Those ripples bumps can be pressed down easily which suggests that there is space between the shingle and decking i e shingles are not properly supported by the decking where there are ripples.
Roof felt rippling.
Lumpy bumpy or curling shingles that do not.
In addition to being unappealing wrinkling can also signal problems down the line.
Item 656632 model 0903000.
Roofing felt is comprised of a base made from natural materials such as wood cellulose or synthetic ones such as fiberglass or polyester and then coated or saturated with a protective coating such as bitumen asphalt which repels water but still allows the product to breathe.
Roofing underlayment or felt is usually required for the ul fire rating to apply since shingles are usually tested with underlayment.
The felt with then expand and wrinkle pushing the shingles up causing the rippling effect.
Roofing underlayment or felt helps prevent unevenness in the roof sheathing from telegraphing through the shingles.
Roofing underlayment or felt protects the roofing from any resins that bleed out of the sheathing.
I had my shingle roof replaced a couple of weeks ago using 25 year shingles and 30 lb.
One can see clearly lots of ripples bumps all over the roof but one section is much worse than the rest.
In high humidity materials may bulge or wrinkle causing ripples and bumps on the exterior surface of your roof.
If during the roof installation sealing was not done using foam or it was done improperly it could be problematic in the future.
They give the roof a finished look while forming a protective seal.
Moisture from the house will get in between the panels and absorbed by the felt.
Roofing professionals agree that a rippling roof is a sign that a home needs to be reroofed as soon as possible.