Water coming into your garage from under your garage doors is a sign the weatherproof seal you need isn't working the way it should. This can happen because of alignment issues, faded or cracked weatherstripping, or physical damage to the doors themselves. If you experience this problem regularly, here's what to look out for.
Weatherstripping Needs Replacing
Every garage door has weatherstripping installed around it to create a weatherproof seal when the door is completely closed. Ideally, no matter the weather, no moisture or wind will make it past the seal. Weatherstripping tends to wear down quickly, especially in more severe weather, however; if your weatherstripping no longer creates a complete seal, it can let water into your garage. This tends to be most noticeable at the ground level, especially if your home is on an incline that causes water to flow toward your doors.
If you have constant serious problems with water coming under your door even when your weatherstripping is in good shape, you can try installing a threshold that attaches to the ground rather than the door. These essentially create small dams on the ground and are better at pushing greater amounts of water away.
Doors Are Crooked
In order to create a complete seal, your door needs to close properly. If a door is even slightly misaligned, it could create tiny gaps between the door and ground, or the door and side walls. A door can be misaligned for a few reasons: the lift cables could be damaged or slipped, the springs could be wearing out, or your door tracks could be misaligned. Sometimes the signs of misalignment will be obvious, but in more subtle cases you can use a level to try to determine if the door is closing evenly.
Water Damage to Wood Doors
If you use solid wood garage doors and it has been a while since they were refinished, there's a possibility that water damage over time could start causing your door to warp or bow. Even small changes in the shape of your door could create gaps, which means that even if your door is properly aligned and your weatherstripping is in great shape, water will still be able to work its way in.
If the warping or bowing is minimal, the problem can be repaired without you needing to replace your doors, but they may need to be removed to do so depending on the type and severity of the damage. If your door is a single panel and there is extensive rot, however, the doors may need to be completely replaced. Damage to heavier doors can make them a safety risk as well, so if you suspect this may be the problem, call for repairs as soon as you're able to.