Does Roof Underlayment and Bitumen are consider SWR?

[Chiun D. Ng]

Does Roof Underlayment and Bitumen are consider a Secondary Water Resistant?

[Kenton H. Shepard, CMI]

Yes. The roof-covering material is the primary barrier, the underlayment is the secondary barrier.

[Blaine Wiley]

If you are speaking of a wind mitigation report in Fl, the answer is no. The secondary water barrier muxt be a self adhering polymer modified bitumen roofing underlayment applied directly to the sheathing or a foam
adhesive SWR barrier (not foamed on insulation) applied on every sheathing seam. It goes directly on the sheathing prior to the felt, or other underlayment.

[ROBERT V. YOUNG]

Mr. Ng.
What do you mean by Bitumen.
The underlayment is a yes but are you asking is a caulk or plastic cement a water proofing layer?
Please explain the use of Bitumen.