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I Forge Iron

Chimney Plan - Looking for Feedback


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Specific question: how do people seal the area between the hole and the chimney pipe? My roof is shingled. 

I will be forging mainly during the winter in Minnesota. I'd like to avoid a leak if possible. The gent at Home Depot said that he doesn't know of a sealant that would hold up to the temperature changes and the small movements you're going to see in even a well-secured chimney. 

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What do they do for wood stoves?  How high above the forge is the roof penetration?  It may be well within silicone caulk temp ranges if there is enough space.    My coal forge 10" chimney is just warm to the touch a yard or so from the opening.

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I just used black roof tar/sealant sold in a tube for a caulking gun.  Have not had any problems.  Like Thomas, my chimney at that level does not get very warm.  So, I don't think you need anything that will resist extreme heat.

"By hammer and hand all arts do stand." 

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Thank you all! I found some roof sealant for about $4 that's rated between -40 and 180 degrees. My chimney starts about three feet below the roof, so I doubt the outside of the pipe will hit 180. Time will tell. 

Now to go cut a hole in my roof...

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Roof Jack and skirt! They make roof jack in different angles so you can match the pitch of your roof and you can trim the skirt or buy an angle one. 

Frosty The Lucky.

 

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Just be aware that building code in most locals requires a specific separation between your chimney for a solid fuel appliance (coal, coke, charcoal, corn... forge) and any combustible materials.  For example if you penetrate your roof and have a shingle over wood sheathing roof with wood beams, or are going through a wooden shop wall.

There are two primary paths to compliance that I am aware of.  You can go with a thimble like Jennifer has, or use a special commercial pre-insulated duct section that is rated for zero clearance.  The thimble is constructed of non-combustible material, maintains the required separation and is typically ventilated with an air gap to the building exterior.

You may not care about the building code, but I assure you your insurance company does.  Typically the requirement is compliance with NFPA 211, which indicates a 18" gap between a metal chimney and combustible materials for a "low heat" non-residential appliance (where the flue temperatures don't exceed 1,000 deg F).  Zero clearnce ducts need a smaller opening (4" larger radius than the flue if I recall correctly), but are expensive.

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Latticino, code is all the way out of my wheelhouse and across state lines, but if I'm going to be doing this for the next forty years I need to gain some understanding. Where does one usually find information on building codes? I'm sure it varies by state, I'm just looking for a place to begin. 

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