12x12 ft patio. Will be mixing my own concrete - i have a borrowed mixer and the materials needed. My soil is clay type and there is no grass. Water tends to collect where my patio will go. Reading online said 2" gravel for drainage and pour 4" slab on top. I will be using a pattern form that is 2" tall. Was told by a friend to press the form into the poured slab up to the top of it. Looking online seems you place the form on the plot and pour concrete into it. Thats fine. Except concrete store guy said no drainage needed, put sand as a base and pour on top. So my dilemma is, I have 2-4" inches of sand as some spots vary in depth. Sand is leveled. But I have approx 3.5" (2x4 form around 12x12 plot) to ground level. So my form is only 2" tall and water tends to collect at that spot. So questions 1) Drainage - do I need it? how do I accomplish this now? 2) Can I add 2" of gravel to raise the patio up? possibly also fixing the drainage problem if thats a concern. 3) Should I not put gravel on top of the sand and add 2" of sand instead then pour on top of that? 4) I have a path way I need to do as well but have not dug. Should I dig 2" and put in 2" of sand or gravel then pour? or dig an inch or so deeper so the pattern form sits an 1" below ground level? 5) Do i need to leave in my 2x4 form in the ground around my patio and pathway to keep/hold it together? Needed or overkill?

I'm having a 400 sq ft garage addition built this spring and the builder is asking if I'd be okay with a cinder block foundation wall as opposed to a poured foundation. I prefer a poured foundation so it matches the existing foundation (stamped brick look), but I believe only about a foot of foundation would be exposed above grade for the majority of the structure, whereas the more exposed portions would be concealed by a deck. He said I wouldn't see the mortar joints and it would have a smooth finish. This doesn't sound too bad, but I have concerns about the integrity of this smooth finish as it ages. I envision chunks of concrete flaking off the wall over time as things settle. I live in northern VA, so there is a lot of freeze/thaw every year (as low as single digits in the winter and as high as 100 in the summer). The foundation will be just under 100 linear ft with an average height of 5 ft. Approximately 2/3 of the wall be 3' to the footer with 1' exposed above grade and the other 1/3 (back of addition) will be 6' to the footer with 3' above grade. He told me the block would be a 40% cost savings, but he didn't say exactly what the savings would be. I was under the impression that an entire poured foundation was going to be maybe $2k to $3k max, so if the cost savings is $1,200, then I'd likely go with poured as initially planned. I'm thinking his reason for using block may have to do with minimum order quantities and/or minimum yardage and the cost of getting relatively small loads of concrete?