cutting corrugated roof sheets

caravan72 · Post by **caravan72** » Tue Sep 22, 2020 5:05 pm

Hi folks, I've built a shelter for my hot tub it will be quite open so hopefully I wont have much of a problem with condensation, haven't ordered the sheets yet but have asked for a quote. My issue is with cutting it, part of the shelter is at an angle so I will have one long cut, the material comes 0.5 or 0.7 gauge.
They don't recommend using an angle grinder for this product but mentions a reciprocating saw or electric nibblers. I'm planning on using tin snips to cut it by hand don't know how difficult this will be, could anyone recommend a pair that will be good to use or any advice on how I can cut this safely, I'm a bit wary of using power tools with this.

aeromech3 · Post by **aeromech3** » Wed Sep 23, 2020 5:03 pm

I don't envy you, I have cut corrugated sheet length ways with aircraft tin snips, not easy and had to cut the waste away every 2 foot at a time, very difficult not to get cuts on ones hand from the sheet. I would have thought your angle cut would have been best done with a 9" angle grinder with the sheet sandwiched clamped between guide wood battens; a grinder is not good if the sheet is plastic coated; also, if galvanised avoid breathing fumes. If you can bench and clamp the length down then a fine jig saw, again use a thin batten guide.
Ironically the many U-tube video's only show cross cutting or nibbling a shape !

caravan72 · Post by **caravan72** » Thu Sep 24, 2020 8:17 am

Hi folks, thanks for the reply areomech3, I have asked the builder in my street to give me a price to fit polycarbonate, just think cutting the iron sheet would be too challenging for me, it will probably cost me about £500 but I feel better going down this route.

Hitch · Post by **Hitch** » Thu Sep 24, 2020 8:43 pm

The reason they ay dont use a grinder is 2 fold...

The heat from cutting can cause the paint to burn off slighlty a mm or two from the cut edge, which will eventually result in a slight lifting of the coating on the sheet...
Secondly, grinding sparks can land on the sheet, and may cause tiny rust specs after a while.

I use a 5" grinder usually without any issue....a decent thin disc and good technique doesnt burn the paint, and cut edges would usually be covered by a flashing of some kind anyway...If ive a lot to cut, i use a cold cut metal circular saw, a bit more specialist though.
I wouldnt use a 9" for it, that does burn the paint, and fires many more sparks.

Nibblers are brilliant for it to be fair, but again, a bit more specialist.

Oridinarily, you overlap the sheet an extra ridge or number of ridges on the last sheet to loose any excess width, cant you just do that to avoid the lengthways cut? You can push up or stretch out the sheet a little here and there too, which helps make up or loose.

Snips would be the last thing id look at using tbh, too much like hard work, and easy to get a horrible wonky and distorted edge.
i'd run with a 4.5" or 5" grinder and thin disc, brush the sheet down before you install to remove the metal dust, and you' ll avoid rust specs.

aeromech3 · Post by **aeromech3** » Fri Sep 25, 2020 11:22 am

As the Op indicated he needed to cut at an angle lengthways, I did't think a 4.5" would clear the corrugation dwell depth enough!

Hitch · Post by **Hitch** » Fri Sep 25, 2020 1:50 pm

Cut the ridges, then turn the sheet over and cut the other ridges

I missed the angled cut bit i admit

kellys_eye · Post by **kellys_eye** » Tue Oct 06, 2020 5:07 am

All the sheets I've cut in the last couple of years (0.7mm or 0.5mm) I did using a 1mm cutting disk in a 5" grinder! Only area of concern is the last inch or so where movement of the cut-off bit can grab the disk but, with care, this is easily avoided. Never broke a cutting disk, always had a good finish line etc. Not bad for a 'first-timer'.

If I can do it, anyone can.........