Cutting Metal Roofing

[fRED mCnEILL]

I know this isn't woodworking but seeing as how I plan to cut it with my skill saw I think it qualifies.

I seem to remember that you can cut metal roofing with a circular saw using a carbide blade put on backwards.
Is that correct?

Thanks

Fred Mc.

[keith micinski]

Yes but what ever you do make sure you where face protection. Not just eye protection a full face shield because pieces come flying out of there something fierce.

[Fred Belknap]

I have cut a lot of it with a circular blade. I bought a Freud metal cutting blade and IMHO it was worth it. Be sure to use good eye and ear protection. Angled cuts need to be thought out, it is easy to cut them backward. Cutting from the back side is usually best.
edit: in a pinch an angle grinder will work.

[Scott T Smith]

I know this isn't woodworking but seeing as how I plan to cut it with my skill saw I think it qualifies.

I seem to remember that you can cut metal roofing with a circular saw using a carbide blade put on backwards.
Is that correct?

Thanks

Fred Mc.


Correct. You can also use a metal cutting blade on your saw (standard direction), or use large tin snips. I prefer the tin snips for painted roofing, and use a circular saw for the thicker roofing found on old buildings.

[Chip Lindley]

Correct. You can also use a metal cutting blade on your saw (standard direction), or use large tin snips. I prefer the tin snips for painted roofing, and use a circular saw for the thicker roofing found on old buildings.

Our church's volunteer builder group just finished constructing walls to enclose a 30'x40' pavillion, covering it with metal siding. (same as the roofing)

It was the pleasure of that church to have the siding put on horizontally...SO...we were ripping 30' and 40' lengths of metal siding to width. NO tin snips there! We used the circular saw/backwards blade method with good results.

Besides face protection against hot cuttings of flying metal, wear hearing protection also! The noise is deafening!

[Mark Bolton]

One thing you have to remember is that cutting any metal that is warrantied with this method will likely void the warranty. Its a very risky way to cut any type of metal roofing that is painted or clear coated. The hot chips that fly everywhere melt into the finish which #1 ruins it, and then down the road will cause a flush of rust as all the embedded chips rust.

We do quite a bit of metal and I know our manufacturer states that it voids the warranty.

Further there is a lot of talk of using shears as a way to roll the galvalume coating down over the raw edge and help prevent corrosion on exposed cuts. In our experience this has never worked as even the factory edges will rust over time. This happens if you touch them up or not.

We cut all our metal with shears or snips simply because you get a much cleaner cut on things like valley's and so on.

Of course if you are just talking galvanized farm panels or you are buying non-warrantied metal and dont care about the finish a skill saw or angle grinder is fine.

Mark

[Max Coller]

The trick of using an old carbide blade backwards works, but there's a distinct danger that you're going to peel a tooth off the blade and send it.... someplace. Maybe into your carcass. Or someone else's. Or, worst of all, the eye or face part of the carcass of someone else who isn't actually even doing the cutting.

Metal cutting blades are cheap. Abrasive metal cutting blades are even cheaper. Practically disposable. Both actually cut much better than the carbide-backwards setup. It just isn't worth it to use a carbide blade in a manner for which it isn't intended.

As others have said, regardless of what you are using, wear full face protection (like a woodturner's face shield) and hearing protection. I wear earplugs with earmuffs over the top when cutting metal siding and roofing. No need to have your most common words be "huh?" and "what's that?"

[Dave Houseal]

Hahaha....I tried the backwards saw blade....um....I highly recommend against it. I got what I needed cut, but I lost every tooth on that blade.

I got an abrassive metal cutting disk, and that worked decent. They're cheap enough too. Haven't tried sheers, but if it cuts it, I'd say that it is preferable to any circular saw cutting method. It's loud as hell, and you're pelted with metal bits.

Mark, what kind of sheers do you recommend? I have some more of this dreaded task headed my way before bad weather moves in.

