Why are the shingles on my new roof buckling, and what should I do?
Short answer. Buckling on a new roof usually comes from what is under the shingles: decking that swelled because sheets were installed without spacing, underlayment that wrinkled or got wet before the shingles went on, or shingles laid over an uneven surface or an old layer. Slight unevenness from a cool-weather install can settle in the first warm weeks, but ridges that stay or grow are an installation issue for the roofer to address under warranty.
Common causes on a new install
- Deck movement. Panels need a small gap at their edges and ends so they can expand. Tight sheets swell with humidity and push up ridges along the seams.
- Wet or wrinkled underlayment. Felt that got rained on before the shingles went on can wrinkle and telegraph through. Synthetic underlayment lies flatter but must be fastened correctly.
- Laying over old shingles. A second layer follows every lump in the first.
- Fastening problems. Nails that were underdriven or missed the deck let shingles lift.
- Attic moisture. Poor ventilation lets the deck absorb humidity and move.
What can settle and what will not
Shingles installed in cool weather can look slightly uneven until summer heat softens them and activates the sealant strips, which usually evens out within weeks. Straight ridges that follow deck seams, waves that grow after rain, or shingles still unsealed after a full warm season need attention.
What to do
- Photograph the buckling from the same spot over a few weeks.
- Check the attic for damp decking or weak ventilation.
- Call the installer under the workmanship warranty, ask what they think the cause is, and get the fix in writing.
- If the installer will not help, a manufacturer inspection can sometimes determine whether the product or the installation is at fault.
See OSB vs plywood roof decking and roofing warranties explained.