I inspected this house today. It had 4 layers (yes four). One original from 1923 of wood shingles and three of asphalt. There were a number of vertical cracks in the shingles as shown, however, the grit was in good shape on the shingles. I would guess that they were not more than 8 to 12 years old. No attic access to check for ventilation but small gable vents were visible on each side.
Could these cracks be a manufacturer’s defect? Obviously there would be no warranty claim with four layers.
Would anyone recommend sealing these cracks to squeeze a few more years of life out of the roof surface or should I recommend time for a new roof?