Ice/water membrane vs metal flashing in the valleys

I am replacing Organic Certainteed shingles on the roof and currently evaluating multiple estimates.

Most contractors state they will put an ice/water membrane in the valleys and the perimeter. However, one contractor prefers to use the metal flashing in the valleys and the ice/water membrane around the perimeter only.

What is recommended? Are there pros/cons to metal flashing vs water membrane in the valley? I appreciate your help.

i use A.P.P. in all my valleys with or without metal. metal can condensate water and what is below the metal is important. metal can be necessary on steeper roofs and certain shingles. keep in mind some of us make most of our income fixing other roofers mistakes.

I assume A.P.P. is an ice/water membrane that I see on Certainteed/GAF/Owens Corning websites. It makes sense to put the membrane under the metal…you can never to be cautious when it comes to moisture.

Which is preferred? Membrane or Membrane+Metal in the valleys

I appreciate everyone’s input

It’s basically a matter of cost and cosmetics. Can you afford the metal, and do you want the open metal valley look?
A shingled valley should last the life of your roof, if done properly, regardless if you have Ice & Water shield under it or just #30 felt.

If the manufacturer requires the use of Ice & Water (I & W) in the valley (because of the shingle type, pitch of roof, harsh climate area, etc) then I would use it with your valley metal.

Of course, if the above is not the case, then you have more freedom to choose what you want o apply in the valley. Some companies will make it standard operation to install Ice & Water in the valley regardless of wether you use metal or not. This is a good thing as I personally believe that Ice & Water should always be installed in the valley!

As for the contractor who wants to overlap the valley metal (I & W)…I am to assume he will place felt in the valley. I would not agree with this method…however…this is how I would do it if you were to overlap valley metal.

  1. I & W the length of the valley
  2. Valley metal
  3. 6" strip of I & W overlapping both sides of valley metal (1/2 of 1st layer of I & W and 1/2 on metal)
  4. Felt should overlapl horizontally at least 6" over the valley metal

I would have to say metal an ice sheild together with a closed valley would be your best bet. Make sure the felt is always covering the ice sheild cuz if you don’t the next roofer will have a hell of a time tearing the shingles off.

I did my house with I & W shield, then metal, under a closed valley. Knowing that many problems occur at the valley, I wanted it as bullet-proof as possible.

If the area you live in adopts Residential Building Code, you must have rolled roofing, valley metal or i&w shield installed in the valley in order to be compliant. I believe properly installed i&w shield is superior to valley metal. No nails needed to install it. Given the minimal cost, I suppose if the roof is in an area where there is very heavy snow (with potential ice dams in the valley) or heavily wooded where debris accumulates quickly potentially causing dams, I could see going ahead and putting valley metal on top of i&w. But again, if everything is installed correctly, that is over kill.