How can I insulate my garage door so rain doesn't enter from under?

There should be a rubber strip across the bottom...yours might be damaged or missing. You might be able to buy the correct one for your door online, or at a home improvement center. If you can’t find the right one contacting the manufacturer should solve your problem. Here are some from the Amazon site.

https://www.amazon.com/s?k=garage+door+bottom+seal&crid=2QUSX2XKTN8HV&sprefix=Garage+door+b%2Caps%2C346&ref=nb_sb_ss_i_1_13

Affixing weatherstripping to the door frame and replacing the rubber weatherstripping at the bottom of the door only takes a few minutes and you save in your heating and air conditioning costs. It will also protect your entryway from the effects of puddled water from rain.

Remove the front door by removing the hinge pins with a punch and hammer. Recruit some help in lifting the heavy door to your workstation. Set the door on a drop cloth where it can lean against something sturdy so you can have easy access to the bottom weatherstripping.

Pull out the old weatherstripping by prying one end out with a screwdriver. The rubber weatherstripping sets inside two grooves in the bottom of the door. Grasp the end and pull gently. Discard the worn weatherstripping.

Measure the new weatherstripping against the door, trimming it for the tighest fit. Press the rubber ribs into the grooves at the bottom of the door. Ensure the rounded end, or gasket, of the weatherstrip faces the outside. Apply pressure so that the ribs are forced into the grooves.

Use a rubber mallet to tap the ribs deeply into the grooves and so the weatherstrip is tightly in place. Tap all the way along the bottom of the door to ensure no sections are hanging down.

Rehang the door, with assistance, then test the door a few times by opening and closing it. When the door opens and closes smoothly and securely, the new weatherstrip will prevent any water from entering the home.

Check the part where it is coming in. The driveway should be graded so it doesn't empty into the garage. Check any downspouts or other drainage that may contribute to the problem. Sometimes something simple can be redirected.

Hi! Here is a great post on what to do if your garage door lets water underneath!

https://www.danleysgarageworld.com/garage-door-leaks/

Hi Diane, sorry you are having water com under your garage door. Hope this helps you. Stay safe. Trench Drain

If the driveway slopes downward toward the garage instead of away from it, the only way to keep the rainwater out is to channel it away before it can run under the door. The best way to do this is to install a trench drain along the front of the garage.Dec 9, 2018

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You can replace the seal - like a strip thing sticky on one side. They make them for garage doors but here is how we did it on house door - Weather striping - https://www.charlestoncrafted.com/stripped-first-time-weekend/

Have you checked the gutters and downspouts near by? They could be clogged and so the water is running off instead of being diverted?

You can buy the rubber weather strips that attached to the bottom of the door. They stop rain coming in.

The rubber strips work very nicely, you can also get a plastic strip for your entry doors, keeps the drafts down.

It depends on what is causing the issue. Ours was a "level" problem so my husband add thin concrete blocks, like pavers, where the door meets the floor. The smoothed off the sides with concrete so it's like we have a small speed bump as we enter. It has worked like a charm.

You need to replace the gasket on the bottom raise the door half way so you could see the bottom take off the bottom and measure it then go to homedepot to buy a new one and put it on

Check your bottom rubber seal. I don't see where insulating the door will do anything to prevent water coming under the door.

Similar to what Annie and Kathy suggested, also check how level/how sloped the driveway is in the area butting up against the garage door. The land may have sunken over time, and may need to be regraded to prevent water from running towards or pooling under the garage door.

Diane: you may need the seal replaced. Here's a DIY video

https://www.youtube.com/watch?v=8XrlEm0HfKw