Cost of adding square footage

[Simon Stahl]

I am looking at a house that I think could make a real good flip. The only downside is that it is really small, but there is enough space in the back to add an additional room. I'm thinking of adding about 300 to 400 square feet. A master bedroom with a bathroom. I know that there are a thousand factors playing in and no one can give me an exact number. All I'm looking for as a very rough ballpark number. 30k? 50k? 100k? I have absolutely no idea.

The property is located in Oakland, CA and I'm looking for the cost for the whole task including the architect, permits, GC, foundation, framing, siding and and and...

Simon