Gap Under Your Garage Door? Here's What's Going On and How to Fix It

You close the garage door and look down. There is a gap along the bottom -- maybe half an inch on one side, maybe an inch all the way across. Daylight is coming through. You can feel air moving in. Leaves are getting in. Maybe you found a snake in the garage last summer and now you are paying closer attention to how that door meets the floor.

A gap under a garage door is one of the most common complaints Charlotte homeowners bring up, and the causes range from a $15 fix to something that needs a professional. Here is how to figure out what is going on with yours and what to do about it.

Why the Gap Matters

A garage door that does not sit flush against the floor is not just a cosmetic issue. That gap lets in:

• Water: Charlotte gets over 43 inches of rain per year. A gap on a sloped driveway means water runs straight into the garage every time it storms. Standing water in a garage leads to mold, rust on tools and equipment, and damage to anything stored on the floor.
• Pests: Mice can squeeze through a quarter-inch gap. Snakes, rats, spiders, roaches, and ants all use the space under a garage door as an entry point. Charlotte's warm, humid climate means pest activity runs year-round, not just in summer.
• Debris: Leaves, pine needles, dirt, and pollen blow in constantly. During Charlotte's pollen season from March through May, a gap under the door turns your garage floor yellow in days.
• Hot and cold air: If your garage is attached to the house -- which most Charlotte garages are -- that gap lets unconditioned air in. In summer, it is 95-degree air pushing into your garage and warming the rooms above. In winter, it is cold drafts that make the garage unusable as a workspace.

The bottom line: a gap under the garage door costs you money (higher energy bills), creates health risks (mold, pests), and makes the garage less useful. Fixing it is almost always worth the time and cost.

Common Causes of a Gap Under the Garage Door

1. Worn or Damaged Bottom Seal

This is the single most common cause and the cheapest to fix. The rubber strip along the bottom of the door -- called the bottom seal or weatherstrip -- compresses against the floor when the door is closed. Over time, this rubber dries out, cracks, flattens, or tears. Charlotte's heat and UV exposure accelerate the breakdown. A seal that was round and flexible three years ago may now be flat, hard, and cracked, leaving a visible gap even though the door itself is sitting in the right position.

How to tell: Look at the rubber strip along the bottom edge of the door. If it is cracked, flat, hard, or missing in sections, that is your problem. This is a $15 to $30 DIY fix.

2. Uneven Garage Floor

Concrete settles, shifts, and cracks over time. This is especially common in Charlotte because the soil here is predominantly red clay, which expands when wet and contracts when dry. That constant movement causes concrete slabs to shift, creating dips and high spots. A garage floor that was flat when the house was built in 2005 might have a half-inch dip on one side by 2027.

When the floor is uneven, the door makes contact on one side but not the other. You might see a gap on the left side but not the right, or a gap in the middle but tight on both ends. No amount of adjusting the door will fix this because the problem is in the floor, not the door.

How to tell: Close the door and look from inside the garage. If the gap varies from one side to the other, the floor is likely the issue. You can confirm by laying a straight edge (a level or a 2x4) across the floor where the door meets it and checking for gaps.

3. Misadjusted Close Limit

Your garage door opener has a setting called the close limit (sometimes called the down limit or travel limit). This controls how far down the door travels before the opener considers it "closed." If this setting is too short, the door stops before it reaches the floor, leaving a gap.

This is common after a power outage, after the opener has been reset, or after any repair work on the door or opener. Sometimes it happens gradually as the door and hardware wear -- the door needs to travel slightly further than it used to, but the limit has not been updated.

How to tell: Watch the door close. If it stops and the opener light comes on (indicating a completed cycle) but the door is not fully down, the close limit is the issue. Most openers have adjustment screws or a digital interface for this.

4. Broken or Worn Springs

Garage door springs counterbalance the weight of the door, making it easy for the opener to lift and lower it. When springs weaken or break, the door becomes too heavy for the opener to fully control. The opener may stop the door short of the floor because it senses too much resistance, or the door may not close evenly because one spring is weaker than the other.

A gap caused by spring problems often shows up alongside other symptoms: the door feels heavy when you lift it manually, it does not stay open when you release it halfway, or you hear grinding or straining sounds from the opener. Spring repair is not a DIY job -- the tension involved is dangerous. Call a Charlotte garage door pro for this one.

5. Bent or Damaged Track

The vertical tracks on either side of the door guide it up and down. If a track gets bent -- from a car bumping it, a basketball hitting it, or just years of use -- the door may not travel all the way down on that side. A bent track on the left side means the left side of the door stops higher than the right, creating an uneven gap.

How to tell: Look at the tracks from the front of the garage with the door closed. They should be straight and parallel. If one is visibly bent or the door sits crooked (higher on one side), a track issue is likely.

6. Shifted or Settled Foundation

This is the more serious version of an uneven floor. If the entire garage structure has shifted -- which happens over decades, especially on Charlotte's clay soil -- the door frame itself may no longer be square. The header (the beam above the door opening) and the side jambs may have moved enough that the door cannot close flush against the floor.

