Add 87% for California premium.

My sister just did it to her place on Lon Island NY, cost about 85k with my brother in law doing the sheetrock, electric and floors.. The real kicker is the town decided after the work was done that the cesspool isn't big enough for the new larger house, still three people living there and no new bathrooms but yea they're gonna have to plunk down how ever much that's going to cost.  their taxes will go up a good bit as well.



So check that out before you do anything too...

Well north of $100 sq/ft. My world is high end custom so I have no idea what more "pedestrian" housing remodel work costs.
I got quoted $75 sqft and that was a bro deal from one of the GCs I work with. For a garage.

Don't forget to factor in the cost of permits. Where I live, building permits are expensive and really difficult to get (unless you are friends with the little Iranian cabal that runs the building department, then they rubber stamp everything for you). People two blocks away (in the unincorporated areas) barely need permits for anything and everything pretty much gets done quickly and cheaply.

A builder friend of mine told me that he was north of $100k into a project before even breaking ground. Permits, environmental impact studies, coastal commission approval, etc. Brutal.

And yeah, we have a ton of "remodels" like that here in San Diego.
We call em "one wall" or "front door" remodels where they leave one wall (usually around the front door) standing and demo the rest of the house. Just barely enough to be considered a remodel.

Working on a house right now that they added a second floor, then a roof deck, then a stone floor and massive marble countertops to said roof deck.
The weight of the deck was pushing the second floor down onto the first floor and ballooning out the exterior walls of the house. They took the entire house down to the studs to fix that. Pretty house but still structurally a mess. Buried somewhere in the bones of the first floor is the footprint of the original house that was built in the 30s.

They say it is always cheaper to go up then out, but I guess like others have said that depends if your foundation can take it.
Remember you are just doing bedroom space and most likely a bath, so it is not going to reach your typical per sq' price of a new build

I would spend a few bucks hiring an engineer first, then if it can be done hire an architect.

with Ca codes? better think 350 to 800 PSF

You really need to talk to an architect and an engineer. I will guarantee you will need an engineer.

If its on any kind of hillside regardless of how slight of grade it can be ridiculously over engineered. Over engineered = $$$$.

I've seen it done and that's exactly what it is. They end up with a basement that's shallow enough to have full sized windows above grade. Sort of like a split level.

Sounds like my first house. They added a porch, them enclosed it to make more living space, then added a porch and enclosed it too, then added another porch again.

Nothing about that place was done right or even passably well. It was all done at a time when building codes were either unheard of or just a polite suggestion. Many days I'd leave for work hoping to return to the local fire department spraying water on the ashes.

Just talked to an architect who's a friend of the family and he told me basically the same thing

Noted...

Noted...

this may or may not be true. i helped finance (i loan money sometimes for construction projects) a reno of a 1 story house built in the 40's. a second story was added. additional foundation work had be done. I its my guess that if the house had been built in the last 10 to 20 years, depending on the foundation, that might be possible to add a 2nd story without additional foundation work. load bearing internal walls though might be a different story. in the end only an engineer can say for sure based on plans in hand. and you may not be allowed to based on local ordinances. my guess based on what you stated as the addition square footage in california, i would budget 200k.

To be clear, I said to start at 100.  That would be absolutely bare bones to inhabit here in FL.  I know a little about the codes in Cali as I've spent some time with my sisters builder out there.  Much of the earthquake hardware is very similar to what we do here for hurricanes.  (We engineer to 150).  I built a house for a former secretary at cost last year.  (She quit 2 weeks after we COd the place.  Bitch). Anyways, decent house, on pilings instead of concrete foundation granted, impact Windows, foam insulation, metal roof, I think we were about 115-120 sticks, bricks, and labor.

Custom stuff here starts at 250-300 and sky's the limit.

Added 25x25 room off the back of our house 15 years ago. Kitchen mainly with small living room tv room.  Did most myself and still was 50k. Took a year to complete. Sucked fucking ass balls. Work 8-10 hrs at reg job and come home for another 6 hrs of work. Every day.
That being said. I noticed two homes that added another floor nearby me. We have full basements and foundations though

Good.. At the very least hire someone to look at it and give you a solid estimate.. Chances are the cost will make you consider other options. Honestly, if its a modern home its probably over built and "could" handle the load.. The only way to know for sure is going to cost some money, which may end up being all for nothing.. The old saying "its cheaper to go up, then out" may not apply here.... Do it right op, this is your home..

 
Or you could just hire a geotechnical engineer to do a subsurface investigation for ~ $1,000 and know exactly what the soils under your house are like instead of just making an assumption.




Best bet would be to meet with some local builders, they'll be able to steer you in the right direction and give you realistic ballpark estimates as to $/sf based on certain levels of finish.


 

I don't know how ca building is, but I do electric in about 20 2nd floor additions to ranchers per year.  It's extremely common here.

I am going back and forth between going out or up on my own house.  Houses here are about $190-220/sq ft sale price, where a second story addition will run you $150/sq finished assuming 1 bath, so in many cases it makes sense.

I cut open the top of a 6500 sqft home and went up with an additional 1080 sqft., then put on an additional 7500 on the main floor and 6000 for the lower floor. Total cost $4.8 million. It was the most miserable year and a half of my life.

Yep.

Done it.



1) House on basement, slab, crawl foundation...how deep is the footings, what size is the foundation/footing?

Have to know if the integrity of the base can support the additional loads...



2) Your basically building a 1200sqft house...since panel, water heater, HVAC will all have to be upgraded for code...

Septic or city sewer sanitation? If septic and adding a bathroom, local codes may require the field/tank to be larger.



3) don't have a clue about CA prices other than they are 120% higher than here.



If I were to ball park it today with MI prices....$120k-$150k.

Again...depending on a lot of factors (codes and existing structure) and what you want in the new area...bathrooms? Kitchenette? just bedrooms/kids play area?

I'm regretting not making this decision.  Don't forget about fun with Zoning variances.

In 2008 we added a 1,000 sf upstairs to our house, three bedrooms and a bath, and completely redid the kitchen for $100,000.
I helped a contractor buddy of mine do some of the work.

wow, so glad you posted this.  We are going to do the same thing.  pay no mind to the idiots that have more money than sense here.

more money than sense.   :)  

what an ignorant comment!

OK, done with this craziness.  Arfcom is FULL of people who have never driven a nail, and find it easier to take out a second mortgage and pay someone to do something an old timer could have done himself.  disgusting.  

Mind you a second story is not a DIY job, it can certainly be done.  There is a roof tear off involved, and praying for dry weather till it's dried in, but it can be done.

Doing an addition at grade start at $100 sq ft and go up depending on trim level.
To add vertical start at $125 sq ft.
Variables
Footing capacity
Plumbing line location relative to your new upstairs plumbing requirements
Duct work location relative to your new upstairs requirements
Trim level
If in California, seismic retrofit for upper level
Electrical capacity at your box - may not be a problem but it is an old house

Get a small house cheap enough and anything is possible.

Jack the whole house up an extra story off the foundation, build another story underneath making sure to support all load bearing walls.  Probably limited to a mirror image of the original floor plan w/o some extensive and expensive re-engineering.