Need high heat calk for metal chimney

meanwhile · #1 10/07/12, 11:10 AM

We successfully installed the metal home-made (half homemade using store bought parts) chimney pipes from the outdoor-wood-fired baking/pizza ovens. Yes, that is a mouth full.

Anyway - we needed to use calk around the top part - up on the metal roof. But, when we fired up the oven, the calk melted and ran down the metal chimney pipe into the inside.

What type of calk will not melt? Thanks.

Bearfootfarm · #2 10/07/12, 12:19 PM

High-Temp RTV should work

Need high heat calk for metal chimney - Homesteading Questions

johng · #3 10/07/12, 12:27 PM

Most home improvement stores carry fire caulk. Its made for caulking holes inside walls to keep a fire from spreading. It should do what you want.

Nimrod · #4 10/07/12, 12:58 PM

I just caulked around the ice fishing house chimny where it comes out of the roof. It goes through a piece of sheet metal which is under the shingles above where the chimny comes out and over the shingles below.

It sounds like exactly what you are doing. The fire break caulk is not what you want. It is made to expand when it gets hot and block up any holes the fire could get through, like in a wall cavity or joist.

I used a high temperature silicon sealent. It's good from -75 to 500 degrees. (I hope it doesn't ever get that cold here.) I don't know if it's the same as the RTV listed by a previous poster or not. I have used the high temp silicon before and it works well. The gap should be fairly narrow, about 1/8 inch, and you have to let it cure before you use it. It's in the section with stove products at Menards and Fleet Farm.

Way to go on designing your own system as long as it's safe. Probably cost less that the factory approved parts.

meanwhile · #5 10/07/12, 02:32 PM

Hello and thanks. We called a fireplace shop but they would not give suggestions over the phone and it is a 1 hour 10 min. drive to their place!

Nimrod: the one we made is a lot cheaper than the store-bought insulated ones and since it is only in an outdoor open shed, then it will be safe enough. We used the metal parts for stoves but not the expensive insulated one.

Thanks everyone. The chimney piece will get hot probably as much as 300 or more. Thanks for the suggestions.

plowjockey · #6 10/07/12, 02:36 PM

+1 on the high temp RTV.

Not sure how hot the pipe will get, but I use it on leaky tractor exhaust pipes, which it seems to hold up really well.

fantasymaker · #7 10/07/12, 08:02 PM

They make a stove cement Id use it....I mean I HAVE used it.

Alice In TX/MO · #8 10/07/12, 08:05 PM

Rutland Fire Clay Company - Stove, Chimney, Fireplace maintenance and Hearth Repair Products.

**fordson major** · #9 10/08/12, 06:46 AM

there was a book had details on making an out door kitchen complete with how to build an insulated chimney with steel five gallon pails, vermiculite and stove pipe up the center.

Nimrod · #10 10/08/12, 07:56 AM

Hi-Temp Silicone Sealant at Menards

FarmboyBill · #11 10/08/12, 09:23 AM

I havnt seen steel 5 gal pails in years now.

||Downhome|| · #12 10/08/12, 09:37 AM

NM I just read read it.

got a pic of the problem area?

meanwhile · #13 10/08/12, 12:20 PM

Here is a photo of the Oven chimney from the bottom side. And if you click the link below, there are more photos of the top part too.

Meanwhile, Back in Saluda | Facebook

Need high heat calk for metal chimney - Homesteading Questions

||Downhome|| · #14 10/08/12, 01:01 PM

What you really need is insulated stove pipe.at the roof at least.
then a silicone sealant will work.

That single wall is intended for "conditioned" areas, meaning heated.

When it gets hot it very well could collapse.

And if that ovens cranking that is a fire hazard.

You could very well make your own in this situation cheaper then the stainless stuff would run you.

Get some of the round duct used in hvac to cover that single wall, at least 2" diameter larger and use vermiculite or perlite to fill the void. You can get big bags from Masonry supply or garden centers.

you could use ceramic insulation and a short piece of multi-wall pipe at the roof.

the last option is to make your own insulated refractory rather then the ceramic insulation. lot of different recipes out there most use perlite as the insulator.

as it is now though the furnace cement is not a option nor the RTV.
furnace cement is not intentioned for exterior use and pretty sure that stacks temps are above the heat resistance of the rtv.

a muffler sealant may work. One I used before was a powder you mixed in water and worked into the void. don't remember what it was called though. I'm also not sure if it will do what you need. but seeing its used on mufflers I would assume.

meanwhile · #15 10/08/12, 04:44 PM

Downhome -
thanks for the tips but I don't quite understand. The black pipe does go through the other metal pipe. There is about 2 inches of space in between the black pipe and the silver metal pipe.

Do you still think we need something else in between the black pipe and the silver metal one? The black pipe is the same pipe as we use on our regular wood stoves and is the heat safe type. The silver metal thing was for another type of wood stove (Lowe's had it) and we just used it to make the lining for the black pipe?

How would we keep the perlite in the silver metal thing if we stuff it in there?

When we looked at the heat / ac type duct work, they told us it was not safe to use with a wood stove. But, they said the silver metal thing was heated safe.

Thank you for suggestions.

||Downhome|| · #16 10/08/12, 05:41 PM

I believe what you are calling pipe is the roof flashing for a smoke stack.

with chimney pipe you have single (suitable for interior conditioned areas) and twin and triple wall. Basically pipe within pipe. One insulating the other with a dead air space.

the triple wall is for a high vent. it better insulated,hence a higher exit. traditional flues work on temp for proper draft. hot air rises. too cool no draft.

my suggestion is to jacket the single wall stove pipe you have and insulate it with one or the other material. or make your own insulated refractory. not use the round duct as stove pipe.

I'm series about that single wall collapsing under the right circumstance.

you need to either condition the inside, or insulate that pipe the length.

around the boot you need the above and 2-2 1/2 foot at least a twin wall pipe!

the single wall under could be insulated in one of the ways I suggested.

meanwhile · #17 10/08/12, 06:10 PM

Thank you. We will re-think it and take another look. Thanks for the tips.

**fordson major** · #18 10/08/12, 06:26 PM

Quote:

Originally Posted by FarmboyBill

I havnt seen steel 5 gal pails in years now.

barn paint and creosote comes in them still, not sure what else but there was a guy at the scrap yard the other day with a whole truck load of them.

catahoula · #19 10/09/12, 08:18 AM

To be honest, I think what you have there is just fine. The high temp sealant found in the wood stove section of the hardware store is all you need. That is a sweet looking oven.

I imagine the life span of that black stove pipe will be pretty short, might rust out in just a few years. You should just build a ceramic chimney to match your oven, it would look quite nice.

Nice work either way, how many times have you built this oven? and you are just now considering the chimney? Heh heh heh

Cheers

NJ Rich · #20 10/09/12, 08:39 AM

I needed a high temp caulk for around the 10 inch range hood exhaust pipe. I went to a place called Dunphy-Smith that is a supply house for heating and air conditioning contractors. That was about 5 years ago and I do not remember the name of the caulk but it was a very high temp resisitant caulk.

The fire suppression caulk is not what you should use. That is meant for a one time heat expanding caulk to reduce the spread of fire. I have used that extensively on major construction projects.

Look for a supply house that services heating and AC contractors and ask for their recomendation. I cannot trust all the people who work for Lowes or Home Depot. Some employees are very knowledgible but some are clueless and I would not trust the safety of my family on some of them.