(Some folks think they are clever and put a brick or stone planter in front of the old garage, thinking this will hide the phantom driveway. It does not, but rather draws attention to it).
This is exacerbated when the brickwork or siding clearly outlines where the garage door was. Again, it is more expensive to re-brick the entire wall or match the siding to the new windows or openings. It is a lot cheaper to just install sliding doors or some other window feature to fit the opening (more or less) making the conversion more painfully obvious.
The main problem, of course, is that unless you build a new garage, you have no garage on your house, and often garages add value to a house - more value than the new "playroom"or "den" or "home theater room" that is now where your garage was.
Garages are useful because they make your car last longer. The are also good places to store things, have a workshop, keep the garbage cans, the litter box, or whatever. They can also be a laundry room, as is the case in our house. Once you remove your garage and replace it with living space, you lose this useful feature of your home. Your cars sit outside, getting acid-rained on and stained with leaves and pollen - and baked by the sun. Your house looks less attractive as it now looks like a used car lot. And now you have no place to store your bicycles, kayak, tools, and camping gear.
And the space you gain - did you really need it? That is the big question. Some friends of mine bought a house with a garage converted to a "playroom." A new garage was built out back, but since you have to drive on the lawn to use it, they rarely put their cars back there. But they do use it for other garage-y purposes.
He decided to use the converted garage space as an office. But since it was adjacent the kitchen, it was quite noisy when the grandkids or guests visited. It was kind of a useless space, not really used for much of anything, but a junk collector. He decided to move his office to a guest bedroom, which they have three of. Was the garage conversion really necessary? Did it improve the value of the home? Did it result it real usable living space? The answer to all three questions was "probably not."
If you have a garage and are thinking about converting it to living space, think hard about it first. It will cost you money and not add value to the house, but likely detract. Are there other rooms in the house you are not using that might provide that same space you "need"? And do you really need the space? There are a lot of houses here on the island that are three or four-bedroom houses with only two people living in them. Yet people board up their garages, convinced they need the "space" for one reason or another, when two or three bedrooms sit empty, collecting dust.
Just something to think about before you get out that credit card to "improve" your home!