I have a bugalow and the current roof has aluminum in the valleys of the shingled roof. We are thinking of replacing it pretty soon, and the neighbor says the shingled valleys are just as good as the aluminum ones, and cost less.

Anyone have personal experience with this issue?

Aluminum valleys are crap, IMO. You're better off with a cut or woven valley. You can have maybe .032" of aluminum (if you're lucky, .027 or even .019 are more common), or .5" of shingles. Yeah, the aluminum won't wear out, but it will dent, puncture, crease, ect. If I'm on a roof, I'll walk all over a shingled valley, but I definitely avoid walking on aluminum ones. If you must use a metal valley liner, go with galvanized, or better yet, copper.

Thanks ... I was asking beause we have lots of snow, ice, rain, here. Valleys tend to freeze up with wet snow, then, get icy. I thought the aluminum valleys would provide less chance of that occuring.

Thanks again for the feed back!

Ice and ice damming are a separate issue, not helped much by metal valley liners. Best bet there is to make sure any attic space is well insulated and ventilated, that solves 90% of the problem- the less snow you melt above living spaces, the less ice that develops on overhangs.

Secondly, ice and water barrier, preferably Grace. This is what can be done from a roofing standpoint. It mainly treats the symptom but it's effective. In heavy snow areas barrier should be installed 6' wide in all valleys and at least 4' past exterior walls on all gutter edges.

Let me know if you have any questions about any aspects of this, I've been in the business for over two decades.

Wow, I don't know about your local building codes. I was a roofer for 5 years before I joined the Navy. We always used galvanized steel roll in the valley, although copper is very common in other areas. It didn't matter if we wove the shingles or made I nice, neat cut. After the first two years using roll, we began using stamped galvanized steel in a kind of a W shape. Should look like this.



This a copper version over galvanized roll. Notice the bottom of the galvanized is not contoured to the corner of the roof but allowed to extend with a 90 degree straight cut.

Some good advice on installing it..
http://www.oldhouseweb.com/how-to-advice/r...g-details.shtml

We usually would install the flashing, nails at the edge of the outside. Run shingles along one side, pop a line about 1/2 inch from the crown on the flashing and cut. Do the other side and repeat. On the owners request, we would cut the shingle at the crown for a very tight finish. It was to code at the time, not sure if still correct. For a more subdued look, you can get galvanized that is coated in a darker brown or grey that would compliment the shingle color.

No code here requires metal valley liner. But if you were a roofer for 5 years however many years ago, I guess me and my 22 years experience (10 of those running my own company) will shut up.

BTW, your second pic, bad idea. Do you know what happens long term when galvanized and copper are left in contact with each other, especially when there's moisture involved? Google "galvanic reaction".

It was a long time ago, I stand corrected.

I'll give you a "galvanic reaction"!

"galvanic incompatibility"

See this fairly often with plumbing pipes, i.e. copper to galvanized ect.
Hey it works for a while.