Foundation slab

[HalfwayHandy]

Hello! I am just getting started with my concrete slab. The instructions say it has to be level, and I am building my slab next to an existing concrete patio and had planned on just matching the grade of the current patio. So I guess I can't do that now. Any suggestions how to easily level this next to a slightly graded slab of concrete and make it look good?

If I match the height of the lowest point of the patio and level it from that point to the house ( where the patio is graded higher) that would leave a dip towards the house where water could sit. and if I do the reverse, match the height of the tallest point, then at the lower end of the patio my slab would stick up over it. I don't really see that as a tripping hazard because the pizza oven will be right there, but I do think that would look weird. Maybe make the whole slab slightly lower than my patio and then finish the outer edge with some tiles or something to disguise the difference of the slope? or is it ok that the bottom foundation is graded a little as long as I level it out at the top of my oven stand when I pour the concrete there and level that out?

[pemer]

I would follow the pitch of the exiting patio and make up differences in heights in base walls. Other wise you are likely to create a trip hazard.

[Chach]

I see this two ways. if you take the high point of the patio and level your foundation from there you cant go wrong. yes the foundation slab will be higher than the patio at a certain point but who cares your building on top of it and you can build to the end of the slab you can get away from having a reveal around it. the other way is to level the foundation from the lowest point of the patio. your building on top of it so why would it matter how low or high this foundation slab is since a wall is being built on it just skip the reveal around the slab and build to the edge of the slab. If you put a good base down and rebar that slab should be good to go. I did mine like that leveled to the lowest point and built to the edge because i didnt want to see the exposed concrete on the low end. we had tons of rain and some -30 degree days and im still good. the only thing I did was add a mico channel drain .the reason why is that my fireplace is on the 45 degree section of my patio so I restricted the natural flow of the water run off from the patio so adding that micro channel redirect the water away from my foundation and stopped the pooling of water. I also didnt want the water to drain between my existing brick pavers and the foundation slab. You should not have to do this unless you change the way rain water runs off. Hope this helps