Looking at a house, and I'm curious on the cost of a potential project. It's a 1.5 half story home with a large covered deck on the back of the house. It's a walkout, so the deck is elevated 10 or so feet off of the ground (with a staircase of course). The house is only 15 years old, and a lot of newer homes in my area (Kansas City) have these (the builders call them Lanais). When I say covered, I truly mean covered in that the deck has a roof that is completely part of the rest of the roof leading me to believe that you could easily close this in to make it usable interior space.

The area itself probably measures 18 feet long by 14 feet wide. The Lanai is situated in that if the back of the house was the top half of a 'H', the lanai would be in between the left and right line and only sticking out a few feet beyond. Of the 2 14 foot lengths, only roughly 4 feet of each are not touching the house. Meaning you'd only have to enclose/add walls/windows to 18 feet plus 2 4 foot expanses.

The deck is elevated but the underlying support beams to be the same kind needed for this, so I think they'd be fine. You'd have to add insulation, enclose them from the bottom, etc. and also had HVAC to the space. Would need to of course do the drywall, flooring, and all normal interior room things to the newly enclosed space.

This is all just hypothetical, so I don't want to bother a home remodeler with these questions yet. Has anyone done this? If so, what was the cost or what type of cost would I be looking at for something like this?