Excuse my ignorance, couple of basic questions

[jbgoheels]

Our home had a gas fireplace insert in a 60" wide x 24" deep wood chimney chase that was cantilevered out of the rear wall of our home. I have built a proper foundation for the chimney chase now, but am not sure how to handle the chase itself. I added 1/2" Hardie Backer to the chase. The OSB you see is the roof decking, so it's maybe 8 ft up from the floor.

First Question: Do I use a register plate or a closure plate for this type of chase? Would it go right above the opening?

Second Question: Do I use a liner or would a double/triple wall stainless steel flue work? Or both? I'm not sure what the difference is. My thinking was that at the register/closure plate, the stove pipe would transition to a double or triple wall flue and then go through the roof, but everything I've seen shows a liner being used.

P.S. We are going to be using a Cubic Grizzly Mini Stove. 3 inch stove pipe to a 5 inch double wall flue. (This is what Cubic recommends)

 

[begreen]

Sorry to say this, but the plan will not work. The Cubic is not an EPA-approved, residential stove. It is only for temporary recreational use. Check with your insurance company on this first.

This is what is called an alcove installation. It has strict clearance requirements that should be tested and documented. The cement board does not protect the studs very much. There is no UL testing listed or alcove installation directions in the Cubic Grizzly docs. What the docs do say is:

Certifications:
None, for recreational use only
(verify your local laws and regulations)

 

[GrumpyDad]

Sorry to say this, but the plan will not work. The Cubic is not an EPA-approved, residential stove. It is only for temporary recreational use. Check with your insurance company on this first.

This is what is called an alcove installation. It has strict clearance requirements that should be tested and documented. The cement board does not protect the studs very much. There is no UL testing listed or alcove installation directions in the Cubic Grizzly docs. What the docs do say is:

Certifications:
None, for recreational use only
(verify your local laws and regulations)

per my insurance guy, cement board over studs does not reduce clearance requirements to combustibles. It only serves to mask the combustibles and that's where people get into trouble.

 

[GrumpyDad]

Our home had a gas fireplace insert in a 60" wide x 24" deep wood chimney chase that was cantilevered out of the rear wall of our home. I have built a proper foundation for the chimney chase now, but am not sure how to handle the chase itself. I added 1/2" Hardie Backer to the chase. The OSB you see is the roof decking, so it's maybe 8 ft up from the floor.

First Question: Do I use a register plate or a closure plate for this type of chase? Would it go right above the opening?

Second Question: Do I use a liner or would a double/triple wall stainless steel flue work? Or both? I'm not sure what the difference is. My thinking was that at the register/closure plate, the stove pipe would transition to a double or triple wall flue and then go through the roof, but everything I've seen shows a liner being used.

P.S. We are going to be using a Cubic Grizzly Mini Stove. 3 inch stove pipe to a 5 inch double wall flue. (This is what Cubic recommends)

View attachment 300084View attachment 300085

I think you need to stop working on what you are doing and do ALOT more research. Cement board does NOTHING to protect your house from catching on fire. And if you have one, insurance likely wont pay out. You must find a stove that can be placed in that tight of an area adhering to clearances.

 

[begreen]

Correct. There is no clearance reduction for a sheet of cement board on studs. Alcoves are tricky to design safely. The stove options that will work in this design are very limited (if any) due to the proximity of wood, especially over the top of the stove. That said, with some modifications, it's not impossible. However, it will cost more.

The Drolet Spark II and VC Aspen C3 have alcove-tested specifications in the manual.

 

[GrumpyDad]

Correct. There is no clearance reduction for a sheet of cement board on studs. Alcoves are tricky to design safely. The stove options that will work in this design are very limited (if any) due to the proximity of wood, especially over the top of the stove. That said, with some modifications, it's not impossible. However, it will cost more.

The Drolet Spark II has alcove-tested specifications in the manual.

Thats a nice little stove! Thats one of the stoves I was consider before I bought my VC Dauntless. What a dark road stove buying can take you down if you let it.

edit I just read that it's 24" from front to back inside the chase. Although the picture would say otherwise. But could he use double wall stove pipe in there or would that need to be class A?

 

[begreen]

Thats a nice little stove! Thats one of the stoves I was consider before I bought my VC Dauntless. What a dark road stove buying can take you down if you let it.

edit I just read that it's 24" from front to back inside the chase. Although the picture would say otherwise. But could he use double wall stove pipe in there or would that need to be class A?

