[Tidybuoy]

My garage has sagged over it's 70 year life and water tends to pool up in the front left corner. Water will stay out of the garage until I open the door and then I will have a 1" puddle in the corner about 24-36" diameter. To combat this, I added a garage door threshold that has a 1" bump and this helps a lot.

To really help with this problem, I am going to add a 4" channel drain along the entire front of the garage area of my house. The water will then be routed to a planter bed that has a drain that slopes out to the street.

My Questions:
Directions state that I must have 4" of concrete under the drain and 4" on each side (if cars drive over drain - that's a yes). Should I be adding rebar to this concrete? It's a small section but want to do this correctly.

My driveway is asphalt. Can use my existing concrete saw blade to cut this or is there a special blade for asphalt?

One side of the new concrete will be the cement garage, the other side will be the existing asphalt driveway. What is the best way for framing this newly poured concrete or would you just use the existing edges of the garage/driveway? Since I don't want to create a gap between new concrete and existing (by pulling framing boards out), I was thinking of using something very thin, like galvanized flashing or something.

I'm seeking advice, especially on the last item. I can do pretty much anything but seem to learn a lot from guys that have already done this.

Thanks, in advance...