Garages and Carports - Stopping Gas Vapors

Hello,

If all goes well I'll soon own my first home and I had a question about gas vapors in an attached garage.

The garage is located under the house as a part of the full basement. Our home inspector said most of the preventative measures needed were already in place (proper wall materials, sealing the sills) but we needed to prevent gasoline vapors from traveling into the basement under the door.

I will need to upgrade the door to a fire resistant door, so I am thinking I can make the changes then. My best idea is build up the door frame so it is above the floor and put in a ramp on either side.

Is there a guideline for how high such a barrier needs to be? The garage door has a small gap underneath and the driveway runs down hill outside, so the trick is to convince the vapors to travel that-a-way.

Thanks!

If the garage floor is the same level as the house, this has to be an older house. That has been against code for quite awhile. Since that is what you describe, a well sealed/caulked threshold and a fire rated door that seals tightly is a must. But you don't want to build up the threshold to the point that it is a tripping hazard, that might be just as bad. And seal all house joints with fire rated foam or similar.