Code and common sense

[TotheMountains!]

I'm a reasonably experienced woodburner, and have set up a number of both wood and coal stove installs. I bought the house I'm in about 18 months ago, and inherited a pretty hinky Chinese bolt-together stove on a too-small hearth. Now I'm installing a used RST stove (I think that's the brand, anyway). The hearth that was in place did not have good common sense front clearance, so I've ripped it out and have a couple of big pieces of 1-1/4" thick slate I'm going to put underneath it to provide 18" to 20" of front clearance.

So here's my area of doubt: The thimble is in a full brick false wall that cuts off a corner of the living room. A masonry flue liner leads from the face of the brick wall to the interior, lined, cinder block chimney. This flue liner has a horizontal run of 18" and a 45-degree bend, to meet the lined chimney. It appears to be well-made, but I scoured it and scraped it and wire-brushed it with muriatic acid, wiped it clean, then patched all cracks and gaps with a full tube of fireplace mortar, using a piece of a cedar shingle as a putty knife.

I think this false, diagonal wall that cuts off the corner of the living room is just conventionally framed: a wooden stud wall, faced by the brick to about shoulder height, then with a piece of sheetrock above it. After all of that, I started to think about how I don't really know what's inside this interstitial space, formed by this false diagonal wall. I assume that it has some wood framing, with the masonry flue passing through to the chimney. I assume, also, that the masonry pass-through is going to routinely reach 500 degrees or so.

What to do? There is no easy way to see what's inside this trapped triangle of wall, though I can take down the sheetrock above the brick hearth wall. Is this a sound installation as I'm going, or a terribly bad idea? Do I rip down the sheetrock to look into this trapped space? Is a sound masonry pass-through all I need to think about, and put worries to rest?

Thanks in advance for all thoughts.

 

[begreen]

It wouldn't hurt to make a patchable inspection hole in the drywall so that you can get a light and an eyeball in there. Can you post a picture of the area in question? If the thimble is masonry it needs to have a generous clearance to combustibles.
https://www.hearth.com/econtent/index.php/articles/passing_a_chimney

 

[TotheMountains!]

Wow, thanks for finding just the article for the topic -- very helpful, but also kind of worrisome. Glad I thought of this issue before connecting.

I will try to post photos tonight. I definitely want to get a look inside this triangular trapped space now. The entire false wall, above the shoulder-height brick mantle, continues to the ceiling in a single panel of sheetrock, and it's just about as easy to take down that one large piece and replace it as it is to cut an awkward little viewing panel and patch it back in. The back of the corner is also quasi-accessible if I cut down the sheetrock on a wall in the basement stairway, as that is where the chimney runs.

One thought: Is there anything like a flexible, insulated pipe segment that I can insert through the 18" masonry pass-through segment and into the chimney, and connect at the thimble to the 6" single-wall stove pipe?

 

[begreen]

Hard to say what will work without knowing where this is starting from. If the current thimble does not honor clearances to combustibles per code then bandaid solutions are just that. What's going to be important is to see exactly what this thimble passes through. Questions that need to be answered are:

• how close is th thimble to combustibles
  
• how does it tie into this chimney
• is this chimney the correct pipe for wood stove use
• and is the chimney correctly installed?

Hopefully whoever installed this paid close attention, but for peace of mind you are going to have to investigate a bit. The type of flue pipe may be able to be determined from above by pulling the cap and identifying the pipe.

 

[ddahlgren]

If everything you can see is poor quality what would make you think the part you can not see is done properly?

 

[TotheMountains!]

As an update, I want to thank you for your responses, as you encouraged me to tear open the trapped space by removing the sheetrock above the brick hearth. I was really excited, at first, to see that the pass-through flue, or crock, appeared to have been properly built up with brick between the block chimney and the brick hearth wall. But on closer inspection, I can see that the entire brick surround has pulled away from the block chimney by an inch or more, probably as the brick hearth slanted forward from the top. The pass-through flue is cracked and exposed into the space where it used to meet the block chimney. While I patched the pass-through flue cracks from inside it, a bright light from the stove side is plainly visible where this junction has been damaged.

In short, had I assumed it was going to be OK and fired up a stove in this set-up, I believe very bad things would have happened. Photos to come . . . now what to do?

 

[TotheMountains!]

