Is this Thimble Safe? (Need a Mason's Help)

[pen]

Here are the circumstances.

Stove was installed in the home in 1981. Stove has been burned every year since. After posting a recent topic highlighting my new wood rack, a fellow member tipped me off on inspecting my studs as they appeared to be very close to the thimble. I was concerned about this in the past, but dismissed it as the stove has never had problems in 27 years, the home has been sold 3 times and inspected each time since its installation, various insurance companies have insured the home, etc, etc. I realize that these things are simply rationalizations (the lies we tell ourselves).

What are the opinions of those who are truly in the know? Is this safe? Is there a Real reason for concern?

I would have thought that there would be evidence of damage if this is a problem considering the length of use? Am I being paranoid? Or is this a situation that the inspectors did in deed miss over the years?

Thanks.

Opened the wall up a bit to inspect (I have since closed with sheetrock and mudded)

 

[begreen]

I'm not sure about the thimble. Given the proximity of the drywall to the single wall pipe I wouldn't be comfortable with it. It sure doesn't seem to be protecting the paper covered drywall from the single-wall pipe. It looks almost flush with the wall. Is this thimble insulated or does it just keep an air gap?

Also important are clearances from combustibles. Is the stove 36" from the nearest combustible? Is the stove pipe 18" or more away from the paper covered drywall?

The stove sure looks in nice condition, almost like new. Has this been used much at all?

 

[pen]

Thank you for the compliment on the stove. The stove has been used every winter since 1981. Last winter the furnace only ran 3 days, and those three days we were away for the holidays. Not bad for the Endless Mountains of Pennsylvania in my opinion. I burned about 5 cords of maple, ash and cherry. The previous owners have done the same in the past. I did sand and repaint the stove this year as I am finishing the basement off.

Yes, the clearances to the combustibles including the drywall and the wood box are safe.

Only question is the proximity of the stud with that 3 inches worth of masonry around the thimble.

What you see there is what it looks like after burning for 27 years.

Yes, the thimble does not stick through the dry wall. All there is around the single wall pipe is the beauty ring and a small air gap. This is 5/8 in drywall. The paper doesn't seem to show visible signs of fatigue, over heating, etc.?.

I am in the process of finishing this basement (the wall behind the wood rack I just drywalled last weekend) so now is the time to make some changes if necessary.

My plans were to pull those studs if others believed it to be necessary and replace with metal studs. However, by the appearance of what I am looking at, it doesn't visually look necessary.

My finishing plans also include tile work around that single wall pipe and down the concrete wall behind the stove, as well as a hearth pad underneath. The rest of the floor in the basement will be epoxy painted.

Some year, when funds are correct I do plan on lining the chimney and including a new eco-friendlier stove. But for the time being, this old beast throws a wonderful amount of heat and goes through a reasonable amount of wood for the winter. With other things on the plate, I can't justify spending the money on the old girls replacement quite yet.

Thanks again for the response.

pen

 

[offroadaudio]

I would personally feel very uncomfortable burning that stove with that thimble.
I don't have lots of experience, but have researched them to death in the last week, as I'm getting ready to install one.
I'd be concerned about the clearance to the drywall (drywall is considered a combustible because of the paper front and back)
I'd also be concerned about the clearance to the wall studs.
To make sure you are safe, google "combustible wall pass through" - and read up.

Good luck, be safe.

'Frank

 

[pen]

I would personally feel very uncomfortable burning that stove with that thimble.
I don't have lots of experience, but have researched them to death in the last week, as I'm getting ready to install one.
I'd be concerned about the clearance to the drywall (drywall is considered a combustible because of the paper front and back)
I'd also be concerned about the clearance to the wall studs.
To make sure you are safe, google "combustible wall pass through" - and read up.

Good luck, be safe.

'Frank

Thanks for the advice. I turned up this suggestions from of all places, hearth.com

I believe that I can make this work quite easily. I have laid tile with good success. I suppose laying brick shouldn't be much more complicated. I'll need to find some recommendations or suggestions for mortar to use, tips etc, but I can make this work.

My only question will be that what happens to the air space between the brick shown here and the chimney? Is that considered insulation enough? The only difference this would make is that the current thimble will have a 12 inch shot before directly "seeing" a stud, whereas it is 3 inches now. Should fiberglass insulation be put in this void?

Are there other suggestions? Recommendations?

Thanks so much guys.

 

[pen]

I am hoping to fix this problem by building a thimble that resembles the picture above but I have a few questions that I want to understand before I open this up and expose everything to air.

