Knoxville Garage Door Blog

There’s a Gap Under My Garage Door!

How to address issues with a bowing, settling concrete slab.

Gap under garage door

Concrete is a fickle creature. Despite its rock-hard solidarity, it often cracks, dips, or settles unevenly over time. Usually, the process is barely noticeable, but when rays of light shine from underneath a closed garage door, you know that your slab has settled, and it’s time to take action.

Common Causes of Slab Settlement

It’s a common saying that there are two types of concrete slabs: those that have cracked, and those that haven’t cracked yet. If you see cracks or slouching in your slab, rest assured that these issues are common and often not a cause for concern. However, it’s a good idea to inspect your foundation for signs of separation or slippage. If you see significant cracks around your foundation, it may be time to consult a professional. Other signs of an issue can include cracks in the drywall around windows and doors, and bowing of the walls.

Settlement issues with garage slabs often occur where the driveway meets the slab. Water finds its way into the expansion joint between these two surfaces, seeping down and carrying away the dirt that had been compacted when the slab was poured. Slowly, the concrete will dip into the void forming below.

Is it Really a Problem?

Foundation issues aside, a gap beneath your garage door can become a problem, often minor, but sometimes more severe. During heavy rains, water will often flow underneath the door and pool in the garage. Constant exposure to the elements can cause tools and steel implements to rust prematurely. Additionally, if your garage is heated or cooled, you are expending energy costs that are being wasted to the outdoors. Perhaps most concerning, many homes in Tennessee have plumbing running through or above their garages, exposing these pipes to the risks of freezing during winter months.

How to Fix the Problem

Fortunately, there are several solutions to this issue. Some are expensive, while others are quite cheap. What you choose will depend on the severity of the issue.

  • Most Expensive Solution - Jacking: Mud jacking or poly jacking are the best, and by far and away most expensive ways to solve this issue once and for all. A contractor will drill beneath your slab and pump mud or a polyurethane expanding foam into the void below, pushing your slab upward until it becomes level once again. On average, this can cost between $500 to $1,700 for a slab, so be sure to get several quotes before choosing a contractor.
  • Cheap Solution - Bigger Gasket: Some companies sell extra thick rubber gaskets that run underneath your garage door. The additional thickness provides a cushion that might level the door against the ground.
  • Cheapest Solution - Threshold Stripes: A rubber threshold that runs along the floor beneath the garage door is often the cheapest solution, and they are available between ½” and 1” in height. The threshold is easy to install, secured against the floor with standard construction adhesives.


Maybe the Door is the Issue

Sometimes an old garage door will sag in the middle, giving the appearance of an uneven ground. Check with a long level to be sure your ground isn’t the issue. If the door is the problem, then it might be time for a new one. The good news is, a brand new garage door is often a great way to spruce up your home’s curb appeal and raise the value of your property.

Looking for a new door? Contact the trusted experts at Overhead Door Company of Knoxville.

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