 

[ddahlgren]

Being that close to the chimney is there some way to run some double wall between the chimney and the hearth and allow for the hearth to move independently of the connector pipe? I am thinking that way it is not going to pull out again. I think it would also be worth your time to put some tie backs between the wall framing and the hearth framing so hearth can not move in of out along with an access hatch in the upper section so you can inspect the connection? cover it with a picture mirror what ever. I would also put 3 or 4 metal angle straps between the double wall and chimney using the appropriate screws and anchors.

 

[begreen]

One option would be to remove all the brick and corner framing. Then put a nice veneer on the chimney, (could be brick or stone), put in a nice hearth in front and directly connect into the chimney liner with regular connector pipe.

 

[TotheMountains!]

begreen: Ultimately, that's definitely what I want, but it's November, and I may want something safe and working for the next five months. Or maybe, as you suggest, I break down the brick and framing, get back to the block chimney, and surround into the corner with concrete tile-backer board for this winter.

 

[fossil]

Yikes. I'm really glad you opened up that wall. I can't think of any way to patch or repair in place what you've got there that I would be comfortable living with. (I know...big help. Sorry. ) Rick

 

[elmoleaf]

Knock down the wood stud & brick & the half-arse clay connector. Temp up some cement bd or gyp as suggested.
Spend the winter burning safely and planning how to properly finish off the area. You could parge & paint the block or go with veneer stone, tile, thin brick. Plan a nice large flush hearth if possible. Design with enough clearances/r-value for a range of stove types/sizes.

 

[Dave A.]

I kind of like the brick, especially the built out ledge. Wouldn't be comfortable with the present connector to the chimney. Would want to redo that. Might leave the top portion of that chimney exposed, finished maybe in a matching brick, stucco, or contrasting stone and have a mantle shelf from where the brick ends back around the chimney. Otoh, if you remove the brick, you will reclaim a little floorspace.

 

[firefighterjake]

Egads . . . that could have been a bad one. Glad you took the time to do some exploration. As for a solution . . . I also do not have a very good suggestion for a Band-Aid approach for this year unfortunately . . . although I completely understand the reasoning.

 

[Oregon aloha]

That's similar to the issue I had with my fireplace face. Mine separated about an 1", the mortar and some brick had also cracked. My brick mason said there was not repair to make it stable or safe as they didn't tie it to the firebox to begin with. So mine had to come down and be rebuilt.

 

[TotheMountains!]

Well, so I have dismantled the brick false wall, toward the goal of tying directly into the chimney. That all went well, and I plan to block in the corner with concrete backer board for a temporary solution for this heating season. I don't mind living with the block chimney exposed in the corner of the room for now. But it turns out that the thimble was original to the chimney construction, and it appears that the brick of the pass-through was built in when they laid up the block. I think the heat in the pass-through created an expansion force that had cracked the pass-through and the brick surrounding it. The chimney could not be moved, so the brick wall was pushed out, cracking the crock and the mortar of this big built-up brick surround.

Now, how do I clean away the remaining brick and pass-through to have a flush surface that I can install a proper black-pipe thimble into? You should be able to see it in the attached photos. I don't want to pound on it much with hammer and chisel, because I don't want to weaken the block chimney at all. I have a diamond masonry blade for my circular saw, but this is an awkward jumble to try to stick it into to start cutting away the protruding brick, mortar and clay pipe. Anyone have a better idea?

 

[Hogwildz]

Also check the clearances and hearth specs required for your particular stove. Some stoves merely need an ember protective surface, other require and insulated minimal protection value for the hearth.
If it requires a certain insulated value, the slate alone may not meet those requirements.

 

[begreen]

The good news is it appears that the mortar mess has separated from the tile crock. I think with a flat 2" blade stone chisel at a low angle will separate the mortar from the chimney. Start at the top to the right of the tile crock working down gently until past the crock. If you accidentally crack the crock, bust it all out and replace. Not that big a deal. You have already done more work than that project would be.

What is the eventual plan? Leave it raw or put a veneer on the chimney? Are you going to leave the chimney exposed or bury it again in a corner facade?

 

[Dave A.]

Angle grinder.

 

[TotheMountains!]

Angle grinder.

Dave A.: Can you show me a link to the tool you're thinking of?

 

[Dave A.]

since you don't really care about making a nice thin cut, no need to invest in a diamond blade unless you'd be using it for other things. Just a regular grinding blade/disc rated for masonry should work at cleaning out the area with lower risk of breakage than by hammering.

Edit: Though as BG says, you should be okay with a hammer and chisel if you don't already have a grinder.

 

[brenndatomu]

Diamond blade for a 4" grinder is the way to go, very versatile, only $15 or so.