Curved roof, gulley nightmare

[janette]

On our extension build, a curved roof joins 2 separate existing buildings with pitched roofs together. We have the curved glulams installed and the weatherproof membrane on.  All we need now is more insulation and standing seam zinc. Of the 3 potential companies to fit the zinc, only one is insisting on gulleys where the curved zinc section meets the pitched slated roof. Those gulleys and the carpentry and leadwork required are going to add significant cost. 2 others are saying it’s no necessary. The company insisting is saying we’ll collect water at points on the down curve where water will pool between standing seam and slates. Has anyone installed a curved roof and got any advice. Thanks. 

[nod]

I drawing would probably get you a better response 

Because the water pools it doesn’t mean it will leak 

Ideally a gully would be belt and brace’s Expensive job to put one in afterwards 

 

[ProDave]

It sounds like they are suggesting a hidden gutter drain which sounds very sensible.

 

Drawings and pictures would help.

[saveasteading]

I've done metal curves. I don't understand your situation though, so sketches or drawings please.

[saveasteading]

I have reread and have in my mind that you are creating valleys. They would need valley gutters, otherwise where does the water go? 

What do the existing roofs have for drainage?