Signs of foundation shift include cracks in the garage walls or floor, doors and windows in the house that stick or do not close properly, and visible gaps between the garage door frame and the walls. This requires a structural assessment before the door itself can be addressed.

How to Fix It: Solutions by Cause

Replace the Bottom Seal ($15-$40)

If the seal is the problem, this is a quick fix. Buy a replacement seal that matches your door's retainer channel (T-style is most common), slide out the old one, and slide in the new one. The whole job takes 30 to 60 minutes. Check our full bottom seal replacement guide for step-by-step instructions.

Add a Threshold Seal ($30-$60)

A threshold seal attaches to the floor, not the door. The door closes down onto the raised rubber strip, creating a tight seal even on slightly uneven surfaces. This is the best option when the floor has minor dips because the threshold fills the low spots. It works in combination with the door's bottom seal for maximum protection.

Threshold seals are glued to the concrete with construction adhesive. Clean the floor, dry fit the seal, apply adhesive, and press it into place. Let it cure 24 hours before driving over it. This is a good project for Charlotte homeowners preparing for winter weather.

Adjust the Close Limit (Free)

If the opener is stopping the door too high, adjusting the close limit brings it down. On most LiftMaster and Chamberlain openers, there are two adjustment screws on the back or side of the unit -- one for up travel and one for down travel. Turn the down limit screw clockwise (usually quarter-turn increments) until the door closes fully against the floor. On newer models with a digital display, follow the travel adjustment procedure in the manual.

Important: Do not over-adjust. If the door hits the floor and keeps pushing, it will reverse (a safety feature) or put excessive stress on the seals and bottom panel. The goal is for the door to just touch the floor with the seal lightly compressed.

Fix the Floor ($200-$1,500)

For uneven concrete, you have a few options depending on how bad the problem is:

• Self-leveling concrete overlay: For minor dips (under half an inch), a thin layer of self-leveling compound can even things out. This is a $200 to $500 job for a concrete contractor.
• Concrete grinding: For high spots, a contractor can grind down the raised areas. Costs vary but typically $300 to $800.
• Mudjacking or foam leveling: If a large section of the slab has sunk, mudjacking (pumping material under the slab to lift it) costs $500 to $1,500. Polyurethane foam leveling is the newer version and runs similar prices.

For most Charlotte homeowners, a threshold seal combined with a new bottom seal handles minor floor unevenness without needing concrete work.

Call a Pro for Springs, Tracks, or Structural Issues

If the gap is caused by spring problems, bent tracks, or foundation settling, these are not DIY fixes. A garage door technician can assess the situation, replace or adjust springs, straighten tracks, and recommend whether the door or frame needs more significant work. Spring and track repairs in Charlotte typically run $150 to $400 depending on the specific issue.

Gaps That Only Appear on One Side

If the gap is only on one side of the door -- left or right -- the cause is usually one of three things:

• Uneven floor: The concrete has settled more on one side. A threshold seal can compensate.
• One weak spring: On doors with two torsion springs, if one is weaker or broken, the door tilts slightly as it closes. One side reaches the floor while the other does not.
• Bent track: A bent track on one side stops the door from traveling all the way down on that side.

Close the door and measure the gap on each side. If the difference is more than a quarter inch, something beyond the seal is off. Disconnect the opener and manually close the door to see if it sits flat -- this removes the opener from the equation and helps narrow down whether the issue is the door/tracks or the opener's settings.

Preventing Gaps From Getting Worse

A small gap becomes a big gap if you ignore it. Here is how to stay ahead of it:

• Inspect the bottom seal every six months. Check in spring after pollen season and in fall before winter. Look for cracks, flat spots, and sections where the seal has pulled away from the retainer channel.
• Keep the garage floor area clean. Dirt, leaves, and debris under the door accelerate seal wear. Sweep the floor where the door meets the concrete regularly.
• Watch for water patterns. After a heavy rain, check if water is getting in. If you notice a new wet spot, the seal or floor has changed.
• Have the door serviced annually. A professional tune-up catches spring wear, track misalignment, and opener setting drift before they turn into visible gaps.

When Is the Gap Too Big to Ignore?

Any visible gap lets in pests and moisture, so technically any gap matters. But here is a rough guide:

• Under 1/4 inch: Probably just normal seal compression. Replace the seal if it is old, but this is not urgent.
• 1/4 to 1/2 inch: Enough for mice and significant drafts. Replace the seal and consider a threshold seal. Check the floor for unevenness.
• 1/2 inch to 1 inch: Enough for snakes, rats, and serious water infiltration. Something beyond the seal is likely wrong -- springs, tracks, or floor. Get it checked.
• Over 1 inch: The door, tracks, springs, or structure need professional attention. Do not ignore this. Call a Charlotte garage door technician.

Charlotte's combination of heavy rain, active pest life, extreme heat, and clay soil means gaps get worse faster here than in drier, cooler climates. The $20 you spend on a bottom seal today prevents the $500 water damage cleanup next month. A well-sealed garage door also keeps your insulation working as intended, keeping energy costs in check year-round.

Need help figuring out what is causing the gap under your garage door? Call to schedule an inspection with a Charlotte garage door technician.