Valley Flashing has to be metallic?

Are valley flashings required to be metallic (I normally see galvanized metal)? I was on a roof yesterday with a modified bitumen looking material used to line the valley under the shingles.

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Hi, @jgorum2. Larry is correct. The IRC code is a great resource, and InterNACHI courses are based upon the IRC. Check out 2021 IRC Section R905.2.8.2 Valleys, and check out InterNACHI® - International Association of Certified Home Inspectors.

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Thanks fellas, That answers my question.

The IRC says no but, roofing covering material manufacturers have the last say…
Valley linings shall be installed in accordance with the manufacturer’s instructions before applying shingles. Valley linings of the following types shall be permitted:

1.For open valleys (valley lining exposed) lined with metal, the valley lining shall be not less than 24 inches (610 mm) wide and of any of the corrosion-resistant metals in Table R905.2.8.2.

2.For open valleys, valley lining of two plies of mineral-surfaced roll roofing, complying with ASTM D3909 or ASTM D6380 Class M, shall be permitted. The bottom layer shall be 18 inches (457 mm) and the top layer not less than 36 inches (914 mm) wide.

3.For closed valleys (valley covered with shingles), valley lining of one ply of smooth roll roofing complying with ASTM D6380 and not less than 36 inches wide (914 mm) or valley lining as described in Item 1 or 2 shall be permitted. Self-adhering polymer-modified bitumen underlayment complying with ASTM D1970 shall be permitted in lieu of the lining material.