There is no code per se that i ve ever seen but the industry standard on concrete is typically 1 4 per foot on exterior flatwork.
Concrete front porch slope.
Correcting or adding a slope involves attaching wood wedges to the concrete porch in strips that create a slope of 1 4 inch per lineal foot.
The concrete floor covering for the front porch will be approximately 8 feet above the ground.
Because this is new construction a walkway from the driveway to the porch steps will also be framed and poured.
Finished aggregate concrete front porch floor aggregate concrete porch floor construction process.
What you can do is grind down the surface of the concrete to expose the aggregate 1 4 inch should be enough you want a rough surface and pour on top of that.
2 footnote 2 swales or drains designed to carry water from foundation are permitted to be provided as an alternative to the slope requirements for any home and shall be provided for a home where setbacks limit space to less than 10 ft.
Or you could try just using outdoor concrete bricks there s a name for em and building up a surface off of the existing concrete patio.
If it s a covered porch it s usually acceptable to be between those two ranges.
The standard formula for the slope of a concrete patio is a 1 4 inch drop for every foot of length.
If the slope is more gradual than this you may run into trouble getting water to run off properly.
Slopes that are steeper than this are fine but you may also wish to consider the ease of mobility on a concrete patio that is too steep.