We have the tin up on the shed roof for the outdoor kitchen. It is an open air kitchen and so we are not trying to totally keep it dry. I know rain will blow in here and there. The roof is to keep it mostly dry and keep hard rain off the Cob Cook Oven and the other ovens.
So - we have the tin roof on. Now, how to cut the hole in the tin so that the stove pipe for the wood ovens can go out the top? I know to buy the rubber boot thing or a metal boot thing for the top side.
But how to cut the hole? Would we just poke a hole with a nail and then cut with tin cutters? Or do we cut it with a saw-saw? Should we make a mark around circle so we measure it first and then try to keep to that line?
Next I use a holesaw (around 2" and cut a hole near the line. On one roof, the battery was dead in the cordless drill, so I used the edge of a screwdriver and hammer to make my hole. Hold the screw driver at a 45 degree angle and hit the side of the blade. It will rip through the metal and you can get a hole large enough for the snips.
Then I use my aviation - tin snips to cut out the circle.
On some standing seam panels, I have had to use my right and left snips to take out a strip of metal to allow access for the snips following the line to stay true.
Use a piece of stove pipe and draw the circle on the roof. Make sure that the proposed hole doesn't cut any rafters or come too close because the stove pipe will get hot. Drill a 3/8 inch hole inside the one you drew so the side of the hole meets the side of the hole you drew. Use a 1/4 inch wide, metal cutting blade for the sawsall to cut out the hole. A sawsall cuts on the pull stroke so if you press the shoe tightly up against the metal it won't deform the metal. Make the hole a blade width bigger than the drawn line so the stove pipe fits easily. You can remove any flashing with a round or half round file.
Definitely make an outline of size hole you need. Lot ways to cut it. Me, I would put metal cutting blade (they are like $2 or $3 last I bought one) in circular saw and and cut in center of circle like you were cutting many pieces of pie, not going outside of the circle you drew. Then either fold down the pie wedges or cut them with tin snips.
I suppose with minimal tools, you could punch holes close together all way around the circle with a nail (hardened pole barn spike is nice for this) and then use a sharpened chisel or even sharpened flat bladed screw driver and cut the bits of metal between the nail holes.
Depends what tools you have and how fancy you want to be.
"What would you do with a brain if you had one?" -Dorothy
"Well, then ignore what I have to say and go with what works for you." -Eliot Coleman
Lot of good advice above. Some things not mentioned:
1) Yes, there is a part (not sure what it is called...maybe ceiling support?) that connects to the insde of the ceiling and proceeds up into the attic. It spaces the pipe and hot air away from the ceiling and insulation in the attic. The pipe from your stove connects into this part.
2) I used a plumb bob to make sure my ceiling hole was centered over the stove vent opening.
3) I placed a bend in my pipe after it entered the attic so that I could cut the hole in my metal roof at the eave. This allowed me to slip the weather cap collar/boot under the ridge cap. This cost a few extra $'s, but I thought it might help keep rain from eventually working it's way through the caulking and into the house.
The hole will not be a circle, but an oval. Fill the valleys with roofing cement (tar) in the area under the boot prior to installing it. Use the roofing cement after installing the boot to complete the sealing on the top edge. Depending on the height of the pipe, you may have to guy wire (I use small eye bolts) near the cap to keep it from blowing over. Use a cap to keep the stove from getting wet inside.
Roll a piece of cardboard around the pipe, then cut IT at the same angle as your roof, in order to get the oval. Measure carefully, or drill a centering hole from underneath to mark the right spot. Then, put the cardboard tube on the roof so it's vertical, and spray paint it so you will have the oval marked on the tin....Cut with a narrow metal cutting blade on a sawzall. Wear safety glasses......
I used sheet cardboard to get the hole properly placed. I drilled a hole big enough to start a ricipicating metal cutting saw blade and followed the line.
Also I split the tin so that part of the roof metal extended past the hole. This is so the boot can be placed under the top half of the roof metal and the boot over the top of the down side roof metal like shingles to help prevent leaks.
Nark out your oval to suit the round pipe. Take a slot tip screw driver and place a corner on the tinm then whack it a few times with a hammer to shear the metal into a gash. Then use snips to cut out your hole. Don't use a rubber boot to seal a chimney or smoke pipe get or fabricate a metal version and screw that on. Then caulk with 1000 degree sealant.
Do not meddle in the affairs of Dragons, for you are crunchy and good with ketchup........
When the stove is where you want it to be take a weight on a string [plumb bob] and make sure that it is centered over the stove outlet pipe. Use a tape measure to ensure it's centered. Mark the spot you are holding the string at on the bottom of the roof and drive a nail through it. Measure the pipe to get the radius and mark the radius on 2 or 3 sides. Place your pipe there and trace your hole cut. Use a hole saw, screwdriver and hammer or whatever other means that you need to start your cut. If you do not have red or green handled snips designed to cut in a circle use a blade and go slow. Put the pipe through and install your flashing assuming that you are not using a chimney support package. Pipe down to the stove. Install the crimped portion so that the creosote runs to the stove rather than down the outside of the pipe.
I drilled a 1/2" hole with a drill, then used tin snips to cut the circle.
A 'thimble' goes through the hole first.
The stove pipe from inside is fitted into the bottom of the thimble.
Another section of stovepipe is fitted in the top of the thimble.
A storm thing [shaped like a traffic cone] goes around the upper stovepipe.
Last a top piece of hat goes on top.
Thank you everyone. We are removing the frame from the floor bed of oven today. and..stacking the "bones" of the Oven. After that we will start on the top part. Thank you everyone for all the advice and tips. We printed and put with the stove pipe to have ready later this week. Thank you very much!
There's no need at all to cut a round or oval hole. As ramblin wreck outlined, you have to have a ceiling support to let the stove pipe transition to chimney pipe. You'll have a level one if it passes through a second floor or ceiling. You'll have an angled one if it attaches directly under a sloping roof.
You'll box the ceiling support with the same 2X? as the roof or floor is constructed of.
When the chimney pipe passes through the roof it will topped with a cone-shaped storm collar. This is typically square, so the opening in the roof tin can also be square. You buy the individual collar that most matches the slope of your roof. The top end of the collar slips under the roofing to shed water. The bottum edge slips OVER the roofing to displace water. For my own chimney collar I added two small strips of extra roofing tin to cover the left and right edges of the collar. I just made one single cut with a metal-bladed circular saw straight across the roofing just above the collar. The gap between the two cuts were covered with the left and right peices of tin.
All weather side of the tin were sealed with regular roofing tar. Any gaps under the tin was filled in with spray foam insulation. Anything flameable (like the spray foam for example) were kept a minimum of 2" away from the triple-wall chimney pipe, and 6" away from the double wall stove pipe.
... you have to have a ceiling support to
... if it passes through a second floor or ceiling.
... You'll box the ceiling support with
... the triple-wall chimney pipe, and 6" away from the double wall stove pipe.
The OP stated that there is no attic or ceiling.
My house has no attic or ceiling either. Stove pipe connects to thimble and back to stovepipe with storm collar and top-hat.
Also not all regions require triple-wall or double-wall.
Tonight we decided to rush things up and we fired up the Oven even though it is not finished! Made some great pizzas and bread sticks but we all got smoke smack in the face and eyes! So tomorrow we are going to buy the vent pipe and work on the chimney.
Photos later. Have to do chores now. Thanks everyone!
ET1 SS: We are going to use the boot things that are heat proof and also the metal thing-y that goes through the tin. We will have to have a curve in the stove pipe since a wood joist is just above it. Photos later! Thank you.