Garage door weather seals are important to keep out both rain and wind as well as rodents, snakes, and bugs. Everyone with a garage door has probably looked at yours and found it dry-rotted, or worn from years of use. This is a flexible wear item for your home and you will need to replace it from time to time. Wear from rubbing it on the ground, contact with debris and filth on the ground when the door closes on it, sun and cold, or even physical tears to the seal are sources of ways it rots or wears out.

The good news is that it is a simple process and costs very little to achieve. This instructable deals with modern door seals which have been around for over 10 years which rely on a double channel track on the bottom of the garage door to mount the seal. Some doors have only one seal channel and this will work equally on them. The older doors might be actually nailed to the back of the door lip and will require a hammer and nails or screws to install those. This is about the channel system most common on today's doors though.

Step 1: Step 1: Gathering Your Materials and Tools

There are only a couple of tools you will need for this task.

Tape measure or some way to measure your door length.
Shears to cut the door seal material to fit your door.
The material to install on the bottom of your door.

It is best to begin with collecting the materials needed so you will not have to halt to find anything.

Step 2: Step 2: Measure Everything and Get Your Seal Ready

Look at this picture to find the three values for ordering your door seal.

Here is what you are after:

Door Length: Take your tape measure and measure your door's length. Single car doors are typically 10 feet, where double car garage doors can be from 16 feet to 20 feet. Measure this and find exactly how wide your door is.

Door Thickness: Look at the end of the door to see how thick it is. Typically they are about 1 inch to 2 inches thick. Next look on the bottom of the door to see the channel configuration your door has. This is the 1-2 inch edge that will contact the ground via the seal. This will determine how wide your seal needs to be. It will come flat and you will have to curl it in a half circle for it to ride in both channels of your door plate on the bottom of your door. typically the width of the seal needs to be twice the thickness of the door, so a 2 inch door will have a 4 inch seal as an example.
Channel Width: Now you need to measure the inside of the channel(s) to see how wide the seal lip needs to be. Typically the channel will be 5/16 inch or 3/8 inch or 1/4 inch... This measurement is how wide the ends of the seal are which will ride in the channel. If you get one that is too small, it will pop out possibly... Too big will not allow it to rest in the channel without carving some off the edge all the way down its lengths.

You will need these three measurements to get the right seal for your door. The double channel seals come in a flat roll and look similar to an I-Beam or letter "H". Go to eBay or wherever you choose to buy the seal material, and look for these three values that you will plug in. I got mine from eBay, and the price was from $18 and up for my door which was 16 feet X 2 inches X 5/16 inches.

Step 3: Step Three: Compare Your New Seal to Your Old

Once you have your seal, lay it out flat and go ahead and remove your old one. Lay it out next to the new one and compare them together.

You can see in my pictures where I laid them both side by side to look them over. The new seal is flat from the box it came in rolled up, and the old one is rotted and deformed where I can no longer lay it flat. Sun, rain, debris and some animals have taken a toll on my old seal... It was 10 years old.

I put pictures of the ends of my old seal as I found it interesting that they folded up the ends and shoved them back into the channel: I am not sure why they did this, but I noticed it was where the seal had failed and worn through. This makes the ends of the seal thicker and in so, not able to compress when the door closes.

Step 4: Step 4: Review of the Mounting Method of Channels

Like I stated before the new seal comes flat, and requires it to be folded over to form a half-circle so that both ends with the perpendicular edges can travel down the channels. Some doors have only one channel and you will have to have a specialized seal with only one "T" edge channel. Most have the two though. I put a picture of my door edge so you can see the channels as well as an illustration of the mounting method for the new seal to match to install it.

Step 5: Step 5: Pulling the Seal in the Channels Down the Door Length

Once you get your channels cleaned out of any dirt or debris, you are ready to begin pulling your new seal into place. It is quick and effortless if you pay attention and don't take shortcuts.

Start at one end of the door and thread the new seal into the channels while folding it over into the "C" shape that is required.
Once you have it started, begin pushing the seal down the length of the door, folding it as it enters the door channels on the end of the door you started with.
Continue until the entire length of the channels are filled completely.

In these pictures, you can see the process occurring. I fed my new seal from the floor up through the door tracks to try to keep it organized as I folded the seal as it entered the channel openings. This should take you maybe 15 minutes as I would fold and push followed by walking the length to make sure the new seal was moving down the channels with no obstructions. You should sense no resistance while it is moving along. Pay attention to its fold and entrance into the channels on the doors first side.

Step 6: Step 6: Trim and Secure Your New Seal to Fit Your Door

When you finish pulling the new seal into place, you should be able to look down your door's length and verify all is in the channels and everything is lined up properly. Look at the end of the other end of the door to make sure the seal is at the end of the channels (see pictures here).

You should end up with a little extra length on your new seal as you can see in the last picture here. Mine ended up being about 1 foot sticking out the end of the door. this is normal.

Put a little rubber cement to stick the new seal to the channels on the ends to keep it from running out the sides of the channels. This is my suggestion

You are almost finished!

Step 7: Step 7: Inspect Your Work and Finalize It

Take your shears and trim the new door seal so that it sticks out of the ends of the door by about 1/2 inch on each side. This will allow the seal to wiggle around without making a leak.

Now you can run your door down and inspect it for gaps and fitment. No water or air should penetrate the new barrier at this point. If your door has any issues with gaping, you might need to adjust the gap via your opener instruction.

I put some before and after pictures to finish up this instructable so you can see the old vs. new seal as well as how it seals out the elements and critters.

I hope this gives inspiration to do this task. It was very easy to do and the parts are quite readily available and extremely cheap.