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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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  • 3 weeks later...

Honest question: how much do I need to worry about fire code? I don't mean, "How much do I need to worry about fire safety?", I'm just wondering when code comes into play. I have an email from the fire marshal of my town giving me permission to forge in the shed, I'm going to respect my neighbors re: smoke and noise, and I'm going to make sure this forge is good for my neighborhood.

When does code become important? When a spark from my forge burns down the next house over? When my roof gets hail damage and the insurance company is looking for a reason not to pay the claim? I'm trying to balance worst case scenarios against the reality that laws aren't written for blacksmiths anymore. They're written for fireplaces, for wood stoves. Even those laws I don't know where to find; I found the website cited earlier utterly incomprehensible. 

Apologies if my tone is tenser than usual; I would really like to get the forge up and running before we get any serious snow in MN, and I'd like to do it for not more than $200-300, and that goal is being carried off into the sunset by worries about vague but terrible consequences for violating fire code. 

Note well: Lattincino, I genuinely appreciate you bringing this up. I am just overwhelmed this evening and trying to figure out my next step. 

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Dear TJ.

Give your local (municipal or county) building inspector a call and ask, "I'm thinking about installing a metal chimney through a frame roof and I was wondering how much clearance I need between the chimney and the roof deck and the joists."  He or she should be able to give you a quick answer.  If they don't know try calling your local fire department but I notice that the Uniform Fire Code references the Uniform Building Code for this sort of thing.  Therefore, I would go to the building inspector first.

Also, it is improbable that you will be producing sparks out your chimney if you are using decent coal or coke.  You might get some sparks is you are burning charcoal or crappy coal.  If you are really worried about it put a piece of metal screen in the top of the chimney, that is how the spark arrestors on steam locomotives work.

I doubt that a hail damage claim would be affected by how a chimney is installed because the chimney is not compromising the integrity and resistance of the roof to hail in any way.

"By hammer and hand all arts do stand." 

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Heck the municipal offices should offer fire/building code booklets as a hand out. Or maybe for a nominal fee. The ones up here are happy to stear folks too do things right. 

I know the local Home Depot has more how to books than a person wants to think about. The local stove and fireplace stores will have detailed how to it according to code, books.

These things aren't secret. Seriously, what municipality wants tax payers burning themselves out for lack of knowing how it's done right?

Frosty The Lucky.

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On Friday I called the building inspector for some guidelines on my forge chimney. This morning he called me back! I was very worried that things were going to get complicated and bureaucratic, but he gave me very concrete, doable steps and useful information.

Short version: 

- Each kind of pipe has as part of its specs a minimum required distance from combustibles (i.e. wall/roof). If I go with double- or triple-walled pipe, that distance goes down. In MN the retailer provides that information, but that I should be fine with standard double-walled. He suggested a sort of double-walled pipe with insulation so I don't burn myself on the chimney, but I think that's less of a concern with my chimney than it would be in a closed wood stove. 
- The other concern is the distance between the top of the chimney and the peak of the roof. He said my run should put me well out of danger for roof fires. 

When my questions were answered, he said, "So, what are you going to make?" I gave him my usual spiel about useful, everyday things instead of swords. He said, "That sounds really cool. When you get everything up and running, I'd love to see some of your product." Thus mirroring my conversation with the fire marshal last year.

Oh, and did I mention? The building inspector's last name is LeForge.

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