Perimeter Seal

A perimeter seal refers collectively to the weatherstripping that fills the gaps along the top and both sides of a closed garage door—the header seal at the top and the jamb seals on the sides. When combined with the astragal along the bottom, the perimeter seal forms a continuous barrier around all four edges of the door.

The header seal (sometimes called the top seal) is typically a flexible vinyl or rubber strip attached to the top edge of the door's top section or to the header framing above the door. It deflects to conform to the door panel surface when the door closes, filling the gap that appears when the top section transitions from vertical to slightly backward-tilted in the open-to-closed position.

The quality of a perimeter seal determines how much outdoor air, dust, pollen, insects, and moisture enter the garage through the door perimeter. A properly sealed perimeter also reduces noise transmission and improves the thermal performance of an insulated door by eliminating convective bypasses around the door's edges—even a well-insulated panel loses effectiveness if cold air streams freely around the edges.

Perimeter seals degrade over time as the flexible material hardens and cracks. Visible daylight around the edges of a closed door, or drafts felt near the door edge when it is windy, indicate that one or more perimeter seal components need replacement. Replacement strips are sold as retrofit kits that nail or adhere to the jamb or door edge.