I need some advise on repairing this back porch issue. This is an older house (built in 70's) and when it rains, the back porch is a swamp for at least a day or two. The porch is about 12' wide by 10' long. It appears that the middle of the yard has been filled in slightly with dirt to fill in the oak tree roots to make the ground smooth which has put the middle of the yard a few inches above the existing edge of the back porch.

I have a drainage pipe that I placed under ground and ran it from the edge of the back porch all the way to the back fence (at a downward slope), but it is constantly getting clogged with dirt and does not serve it's purpose.

I would like to expand the size of the existing porch and I was thinking I could place concrete bolts into the existing slab for an anchor and pour new concrete on top, but not sure if that would work?? The "new layer" could be roughly 4" near the house and a wee-bit thicker as it slopes down to the yard since the existing slab is a little too low.

Would this be a good idea or will the "new" layer end up chipping off? What about water seaping in between the concrete layers? Is there something I should put onto the old layer to allow the new layer to "adhere"??

Or, should I just bust out the old and pour a completely new slab?