Do shingles flatten out?

Yes, asphalt shingles do flatten out after installation, but the timeline depends on temperature, storage, and installation conditions. When shingles are new from the bundle, they may have a slight curve or waviness from being stacked and stored, especially if stored on an uneven surface or in heat. Once installed on a roof, they need warmth from sunlight to relax and conform to the roof deck. In warm weather above 60 degrees, shingles typically flatten out and seal within 1 to 4 weeks. The heat softens the asphalt and allows the shingle to relax and the factory-applied sealant strip to bond. In cooler weather, flattening takes longer, sometimes 1 to 3 months, and if installed in winter below 40 degrees, shingles may remain slightly wavy until spring when temperatures rise and they finally seal. However, if shingles do not flatten out after a full warm season, it usually indicates an underlying issue rather than normal settling. Causes of persistent waviness include uneven roof decking, plywood seams not spaced properly that have swollen, wrinkled underlayment underneath, or installing new shingles over an existing uneven layer. True curling or buckling from age or moisture will not flatten out and indicates deterioration requiring repair or replacement. So minor new-roof waviness is normal and temporary, but long-term waviness is a defect.