# Sealing air gap around chimney in wall?



## Slow1 (Jun 17, 2009)

Here is what I have going - 

I have a class A stainless chimney exiting through my wall.  I know that there has to be a 2" air gap around it (at least that is what I have read) but there is also the thimble (?) on the inside that surrounds it has less than 2" and something like it on the outside.  Now the end result is that there is a lot of air that can blow through this hole in the wall around this chimney.  Is there some sort of high temp foam or something that can be used to seal around this to keep the wind from blowing through?  Or is this just one of those things one has to deal with if you want to have a stove? (that would seem rather odd to me...)

For the summer (to keep the cool air in and hot air out) I've taken to stuffing some plastic wrap in the gap between the SS and the thimble, but clearly that can't be there when we burn.

Suggestions?  Thoughts?

Thanks.


----------



## Wood Heat Stoves (Jun 17, 2009)

brand of pipe?
pics?

the air gap needs to be left alone. however, some high temp silicone might seal your thimble cover ok....post a pic or two...


----------



## Slow1 (Jun 17, 2009)

Pipe is Simpson DuraVent.  Pictures here:

Note that you can see where I have stuffed the plastic wrap to fill in the gap where the air flows in/out...

(Yes, I know the pipe is missing the stove... it has been removed as I prepare for the replacement)


----------



## Wood Heat Stoves (Jun 18, 2009)

black high temp silicone should work to seal that Dura-tek thimble cover


----------



## BrotherBart (Jun 18, 2009)

For stuff like that I use fiberglass stove gasket rope.


----------



## Slow1 (Jun 18, 2009)

Then can I use 'normal' caulk around the outside of the thimble cover or is there clear/white high-temp silicone to use between the cover and the wall? I figure once I seal between the pipe and the cover that very likely the air will just try to push out around the edges since that isn't sealed...


----------



## Wood Heat Stoves (Jun 18, 2009)

BrotherBart said:
			
		

> For stuff like that I use fiberglass stove gasket rope.



good call, use 500* silicone to hold it in place


----------



## Wood Heat Stoves (Jun 18, 2009)

you could  use regular caulk around the outside,
 i'd use 500* where touching pipe, find black, silicone isn't paintable


----------



## Todd (Jun 18, 2009)

What about a trim collar? http://www.hartshearth.com/productcart/pc/viewPrd.asp?idproduct=3981&idcategory=514

Why is the stainless chimney coming through the thimble? It should terminate at the bottom with a tee and the stove pipe should go through the thimble and connect to the snout of the tee?


----------



## Wood Heat Stoves (Jun 18, 2009)

Todd said:
			
		

> What about a trim collar? http://www.hartshearth.com/productcart/pc/viewPrd.asp?idproduct=3981&idcategory=514


a heat fab collar for his duratek??

huh??

he has a trim collar already!! its his thimble cover


----------



## Slow1 (Jun 18, 2009)

Todd said:
			
		

> Why is the stainless chimney coming through the thimble? It should terminate at the bottom with a tee and the stove pipe should go through the thimble and connect to the snout of the tee?



The tee and cleanout are outside (which as you realize I'm sure makes for a 90* bend) that has this pipe attached and is run through the wall.  My chimney is actually outside the house:


----------



## Todd (Jun 18, 2009)

I thought there should be a finishing collar to fill that gap? Is the thimble the same brand and size as the chimney pipe? Do you also have a gap on the outside? Just doesn't look right to me. How was your VC hooked up to this?


----------



## Slow1 (Jun 18, 2009)

I don't know make/model of the black piece - I can ask the sweep who installed when I see him again I suppose.  I plan to ask him what he thinks of the gap anyway.  I'd just rather already have a good idea of the right answers first so that's why I'm asking here now.

As to gap on the outside - I imagine there must be some out there given the amount of air flowing through (has to come through the siding etc somewhere eh?) but I have not climbed up to take a look.


----------



## Wood Heat Stoves (Jun 18, 2009)

the class a chimney must penetrate the wall.
looks like a nice/ appropriate install to me!!
although the class a doesn't need to stick out so far, 2" would be aok


----------



## Slow1 (Jun 18, 2009)

Originally there was a 90* elbow down right there than went straight to the stove and that made for the min clearance so it actually worked out quite well.  New stove, if I go with min clearance to back, will not need as much distance from the wall so I'll need to shorten this piece (i.e. replace it with a shorter section).  I haven't yet decided exactly how I want to go about that one yet.  Stove might look fine a bit farther out from the wall - nothing says you have to install to minimum clearance even though it seems folks try for it.


----------



## jtp10181 (Jun 18, 2009)

Yeah, install looks fine and proper to me. We use simpson duravent on every job. Just need some silicone caulk to seal out the draft. I would get some black for inside and some clear and do the outside also.