[Marty Paulus]

At under $10 it doesn't seem like its worth the headaches of trying to turn the carbide wood blade around and risk destroying it.

http://www.homedepot.com/Tools-Hardware-Power-Tool-Accessories-Saw-Blades-Circular-Blades/h_d1/N-5yc1vZ1xi0Zb8ndZ1z13133/R-202021701/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

They also have a carbide tipped metal blade but that was $40. If you have a lot of cutting to do it may be worth the extra $$

[David Winer]

[QUOTE

I seem to remember that you can cut metal roofing with a circular saw using a carbide blade put on backwards.
Is that correct?
Fred Mc.[/QUOTE]
I recently needed to cut angle iron (actually mild steel) legs from some fifty metal lockers for our canoe club. These were not just sheet metal and the prospect was pretty daunting at first. But with advice from an experienced sales person at out local "pro" lumberyard I bought a Freud Diablo Ferrous Metal blade, carbide tipped, for the job. Around $45. Well worth it! In a good circular saw it ate the legs right up. Afterwards, the blade showed no sign of wear to the teeth.

As others note, wear protective gear. I used full face mask, hearing protectors, and gloves. I rigged up a fence so the cut could continue in a line to take off a row of legs. Lots of sparks and "shrapnel" so don't let anyone be close while sawing. Oh, and feed slowly of course--you should get a feel for it by starting very slow in the cut and trying faster. Actually it cut surprisingly fast.

[Mark Bolton]

Mark, what kind of sheers do you recommend? I have some more of this dreaded task headed my way before bad weather moves in.

We do most of our cuts that matter with wiss offsets. You have to have a set of lefts and rights but the offsets are the best because they get your knuckles up away from the sharp edge of the cut. They also let you maneuver around better as your hands are angled up and are away from the cut.

The main thing to remember is, as rule, your waste piece goes up meaning the lower jaw of the snips/shears goes UNDER your waste piece. This piece rolls up as you cut so it is of course destroyed (a big curl) when you are done. Your workpiece is left flat. With most profiles of metal roofing (classic rib is most common around here) depending on what you are doing you often have to switch back and forth between the lefts and rights to get over and around the ribs. Once you make a few cuts it usually becomes obvious which pair you need because one will fit and the other just wont. The waste-up rule doesnt apply 100% of the time but its generally the best.

For the cuts that dont matter (ones under trim like ridge, corners, and so on) we often use a set of milwaukee three jaw electric shears. They work pretty well but there is no way for them to not scratch up the metal beside the cut as you run up and over the ribs.

I have talked to other contractors who have used these shears that go on a cordless drill and they like them but I have never used them. I just find cutting by hand where it matters is the only way to get a nice clean cut. When your cutting in a valley that someone can sight directly up a crappy cut looks, well, crappy.

These are the snips we use:
http://ecx.images-amazon.com/images/I/41NXBOTSEJL.jpg

Those are the lefts, green handle for rights. Its also important to keep the shears at a right angle to the sheet. If you let the sheet lay over in between the jaws it will spring them almost instantly and the snips begin to cut poorly.

We commonly install 29ga galvalume which is pretty tough stuff so its hard on snips.

This all sounds fussy but we treat these metal roof's like an automobile finish kind of. If you are hard on them during install, scratches, walk all over them, drag the panels around, they look like hell in short order. Even fine scratches become wide rusty scratches in a year. We try to get them on clean and crisp so they look good for as long as possible.

Another good tip with metal panels if you dont already, is to pre-drill your panels in the pile before you put them up. Lay out your screw locations on the top sheet and drill the entire stack at once with a clearance hole for the screw. Serve's many purposes, keeps your screws dead straight which looks much better. Saves you from trying to shove the screw through the tin on the wall or roof and the random times that the screw rolls out of the bit and you slam your bit into the tin leaving a dent and a scratch. And also often times a small shaving comes off the tip of the screw and gets hung on the washer as the screw runs in. It whips around an puts a circular scratch around every screw which later rusts. After pre-drilling once you will never go back to shoving them through.



