OT: building a flue

[Mark]

I can't find a block layer willing to build a flue for me, so I am going to do it myself. The problem is, I've never done it before. I need to know how the liner is installed. Does it sit on angle iron, like a lintel, inside the block? How do you cut a nice clean hole in the liner to slide the round flue pipe in it? I ran a search and found lots of nothing! Any suggestions?

 

[Dave_Id]

You can save yourself a whole lot of labor by installing triple wall, or perhaps just a double wall pipe sold at your local Home Depot. I've built 3 chimneys in my younger days. You need to start with a good foundation, or I built one right on the garage floor. Start with the square chimney blocks, and your lowest one will need a cleanout installed. The flupipe (I used the square 8 inch tile pipe) will sit and cemented right to the floor. Just built straight up from there. Knock a hole in the flu pipe where the pipe from the stove goes thru. I think, if I remember right, they sell a square block with a hole already in it to install the sleeve. Don't worry about the connection from sleeve to the flue pipe. Knock off the mortar on the inside of the flue, so it'll be relatively smooth. When you get as high as you want to go, take mortar and taper up to the flue pipe so rain water can run off. If the chimney is inside the house, you may want to install a rain cap, or water many end up in your basement. I may have missed a few things, it ain't hard, but it'll take a good day to build with one person helping to mix mortar, hand you the materials, and help drink beer.

 

[Tim B from MA]

For the flue pipe, mortor goes only at the joints between the sections of pipe, don't fill then entire void between the flue pipe and chimney block.

Also, make sure you have a good strong concrete foundatino and footing to start with (if your chimney is tall and heavy, the concrete floor of a garage may not be strong enough). I poured a nice foundation for mine, but in did not put a footing under it. I have clayey loam in that area and the chimney moved ever so slightly and got some cracking. Luckily I could strap it to the existing chimney so it is safe, but wish I'd done better to begin with.

 

[Mark]

I didn't know you ran the liner all the way to the bottom...that answers that question! in fact, you pretty well set me straight. I'm building this out in the garage and the floor is 6" thick and 4,000 psi concrete....I don't think it'll go anywhere. Does the flue/chimney have to be above the ridge of the roof to draft properly? The wind tends to blow west to east here and I am going to build the flue on the east side of the garage. It will be built along the outside eastern wall...if it has to go up higher than the ridge of the roof...it sure is going to look weird.

 

[Jim in NC]

I have helped a mason built a couple of flues. He would start the liners just below where the thimble would connect to the flue. He used angle or flat iron at a mortar joint to support the liners. You can get flue block with half circles cut in one side. Put 2 of these together and you have the hole for the thimble to go through to the liner. You will have to cut a hole in the liner.

 

[Anonymous-0]

Around her the flue height must be two feet higher from a point where the roof is a horizontal ten feet away.

 

[CWL]

Have you checked with your insurance company about covering the building and contents yet? I tried to find an insurance company that would cover my garage and allow me to put a wood burning stove in it. I got the same basic answer from every one of them that I contacted: “If there is a vehicle in the garage they will not cover it!” I was very disappointed with that response. I wanted to put a good quality UL listed wood stove in with all of the proper installation. I even asked about having the installation done or inspected by a certified installer. Nothing mattered to them. If it had a wood burner and a vehicle inside, it would not be covered. Oddly enough though, a corn stove would be just fine with them. The thought of spending $2K on a heat unit for my shop was a little more that I could go along with. I could also put in a propane wall furnace or a propane unit heater. The makes no sense to me because both of the propane units have an open flame! I finally put some numbers together and found that I could install and operate an electric unit heater and get by cheaper than propane. It works great until it gets down around 10-15 degrees and a strong wind blowing, but that doesn’t happen that often in S.C. Ks. I’m heating a 24 x 32 building with a 10” eave and open rafters, but it is well insulated. I figure that the 10 Kw 220V unit heater I installed costs around $0.55 per hour of run time. On average in the winter when I am out working in the shop once it gets up to around 68 deg. it runs about 45 minutes for each hour. The thing that I like most about it is that I have no roof penetration because there are no fumes to get rid of. Just some BTDT food for thought Good luck!

 

[Dave_Id]

The rule of thumb for draft is: When you measure away from the chimney 10 ft to the nearest roof part, the chimney should be 2 feet above that. It's hard to explain. Picture a triangle. The side adjacent or base of the triangl is 10ft to the nearest part of the roof to the chimney, and the side opposite will extend 2 ft above to the top of the chimney.

