20" galvanized versus ice & water shield


Am getting the entire roof on the house replaced.
Have two estimates. Both are the nearly the same.

  • One states '20" galvanized metal under valleys.

  • Another states ‘ice & water shield’

What is better? As for weather conditions - I live in Atlanta, Georgia.


Go for the I ce and Water sheild

Thank you for the response, The Outlaw roofer.
Can you please elaborate on why that would be better?

I use a three part system in the valleys prior to putting down shingles.

First, 3ft of ice and water shield.
Second, 15# fiberglass felt weaved in the valleys.
Third, 20in 26 gauge galvanized rolled valley flashing.

Why? Because call backs get expensive and in Minnesota we get some really nasty weather. Is it overkill? Yup.

Ice and Water shield may not ever be code in your area. If you want it go for it but you may not need it. It’s intended to be used when ice dams may occure at the eaves. It’s also intended to be used in valleys were a lot water will flow and snow and ice will sit for long periods.

The idea of ice and water and then rolled valley flashing is if you cut too deep with a closed valley method you won’t cut beyond the valley flashing into the ice and water shield.

I can honestly say that with the three part system have not had one call back in several years and hundreds of roofs.

Go with just I&W sheild in the vally. the galvanized is just a waste of time and material.

I like the watershield, or any sbs in the valley. I don’t have a problem with putting down galv. valley, but I wouldn’t do it without an sbs, or watershield.

we use #30 felt or I&W and 24" W shaped valleys


I like the open metal valleys myself.

If I was depending on a closed valley to keep the water out. Then I would use Storm Guard.

If I was using a metal valley, them felt would be all I used.

This is for your area. Where I am we use Storm Guard under the metal valleys to.

Go with the contractor you feel most comfortable with.
Both open metal valley and Ice and Water applied closed valleys work well when installed correctly.

Roofers will endlessly argue the pros and cons of both products.

Personally, I can’t come up with a convincing argument why to choose one over the other.

If your contractor installs 20" galvanized metal it has to have ice & water or felt under it.Otherwise you’ve got no protection when you get condensation on the backside of the metal.


There are alot of slate and cedar shingle roofs out there with galvinized valleys. No felt or storm guard under the valley. They have been working fine for a hundred years. 50 on the cedar.

around here a galvanized vally will turn to rust in about five years. almost all open vallys are copper, lead coated or aluminum. Galvy would have to also be painted. regardless it only makes good sence to install I&W shield under your metal vally, as well as strip in the sides.

I personally like ice and water because it adheres very flat. Metal or even roll roofing can tend to visually be detected as the shingles adhere/settle.

I roofed many a house (and still do) without ice&water. I am in southeast Virginia. We don’t need it here except for warranty purposes.

The builders won’t pay for it so they don’t get it.