100% - I believe he nailed it (pun intended).

Are you running HVAC vents to it? If not I would use blue wall sheetrock or plywood and paint it. Much easier to hang cabinets etc on plywood.

 

never heard of water running through a garage to a drain in the back, I wouldn't put up with that, something else needs fixed also.

 

First you ought to take care of that water problem in your garage. Are you aware of the "trench drains" they sell at Lowes. About 6" inches by 6" with a grate in the top. This can be buried outside your door and a drain at one or both ends to take it somewhere else.

And as mentioned above, I'd really think about OSB for the side walls. Take your time and butt seams together and top coat with a good semi gloss paint. did this in both my garage and shop and would do it again. Stuff is tougher than drywall and can handle screws for lighter stuff without anchors or things like that. And, you space doesnt look too large. Think about a bit of reading on concrete, section that floor into smaller sections and mix your own with a friend or two. Or if your lucky, do you have one of those places around that will sell you cement, mixed in a trailer, like U CART

 

Sorry, but a tie-beam spans between two structural columns. The tie-beam and columns carry the weight above. That framed wall could be knocked out and the roof above will remain supported.

 

The concrete is not large enough to require expansion joints. Fiber mesh is acceptable to replace any other reinforcing. Use 3500 PSI concrete with a vapor barrier and you should be more than fine. Try to cure it slowly the first 3 days to minimize cracking, although that may be hard indoors.

 

lay a few pieces of rebar in there along with the mesh and I seriously doubt that you will have any cracking. Keep it moist by spraying a little water on it for the first 3 days as long as you outside temp is above freezing. Whatever you do don't pour concrete when you know the temp will drop below 30 degrees. Don't know where you are located so this may not be a problem for you.

 

I am not the best expert on concrete, but seeing that I do work in a concrete plant. I offer my advice. If you do go with concrete do not put down plastic. Put down limestone, plastic holds the water into the concrete and makes it come to the top, thus making it brittle on top. although some building codes still require plastic, if we have to put it in, we poke holes all through it before pouring. the gravel will let the water if any flow under without any harm. If you have a moisture problem then I suggest a french drain outside of the foundation. this catches any water and carrys it away from the building. Rebar is the best option but fiber is almost as good and cheaper and easier. good luck whatever you decide

sorry I missed it but do not put water on it either, this also makes the top brittle and causes it to flake as will the plastic. let it cure by itself.

 

I've had dirt, wood and concrete floors. I like the concrete best.

If it was me, I'd pass on the permits and engineers. I would also remove the windows for privacy and security.

If i was going to heat the space I would pour the concrete on 2" foam board. Makes all the difference. Why insulate the walls and not the floor is the way I look at it.

 

It you are able to build a wood floor, you are certainly able to pour concrete. I would go with a 4" slab with fiber. As many others suggest, redo the drive leading into your garage top divert the water away from your structure. After you get your floor make sure to seal it and then start on your work bench and storage shelves and cabinets. nice aarea to keep the scooter. Good Luck!

 

Agreed, but based on the picture I don't see anything that resembles a structural column. Based on the OP's description of the room I think that wall is holding up the beam. That was my concern for him.