"Two things that influence whether poured concrete is a good choice ... do you live in a mild climate where the footer need not be excessively deep and can you get a concrete truck along the wall to pour directly in the forms. It's not only just the depth of the footing that has to be calculated in earthquake country ( of which this particular location is on a very active fault line ) it is the width of the footing as well as an appropriate steel schedule . Having the concrete truck be able to pull right up to the forms is irrelevant. Pumpers are easily available . My office is not that far from this site and I have worked in this county and the counties surrounding this area. The cost for permit submittal is about the same as in other surrounding counties with the exception of some areas in Carmel. The average course of action in construction with these common retaining walls is to remove the rotting wood and replace with pressure treated wood. This will sail through the permit department especially if the concrete piers are in good shape and the cost of the permit will be in the couple hundred dollar range. There will be no additional engineering costs if you simply replace the wood. The planning department may want to see a drainage detail , of which you can use a standard detail that is provided in the UBC. They even had their own detail booklet put together ( about 20 years ago ) that homeownera and designers could purchase for a couple of buck that had common details for retaining walls documented. It also will not cause any problems when the house is sold and goes through the re-sale inspection process.

I was speaking about the difficulty of a greenhorn working with mortar in general, not specifically with embedding "tiles." In my case it was bricks. I am in zone 9 and since our soil is primarily sand, it is common here to place concrete on solid soil (as opposed to humus-rich spongy soil,) without using a gravel bed below. In the case of the photo above, it looks like some of the small tiles were prefabricated into larger pavers and that these were embedded in mortar, along with individual small tiles. Investigate the process of setting thin pavers in mortar over a concrete slab.

thanks, not sure about the floor. I recall playing some sort of rollerball/deathball game as a kid, so unfinished would be better, but a rug or carpet would be better for knee football (and warmer) on the floor, like to do legato, but seems a little expensive. still trying to figure out how to rig a perspex screen in front of the flat panel to keep flying objects from smashing the screen

The main reason for cracks is bc nine times out of ten when the contractor lets the concrete set up and start to dry and then goes again and adds water to it it causes the concrete to become weaker and weaker the more times it cures and then water is applied again. Also it can happen when 2b is put down and not compacted before a pour the ground and 2b shifts with causes the concrete to crack. The 1 inch cut thats done in the concrete is so when or if the concrete should crack break bc of movement or weight it would break evenly and not cause a spider web break. Its never really recommended to pour on a very hot day and if you can avoid it then avoid it bc its better on a cool day being the concrete will dry on its own anyways either in cold conditions or under water but will not avoid the cause of flaking or cracking by doing so. No one should ever add water if qhen the concrete sets up and if you push your finger down in it and see your print or feels dry. But that's if the pour was done in the last 4 hours bc with in that time your able to fix it after 4 hours then no water or anything bc you can mees up the cycle if its curing process. But if it rains within the 4 and 8th hour its ok bc it will be hard enough so the rain water don't mess anything up. Now if you notice that the rain drops caused a problem and theirs standing water its ok to take a garden hose and pull the access water off and try to fix it but try not to cause more damage then it has bc remember you didn't want to mess the process up that has started or create more damage.