Wet or buckled felt can leave a visibly uneven finished roof. Covering it does not remove the underlying problem
GAF technical bulletin: Buckled felts prior to shingle installation.
What this means for your roof
Wet or buckled felt can leave a visibly uneven finished roof. Covering it does not remove the underlying problem. GAF calls for suitable underlayment condition before shingles are installed.
A useful question for your contractor
Ask whether the deck and underlayment are dry, flat and ready before installation continues.
Ask for the answer to be tied to the actual roof condition and the exact product being installed. Keep the agreed repair or installation detail with your estimate and project photos.
Bulletin revision: February 1, 2021. This is the date of the manufacturer source, not a claim that this website guide existed on that date.
Read GAF: Buckled felts prior to shingle installation
This homeowner summary explains the cited bulletin. The complete manufacturer document and current product instructions govern the installation details. A requirement for one manufacturer or product should not be transferred to another without checking.