Thread: Cutting corrugated colorbond

there are a couple of power sheers worth a look.
there is a cheep metal sheer that cuts by removing a 6mm(or so) strip. they leave a very good edge but arent much chop on curves or corigated.

then theres the roofers friend.

looks like a set of ofset aviation snips atached to a drill. Aparantly they are fabulous.

available mounted to an electric or an air drill, the electric variety were mounted to a metabo drill last tyime I saw a set.

If you cut it you break the protective barrier no matter what you use. Metal cutting blade in the portable 9 1/4 worked like a charm and is still there 10 years on. And I reckon about a quarter the time of all those with snips so you decide.



Jamie

Jamie,
Colorbond and zincalume are self healing. If you scratch it or cut the end of the sheet apparently the zincalume (or some of its components) will actually migrate to protect the scratched surface (we're talking fine scratches here).

Mick

If that is the case Mick - and I'm not doubting your expertise but then the obvious applies- cut it easy and quick.

After several years in aviation engineering where a lot more variables are in play, then if you cut it - seal it, if that is what is needed. Domestically in a vertical orientation it should not be a problem because the raw surface will be on the inside. On roofing - well I'll admit that there may be some risk but any metal that is cut needs to have the sharp edges removed. Expansion and contraction will ensure degradation of the join/overlap without it, apart from a safety perspective.

The protective coating on these products is only microns thick so if you cut the sheet it will expose aluminium alloy. Some alloys actually produce an oxidation that is similar to anodising but still not that of the whole sheet product, anodised or alloyed with zinc. Anodisation discussions could go on forever here and I will resist. It is these alloys that are used in tinnies and they can be eroded very quickly if the right circumstances exist. There are also alloys which are extremely resistant to oxidation even in salt water but they are also expensive.

In housing applications I would doubt if there is any justification for protecting raw edges except in seaside atmospheres. At the end of the day if you cut it, remove sharp edges and seal it if the risk exists - if not delete the last step.

Colorbond-style roof sheet products come from a continuous roll of coated steel. It is rolled to the desired profile and then cut to length with a guillotine. Nothing is done to the edges after cutting.

Journeyman Mick & Silent C are correct as an ex Lysaght Rep
I suppose I should know.

The action of shearing takes some of the zincalume coating into the sheared edge and protects it. Actually tearing the sheet as was suggested earlier this does not happen.

But at the end of the day it doesn't matter how you cut the sheet even cutting it with a saw, angle grinder, shears, nibblers, tearing it or using your teeth it wont make much difference in the amount of corrosion, provided the cut edge is protected from the elements by flashings and cappings it will be minimal and ok and will see just about any of us out in our lifetime.

The usual thing is to cover the cut edge for asthetic reasons because if you use a saw or angle grinder it will burn the paint and make it look crappy anyway.

If you are within 100 metres of the surf Lysaghts recommend stainless steel Colorbond and from 100m to 500m they recommend what they now call Ultra Colorbond that used to be called XSE for Extreme and Severe Envionmental.

Actually the biggest cause of corrosion in Colorbond is using non approved fixing screws and if you use them you will void any Lysaght Warranties and you will find that Lysaght will only recommend Buildex Screws made by W.A. Deutchers.

Interesting this thread has gone from how to cut a few sheets of Colorbond to the consequenses of what will happen to it when you do cut it. Talk about getting side tracked.

Well that's the end of todays lesson.

Long time between posts on this thread!
I saw Glenn's post using the piano wire and thought... maybe??? Anyway infor doesn't go out of date so I thought I'd add this for the next person.
I tried this method for an angle cut across the corrugations - didn't have any piano wire so used fencing wire... slightly bent edges with the thicker wire, but those are covered by flashing in my case. Otherwise - worked like a charm. Great suggestion - silent, quick, cheap and easy. Thanks Glenn!
Robert

Probably the easiest way, and providing you have a circular saw, is to use an old high speed steel blade. BUT it must be put in backwards. It lasts a very long time and can be used to cut roofing profiles across or along. The main downside is that it is very noisy.

Wear ear muffs (and safety glasses) and make sure neighbours have gone out.

Regards
Paul

At Super Cheap Autos there is a cheapy nibler,best way no burrs or damage to the surface from the junk you get from a saw or cut off blade,and a straight cut