Installing chimney/ need advice

[dug]

Gonna fire up the chainsaw and put a hole in my perfectly sound roof tomorrow to install the stove pipe. I have a pretty good plan of attack (I think) but am a little unsure of a couple things. Just kidding about the chainsaw part by the way 

1st question:

I need to jog the pipe about 3 feet over, not exactly ideal I know but I need to avoid some open beams. A small planning blunder but I didn't think it would be that big of a deal, so I ordered two 45 degree elbows to make the offset. While going over the instruction manual I read read that they only manufacture these elbows in 15 or 30 degree units. You are not allowed to combine a 15 and a 30 to make a 45. Surprising, especially since I'm holding their brand of a 45 degree elbow in my hand. 

So will this draw O.K? I didn't think anything of it because I've seen stoves make a 90 degree out the wall and another one up.  The top of the stack will be located very near the peak, and extend 2 feet above it. It is an open cathedral ceiling and the total chimney height will be about 20 ft.

Also, how much harder will this be to clean? I have to admit I have never swept a chimney.

Question 2;

On the roof I am able to tuck the chimney flashing under the ridge cap, which seems very tidy but the storm collar is totally reliant on caulk, which I do not like. It is a thin flat piece of steel that you wrap around the chimney and clips together. Is that all there is to it? Just a bunch of caulk and call it good?  Silicone?

Thanks!

[MountainDon]

The storm cap fits the insulated pipe very tightly. Installed just above where the flashing cone meets the pipe is is very effective when silicone caulked. Those have been done that way for decades.

Re the bends. I've had a chimney with a three foot section of straight pipe between two angles. I don't recall if they were 45 or 30 or 15,    The big difference in that installation was that chimney was supported by the ceiling mount below the jogged section. The upper lengths were then held in place by some extra brace/mount and then the pipe passed up through the roof and was steadied again by the flashing cone. I don't know what to expect with the elbows and jogged pipe hanging from an upper mount. Will the jog apply a torque to the hanging pipe; make it difficult to stay vertical?  No idea on that for sure, just babbling as things pop into my head.

[MountainDon]

Cleaning the chimney with the elbows was no big deal. I used flexible thread together fiberglass wands and pushed the brush down the pipe from the top, pulled back up and repeated once. Still have and use the same wands. 30 years old.

[dug]

 

I don't know what to expect with the elbows and jogged pipe hanging from an upper mount. Will the jog apply a torque to the hanging pipe; make it difficult to stay vertical?  No idea on that for sure, just babbling as things pop into my head.

I was wondering the same thing, I guess I'll find out. If it won't hang right I figure I can make some sort of bracket spanning two beams that holds it.

Thanks for the info on the brush, nice to know I'll be able to clean it out O.K.

Cutting the hole in the roof- the chimney needs to be 2 inches from combustibles so do I just cut the entire hole 2 inches larger than the pipe? The only other option I can think of would be to cut just the sheathing opening larger, which seems a bit tricky.

[MountainDon]

dug, you got me wondering about chimneys.

On reflection I think the offset installation I did probably used 30 degree elbows. I have Selkirk chimney and dug out the info I had saved on them. In there I found the statement that "Forty-five-degrees (45°) Elbows may be used only with oil or gas appliances."   IIRC you have Simpson Dura-vent. I did a google. I found this page. It states that "A 45-degree elbow in any U.S. all-fuel chimney installation does not comply with the International Building Code."

I think that may be why when we read info on installing a wood stove chimney the charts are only referencing 15 and 30 degree elbows.  http://www.whitecaps.com/docs/offset_chart.php  I think you should look deeper into this before cutting that hole in the roof.

I also have doubts on using the elbows below the mount that carries all the weight of the chimney. I can only find installation directions for elbow use under the ceiling support mount and there they show the elbows above the support.  I'm pretty sure you will need to brace the pipe at the lower elbow in order to get a safe vertical hanging pipe

I hope that doesn't mean you may have issues with the materials you bought.



As for cutting the hole, do remember that because of the roof slope the hole will actually be an oval or an ellipse to maintain the 2 inch clearance.  I found it would have been a lot easier if I had the chimney parts and stove on hand when the roof was sheathed but before the metal was applied. Hindsight is wonderful. I chewed away the OSB under the metal in a few spots, chiseled and nibbled.

[dug]

I hope that doesn't mean you may have issues with the materials you bought.

I can probably send the 45's back and get 30's, it shouldn't affect the rest of the parts I got, or where I want the chimney to exit. Bummer though, I was really fired up to get this done today (25 degrees now!).

