My old patio has cracked and settled almost 4" towards my house. It therefore is graded the wrong direction and directs rainfall towards my house, rolls down the patio and straight into the basement. I had a contractor out once to look at it and he said that he could repour a concrete slab over top of the old one - and grade it correctly, so that the new slab aims away from the house. I do recall that he said it was a special type of topper cement. I would like to try and do it myself (to save the money) but am unsure of the tools I will need to rent and the process. How do I construct the form? What do I use, 2x4s? Is there something else I should use to line the form with - like plastic? What tools do I need to rent? How do I calculate the amount of concrete I need? Can anyone else confirm that there is a special type of topper cement? Is there a weather / temperature requirement? I assume that the basic process is to construct the form and then start mixing the cement and pouring it on, maybe smoothing it with something - starting at the far corner and working away from the house - then going back later and scoring it to make the break lines like a sidewalk grid? Any step by step or what-to-watch out for advice would be truly appreciated. THANK YOU SO MUCH!

It may not be cost effective to do what you plan. If your slab is tilted 4" you need to add 6" to get the correct grade, this gives you a 2" thick slab on what is currently the high side. That is a lot of concrete and youwould use less by breaking the old one out and pouring a new pad. Have you ever looked into concrete jacking, much cheap than both of the other options

First you need to determine why the old slab settled. What is to keep the new slab from settling? This problem is usually caused by water intrusion getting under the slab and washing out the dirt or very poor compaction before pouring the original slab. Unless this is a VERY small patio, don't try this by using bag mix, the work will kill you! Fix the problem, have it reformed and then use a redi-mix truck .