# Forum Home Renovation Roofing  bending corrugated roofing

## manofaus

Was looking at a roofing installation the other day, where they have bent corrugated colorbond sheeting over the top of a our amenities building. As in a complete arc. I thought that you could only have it on 6 deg pitch or more.. Will it leak? or do they seal between the sheets or something, just curious is all.

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## manofaus

https://picasaweb.google.com/EzyHome...02367597205282
is the sort of thing I was looking at.

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## ringtail

Piece of cake. They ( roofers) use a on site profiling machine that puts whatever radius you want ( within reason) into the sheets. The sheets themselves are much thicker  .8 mm from memory and are called custom blue orb. No need to seal between the laps as all the sheets are the same. One of my front decks has a tighter radius than the one in the photo and has never leaked in 11 years.

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## Pulpo

I put some normal corro on a 12.5m radius curve, length of the arc was only 7 metres. 
Walked it on sat down beautiful if fact seems to fit better than straight. 
The roofers said he had put it on as tight as 8m radius. 
more than that need pre rolled. 
Pulpo

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## The Roofer

Exactly right Pulpo! 
Have installed down to 8 meter radius - just make sure you move roof battens a bit closer - otherwise can bend on top. 
The roof suppliers will only recommend down to 12 meters or so (refer to their Tech Manuals online) - as they won't guarantee it under this. 
The Blue Orb is a lot more expensive!

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## ringtail

I think mine is pretty close to 6.5 mt radius and has no battens just 3 beams - one ridge and 1 each side running at 90 degrees to the sheets obviously

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## The Roofer

Hi Ringtail  
What's the length of the arc? Just interested that you got to 6.5 meters - well done - I haven't been game to try.

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## ringtail

My deck is about 5 mt wide and the roof projects out, or rolls past about 400mm from one side. The other side finishes at the top of the beam for the gutter. Probably have a photo somewhere but I do recall seeing 6mt radius on the plans. Whether it ended up at 6 is a different storey.

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## BLWNHR

> I thought that you could only have it on 6 deg pitch or more.. Will it leak? or do they seal between the sheets or something, just curious is all.

  I think the others have missed your point, or failed to explain it fully. You were meaning that if there was a end-to-end lap in the sheets near the top of the roof it could leak as it was quite flat, correct? 
What the others are saying is it isn't a problem if the sheets are full length and rolled on-site to suit the roof. What they haven't mentioned is what happens if the roof is a substantial length and the sheets need to be made in multiple parts (about 10m maximum from my experience). Yes there is a very real chance of leaks. I had some involvement with a school gymnasium that had a very large radius roof on it, but it was also very wide. Even at 10m/sheet it had a coupld of laps in it and there was a water ingress issue.

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## The Roofer

BLWNHR, 
You correct in the above - but all convex forced curved roofing has to be laid in strict accordance with the BCA which follows the "_Installation Code for Metal Roofing & Cladding_" *SAA HB39-1997* (a new code is coming out shortly from Australian Standards). In this, the guidelines are strict and in the examle above that leaked would have had installation problems probably. Large curved roof areas - much larger than above have had no problems. But the time involved to explain the whole installation procedure would too great here in this forum. 
A couple of points are:
1. That all side laps should be sealed over the crest of the curve to the point where the slope is greater than the recommended minimum slope stated for the sheet profile (corrugated in this case) - but this also varies between suppliers of corrugated. 
2. Also if end laps are required (often in large roof areas) then each alternate sheet laid from opposite ends an below the crest, down far enough below the minimum stated slope once again. If this is not possible - then longer sheets have to be supplied. 
3. Purlin and batten spacing are also critical. 
Many many more requirements. 
If *manofaus's* project is a large as per above - he should seriously consider getting a specialised roofing contractor.

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