Fix Water Leaking Under Garage Doors

Garage Door Water Leak

Fix water leaking under garage doors by adjusting your opener travel, replacing bottom seal and installing threshold kits. If these projects don’t stop water from entering your garage you may need to take things a step further. Adjusting soil grade, gutter installation and trench drains may be your last resorts. Most of the garage door related projects can be done yourself inexpensively. All materials can be ordered online or picked up at your local garage door dealer.

Adjust Opener Forces & Limits

One of the best ways to fix water leaking under garage doors is by adjusting the opener.  With the lights off in your garage close your garage door. If you can see daylight under the door you may need to adjust the travel on the back of your operator. Using a step stool find the dial on the back of your machine. Turn the dial one or two notches and adjust as needed until the daylight under your door is eliminated. You may have to run your motor several times to get these settings just right. If adjustments don’t solve the problem you may need to replace your bottom seal.

Replace Gasket Seal

The bottom seal on your door is commonly called astragal or gasket. It get installed on an aluminum channel on the bottom of your garage door. Over time the bottom seal can wear out or become damaged from dry rot and rodents. Cut off a sample piece of your rubber seal and bring it to your local overhead door professional. Common types of bottom seals are J type and T type , fitting into one channel and two channels respectively. To prevent the bottom seal from flattening out over time you can install an old garden hose or backer rod under the gasket.

Threshold Kit Installation

Rubber threshold kits should always be used when water leaks under your garage door. These kits resemble mini speed bumps to block the rain from entering your garage. They can also be driven over and are quite durable. Prep the surface of your concrete by using and  angle grinder to clean off the surface. Eliminate all debris, mold and dirt from the entry way. You can even notch the concrete with small indentations for the liquid nails to adhere to. Install the threshold from jamb to jamb with the long side of the threshold facing outside. Align the threshold so that when the door closes it hits the raised bump and water can run off the slope.  Always install threshold kits in dry conditions with temperatures above 40 degrees.

Adjustable Bottom Retainer

If you concrete is humped in the middle or slopes one direction it can present a problem. Luckily adjustable bottom retainer exists. This aluminum retainer goes over the garage door in the shape of the letter “U”.  It can be adjusted to accomadate concrete surfaces with a slight grade. It can also be cut in half to adjust to concrete surfaces with humps. T type bottom gasket is used on adjustable bottom retainer. Bottom retainer can be expensive since it is made of aluminum and must be shipped on a semi truck due to length. However, it will be a cheaper solution that most types of concrete work.


Garage Door Guide Cal
Hello, I’m Cal – owner of Garage Door Guide LLC    

I write tutorials about garage door repair, installation and maintenance. With over a decade of experience in the overhead door industry I’ve learned a lot and I’d like to share my knowledge with you.

2 thoughts on “Fix Water Leaking Under Garage Doors

  1. Doug says:

    Hi size backer rod would you install inside (pull thru) the door seal? I’d like to try that before replacing the seal as it’s a new garage door installation.

    • Garage Door Guide says:

      That depends on what size seal you have on the bottom of the door and the thickness of your door. Most doors are 2″ thick so certainly smaller than that…1″ to 1 1/2″ seems about right. An old rubber garden hose line also does a decent job if you have some laying around.

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