1. I am ok with what I am doing on the interior wall, 12 inches of masonry all the way around. However, what about on the outside wall of the house? I am assuming that when I open the wall I am going to see the ouside of the house's black board (masonite?) with a simple hole in it that the current 3 in thick thimble goes though. I highly doubt that I'll be able to see the chimney as the picture suggests. How do I address this? Do I cut the black board back and put the same 12 inches of masonry around out there as well?

2. The air space shown in the side view of this picture> Is it simply an air space so that the current thimble / crock has a direct view at the stud that is 12 inches away? Or do I turn my last course of brick on end to lock the air space in? Do I put a 4 inch strip of fiberglass insulation around the outside to protect the studs?

3. BeGreen and other research have mentioned an 18 inch clearance from the stovepipe to combustibles. If I do this thimble to 12 inches out on all sides, won't this fall shy of that 18 inch mark to my drywall? Or even a trim piece that could be used to match the drywall to the brick? Should i go 18 inches on all sides?

4. What suggestions are there for mortar?

I really appreciate everyone's help and suggestions. I want to do this right and be safe. I am very apt with this sort of project, however I need the guidance from those of you doing this day in an day out to do the setup correctly as I can't seem to turn up answers to these questions.

I tossed and turned all night last night thinking about this.

Thanks

pen

 

[offroadaudio]

I'm right there with you pen - I thought about mine for about a week - all day and night!
One suggestion that I will make - again based on book knowledge, not experience yet - I would buy a length of class A HT chimney pipe to pass through the wall.
This lowers your clearance to combustibles to 2", saves all of that masonry work and demands a smaller hole on the outside of the house - yes, you'll have to cut away combustibles there as well - an 8" diameter hole is better than a 2' x 2' square.
The pipe is expensive, but it might be a wash for you not having to do all of the masonry work.
I hope that helped.

 

[ansehnlich1]

Pen, I feel like I got you started on this thing, sorry if it's been causing you anxiety. I know it caused me to be meticulous when we were building our hearth and chimney.

Here is a link to the Jotul Oslo manual, on page 6 it describes the wall pass through and then on page 14 it shows a picture similar to the one you already posted.

(broken link removed to http://www.jotul.com/en-us/wwwjotulus/)

Our stove thimble assembly is brick, 30 inches square, framed out just like in the picture. We have a 6 inch clay thimble that passes through the brick and is mortared into the clay flue tile of the chimney.

Current code where we live specifies a 1 inch gap between the brick chimney and the outer wall of the house. There is nothing in this gap, it is airspace.

I found this schematic online, it shows one way to handle the exterior wall of the home. It does NOT show a thimble assembly though.

(broken link removed to http://gov.allconet.org/permits/04/DWG) 61 - Masonry Chimney X Section.pdf

hope this helps!

 

[pen]

I'm right there with you pen - I thought about mine for about a week - all day and night!
One suggestion that I will make - again based on book knowledge, not experience yet - I would buy a length of class A HT chimney pipe to pass through the wall.
This lowers your clearance to combustibles to 2", saves all of that masonry work and demands a smaller hole on the outside of the house - yes, you'll have to cut away combustibles there as well - an 8" diameter hole is better than a 2' x 2' square.
The pipe is expensive, but it might be a wash for you not having to do all of the masonry work.
I hope that helped.

Thanks for the advice. I think for my application I will actually prefer to go with the masonry. I would have to remove the current masonry work from around the crock to find a zero clearance pipe that would fit. Eventually, an insulated liner will be added in the current crock anyway to drop it from an 8in diameter down to a 6 to accomodate a new stove (again some decade).

I agree though, that I feel that the zero clearance pipe is the best solution.

thanks,

pen

 

[pen]

Pen, I feel like I got you started on this thing, sorry if it's been causing you anxiety. I know it caused me to be meticulous when we were building our hearth and chimney.

Here is a link to the Jotul Oslo manual, on page 6 it describes the wall pass through and then on page 14 it shows a picture similar to the one you already posted.

(broken link removed to http://www.jotul.com/FileArchive/Technical) Documentation/Wood Stoves/Jøtul F 500 Oslo/Manual_F_500_USA_P11_180808.pdf

Our stove thimble assembly is brick, 30 inches square, framed out just like in the picture. We have a 6 inch clay thimble that passes through the brick and is mortared into the clay flue tile of the chimney.

