Estimate for Addition to existing house

I am curious on expertise of those who has extend their house in recent years. Let’s say you have 1500 sqft house (3/2), and we want to extend to like 1900 sqft (adding a bedroom and a bath room).

Option 1: extend on the single level (permitting set back requirements)
Option 2: add second story

Any advice on cost per sqft for that additional 400 sqft?

Extend is cheaper. Cheaper still buy a bigger house and sell yours tax free.
A 400 sf addition on top of a 1500 house will look bad

Rarely will a second story addition work unless it is at least 800-1000sf…100sf is needed just for stairs…Then there may be a hallway needed up stairs…Plus what space is lost downstairs? Will you loose a bedroom for the stairway?

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Yea, I agree. I still prefer the option 1 of extending the space in single floor. I want to do option 2 only in limited cases, on top of that, I normally find second story addition ugly.

@Elt1, any thought on rough estimate per sqft 400-500 sqft addition?

Maybe this old thread will help


I remember talking to my contractor about it maybe last year or so. $200-$250 per sq ft for rough cost. But I might be remembering wrong since it’s long ago.

I got quoted roughly $250-$300 / sqft awhile back. Given all the shortages on labor, I am guessing that might be closer to $400-$500 these days but wanted to validate that more.

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Currently I’ve been hearing $400/ft from friends who want to do additions.
I paid $300/ft a year ago but had to do a bunch of things like source some material myself, use discounts on Lowes,etc

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Extending out back if setback reqs are met is a no brainer …too many headaches associated with 2 story and 400 sq ft is too little. Creating a bedroom is nowhere close to what is needed for a bathroom as plumbing, electrical etc is needed. The national average cost of adding on a 100 sq ft spa like bathroom is $75k with bay area estimates going up to $150k ( labor + material). Until earlier in the year contractors just threw out numbers and you were lucky if they return your calls. Things have softened a bit now ! You should call around for estimates

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