The floors of your new space are a unique issue. Your garage is built with drainage in mind. Code requirements mandate that the concrete slab has a slope built into it to ensure water drains away from the home. The installation of the subfloor will correct the slope issue of your floor. Using a subfloor allows your new space to be converted back into a garage should the next home owner wish to do so.
Although many people use it as the catch-all of the house, the garage offers valuable storage and potential living space that can often be more effectively used with a remodel. Some people remodel the garage to turn it into an extra bedroom or living space, while others remodel it to make it more functional as a storage and workspace. Total cost depends on the size of the garage, age of the house, and the remodel purpose, but you can plan to spend an average of $6500 for a garage remodel with a common 600 square foot garage into a more functional space. Although it is possible to remodel a garage yourself, especially for smaller projects, hiring a professional contractor is always recommended.
A 'Ready to Sell' garage remodel will give you the best ROI possible without the need for a permit. It may include finishing interior texture (already sheetrocked), painting, and changing a few light fixtures. This level is perfect for those who are preparing their home for sale and tends to be cosmetic in nature in order to present the home well to potential buyers.
SketchUp has a massive library of over 2 million free user-created models to get you started in what they call the 3D Warehouse. You don’t have to re-invent the wheel… you can just download it! Need to add a garage door to your plans? It’s in there. How about a workbench? That’s in there, too, available to drag-n-drop right into your design. In fact, many of the items you’ll find you want to add to your own plan can be turned into plans themselves—like a homemade workbench.
Paint manufacturers have recognized these problems and have come to the rescue with new solutions. But a word of advice: If your garage floor sees heavy water leakage, if it's badly cracked or if it's damp and slimy all summer, don't apply any coating. In those cases, you're better off simply keeping it as clean as you can and then calling it quits.