Mark

[Noah Katz]

You can get pneumatic nibblers that cut 16 ga for cheap (ebay, Harbor Freight etc), electric ones for more

[Dave Houseal]

We do most of our cuts that matter with wiss offsets. You have to have a set of lefts and rights but the offsets are the best because they get your knuckles up away from the sharp edge of the cut. They also let you maneuver around better as your hands are angled up and are away from the cut.

...

Mark

Thanks for all the tips Mark! I will have to pick up a set of those shears before I make another run at this.

I somehow doubt that all the contractors installing metal roofing exercise such care. I'm guessing you have some very satisfied customers.

[Charlie Jones]

I made a metal roofing cutting blade following the directions on "woodgears.ca" . take an old 7 1/4 circular saw blade and hammer the carbide teeth off, then sharpen the tops of the teeth to a point. i haven't tried it yet.

[David G Baker]

I didn't read all of the posts to see if it was mentioned, you can cut metal roofing length wise by scoring it with a box blade and straight edge, then fold it until it snaps. This method may take some practice before you master it. When I cut across the metal roofing I use a fine tooth plywood blade mounted on the saw so it turns back wards and make sure the roofing is well supported, I use blue foam board for support. I did an 18'x50' building's siding using the above method. Eye and ear protection is strongly advised.

[hank dekeyser]

Ummm carbide running backwards equals no more carbide. Normal non carbide blades backward for vinyl siding = yes, steel = no.

Get yourself a metal cutting sawblade, or snips, or shears, or, or - The main dif between steel cutting blade and wood is the hook angle and number of teeth. The steel blade will have close to no hook (like 10 degrees) standard carbide blades work too, just not as clean.

When we do steel buildings or roofs, we use a big snips for cross cutting and a nibler or "double cut" for rips. You would be amazed how some of the guys out ther pretty much just hack the crap out of steel - for the most part you always have one end that has a trim piece covering it. hack away - you'll never see it.

I do a fair amount of steel buildings and would NEVER drill all my holes in a pile ! thats just asking for a big scratched up rusty mess (plus, the purlins alternate every other one, so you holes wouldnt line up every time)- use the self tapping stinger screws that don't drill the wood but pretty much just pierce a hole and start threading.

[Mark Bolton]

I do a fair amount of steel buildings and would NEVER drill all my holes in a pile ! thats just asking for a big scratched up rusty mess (plus, the purlins alternate every other one, so you holes wouldnt line up every time)- use the self tapping stinger screws that don't drill the wood but pretty much just pierce a hole and start threading.

We have run hundreds and hundreds of panels this way. Given this is a woodworking forum my assumption was residential construction over wood framing so staggered steel purlins on a commercial building is more than likely not applicable to 99.825% here. Further i have no idea what buildings you are assembling with staggered purlins. Every commercial building we have been a part of have z purlins that nest together at the laps so all purlins are in line. Staggered screws on the exterior of an expensive building would look like he**.

What I assumed here is metal panels over wood framing or osb/ply sheathing in which case self drilling screws are no good because they have very poor retention in wood. Most metal installations over wood use a self piercing screw with a very sharp point.

With regards to drilling in a pile it is absolutely the best way to go and unless youve tried it you have no idea. The panels get craned off the truck perfectly aligned and banded so marking the top sheet makes for perfect alignment of all subsequent panels and screws. There is no easier way. Snapping chalk lines to keep screw runs straight is a waste of time and on a roof with any pitch chalk is idiotic to have under foot. If you are not concerned with keeping you screw runs straight and aligned then well, I guess we can leave it at that.

After reading my post if you think there is a single scratch on our roofs when we are done I can't help you. I have drilled stacks of 50 or more panels and a small pile of chips at each location is simply shaken off the top sheet when it's carried to it's location.

A commercial steel structured metal building is a little different but the same principals apply. If you look down a run of screws on a 200' steel building, sidewall or roof, and the screws are swaggering up and down by a couple inches you have just found a pretty clear hack-o-meter.

