Metal Roof Question

knightstead · Aug 30, 2021

I finished installing a new metal roof on my smokehouse over the weekend and had planned on cutting the exhaust stack hole before putting the metal up. I didnt have all the parts and pieces to get an accurate location so we went ahead with the roof so that things stayed dry. Now Ill need to cut an 8 inch round hole in the metal. Any recommendations on the best tool or trick for the job? Thanks in advance.

knightstead · Aug 30, 2021

larbear · Aug 30, 2021

Drill a 3/8 ths hole with a bit then cut the hole to size with aviation snips.

MARK ROBKE · Aug 30, 2021

I would drill a hole from the inside, maybe using a plumb bob to get exact center. Then cut it the rest of the way, outside, with snips. Mark.

knightstead · Aug 30, 2021

Thanks, thats what I was leaning towards just wasnt sure if there was a better tool. I have a good 7/8 hole saw, it might be a big enough hole to get the tin snips in. Flashing boot is 12 inches, so even if its not pretty itll be covered up.

jm. · Aug 30, 2021

Would be really nice IF the hole could be in the flat part and not in one of the ribs .

knightstead · Aug 30, 2021

Totally agree but the ribs are 9 inches on center and the flashing is 12. So I can either center the hole in the middle of one rib, or center the hole in the valley and have the flashing up on two. Im thinking the first option would be better.

sooner88 · Aug 30, 2021

Cut hole with hump in tin in center of hole so water can get around it

SDE · Aug 30, 2021

On a sloped roof you need to cut an oval hole if the chimney is straight up. Round isn't going to work.

Stephen Newell · Aug 30, 2021

What I would do is use a plumb bob to transfer the location for the pipe to the ceiling. Then drill a hole about 1/4 in diameter at the center. Then if you wish to spend the money on a large hole saw drill the hole with that or cut it with a jig saw with a metal cutting blade. Use an ample amount of gutter and flashing caulk when installing the roof jack.

Turkeyfoot · Aug 30, 2021

Nice looking smoke house. My grandfather had one about the same size. He raised hogs and did hams and bacon.

Steve@Advance · Aug 30, 2021

No easy way I know of. Find the center, drill a small hole. Take measurements off that hole and lay out a cut line. Remember, you will be cutting an oval because of the roof pitch. Then start hacking away with left and right snips until you get it big enough for the pipe to fit. You can clean up the edges with a 4 inch grinder if it will be visible from below.

I take that you have a Master Flash type boot, with a flexible metal base to conform to the roof panel. Just be sure not to get the hole too big or off center that the screws won't catch.

knightstead · Aug 30, 2021

Thanks, my grandpa had this built and raised hogs as well. Im honestly not certain why its so large. Its two rooms, only one actually smokes. I believe the other was for processing, but thats a guess. I know my dad said it was built after the old wooden one and several acres caught on fire. Its fifty plus years old but never been used in my lifetime (33 years). Im looking forward to bringing part of the farm history back to life.

Check Break · Aug 30, 2021

(quoted from post at 17:23:47 08/30/21) I finished installing a new metal roof on my smokehouse over the weekend and had planned on cutting the exhaust stack hole before putting the metal up. I didnt have all the parts and pieces to get an accurate location so we went ahead with the roof so that things stayed dry. Now Ill need to cut an 8 inch round hole in the metal. Any recommendations on the best tool or trick for the job? Thanks in advance.

Make a paper pattern. Transfer the pattern to the roof and use a nibbler to cut the hole.

knightstead · Aug 30, 2021

Yes thats the style flashing, its a Oatey 14055. Sounds like the consensus is that there is no easy way. Ill just take my time with tin snips and do the best I can.

knightstead · Aug 30, 2021

Ive never used a nibbler but I just found some
cheap ones on amazon that attach to a drill. Might
be worth rolling the dice and seeing if they will
tackle the job.

smileykeith · Aug 30, 2021

a sabre saw works great with a fine tooth blade

Check Break · Aug 30, 2021

You can buy a hand powered one that's a lot slower but easier to control the first time around. They used to be cheap but you know how that is now.

zuhnc · Aug 30, 2021

Wear some heavy gloves, and don't slide off the roof. Those sharp edges will cut you badly. A roofer friend was installing a metal roof, slipped, grabbed the edge, and almost cut two fingers off. He got lucky, and now, after six months, he has full use of the hand. Be careful. Nice looking building.

John in Md. · Aug 31, 2021

Leave the tin alone and run it out the back gable above the blocks. No leaking roof.

cjunrau · Aug 31, 2021

I agree with this. I never understood why people want to go through roof instead of gables. I go through gables all the time and never any problems or leaking roofs.

showcrop · Aug 31, 2021

I have never had any luck trying to cut a circle that small with tin snips. Just an exercise in aggravation. I second Keith's suggestion of a saber saw. Once you have the small center hole tape a circle with pieces of masking tape to protect the paint, then mark the circle on the tape using a compass, enlarge the center to 3/8, then cut it with the saber saw with a metal cutting blade.

Richard G. · Aug 31, 2021

Good for you.
I love bringing old things back to usefulness.
Richard in NW SC

Richard G. · Aug 31, 2021

I vote for the nibbler on a battery operated drill driver.
Got a nibbler I bought several years ago and will never go back to hand snips.

caterpillar guy · Aug 31, 2021

Mark your hole and then with a cut off wheel in a disc grinder cut the hole right out no muss and no fuss. No cut hands or finger either. With the disc on edge it will go right around the line with little problem. We cut the holes in bins sides for the unload auger that way. So easy. Just stay on the mark according to whether it needs to be cut in or out side of the mark. An oval hole is going to be needed for a pattern with w hole at the peak. Going out the end would save a roof hole.

Texasmark · Aug 31, 2021

Agreed. I bought mine at HF and it has served me well over the years.

Turkeyfoot · Aug 31, 2021

My grandpa had wooden troughs about three feet high built off the cement floor along one wall. That's where he stored the hams packed in salt.

Metal Roof Question

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