I am planning on adding a front room to my house and it requires a foundation to start. Live in Ohio, so I understand that a certain depth has to be dug for the foundation and footer. Now, is there a precast foundation that can be done without doing concrete block? The room size is 8x12 and so the foundation will be attached to the existing foundation on the house with I assume special steel bars. I am not planning on doing a basement, so that is not being planned. Is this a process that would be too expensive to be done, since only 3 sides are being done? I am also planning to do a prefabricated walls. Hopefully, this will save on labor costs.
Am I over exaggerating on this type of planning?
I don't think you are going to find a precast foundation unit that will be economical. They would be specialized and have to be over-designed because of the non-uniform bearing on the soil. You would also need to rent and schedule a crane. - It is very difficult to beat a strip footing with a block or pourd concrete stem wall.
If yoy had several hundred or thousand units and a crane onsite you could come up with a reasonable cost once you developed a method of creating a solid base for bearing.
To give you a comparison, most places in Russia andthe republics do not have ready mix delivery. Before they had modern concrete block (15 years ago), a basement for a house was built out of 30"x 30"x 60" solid concrete block (4000-5000#) made from the waste concrete at a precast concrete products plant. They were set with a crane using mortar spread with a square nodes shovel. Despite being very advanced in precast, this was the best solution they could come up with. - Now, normal concrete block basements have replaced much of this archaic process.
Pre-cast and pre-assembled units are not economical unless you have very large volumes.