What Gets Into a Long Beach Garage, and the Gap It Came Through

Published August 20, 2026

Most people find out they have a problem in one of three ways. Something moves overhead at night. There are droppings along the base of a wall, always along a wall and never in the middle of the floor. Or the garage door has started closing halfway and running back up for no reason anybody can find.

Those look like three separate issues. They are usually one, and the one is a gap somewhere around the perimeter of a garage door.

The Sizes That Matter

The numbers are smaller than people expect, and knowing them changes what you look for.

A house mouse gets through a gap of roughly a quarter of an inch. That is about the thickness of a pencil. A roof rat, the climbing rat that is well established across Long Beach, needs something nearer half an inch. The rule of thumb is that if the skull fits, the animal fits, because the rib cage and shoulders flatten in a way that looks impossible until you have watched it.

Now go and stand inside your garage with the door shut and the light off, in the middle of the day, and look at the bottom edge. If there is a line of daylight anywhere along it, that gap is not a quarter of an inch. It is considerably more. Do the same at both side jambs and along the top.

That five minute check tells you more than any amount of speculation about what is living in the roof space.

Roof Rats Come In High, Not Low

Long Beach has an old and comfortable roof rat population, and it matters that they are roof rats rather than the ground dwelling Norway rat. Roof rats climb by preference. They live in palm skirts, in dense ficus, in bougainvillea and in fruit trees, and they travel along fence tops, cables and eaves rather than crossing open ground.

The practical consequence is that they do not necessarily approach a garage across the driveway and squeeze under the middle of the door. They arrive at the side, drop onto the jamb, and work at the upper corner or the gap behind a track bracket. Plenty of homeowners have a perfectly sound bottom seal and an open corner nine feet up.

It also means a fruit tree overhanging the garage roof is part of the problem, and no seal fixes that.

Why Exclusion Beats Trapping

Trapping is not wrong. If something is already living in the building, it has to come out, and traps or a pest control contractor are how that happens.

The mistake is stopping there. A trap is a response to the animals present today. It does nothing at all about the opening that let them in, and a garage with an open corner is a resource with a queue. Clear it out in March, and by June you are back where you started with the same droppings along the same wall.

Exclusion is the half that ends the cycle. The building either has openings or it does not, and unlike trapping it is a finite job with a finish line. This is also the order of operations that matters: find out whether anything is currently nesting inside before you seal, because sealing a population in makes everything worse and you will be chasing a smell for a month.

The Weak Points, In the Order They Fail

The ends of the bottom seal

The astragal is the rubber or vinyl strip along the bottom of the door, held in an aluminum retainer. It almost never fails in the middle. It fails in the last few inches at each corner, where it works its way out of the channel, curls, or tears off completely. Nobody looks at the corners, because the eye reads the length of the seal and sees rubber.

Retainers split too, particularly near the water where salt gets into the aluminum. A new seal fitted into a split retainer will not hold.

Where a settled slab meets the door

Concrete moves. On garages built in the fifties and sixties, and there are a great many of them in Long Beach, the slab has had decades to settle at one corner or crown in the middle. The door is straight and the floor is not, so the seal touches at one end and stands off at the other.

No bottom seal solves this, because the fault is not on the door. The fix is a bonded threshold, a raised vinyl strip glued to the concrete that the door closes onto, which bridges the shortfall from below.

Missing or dead side stripping

The vinyl stop molding down each jamb is what the door closes against on the sides. On older garages it is frequently missing on one side, knocked off at some point by a car door, or painted so many times that it no longer makes contact. That is a full height gap, and it is at exactly the height a climbing rat arrives at.

Track brackets, penetrations and vents

Small, awkward, easy to miss. The triangular gap behind a track bracket where it meets an uneven wall. The oversized hole somebody drilled through the block for a hose bib or a run of conduit. A wall vent that lost its screen years ago. Individually they look like nothing. Any one of them is a front door.

What Happens Once They Are Inside

Here is where a pest problem turns into a garage door bill.

Every residential opener has to provide entrapment protection under UL 325, which means a pair of photo eyes low on each track and a run of light gauge two conductor wire back to the motor head. That wire is almost always stapled along the wall a few inches off the floor, because that is the fastest way to run it.

Rodents travel along walls. The wire is soft, the insulation is good nesting material, and the height is perfect. Once the insulation is off, the two conductors touch intermittently or the strands corrode open, and the opener reads a sensor fault. Its logic is deliberately pessimistic about safety, so it refuses to close, or it starts down and reverses.

What the homeowner sees is a door with a mind of its own and an opener blinking a code that says the beam is obstructed when nothing is anywhere near it. What usually follows is a realigned sensor, then a replaced sensor, then in some cases a replaced opener, none of which touch the actual fault.

The other half is the motor head itself. It is warm, enclosed, above ground and undisturbed, which makes it attractive, and the space behind the light lens on a chain drive unit is a common nest site. The nest is a nuisance. What the urine does to the logic board over a few months is not. Corroded traces and connector pins take an opener out permanently, and no repair brings that back.

Materials That Work, and One That Does Not

Openings that are gaps get seals: a correctly profiled astragal, a bonded threshold, proper vinyl stop on the jambs and header.

Openings that are holes get metal. Galvanized hardware cloth in a quarter inch mesh, cut generously and fixed down properly, or copper mesh packed in and mortared over.

Expanding foam does neither job. Rodents chew through it without much effort and will then keep using the tunnel they made, which is worse than the hole was, because now it is hidden. Foam has its place in stopping a draft. It has no place in exclusion.

The Ten Minute Check, Done Properly

Shut the door. Turn the lights off. Wait a minute for your eyes to adjust and then look along the bottom edge, up both jambs and across the header for daylight. Note where it is, not just that it exists.

Then look at where the sensor wire runs, and follow it with a flashlight as far as you can. You are looking for shiny copper, for insulation that has been gnawed to a taper, and for the fine shredding that goes with it.

Then look up at the motor head, at the light lens and at any opening in the chassis, for nesting material hanging out of it.

Then go outside and look at what is touching the roof and the fence line. If a branch bridges to the eave, that is a road.

When Sealing Is Not the Right Spend

If the bottom section of the door is rotted through or bowed enough that it no longer runs straight, seals will not follow it and you are into a section replacement or a new door. Say the same for a door that has been hit by a car and never properly straightened.

And if there is a live population in the garage right now, sealing comes second, not first.

Everything else, which is most cases, is a modest job. A bottom seal, both jambs, a threshold where the slab has moved, and the two or three penetrations that got missed. It costs a fraction of what a corroded logic board and a new opener cost, and it is the difference between fixing this once and fixing it every year.

If you have seen daylight under the door, or the opener has started behaving oddly, call Catanddogspiration on (562) 689-5506. We will look at the perimeter, the wiring and the opener head together, because in this city they are usually the same story.