OK, good news/bad news.
Good news, putting an addition on your Austin area home can be great. Because at the end of construction, you'll have that extra space you've been craving! Have you outgrown your house but you don't want to leave your neighborhood? Do you need a place for the teenagers to hang out? Have you always wished you had a private retreat or an extra bathroom? Adding on to your home can be the solution.
Bad news, it costs money. Real money, not TV money. Those weekend remodeling shows breeze right past the price. How many times have you watched HGTV where the voice-over says '$1,200 for new quartz counter tops' as the camera pans through a fabulous new kitchen complete with oversize island featuring waterfall edges and farmhouse sink? That might be the cost of the raw quartz slab, but it certainly doesn't include the cost of the cuts, installation, extra details.
Let's cut to the chase. In the Austin area, a quality addition to your home will start around $175/square foot. Depending on the finishes you select (light fixtures, plumbing, flooring, tile) it can go up from there. It can also go down, if you're thrifty. So if you want to add a room, take length x width and multiply by $175 to get a general idea on price. If you're fancy and want imported tile made with platinum and diamonds, add $ accordingly or plan to cut back somewhere else.
Why does it cost this much? Because adding on isn't as simple as cutting a door and adding a box. It's COMPLICATED. A homeowner hopes it's just some lumber, sheet rock, and paint. A good builder knows it's also electrical upgrades, HVAC changes, perhaps some foundation work, roof adjustments, plumbing changes. Any builder who downplays those possibilities should be avoided. You WANT the bad news up front, not after the walls are knocked down.
Sure, there are probably Austin area builders who will do your project for less. But more than any other purchase, with construction you really do get what you pay for. When you aim for the lowest possible price, you lose quality, functionality, comfort. You'll get less insulation, cheaper windows, tradesmen with lesser skills. Nobody wants to look back and think 'I wish we'd done this right when we had the chance'. Do it right this time.