Garage door seals and weatherstripping

Most water gets in at the bottom, and the seal is only part of the answer. DASMA's guidance on water under sectional doors calls it a common occurrence and starts the fix with the concrete: a slab that slopes slightly toward the outside where the door rests, or a notch in the slab that the door closes into. Even a new seal will leak on a slab that pitches back toward the garage.

Wind-driven rain is its own problem. DASMA is frank that sectional doors are not leak-proof or watertight: water can drip in when a wet door opens, collect in the section joints and run to the ends, or get driven through the sides and bottom in strong wind. Delaware's winter and spring nor'easters and autumn tropical systems bring exactly that kind of rain. Enhanced perimeter seals, a heavier bottom seal and an aluminum or rubber threshold all help, DASMA says, but none of them turns a garage door into a window.

A new bottom seal fixes gaps from a torn, flattened or shrunken seal, and a new retainer fixes a seal that keeps sliding out. Near the ocean, check the retainer as well as the rubber: FEMA's coastal guidance puts the worst metal corrosion within 3,000 feet of the ocean, and a corroded retainer won't hold a new seal. What a seal can't fix is a door that doesn't close level. If light shows at one corner only, the door may be out of adjustment, the cables may be uneven, or the slab may have settled, and the fix belongs there.

Temperature plays a part as well. DASMA's sheet on thermal bowing explains that insulated doors bow toward the warmer side when there's a big temperature difference between inside and outside, which can leave a gap at the top or make the top section rub the header. A dark door facing the afternoon sun in July or a heated shop in January is the classic case, and the cure is usually adjusting the track or the header seal, or adding struts, not stacking on thicker weatherstripping.

Yes, especially on an attached garage. Haas notes that the air infiltration seals on its 2000 Series exceed the ASHRAE 90.1 standard when the door is installed with the standard bottom seal and a common vinyl door stop, which is a reminder that a door's energy numbers assume good perimeter seals. With the seals gone, the insulation inside the door can't do its job, and the house wall next to the garage feels it.

Gaps also let in leaves, dirt and the occasional mouse. If you heat a shop or the garage stays humid, watch for condensation too. DASMA says condensation on a garage door is normally not a defect but a sign of warm, humid air meeting a cold door surface, and recommends good ventilation and tight seals around the glazing and between sections.