Double-wall stovepipe can be used up to the ceiling support box. Note that most stoves require a 7' minimum ceiling height. There are a few exceptions, but this is an example of the caveats of an alcove install. In order to have a low opening as shown, the alcove front and ceiling would need to be made entirely non-combustible.

There are many past threads here where people work through these restrictions. They do this by careful stove selection and constructing the alcove to meet all clearance specs. At 60", the width is good here. It's the low front opening that needs to be addressed one way or the other. The cheapest way would be to raise the opening height to the required ceiling height of the chosen stove.

 

[jbgoheels]

Thanks for the info! I'm glad I asked. We'll be returning the Cubic. I think next steps are to take down the fiber cement boards. Cut out the alcove and put in brick or stone. Thinking something similar to this.

 

[begreen]

Yes, that would work as long as the alcove clearances are honored. The cement board can stay up. It will be needed to provide a substrate for the brick veneer to adhere to.

 

[jbgoheels]

Yes, that would work as long as the alcove clearances are honored. The cement board can stay up. It will be needed to provide a substrate for the brick veneer to adhere to.

Yep, this may allow the stove to sit out a little farther from the back wall. Thanks for the clarification!

 

[begreen]

Yep, this may allow the stove to sit out a little farther from the back wall. Thanks for the clarification!

PS: There are no ignorant questions when safety is involved. I'm glad you paused. Don't hesitate to keep on asking. And welcome.

 

[GrumpyDad]

Thanks for the info! I'm glad I asked. We'll be returning the Cubic. I think next steps are to take down the fiber cement boards. Cut out the alcove and put in brick or stone. Thinking something similar to this.

View attachment 300100

That brick could be cardboard, paper, wood paneling...doesnt really matter. The key is, what are the stove clearances to the combustible materials. So behind that cement board is where you would start measuring to the sides of the stove. Each stove has a different listed clearance usually for all six sides. For example you may think you are goodchi on the left/right sides, and the back to the back wall - then come to find out that your queen anne legged stove requires a certain R value between your non combustible pad and the combustible subfloor below. Luckily, my stove and many others did not require anything other than the non combustible hearth pad. My side clearances are 12" and the stove sits in a corner. That wall gets REALLY hot, and Im noticing the wood is starting to cup and gap already with minimal use. So I'm going to need to replace that with stone veneer because eventually that wood is just going to look aweful. Yes, Im within clearance, actually I'm 13.5" from the side wall. Had I known, I would have built my hearth pad largest and slide the stove over another few inches. I could still fix it and probably will next summer but that means removing a tile edging that I meticulously bend around corners to avoid rough edges, then adding onto my heart with this pebble pieces that I built my hearth pad out of.

Do yourself a favor and read read read on here, and give yourself some wiggle room. Look at stoves that interest you, read up about them and based your decisions on what stove you like, that seems to have a good reputation, that will work in your space. The list of candidates will kinda sort itself out for you with those things in mind.

Folks like BEGreen, seem to have seen it all and can give free (non legally binding) advice that will save you $$$$ down the road.

 

[cahaak]

I have an installation in almost the exact same alcove situation as you. I have a Drolet Myriad installed. Rear clearance is not a problem and I have 6" class A insulated double wall chimney that goes up the entire chase through the roof topped with a standard roof cap. Again, no issue here as you will meet all clearance requirements (there is / was no need to line the chase with cement board). For a 60" wide alcove and a ~24" wide stove, you won't have any issues with side clearance either. In any case, would recommend that the back and side of the alcove be done in tile, stone... It looks great, is non combustible, and holds some heat.

As others have noted, the alcove ceiling is supposed to be 7' to meet code. Mine is not that high, but I tiled the top on cement board and also have 8" of rock wool behind all of that. I have been burning for several years now and the most important thing is that the top of the alcove be flat, or slope out so that no excess heat is trapped up there - it can easily spill out. I have checked the temperature of the top of my alcove, which is just over 6' many times and it actually does not get very hot at all, it can easily be touched by hand even when the stove is being fired quite hard.

So, as long as the rear clearance on your stove allows you to position it so that the class A can go straight up the center of the chase, you can use a large number of stoves in that application. As also noted, you should use double wall black pipe from the stove up to the transition fitting to the class A. My istuation involved tearing out a zero clearance manufactured fireplace, which is why I ended up with the alcove situation - similar to yours.

 

[jbgoheels]

This is where we ended up. Drolet Escape 1200. Double wall stove pipe and then triple wall stainless steel flue through the roof. Meeting all clearances. Thanks for all of the help on this forum.

 

[EbS-P]

That look right smart!! Great design!