What Most People Get Wrong
Most homeowners here think a drafty garage door is a weather problem. It isn't, not really. Downey's climate band is mild temperate - no hard freezes, no monsoon season, nothing that stress-tests a seal the way a harsher climate would. So people assume the door is fine because the weather is fine. What actually happens is slower: the bottom seal on a door installed when the house was built, somewhere between 1943 and 2012 with most of the stock going up in the 1960s and 70s, has simply outlived its rubber. Vinyl and rubber astragal seals don't fail from cold snaps in this area. They fail from decades of sun-flex and compression against a slab that's shifted a half-inch since Eisenhower was in office. The seal looks intact from six feet away. Up close, it's cracked along the compression line and has stopped doing its one job, which is closing the gap between the door and the slab. People replace openers, springs, even whole panels before they ever look down at the four dollars of rubber doing none of the sealing.
The Problem
A worn bottom seal or brittle side stop doesn't flood a Downey garage - the mild climate means you're not fighting standing water or ice most years. What it does is let in a steady trickle of outside air, dust, and the occasional rodent looking for a dry spot. Over a house built in the early 1960s, that gap has usually been there long enough that owners stop noticing the draft at all; they just notice the garage is never quite the temperature it should be, or that stored boxes near the door edge pick up grit. On the 1960s-70s tract construction common across this stretch of the county, slabs were poured without the expansion joints you'd see in later code, so the gap between door and floor widens unevenly along the threshold. One side seals, the other doesn't. That's a track and seal fit problem, not a door problem, and it's why a flat strip of weatherstripping bought off a shelf rarely solves it on its own.
What to Check
Start at the bottom seal - press a thin flashlight beam along the base of the closed door from inside the garage at night. Any line of light means a gap. Next, check the stop molding on both sides of the jamb; on 1960s and 70s framing it's common to find the wood has shrunk slightly off true, leaving a wedge-shaped gap that's wider at the top than the bottom. Run a hand along the top seal where the door meets the header, since that one gets forgotten most often. One honest limit here: if the slab itself has settled or cracked unevenly, which shows up on some of this older housing stock, no seal adjustment fixes that - you're looking at a floor repair first, or accepting a partial gap. Weatherstripping can't compensate for a slab that's no longer flat. Everything else - seal, astragal, stop molding - is a straightforward fix once you know which one is actually letting the air in.
