chimney flue height

[jake22si]

I was just wondering if there is a minimum height requirement for the clay tile over the crown? 1", 6" ??

 

[bholler]

I dont think there is a set requirement. but i could be wrong. The few times i work with clay i leave about 2"

 

[Isaac Carlson]

you want enough to get the top out of the turbulence from the cap and chimney, but not so much that the tip gets air cooled. You can get some nasty creosote buildup on the rim if it gets cooled by winter wind. 2-3 inches should be plenty and will allow a cap to be solidly attached. I would not go above 4" personally. I see a lot of liners going up 6 inches around here and they all have black around the top.

 

[bholler]

you want enough to get the top out of the turbulence from the cap and chimney, but not so much that the tip gets air cooled. You can get some nasty creosote buildup on the rim if it gets cooled by winter wind. 2-3 inches should be plenty and will allow a cap to be solidly attached. I would not go above 4" personally. I see a lot of liners going up 6 inches around here and they all have black around the top.

I agree with your reasoning but uninsulated clay is going to cool quickly i dont think it matters much how far it stick out of the chimney honestly

 

[jake22si]

I am asking because I just repaired the top couple of block and flue. I bought a precast crown and I' ve only got an inch over the crown. I suppose I could cut a 3" section out of the old flue and put it under the top liner to get it over the cap more

 

[jake22si]

Don't know how to fix sideways pics but I guess it's just above the crown. I'm gonna cap the flue. I can silicone the cap to the flue or make an extension to screw it to out of sheet metal. Then I was gonna silicone the gap between the crown and flue as high as I can

 

[jake22si]

Oh and that is an old section of flue in there just until i figure out what to do

 

[bholler]

Well what is venting into that chimney? What condition are the liners in ect?. 3" pieces of clay liner are very prone to breaking so i would pull out that top liner cut a few inches off then add a 6" piece to raise it up a couple inches. Then pack between the liner and top ring with fireproof insulation and silicone over it. But i would have the old liners evaluated to see if it needs lined

 

[jake22si]

Wood stove, I pulled 4 sections of liner 3 new and i need to buy another new section thats why the top liner is old. They cast the cap up there previously that is probably why I have the height difference now with the pre cast.

 

[bholler]

Wood stove, I pulled 4 sections of liner 3 new and i need to buy another new section thats why the top liner is old. They cast the cap up there previously that is probably why I have the height difference now with the pre cast.

Ok what does the rest of the liner look like? Did you use fire clay to put together the new liner sections?

 

[Owen1508]

NFPA -10. 7.2.13.3 says..."the lining shall extend for the entire height of the chimney to a level not less than 2 in above the crown ,splay or wash."
As always I would suggest. Checking with local codes, which most likely are the same.

I also agree with the above reasoning of there is a thing as too much. Just MHO

 

[bholler]

NFPA -10. 7.2.13.3 says..."the lining shall extend for the entire height of the chimney to a level not less than 2 in above the crown ,splay or wash."

Ok then there is the answer. I always went with 2" so i guess that was a good thing

 

[jake22si]

The rest of the liner is good, the top 4 block were replaced with brick mortar and the flues I used refractory mortar. I'm just gonna have a piece of stainless bent to fit over the flue and screw it on to give me the min 2" clearance over the cap, then I can screw the rain cap to that extension

 

[bholler]

the top 4 block were replaced with brick mortar and the flues I used refractory mortar.

That is good

The rest of the liner is good

I only ask because it would be very uncommon to have the block deteriorate to the point of needing replaced while the liners are in good shape. Have you had the chimney properly inspected? Does it have proper clearance? what stove is it venting?

 

[bholler]

I'm just gonna have a piece of stainless bent to fit over the flue and screw it on to give me the min 2" clearance over the cap, then I can screw the rain cap to that extension

That will work but if you are staying with the clay it would be a whole lot cheaper to just extend it with clay and be done with it.

 

[jake22si]

I could see all the way down about 20'. The block above the 2nd roof line was the only ones needing replacement, was originally outdoor chimney until a mudroom was added, rest of the block is solid. Someone did a patch job towards the top years ago

 

[bholler]

I could see all the way down about 20'

Ok but could you see if there were any cracks? Was the mortar still in all of the joints? Do you have the required clearance to combustibles?. If you are comfortable with it that is up to you but i can tell you from years of experience very little can be seen from above.

 

[jake22si]

All nice and straight below the roof line, cleaned it and no visible cracks. I can't re-line this without breaking all the flue tiles so as of right now it is better than it was before.

 

[bholler]

All nice and straight below the roof line, cleaned it and no visible cracks. I can't re-line this without breaking all the flue tiles so as of right now it is better than it was before.

ok then it is your choice.