Covered Slab Slope

[Streetcar]

If you have slope away from house, you do not need a step between porch and house.
Make sure existing concrete is clean and use bonding agent when placing topping slab

 

[davidjlinhart]

1% to 2% is standard IBC (International Building Code) for all civil grades exposed to wind driven rain for drainage. Depending on the expanse of your flatwork, 1% is a hard slope to hit with finish work, without the likelihood of puddles, due to the fact that it is so gradual. In Portland Oregon, where I work doing heavy commercial construction, 2% is the industry standard. Whoever commented that 2% is too steep, has obviously never walked on a sidewalk or patio in the Pacific Northwest.

 

[RNeumann]

The problem (besides drainage and code) with less than 1/4" - you risk some bird baths. With the size of your slab you may get away with it. It depends on your screed board, form work, concrete application and the finisher you hire.