Cost for adding square footage

I am thinking of adding 500 square footage to my house in Cupertino i.e., addition of 2 bedrooms and 2 baths. What will be the construction costs? I am not looking for anything fancy. 2 simple operable bathrooms would do.


This has been discussed many times before. The most recent was here Market still hot. Budget 250/sqft, but beware it may cost you more. If you get it done for less that will be a nice bonus for coming in under budget.

Does $250 include architect, permit and miscellaneous fees?

No…And for a 500sf addition figure $500/sf plus all the soft coats

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That puts your costs at 250k just for construction. Add in all the other stuff and you are at 300k+. Elt1 probably has more development experience than the rest of us. Generally, people want to hear that it can be completed on the low end of the pricing range, but you have to be careful with the low bids. People who can get the work done at the low end of the range already know they can do it. Contractors know what they can charge. They know the market rate for the type of work they perform. There are many different types of contractors from a professional approach to the one that will disappear after collecting enough money. If you are new to construction, find good people to help you along.

Yes. $250 per sf sounds way too low to me. Maybe if you plan on doing most of the work yourself. A couple years ago I heard from architects $325+/sq ft for new construction and $400+/sq ft for remodel. I’d imagine it has only gone up at this point…

How about adding a bathroom inside an existing house? Say the house is a 3/1 and I want it to be 3/2.

I’d guess $20k to 30k to add a bathroom. Assuming the plumbing doesn’t need to be completely rerouted and the sq footage is taken from an existing room.

No economy of scale on a small job…Plus the soft costs per foot are much higher. .Plus you have to figure in the costs of remodeling the existing building…Changing or adding a hallway, possibly loosing a bedroom for that hallway, seismic upgrades…code upgrades…Adding an addition is not for amatuers…Even as a pro I won’t do it any more…Even though my wife is insisting on doing one on my residence…often cheaper just to sell and buy a bigger house and a lot less headaches. .Reconfigure your existing space, sell all your junk…Try rearranging and redecorating. .Maybe put an illegal temp bedroom in the garage…But spending $2-400k for a couple of bedrooms doesn’t pencil…
Master suites, kitchens and family rooms add a lot of value…Additional kids bedrooms may only add $30-50k each in value…baths maybe only $15k


There is a house with an added on second story over garage. I think it is on Blaney. It looked horrible and new owner tore the entire home down start from scratch. You are better off start it over.

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