I’m a mason working in an area devoid of building codes and cannot afford an engineer. I’m building a 16-foot diameter circular gazebo that will have a concrete floor. I will lay 12-inch half blocks side by side in a circle beginning 9 feet below grade and would like to use this space under the gazebo as a basement.
The floor above this basement (or the basement ceiling, depending on how you look at it) must be concrete. So I will pour the wall solid and pour the floor at the same time, tying it in with the wall with a grid of 1/2-inch rebar on 8-inch centers to reinforce the floor. Is this rebar spacing, 2 inches up from the bottom of 6 inches of 2000 psi concrete, sufficient for this application?
With this limited information, it’s not possible to determine what you are proposing is sufficient. For instance, what loads will the floor have to support? Will there be reinforcing steel in the wall, and if so, will you provide sufficient overlap with the slab reinforcing for this to act as a monolithic structure?
These are the types of things, among others, that an engineer would consider in designing such a structure. Even if there were a building code in your area, you should have engineering input on the project you describe.
Given what you have outlined above, perhaps a better question to ask is: When the ready-mix truck pulls up to deliver the concrete you ordered, will the driver will be willing to unload into your formwork?
This is the kind of project that demonstrates why there are engineers, and why there are lawyers.
The answer is from Tom Klemens, senior engineering editor. He can be reached at firstname.lastname@example.org