Raised concrete floor

I have a pole building with a lean-to attached (see pic). The lean-to floor is 4 feet below the pole building floor (both floors are concrete). I'd like to enclose the lean-to and raise the floor to the same level as the pole building floor.

I first considered a wood floor, but if done sturdy, the material cost adds up fast. I'm wondering if it's anywhere close to economical to add a concrete wall on the open face of the lean-to, fill in the whole area and pour a concrete floor on top. That would open up some options I wouldn't have with a wood floor, but not sure about cost.

Thoughts....ideas?

Thank you!

 

Unless you have free fill dirt, and a compactor, I think a wood deck might almost be cheaper. I don't see where you give us any measurements as to the size. 20x50?

 

Sorry....the lean-to area is 15x40.

 

What would it be used for, if high weight then concrete is needed, general storage then I would think the cost of a heavy duty wood floor would be less, especially if you were considering doing the wood floor yourself vs having the concrete work subbed out!

 

Depending on what you're going to do with the space, whole lot easier to add insulation and maybe a source of heat under a wood floor.

 

Always dreamed of having my own wash bay with floor drain; concrete could get that done. I don't need the floor for anything especially heavy. Wood will work fine and could do myself; just thinking about the time and effort. Concrete work would be sub'ed out and get the project done a whole lot faster.