Alternate Wall Protection Details?

[Bill 700]

I could use some advice on how to document an alternate wall protection detail for a wood stove installation for my building inspector.

The stove manual calls for a min. clearance to combustibles of 10" for the stove and 13" for the stove pipe. The location of the rafter above the stove dictates that either the stove sits way out into the room, or that I slide the stove closer to the wall such that I end up with an 8" clearance from the back of the stove to the wall and 11-3/4" from the stove pipe to the wall.

The manual says "If an approved wall board is used this will reduce your clearance by two thirds (2/3); however a one inch (1") air space has to be between the board and the wall."

I was going to use the details shown on the Durock Submittal Sheet # 10310, but it states that the min. distance is 12".

So, what I would like to do is to fasten 1/2" of Micore 300 (R value 1.03) to the wall, then add 1/2" of Durock on top of that. I could use 2 layers of the Micore if needed.

I'm only reducing the stove clearance from 10" to 8", and the stove pipe clearance from 13" to 11-3/4" (measured to the face of the existing drywall).

Can it be documented that this would be OK?

Or would it be correct to just submit the USG cut sheet that states that Durock is non-combustible, and rely on the stove manual for the 2/3 reduction? (My reduction is only 1/5 as opposed to 2/3 - 20% vs. 67%, so I would think that this should be OK.)

Other options?

Thanks in advance for your advice!

Bill

 

[kuma.jason]

I don't know whether or not your local building dept. uses NFPA Code 211 or not, however, it states that "After reduction, clearance shall be not less than 12" to combustible walls and not less than 18" to combustible ceilings". Exception: "Appliances listed for intallation with a clearance of less than 12" to a combustible wall or less than 18" to a combustible ceiling shall be installed in accordance with the terms of their listing and the manufacturers instructions." In that case you would only get the full 2/3 reduction if you started at a clearance of 36" or more. As a manufacturer, when we list minimum clearances, 6" on most of our stoves, it means absolutely no closer than 6". If we had a listed clearance of 14", it could be reduced to 12" according to NFPA. The best option may be a slight offset in the connector pipe. Hope this helps.

Jason

 

[Bill 700]

Jason,

Your explanation helps a lot. It seems to explain where the 12" min. came from on the Durock spec sheet.

OK, NFPA 211 says “Appliances listed for intallation with a clearance of less than 12” to a combustible wall or less than 18” to a combustible ceiling shall be installed in accordance with the terms of their listing and the manufacturers instructions.”

And the manufacturer's manual lists a clearance from the back of the stove of 10" without the side heat shields, and 12" with the side heat shields. Then it goes on to say “If an approved wall board is used this will reduce your clearance by two thirds (2/3); however a one inch (1") air space has to be between the board and the wall.” There is no mention of the 12" minimum in the manual. So, is there a logical argument that I would be installing the stove in accordance with the manufacturer's instructions?

I'd like to avoid putting elbows in the flue pipe if I can. Could I get a 2" offset with one elbow?

Thanks,

Bill

 

[kuma.jason]

I have a call into Omni Test Labratories to ask about clearance reduction. Omni is where all of the Kuma Stoves are tested for safety and clearances. You might try calling the manufacturer of your stove to ask for clarification. You are right, according to the wording in the manual, it seems you would be following the manufacturers instructions. You could also check with your local building dept. to see how they interpret the manual. I'll reply as soon as I get a call back from Omni. Avoiding a connector pipe offset is the best option, if possible. I think you'll find 4"-5" to be the smallest offset possible with double wall connector.

 

[madison]

I would take all the manuals and material spec sheets and drive down to your town/city building department and see how they interpret the code, they are typically very helpful. A few pictures of your room could also help the inspector with his interpretations of the installation requirements.

 

[kuma.jason]

I just got off the phone with Omni. The short answer given was: No reduction of clearance on a stove with a listed minimum clearance of 10". I was specifically asking about the Kuma model Sequoia, which has a listed clearance of 10". Madison made a good suggestion, taking all applicable info to the building department. The local building inspector gets the final say, and they usually base their inspection on the Manufacturers installation instructions. I have seen inspectors fail a lot of installations just because the stove manual was not available for reference at the time of inspection.

 

[Wood Heat Stoves]

as for the pipe, why not use close clearance interior like DVL? which has a 6" clearance.

as for the wall, adding extra r zalue is a good idea, but nfpa reduction is based on the air gap, not the non-combustible material....

be sure to leave the channel open to air at the top(100%) and bottom(50%) for air to "chimney" thru the shield....

lots of good advice above, your local inspector should be your source, he will be interpreting the manual/code

 

[Bill 700]

Jason,

Many thanks. I'll do a CAD drawing of the proposed installation details and make a copy of the installation manual and take both to the building department to get my permit.

It seems strange that you can put a stove 10" away from a combustible wall, but if you protect the wall it's still 10". Maybe there was no testing done to less than 10".

If I have to maintain the 10", I think that one adjustable stove pipe 90 might give me the 2" offset that I need (by rotating the middle slide connection on the elbow 180 degrees). But I sure would prefer a straight shot all the way up the stove pipe and chimney.

Thanks again for your help.

Bill

 

[Bill 700]

Dave,

Thanks, I was considering a double wall stove pipe for the stove pipe clearance, or maybe a stove pipe pipe shield.

Years ago I worked for the Charles Co. in Ohio that made the Adapta-Place for installing wood stoves in fireplaces. We made a stove pipe shield that had a 1" 90 degree bend on each side of the shield and and a sheet metal U spot welded top and bottom at the center. The shield would pretty much "snap" onto a stove pipe, center itself, and hold itself in place. The other shields were tedious to get lined up exactly right. Then you added a couple of screws to secure it. Does anyone still make a shield like this?

Bill

 

[Wood Heat Stoves]

not that i am aware of, just the straight kind..

dvl looks better, and has closer clearance, plus a stainless inner liner, so it will last longer!

a 2" offset isn't possible with dvl...

 

[kuma.jason]

Bill,

What brand and model is your stove? Maybe some of the installers here could look up the manual online and share how it reads to them. I would be glad to take a look, I was a licensed installer for quite a few years before moving to tech support and sales. Like Wood Heat Stoves suggested above, double wall connector, like Simpson's DVL, is a much better pipe all around. Also, feel free to call me if you have any other questions. 888-714-5294.

Jason

 

[Bill 700]

Jason,

Thanks, I've already talked with the manufacturer's tech support line and ran the clearances past them and they said that it sounded OK as long as I used "an approved wall board" and a 1" airspace.

I have some unused very heavy gauge corrugated metal decking, the kind that is used to support elevated concrete slabs, probably 20 gauge or thicker, that I showed on the CAD drawings that I will submit to the building inspector. If the building inspector does not approve the corrugated metal (ribs run vertically), then I will probably use 1/2" Durock, tape the seams with the recommended mesh tape and latex fortified portland cement mortar, and then parge the entire surface with the mortar to get a stucco look.

I used to install wood stoves about 30 years ago in Ohio. I did have a certification at that time, the acronym WHERF comes to mind, but I don't think that is quite right.

Thanks again for the help.

Bill