 

[Mark]

All of you have been great help to me. I understand completely the description of how the flue should be above the ridge. Now if I can just figure out how the hell I am supposed to stack those blocks that high....I'll be ready to start!

So far as the insurance companies are concerned %!*#^%'em. I refuse to be held hostage by them. My homeowners was recently canceled because I refused to put handrails at my porch steps. I told them I had built this house 26 years ago and hadn't fallen off the porch yet, and it was their responsibility to indemnify ME, not the other way around! I found another insurer post haste.

 

[Anonymous-0]

You should consider Metalbestos chimney pipe. It is
quite expensive BUT you don't have to run it all the
way to the floor, you can start at the ceiling and
go up. A lot easier to install. Metalbestos is
double wall insulated pipe . A 6 inch chimney is
8 inches OD. An added benefit, it seldom needs
cleaning other than the cap on top. I clean mine
once a year, and at other times just beat on the cap
with a long pole. Many sites on Google for
Metalbestos. Metalbestos works on the principle of
keeping the smoke warm til it exits the chimney,
while triple wall tries to cool the smoke with
outside air which results in more creosote buildup
Metalbestos pipe.

 

[steve n carol]

(quoted from post at 08:11:34 09/14/07) I can't find a block layer willing to build a flue for me, so I am going to do it myself. The problem is, I've never done it before. I need to know how the liner is installed. Does it sit on angle iron, like a lintel, inside the block? How do you cut a nice clean hole in the liner to slide the round flue pipe in it? I ran a search and found lots of nothing! Any suggestions?

Concrete/cement or clay flue liner?

Start the flue liner atop the smoke shelf, not on angle iron, (expands at a different rate).

Use 'fire clay' mix in the firebox and between liners. Also parge the interior of the 'smoke shelf', for a smooth transition/flow.

Don't understand why you want to slide flue pipe into the liner?????? but, use a saw if you want, how big of a hole? Use a 4" grinder / a diamond or carborandum blade. Take your time.

I have downloaded County ordinances (diagrams) of chimney construction.

As the man said about the foundation.......listen to him, he's right. It's not pressure it's also about mass.

We grout ours solid on here, it's a rebar/earthquake thing, You do like you want, I've seen where critters can make they're homes there too.

....sl, been there, did that, use zero clearance now....

 

[Anonymous-0]

You would be better off putting in a stainless chimney.They run much cleaner.Liners should start at the bottom.Steel supports will rust away.A masonary chimney should not be attempted until you have helped a mason build one.Solid blocks weigh 100 lb and are too much to handle alone.Bricks should be used at the top, concrete blocks tend to crumble.October is the last month you could build a chimney around here.My son and I replaced an old chimney in the kitchen last year and it was slow hard work.Bricks cost a buck each here.I sent 500.00 for materials for a 20 foot chimney.I reused brick on the top.Your ins co may refuse to insure your shop if you use wood heat in it.I have a farm policy and have been harrassed by the ins co for 5 years.They tried to cancel me because the house needed painting.Got it painted and they still tried to cancel.The maine state insurance commission told them to back off after a hearing was held.I am looking for another ins co,tired of being bullied.I have a tv shop next to my house where I fix electric fence chargers.The tv business went to china years ago.They want me to quit using my shop, stop selling eggs and vegetables.I ve talked with many people who have no insurance now.Fuel oil prices are 2.50 -2.70 here and I expect to see 3.00 soon.My neighbor was forced to take out his wood stove by his ins co. after 8 years of use with no problems.He could not afford 2000 gal of oil so sold his place.He had a mortgage so couldnt go without ins.Talk to your agent BEFORE you put a wood stove in your shop...

 

[Mark]

I'm not building a fireplace...this is going to be just flue block with a fire clay liner...I am going to hook a stove to it....hence run a stove pipe to it. I didn't know there was a smoke shelf in a flue for a wood stove.

Maybe I wasn't clear in my original post...I'll have to go back and see if I said I was building a fireplace. If I did, I apologize. It is just a flue for a wood stove in my garage.

The last earthquake we had here in eastern Kentucky was about 38-40 years ago...probably didn't make the history books. I do recall it knocking me off my feet as I walked through the living room. New Madrid Fault must have buckled a little. I don't recall any chimneys or houses falling down....might have cracked a foundation or two.