----------



## Wood Heat Stoves (Jun 18, 2009)

Todd said:
			
		

> I thought there should be a finishing collar to fill that gap? Is the thimble the same brand and size as the chimney pipe? Do you also have a gap on the outside? Just doesn't look right to me. How was your VC hooked up to this?



metal bestos requires a finish collar(in some cases), he has dura, looking good!!


----------



## Wood Heat Stoves (Jun 18, 2009)

Slow1 said:
			
		

> I don't know make/model of the black piece - I can ask the sweep who installed when I see him again I suppose.  I plan to ask him what he thinks of the gap anyway.  I'd just rather already have a good idea of the right answers first so that's why I'm asking here now.
> 
> As to gap on the outside - I imagine there must be some out there given the amount of air flowing through (has to come through the siding etc somewhere eh?) but I have not climbed up to take a look.



 he did a fine job! duras install manual doesn't adress this issue very well if i recall


----------



## begreen (Jun 18, 2009)

From the DuraVent installation manual, pages 17-19:

3. Install Wall Thimble: The Wall Thimble is a three piece unit which includes the cover plate, sleeve extension, and the back portion with shield. On the outside wall, install the back portion of the Wall Thimble. Center the back portion of the Wall Thimble (with shield inside wall) in the framed opening of the outside wall. *Be sure to seal the flange of the Wall Thimble around the wall by using a non-hardening waterproof sealant.*

6. Install Branch onto Tee: From inside the house, attach the Chimney Branch (a 12" or 18" Chimney section, depending on wall thickness, positioned horizontally used to pass through the wall) to the Tee by twist locking it clockwise. Important: The Chimney section used to penetrate through the wall must extend at least 6" into the room (Fig 25 & 27). *Use high-temperature sealant (500 deg F) to seal between the Wall Thimble and the Chimney on the outer wall.*


----------



## Slow1 (Jun 18, 2009)

Thanks everyone for the replies - I think that BeGreen about settled it with that quote from the manual...  Now I'll just have to pick up some of that sealant once I get the new stove in place.


----------



## Wood Heat Stoves (Jun 18, 2009)

BeGreen said:
			
		

> From the DuraVent installation manual, pages 17-19:
> 
> *Use high-temperature sealant (500 deg F) to seal between the Wall Thimble and the Chimney on the outer wall.*



i knew that stood out in my head for a reason..


----------



## Todd (Jun 18, 2009)

BeGreen said:
			
		

> From the DuraVent installation manual, pages 17-19:
> 
> 3. Install Wall Thimble: The Wall Thimble is a three piece unit which includes the cover plate, sleeve extension, and the back portion with shield. On the outside wall, install the back portion of the Wall Thimble. Center the back portion of the Wall Thimble (with shield inside wall) in the framed opening of the outside wall. *Be sure to seal the flange of the Wall Thimble around the wall by using a non-hardening waterproof sealant.*
> 
> 6. Install Branch onto Tee: From inside the house, attach the Chimney Branch (a 12" or 18" Chimney section, depending on wall thickness, positioned horizontally used to pass through the wall) to the Tee by twist locking it clockwise. Important: The Chimney section used to penetrate through the wall must extend at least 6" into the room (Fig 25 & 27). *Use high-temperature sealant (500 deg F) to seal between the Wall Thimble and the Chimney on the outer wall.*



You forgot the part about installing the finishing collar to hide that silicone globbed gap.

7. Install Cover Plate and Finishing Collar: After the Chimney Branch is
secured in place (penetrating at least 6" into the room), slide the Cover Plate over
the Branch and attach it to the framing using (4) 1-1/4" long, round head wood
screws. Be sure that the Branch is centered in the opening of the Cover Plate. Twist
lock the Finishing Collar on to the female end of the Chimney Branch by twisting
clockwise


----------



## jtp10181 (Jun 19, 2009)

He has the finish collar on there already. Its the small black ring that goes in the end of the silver class A pipe to transition the pipe over the durablack or DVL.


----------



## Todd (Jun 19, 2009)

jtp10181 said:
			
		

> He has the finish collar on there already. Its the small black ring that goes in the end of the silver class A pipe to transition the pipe over the durablack or DVL.



Ok, maybe I don't understand, I thought there is suppose to be a finish collar over the class A to hide the gap between it and the thimble gap?


----------



## jtp10181 (Jun 20, 2009)

Todd said:
			
		

> jtp10181 said:
> 
> 
> 
> ...



The thimble covers the hole in the wall, and the pipe is only slightly smaller than the hole in the thimble. That small gap is bridged with black silicone, and if you are good with a caulk gun it looks good when done. They also make some of the short class A painted black, which you are supposed to use where it sticks into the wall, but no one does.


----------

