Leak front driver side floor of 1999 Honda Civic

This is my first post. Hoping someone has some advice. My 1999 Honda Civic has a leak where the plastic meets the rug by the drivers side floor. It is a about 7-9" from where the driver door opens. It only happens when it rains. I tested the moon roof drain hoses. They work fine. Any one have any suggestions on what is causing this? And/Or have any idea how much this might cost to get fixed?

With ‘plastic that meets the carpet’, you mean the door sill?

If it’s the soor sill or the kickpanel, there’s an excellent chance that what you’re seeing is only the “tip of the iceberg”. There’s an excellnt chance that you’re experiencing rotting of the area below the A-pillar above where it meets the sill. This area is a part of the structural integrity of the vehicle, and part of the crush path for accident energy absoption, and if it’s rotted the car may no longer be safe.

The only way to find out its to remove some panels and inspect it. The inner wheel well, the kickpanel cover, and the sill cover all need to be removed.

Another possibility is that the seal between the window and the door skin is bad, and water is running into the door and then out through a crack in the inner door panel.