Current code where we live specifies a 1 inch gap between the brick chimney and the outer wall of the house. There is nothing in this gap, it is airspace.

I found this schematic online, it shows one way to handle the exterior wall of the home. It does NOT show a thimble assembly though.

(broken link removed to http://gov.allconet.org/permits/04/DWG) 61 - Masonry Chimney X Section.pdf

hope this helps!

I appreciate you making me nervous! I needed that. I have become casual in its regard because I assumed the inspector and others involved over the years had done their job. I know better than that but it took your comment to get my going on the investigation.

Any chance you can try that first link again? The way that Jotul is spelled funny doesn't seem to be translating and is screwing things up.

Thanks again,

pen

 

[rustynut]

hi there,
had a friend that had the morter on the joint getting old between the block chimney and pipe without him knowing
loosened up enough for a piece to come out
in this area the fire pushed out that little hole like a propane torch
this happened while he was asleep
two good things
he woke up
and
he had insurance
burned the cabin down
check it over good
rustynut

 

[ansehnlich1]

Ok pen, I couldn't get that Jotul link to work, so I placed a different link in there for you, it goes to the technical documentation page....then look up the F500 Oslo manual to get to the picture of the wall pass through.

The other link will work if you cut and paste the whole thing into your web browser.

 

[pen]

Ok pen, I couldn't get that Jotul link to work, so I placed a different link in there for you, it goes to the technical documentation page....then look up the F500 Oslo manual to get to the picture of the wall pass through.

The other link will work if you cut and paste the whole thing into your web browser.

Thank you. I was able to find and view the manual.

Just to be clear, your brick/mortar front has an air gap behind it with nothing in it but air? So technically, the brick front just keeps the crock from being near to any combustible wall material. But, behind the brick there is an air space that works to insulate the stud that is at least 12 inches away? I would have thought that there would be insulation or something in here, but apparently not.

If so, then my only concern is going to be what is over the outside material of the house (the area betwen the chimney and the inside of the house) is as I will not be able to see the chimney when I remove this drywall. From what I can see behind the chimney from the outside, it is definately a different substance (some sort of fiber board) that is different than black board that surrounds the rest of the house. It had better be some sort of fire board because I don't know how I could get behind the chimney to replace it otherwise.


pen

 

[ansehnlich1]

Just to be clear, your brick/mortar front has an air gap behind it with nothing in it but air? So technically, the brick front just keeps the crock from being near to any combustible wall material. But, behind the brick there is an air space that works to insulate the stud that is at least 12 inches away? I would have thought that there would be insulation or something in here, but apparently not.

If so, then my only concern is going to be what is over the outside material of the house (the area betwen the chimney and the inside of the house) is as I will not be able to see the chimney when I remove this drywall. From what I can see behind the chimney from the outside, it is definately a different substance (some sort of fiber board) that is different than black board that surrounds the rest of the house. It had better be some sort of fire board because I don't know how I could get behind the chimney to replace it otherwise.

Yep, only thing between the brick thimble assembly and the chimney is an air space. You don't want any combustible material in that area. I think your reference to a black fiberboard on the exterior of your home means that you'll have to remove that too when you break through the wall to build the brick thimble assembly.

 

[pen]

Sounds great. Now it's just a matter of getting the brick and mortar.

Time to learn something new!

I appreciate everyones support.

pen

 

[ansehnlich1]

Sounds great. Now it's just a matter of getting the brick and mortar.

Time to learn something new!

I appreciate everyones support.

pen

Keep the following in mind when you go for your mortar:

"Refractory mortar must be used at the junction of the chimney
and the pass-through liner. The pass-through liner must not
penetrate the chimney liner beyond the inner surface of the
chimney liner. Use extreme care when constructing the hole
in the chimney liner, the tiles can shatter easily. See figure 4."

 

[pen]

Sounds great. Now it's just a matter of getting the brick and mortar.

Time to learn something new!

I appreciate everyones support.

pen

Keep the following in mind when you go for your mortar:

"Refractory mortar must be used at the junction of the chimney
and the pass-through liner. The pass-through liner must not
penetrate the chimney liner beyond the inner surface of the
chimney liner. Use extreme care when constructing the hole
in the chimney liner, the tiles can shatter easily. See figure 4."

I saw that in the manual. They give very nice directions. I plan on inspecting this and if it appears to have no flaws, then I will be leaving it as is since the current crock and thimble will stay in place assuming I don't find a problem. To solve my problem, I simply am going to be removing these studs, installing a header, adding the brick and mortar to the inside and making sure the material used for the outside wall around the crock is appropriate and fire rated.

