Debbie from CA asked:
Attaching the synthetic underlayment is done with nails or staples. Can water seep in at the nail hole or staple hole?
This is what roofing expert John Kenney from Cotney Consulting Group had to say in response to your question:
Synthetic roofing underlayments must be installed with either cap nails or staples. These underlayments do not seal around the fasteners, so they are considered water-resistant and not waterproof.