing as well; they are perpendicular to the lengthwise LB wall; there is one on the other end as well. It is this doubling up of frame members that restrict side to side leeway in mounting the pipe supports.

I've thought about locating the system in another location to avoid this but the route I've chosen is really the best except for these clearance issues.

 

[jetsam]

Since you're still in the planning stages...

If the basement is not already insulated (including the floor), I would really urge you to search for basement stove threads here before putting a stove in the basement. Read some stories that people have posted. Basement stoves suffer from severe heat loss when they radiate directly into uninsulated walls or floors, and if they end up suffering from air replenishment issues, you generally can't put an OAK on them, so you're down to "open a window in the basement".

That's not to say that nobody heats from the basement- lots of people do - but there are additional challenges you should be aware of before getting into it.

Regarding the offsets, try to avoid them. They're bad for draft, which should not be an issue for you since you will have a long flue. However, you do have to sweep that pipe out. You may end up cussing yourself years later when you have to go get a broken sooteater out of the middle of the run.

 

[bholler]

Just change the framing. You don't want more than one set of offsets.

 

[moresnow]

When I drop a plumb bob from the roof rafter, it points nearly dead center between the ceiling joists in the attic. Both are 16" OC.

Nice to hear that your using a plumb! Surprising how many have never heard of, or seen one
As mentioned above I would hold the roof penetration location and frame your way down to the stove. Avoiding venting offsets in a basement install that has the potential of being draft sensitive is fairly widely accepted.

 

[thisoldgoat]

Thanks for the responses.

Regarding basement heat loss, I should mention that this home has a split level floor plan and a fully insulated treated wood foundation, the "basement" being the lower level. We once used a radiant kerosene heater down there during a power outage on a bitter cold day which heated the whole house nicely, so we are not too concerned about heat distribution; convection thru the foyer area was doing it's thing. Also, we are OK with cracking a nearby window for some fresh air.

Regarding the additional offsets, the advice given here makes sense to me and I shall seriously consider it.