Thanks again for taking interest and being such a great help.

pen

 

[ansehnlich1]

I see what you're planning to do. That'll work, just keep combustibles 12 inches from the thimble.

Take pics along the way and post 'em here, it'll be nice to see the progress.

What is that current thimble surrounded by now? It's hard to tell in the pic, is it brick around there now?

 

[pen]

that's the best I can tell as well.

It is going to be at the earliest sunday but with many things going on it is more likely around christmas when I have some vacation for me to get to this. Right now, I feel much better by inspecting the studs and seeing that there is no sign of charring. While I know the situation is not right and needs corrected, I at least know that it is not on the verge of self destruction.

When it comes time for the project I will share my progress. I love pictures, so it'll be non-56k friendly for certain.

I think I will actually end up facing the brick with tile to match what I will be lining the concrete wall behind the stove with and the hearth pad. I think its time to pick that out as well.

pen

 

[stoveguy2esw]

look at page 7 of this manual , the insert on this page is straight out of NFPA211 hopefully it will show you what you will need to do the thimble correctly.

http://www.englanderstoves.com/manuals/30-NC.pdf

im not liking what im seeing with that thimble

 

[pen]

look at page 7 of this manual , the insert on this page is straight out of NFPA211 hopefully it will show you what you will need to do the thimble correctly.

http://www.englanderstoves.com/manuals/30-NC.pdf

im not liking what im seeing with that thimble

thanks. That is the same as how Jotul presented the information also.

pen

 

[webbie]

Yep, what you have is wrong, as you already know.
As to that wall patch, there does not have to be an air space between the brick - basically a giant heat sink to soak up the heat. In your case it can be inside the wall, and then you could finish it even with the wall using cement parge or even wonderboard.

Or, you can get one of the prefab thimbles like made by Heat-Fab, etc.
(broken link removed to http://www.woodstove-outlet.com/woodstove/Ocp21480.htm)

 

[pen]

Yep, what you have is wrong, as you already know.
As to that wall patch, there does not have to be an air space between the brick - basically a giant heat sink to soak up the heat. In your case it can be inside the wall, and then you could finish it even with the wall using cement parge or even wonderboard.

Or, you can get one of the prefab thimbles like made by Heat-Fab, etc.
(broken link removed to http://www.woodstove-outlet.com/woodstove/Ocp21480.htm)

Thanks for the advice. With the healthy price tags on those pre-fabs, I think i'll stick with the brick and mortar.

I think i will actually be finishing the front with tile, but will have to make that decision once I get the brick all in.

pen

 

[justneedit]

Hi, Two thoughts I would like to add. First, bricks are heavy. Make sure you have enough wood framing to support the weight of the bricks you're going to be laying inside the wall. Your sketch shows just a single 2x4 running horizontally with no verticle supports under it. Second, if you are planning to run tile on the wall behind your stove why don't you replace that sheetrock with wonderboard or durock brand cement board? This will be a better tile backer and also it's fireproof. Good luck.

 

[pen]

I did all those things.

Didn't need to worry about the weight because there is a concrete knee wall right behind the stove that I built this on. Also, I removed the blackboard (cheap replacement for plywood used on the ouside of the house) so that it was 12 inches away from the thimble and replaced with concrete board.

I then bricked the entire thimble in (2 layers) Behind what is seen, I added brick to what was existing to blow it out 12 inches. Then, I tied that into the big 5 brick wide wall protector behind.

All said and done, there are 57 bricks in the front that are visible and another 35-40 (I forget now) behind what is visible surrounding the thimble. About 120lbs of mortar involved

If that is not enough of a heat sink, then I give up!

Considering the original wood was not damaged after 27 years 2 inches from the thimble, I feel very confident that I am safe now. No combustibles are closer than 14 inches to the crock.

I'll start posting pics. Now I need to ask how long I should wait until I fire up the stove?

They are calling for 12 degrees tonight. I finished laying brick at about 2am last night!

Is about 16 hours 6pm tonight, enough time to cure? Or should I let it go a full 24 or 48?

As much as I hate using the oil furnace, I would much rather use it tonight than crack the brick I just installed.

I am fairly proud of the results for my first time. I definately learned a lot doing all the research, talking to you guys, and then of course doing the work.

Thanks so much for helping me make my home safer! Especially thanks to ansehnlich1 for making cognizent of the problem and getting this started.

pen