Both numbers are well below what Brown said. Heâd said that the elderly account for two-thirds of the cost, when in fact theyâre just over 20 percent, and that children account for one-third, when theyâre actually less than 20 percent.
A 20-by-20-foot garage totalling 400 square feet would cost between $16,000 and $24,000 without an apartment, and anywhere from $20,000 to $35,000 with an apartment.Homeowners who are skilled at construction and can do some or all of the work themselves can cut an enormous amount off of those numbers. 20-by-20-foot garage totalling 400 square feet would cost between $16,000 and $24,000 without an apartment, and anywhere from $20,000 to $35,000 with an apartment.
1 According to HomeAdvisor.com, a new garage costs between $9,000 and $45,000, with an average cost of roughly $20,000 to $30,000.2  Per square foot (psf), expect garage prices to begin at $30 to $50 psf for basic materials.3  Using higher end materials could increase costs by 15 to 25 percent ($35 to $65 psf). Remodeling Magazineâs 2011-2012 Cost vs. Value Report puts the cost of a midrange garage addition (a detached, 26â x 26â two-car unit with asphalt shingle roofing, 5 double-hung windows, door w/ automatic opener, and more) at $50,000 to $60,000.