[george newbury]

Resurrecting this thread because there's some good info in it and I've a similar problem -
I had a 40x60 metal roof replaced. I've now got about 40 or 50 of 25 foot long pieces of the old metal roofing 26 gauge (or thicker?) which were taken off my roof and I want to cut them shorter. Most have about a 4' end that is either rusted, covered with patching latex or both. I plan to use the "good portion" for vertical walls for sheds etc.

Heavy duty tin snips seem like an inexpensive solution but a REAL pain in my hand. The circular saw with a special blade sounds interesting, but perhaps hazardous, and I had been thinking about an air powered nibbler.

What's the current best solution?

[Mark Bolton]

Electric three jaw shears would work better than nibblers I'd say. A pair of the shears that go on a cordless would work. Both if you don't care about cut quality because ridding the shears up and over the ribs does some munging up. Where this isn't warranteed metal id just go with a carborundum blade in the skill saw or a fine metal cutting blade. It would be the fastest and distort the profile the least. There is simply no alternative for a pretty cut other than hand shears and knowing how to use them. Lengthwise cuts are best with a razor knife and folding the material til it snaps.

[Chris E Smith]

I have used a plasma cutter and a clamped on fence with good results. A friend did an entire garage interior the same way. Beware that the fumes from cutting galvanized material are toxic however.

[Jerome Stanek]

The pole barn builders here use nibblers to cut across and unishears for the length

[Mark Bolton]

I have used a plasma cutter and a clamped on fence with good results. A friend did an entire garage interior the same way. Beware that the fumes from cutting galvanized material are toxic however.

Thats some high dollar metal siding. I would guess the bare/burnt edge would be a nightmare if it were new metal and exterior. Rust would take over quickly even with touching up.

[Erik Loza]

We just had the steel roof done on our house. They used electric nibblers.

Erik Loza
Minimax USA

[Mark Bolton]

I had a 40x60 metal roof replaced.


George,
I was wondering how old your old roof was (if you know)? Modern roof or older metal. Ive long been skeptical of sheet panel roofs though Ive installed a lot of them. I find myself wondering what will be happening in 20 years or so when the roofs are still sound as far as keeping dry but look bad and homeowners begin to regret their decision. Metal and asphalt have the same cosmetic lifespan and warranty for the most part however tin roofs tend to look bad, and experience problems, much more quickly in my opinion.

Old timers always say metal will last a hundred years which I dont doubt to be true with coating/painting however I dont think most homeowners of today will be satisfied with a mop painted roof over top of their pretty house. If you get up on nearly any metal roof, even a well installed one, in just a few years you see large amounts of chaulk/haze, you will see rust in numerous places, and so on. It just gets me thinking.

When we install metal we try to handle each sheet as close as possible to the way you would handle a freshly painted fender for your vehicle because thats exactly what it is. Extremely fragile finish, extremely easy to scratch, and every nick/scratch in the finsh WILL rust in short order.

In our area metal roofs are thrown on like monkeys in the circus. Dragging panels over each other, sliding them on top of each other on the ground and on the roof. They are often pretty beat up before the last screw is run.

I suppose the plus is metal is recyclable as compared to shingles going in the landfill so thats a plus. And zipping off a metal roof an installing a shinny new one in 25-30 years is a bit easier than asphalt too.

Ive always been an asphalt guy but I dont mind metal as long as you can keep the roof penetrations to a minimum. I feel they have a long way to go if you have a chopped up roof, sky lights, valleys, lots of chimney/vent flashings, and so on.

Just interested in the opinions of those who have gone that route.

[george newbury]

George,
I was wondering how old your old roof was (if you know)? <snip>

About 30 years. The main problem, as a former roofer in the '70's, is it was essentially FLAT. On a 40' span there was only about 2 inches AT THE MOST of a center ridge. Now it's about 8".

Lot's of the metal is still pretty good, but where it's rusted I'll cut it off with the metal cutting blade for my circular saw which I bought today, with the proper PPE.