I'm designing a new house for myself, and I've always wanted a basement so I would have unfinished hobby space. The kind of space where you can get messy stuff on the ground like water, paint, sawdust, whatever, and nobody cares because it's just a basement.
In talking to concrete contractors, however, a full basement costs 3x as much as a slab, for only double the square footage of the main floor. In other words, I could have the same square footage for a lot less money by having a slab on grade that's twice as big, rather than putting a full basement underneath.
So, I want a "basement", but I don't care if it's actually below grade. So I was considering a design where there is just one floor on grade, and the "basement" is on the same level as the rest of the house.
By "basement", I mean a big (~800 sqft) unfinished room with a concrete (or epoxy) floor, unfinished walls, a floor drain, and everything an unfinished basement would have, just on grade level, not underneath the house. Unlike a garage, though, it would be climate controlled and not have any vehicle doors.
Are there any issues with having an unfinished room like this on the main level? Has anybody done it before? What would such a room be called? Would there be code issues, where inspectors wouldn't be able to figure out how to classify it?
Edit: Just to clarify a bit, by "unfinished", I meant not doing trim carpentry, not installing a finish floor over the concrete slab, and maybe not doing drywall if allowed by code. It would still have electrical sockets, lighting, insulation, air ducts.
Code has specific requirements based on what type of room it is. There are certain things that a "garage" requires, certain things that you can't do it a "closet", etc. I know that I don't want it to be a "garage" because "garages" have to be lower than the house for carbon monoxide, have steel doors, fire-rated drywall board, etc. "Garages" also use GFCI breakers where "bedrooms" need pricey arc-fault breakers. Bedrooms need egress windows. etc, etc.
So the essence of the question is, what should I call the room on the plans, so that it's governed by the most appropriate codes for what I'm trying to do? (My intent is to use it like an unfinished basement).
Best Answer
The full basement may cost 3 times what the corresponding slab size may cost from a concrete perspective. But you have to also consider the cost per square foot to build the structure that covers the slab/basement. If you double your slab size you need twice as large of structure to cover it. On the other hand the structure footprint is the same size whether it has a basement or a slab under it.