It would be easy to support the top elbow in my situation, but the bottom one would be more of a challenge. I'll have to contemplate the problem a bit more. Just wondering, How do the stoves that exit the wall and go up get around this? I see lot's of those.

As for cutting the hole, do remember that because of the roof slope the hole will actually be an oval or an ellipse to maintain the 2 inch clearance.

I made a template using 30# felt paper rolled and taped in the same diameter as the chimney, and cut at a 45 degree angle so I can mark the hole more accurately. Hoping that works out O.K.

[MountainDon]

How do the stoves that exit the wall and go up get around this? I see lot's of those.

There is a special wall exit mount kit that supports the exterior chimney on a shelf like bracket, supporting the entire run of exterior chimney

FWIW, I also read that the elbows are not listed for use in an exterior run of chimney, only inside the building.

[dug]

So is the offset limitation of 30 degrees due to achieving proper support of the chimney rather than it's ability to draw well?

I figured out a way that I could make the top elbow land directly between two beams spaced 5 ft. apart and I think I could build a steel support between them to make it very secure.

I've been pouring over the manual and found something I missed about the support box-



This is an image I pulled off the web that shows how it is supposed to penetrate the roof and fold down flat. This one shows it going over the decking but my manual says it can go on top of the roof as well. I will have to trim mine a little tighter to fit on the flats of my metal roof.  I guess this would be to support the box and stove pipe below more effectively, though I thought nailing it to the rafter framing would be sufficient.

[MountainDon]

So is the offset limitation of 30 degrees due to achieving proper support of the chimney rather than it's ability to draw well?

I don't know, dug.    

If you are going to use that folded over technique with nailing.screwing to the roof I would first secure the support to the rafters/framework before bending it. My reason is to ensure getting that box 100% level, or at 99 44/100ths   , before bending. I had excess length on the straps for my ceiling mounts and bent them over like that after I got the unit level. It is the levelness of the support that makes the pipe vertical, or not.

I used truss head screws for temporary when setting it level, then nailed and removed the screws and put more nails in the screw holes.

[dug]

Thanks a lot for all the help Don. I am trying to work all this out right now and I do not want to screw it up!

I was thinking the same thing about getting the box plumb and temporarily secured before bending the metal over. It's a bit confusing to me but the manual says the box must extend to cover the sides of the sheathing. Not sure why? 

So the challenge now is to cut the rectangular hole accurate because I no longer have 2 inches of leeway to work with. I made another template, this time using the box that the support box came in, to mark the hole. 
Going to go give it a shot now. 

[metolent]

Hi Dug,

Any chance you have any pics of how you supported the 15 or 30 degree bends in your chimney?  I basically have to do the same thing since I have a ridge beam in the way and will have my stove centered directly underneath.

matt

[dug]

Any chance you have any pics of how you supported the 15 or 30 degree bends in your chimney?  I basically have to do the same thing since I have a ridge beam in the way and will have my stove centered directly underneath.

matt
Posted on: November 18, 2010, 09:19:15 AM

Right now the stove is in a temporary spot with the stack going straight up. The lower elbow will be directly under a rafter tie so I think I can easily run a bracket down from the beam that attaches to a clamp around the elbow. I'm hoping to make it look nice using wrought iron or something.

It seems if I get the bottom one locked in real good the rest may be pretty solid and I may not need to secure the top elbow. If I have to I'll figure something out, though that one will be more of a challenge. Guess I'll cross that bridge when I get there.

[KWillets]

1.  I believe the 45 degree limitation is on the chimney, not the chimney connector.  It's common to offset the connector a bit to get around framing.  The pipe should hang from the ceiling box without extra support, although I've never run pipe that high.

2.  High-temperature automotive silicone is good for sealing the storm cap, but regular silicone caulk will probably do.  You could add another cap if you're worried about leaks.

[dug]

1.  I believe the 45 degree limitation is on the chimney, not the chimney connector.  It's common to offset the connector a bit to get around framing.  The pipe should hang from the ceiling box without extra support, although I've never run pipe that high.

Something I recently learned: The limit is on the connectors (30 degrees) due to the tendency of the elbows to accumulate creosote. There is also a limit as to how far you can offset the vertical run, something like 3 1/2 or 4 feet. I think that is why you are allowed 90's if going through the wall (two 45's being better), but they are required to have clean outs.

This was not straight from the horsed mouth, so to speak, so someone correct me If I have been misinformed.

[MountainDon]

What I recall is a maximum six feet of pipe from one elbow to the other, which is probably about a 4 foot offset depending on whether or not it's a 15 or 30 degree elbow set.