Garage Door Won't Close All the Way or Leaves a Gap? Settling Slabs and Sacramento Soil

First, Read the Gap: Is It the Door or the Opening?

Before you blame the door, look at the shape of the gap with the door fully down. The single most useful diagnostic question is whether the bottom edge of the door is straight or not. Stand inside the garage in daylight and look at the line of light coming under the door — that light line tells you almost everything.

If the door's bottom edge is dead straight but the daylight is wedge-shaped — pinched on one side, wide on the other — the door is fine and the opening is out of level. That points you toward the concrete and framing. If the bottom edge of the door itself is curved, bowed, or kinked while the floor looks flat, the problem is in the door or its hardware.

• Even gap across the whole bottom: usually a limit/travel setting on the opener telling the door to stop early.
• Wedge gap (tight on one corner, open on the other), but the door edge is straight: the floor or frame has moved — common with Sacramento-area soil.
• Curved or kinked bottom edge while the floor is level: a warped bottom section or a bent/binding track on one side.
• Door starts down, then reverses and goes back up: think safety sensors or an obstruction, not a gap problem.

The Four Usual Suspects (and How to Tell Them Apart)

Most 'stops short' and 'uneven seal' complaints trace back to one of four causes. Each leaves a different fingerprint, so you can usually narrow it down from the driveway before any technician arrives.

Two of these are quick adjustments and two are not. Knowing which is which keeps you from paying for a track straightening when a sensor was simply nudged out of alignment — or from chasing the opener settings for weeks when the real issue is a cracked, tilting slab.

• Limit / travel setting: the door closes fully but leaves a small, even gap, or it slams and bounces back up. The opener thinks 'closed' is a hair too high or too low. Often a true adjustment, not a repair.
• Safety sensors (the photo-eyes near the floor): door won't commit to closing, reverses partway, or the opener light blinks. A bumped bracket, a spider web, or low-angle Sacramento afternoon sun hitting the lens can all trigger it.
• Warped or damaged bottom section: the door's own edge is no longer straight — heat, moisture, or an old impact bowed it, so it seals in the middle but gaps at the corners (or vice versa).
• Bent or misaligned track: the door binds, slows, or hangs up on one side and the rollers don't seat evenly. You may hear a rhythmic catch at the same spot every time.

The Sacramento Culprit Most Homeowners Miss: Expansive Clay Soil

Much of the Sacramento Valley sits on expansive clay — soil that swells when it soaks up our wet winters and shrinks as it dries out through a long, hot Central Valley summer. That seasonal swelling and shrinking lifts and drops the ground under your garage slab and footings, and the slab doesn't always move evenly. One corner can heave up a fraction of an inch while another settles.

A garage door is built to close against a flat, level opening. When the slab tilts or the frame racks even slightly, the door — which is still perfectly straight — can no longer meet the floor evenly. You get a seal that's tight on one side and a visible wedge of daylight on the other. The giveaway is seasonality: many homeowners notice the gap appear or worsen in late summer when the clay has shrunk most, then partly close up again after the first heavy winter rains swell it back.

This is the case where the door isn't the patient — the building is. A technician can sometimes compensate with a tapered or thicker bottom seal and by re-leveling the door's travel, but if the slab has cracked or tilted significantly, the real fix lives with the concrete, not the garage door. An honest assessment names that line clearly instead of selling you a new door for a foundation problem.

Quick Adjustment vs. Structural: What You Can Safely Check

There are a few safe things to look at yourself, and one whole category to leave alone. The safe checks are visual and require no tools and no contact with anything under tension.

What you must not touch: the springs and cables. The torsion or extension springs above and beside the door are under extreme, stored tension and are not a DIY adjustment — a slipped winding bar or a snapped cable can cause serious injury. If your diagnosis points anywhere near the springs, lift system, or cable drums, stop and bring in a trained technician. The same goes for trying to 'persuade' a bent track back into place by hand while the door is loaded.

• Safe to check: wipe the two photo-eye sensors and confirm both small indicator lights are steady, not blinking, and that the brackets haven't been kicked.
• Safe to check: clear the floor track of pebbles, leaves, or a stray door stopper that could hold the door up by a fraction of an inch.
• Safe to look at (not adjust): whether the bottom edge of the door is straight, and whether the daylight gap is even or wedge-shaped — note which corner is tight.
• Safe to note: whether the gap changes with the seasons, which strongly suggests soil and slab movement rather than the door.
• Leave to a technician: any limit/travel reprogramming, track straightening, roller or bottom-section replacement, and absolutely anything involving springs or cables.

What to Tell Us So We Arrive Ready

Because this symptom has four very different causes, a few details up front let a technician show up with the right plan instead of guessing on site. When you request a free quote, the more of these you can describe, the better.

Helpful details: which corner gaps and which corner seals; whether the door's bottom edge looks straight or bowed; whether the door stops short, reverses, or bounces; and whether you've noticed the gap come and go with the seasons. A quick photo of the closed door from inside, with the daylight showing, is often worth more than a paragraph. Note that any repair pricing depends on the actual cause — a sensor realignment, a new bottom seal, and a tilted-slab situation are very different jobs — so we confirm the specifics with a quote rather than quoting blind.