Best flashing material for valley.

Frere Jacques · 08-03-2015 10:34pm #1

Hi all,
I'm extending a garage which is 19' x 11'. My plan is to build another 19' x 11' next to it, install an RJS and take out the dividing wall. The original flat roof of the garage would be replaced with a low pitched A frame roof and the new section would have an identical parallel low pitched roof. I need the two pitches like this for a number of reasons, both legal and practical for the use of the garage.
My problem is I'm introducing a valley between the two walls which is not ideal but necessary. I'm wondering what is the best way to go about flashing this valley. I was originally thinking lead but I'm wondering if copper or just a long roll of 20" wide galvanized steel would work. I'm not overly concerned about cost, my wife will use the rainwater for watering the veggies but I'm assuming the short contact of rainwater on the lead isn't going to knock us over. I just want to know what people would suggest in terms of ease of installation and weatherproofing over a 50yr time frame.
Any hints or tips would be welcome.
FJ.

mykillokneel · 08-03-2015 10:40pm

If using lead, make sure you step it at joints so water doesn't run back. If your looking for 50 years you won't get that out of lead these days.
Fibreglass is best in my opinion.
Also construct valley wide enough so it doesn't get blocked up by leaves etc or should I say wide enough to clean when it gets blocked!

hexosan · 08-03-2015 11:22pm

What about a length of stainless steel valley if cost isn't an option. It'll certainly out live you.

sterlo · 09-03-2015 7:59am

The best options would be copper, lead (7lb heavy gauge with steps) or zinc, all will get you 50 years plus if laid properly by a competent roofer

no1murray · 09-03-2015 8:06am

I would go with fiberglass, it doesn't look the best but you won't have issues down the line.

sterlo · 09-03-2015 8:07am

no1murray wrote: »

I would go with fiberglass, it doesn't look the best but you won't have issues down the line.

Any idea what lifespan you'd get from fibreglass?

no1murray · 09-03-2015 8:35am

They recommend that a fresh gel coat it added after 30 years. A roller, a can of the gel coat and and about an hour should do it. The gel coat it the outmost layer that contains the colour.

bertie 56 · 09-03-2015 9:45pm

316L grade stainless steel will be my choice

Frere Jacques · 30-03-2015 8:33pm

Thanks for all the options folks.
I'll had a chat with a friend who is a carpenter and he was leaning towards the stainless option. I know the 316L would be pretty good for corrosion resistance but I'd be slightly worried about the expansion of a continuous lenght that he suggested. I guess I'll get a few prices from a few local lads for the different options and take it from there.
Cheers all.
FJ.

Best flashing material for valley.

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