I'm going to do my best to answer your question but the honest answer is that there are a lot of variables that will affect your answer, and without those variables, nobody can give you a really accurate number. It's like asking "what does it cost to eat at a restaurant?" or "what does a vehicle cost?". Also, Cunningham's Law should help here as well.
Factors that will change your answer:
-Your location
-Your exact specs
-Are you doing a first floor addition or second?
-Exact materials
-Etc
Here's my stab with some wild assumptions made. Before I start, I'm guessing $100k total. I'm assuming you live in a typical suburb in Texas.
$5,000 - architect
$1,000 - engineer
$1,000 - permits and permit runner
$7,000 - demolition
$3,000 - site prep
$12,000 - concrete materials and labor
$12,000 - framing labor
$10,000 - lumber package
$7,500 - stucco
$6,000 - roof (only new portion)
$10,000 - electrical labor and materials
$15,000 - plumbing and bath (this is the biggest "IF". This could be almost nothing or easily $30,000 depending on what you want to do and how your home and sewer lines are laid out. I said $15k as a pure guess.)
$10,000 - drywall
$3,000 - doors and trim
$5,000 - paint labor
$500 - paint materials
$3,000 - flooring materials at $6 PSF total
$3,000 - flooring labor at $6 PSF
$2,000 - fixtures
$116,000 total per above. ~$100,000 is probably a good guess. You can do a lot of work yourself and save a ton of money. Good luck! Post pics if you follow through.
Edit:
$500 - porta potty
$1,000 - builders risk insurance
$1,000 - extra utilities
$5,000 - windows
$123,500 new total
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