Cutting metal roofing - theory and practice

[Stephen Tashiro]

In practice, do professional roofers cut metal roofing with circular saws?

Directions for the metal roofing that I have seen say not to cut it with circular saws or grinders -or abrasive disks in general. So I gather that the theory of cutting metal roofing implies using shears or nibblers ( be they powered or hand operated). I find that shears don't work well in cutting across ridged surfaces. So that leaves nibblers. However, there are many videos online showing people cutting metal roofing with saws. Are there special blades that make this an approved method?

[Christopher Herzog]

We used to do the circ saw with blade backwards. Good for long cuts but I hated short angle cuts with it. Now we use the angle grinder with a diamond cutting wheel. Probably not as good on the long runs but angles are way better. Recommend the trigger type grinder and not the paddle switch.

My two cents....

Chris

[Edward Weber]

These days there are circular saw blades specifically designed for cutting metal. No need to install blades backwards like many used to do.
https://www.diablotools.com/explore/.../steel-cutting

[Tom M King]

For some cuts, the circular saw is the easiest way. You need full face shield, long sleeves, gloves, and have everything covered. The little chips are hot. The last time I did it, I used a carbide tipped Irwin blade, and it did fine.

I won't ever put another exposed fastener roof on anything, but even for standing seam, sometimes the circular saw gets the call. Mostly, for the angled valley cut, but the little 12v one handed bandsaw gets the call for shortening the standing seams then.

edited to add: The toothed sheet metal cutting blades are a factor of 10 faster, and 20 less messy than an abrasive blade. It mostly just throws chips. The abrasive blade puts stuff in the air that you don't want to breathe.

[Scott Winners]

I use a metal cutting blade in my circular saw for metal roofing, they are like eight bucks at the home store. The key for me to get clean cuts is to have a sacrificial piece of 2X4 under the cutline and clamp the metal down real good so you can acutally cut to the line without the metal moving around under the weight of the saw. So one 2x4 or 2x6 under the cutline, another above the sheet metal and offset as a saw guide, and every clamp you can fit. Outdoors, and with wind is good.

I am still using exposed fasteners on wood sheds and garden sheds and tool sheds, and house walls where appropriate; but I am not wild about exposed fasteners on metal roofs for climate controlled buildings.

[Tom M King]

I put standing seam on our chicken coop.

[Jim Becker]

Many contractors that do a lot of metal work due to the nature of their business are using made-for-purpose shearing machines as well as hand-held electric shears.

[George Yetka]

I believe they say not to cut abrasively due to fire risk. If they put that warning on there they cant be sued when someone is grinding an opening on the roof and accidently set the building on fire

[Brian Elfert]

My understanding is they don't want the hot chips hitting the finished surface as it damages the finish.

[Ken Combs]

My understanding is they don't want the hot chips hitting the finished surface as it damages the finish.

My understanding also. The hot metal actually burns into and bonds to the painted surface and won't wash off. That lead to a tiny speck of rust. Lots of specks grow into a nasty stain and eventually a huge rusty spot.

[Tom M King]

Even cutting with the toothed blade, I always cut it face down. The chips from the little bandsaw aren't hot enough to melt into the surface coating.

There are all sorts of specialized roofing tools, but the prices on even the simplest ones are high enough to come up with some other method, if you're not doing it all the time. I've made a number of improvised solutions, some using stuff I already had.

[Rollie Meyers]

For cutting light gauge sheet metal look into a Kett shear, I have a obsolete model, but blades are the same for newer models.

https://www.kett-tool.com/