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how much does it cost to add an addition to a house?

Original post made by curious, University South, on Apr 20, 2009

I am just starting to consider adding an addition to my 95 year old house. I have no idea how much this kind of thing costs. I know I can't get any kind of exact numbers from a forum, but I'm wondering approximately what the ballpark is in our area, I guess per square foot. What if it's just a one-story addition in the backyard? What if I added a small bathroom? What if I wanted a small room on a second story above it, maybe with a bath of its own? Or if I wanted to dig out during the foundation process so one day I could finish a tiny basement someday? Do I have to get an architect, or are there designers who can do the planning?

Comments (35)

Posted by Palo Parent
a resident of Greenmeadow
on Apr 20, 2009 at 10:21 am

Ballpark: Figure on minimum $350 to $400 per square foot for new construction.

Posted by Walter_E_Wallis
a resident of Midtown
on Apr 20, 2009 at 10:26 am

Walter_E_Wallis is a registered user.

Figure on a year or so to get the paper work done. Everyone has veto power over you.

Posted by Neighbors rule
a resident of Another Palo Alto neighborhood
on Apr 20, 2009 at 10:37 am

Walter, is correct. Your neighbors ultimately control what you can and cannot do with your house. Do not expect any help or support from the city council, they will always side with the vocal minority.

Posted by How do you know
a resident of Another Palo Alto neighborhood
on Apr 20, 2009 at 11:27 am

How do you know they are a minority?

Posted by Neighbors rule
a resident of Another Palo Alto neighborhood
on Apr 20, 2009 at 11:30 am

Does it matter if they are a minority or a majority--should neighbors have a say in routine remodeling of a home??? It seems to me that in PA the neighbors have more of a say than the property owner.

Posted by curious
a resident of University South
on Apr 20, 2009 at 1:34 pm

Really? It always costs $350/sf? I thought you could possible do it cheaper than that, especially in this economy.

Thank you to the one person who had any information. Thumbs down to the 4 pot-stirrers who feel they have to chime in on every thread.

If anyone has has pertinent info, please post and I thank you in advance. If you want to complain about the way things are, please start another thread.

Posted by Neighbors rule
a resident of Another Palo Alto neighborhood
on Apr 20, 2009 at 1:48 pm

Of excuse me, Curious, for expressing my opinion--I did not realize that what I was saying was not relevant. I guess you will find that out when you try to do this remodel.

Posted by Resident
a resident of Another Palo Alto neighborhood
on Apr 20, 2009 at 2:33 pm

Firstly, ask anyone in your neighborhood that you know who has done remodling how they went about it, what it cost, how long it took, and how much over budget and over time they went.

Secondly, find an architect (neighbors may be able to help) with experience doing the type of work you want in Palo Alto (other cities are different).

Thirdly, make sure you really want to do this because it is a great strain on you, your family, your job, and your lifestyle.

Lastly, good luck.

Posted by palo alto mom
a resident of Embarcadero Oaks/Leland
on Apr 20, 2009 at 2:44 pm

$350 a square foot is a reasonable middle of the road, but a one story addition on a slab will be much less then a 2 story with a basement. Bathrooms and kitchens are of course much more then a simple bedroom or familyroom addition.

I'd suggest either hiring an architect with LOTS of experience in Palo Alto (the Palo Alto process really does exist) or a contractor (again, with lots of PA experience) for an hour or two or his/her time to get some info and ideas before you proceed.

Posted by Walter_E_Wallis
a resident of Midtown
on Apr 20, 2009 at 3:29 pm

Walter_E_Wallis is a registered user.

Hey Curious, how many years construction experience do you have? Time is relevant, and it is far better to know up front the time line on any project. I comment from 45 years experience in the construction field.

Posted by curious
a resident of University South
on Apr 20, 2009 at 4:45 pm

Thank you to the responders.

I have very little construction experience. 18 years ago I put a small addition on my 1st Palo Alto house, no bathroom or kitchen, just pushing out a wall by 15 feet to enlarge a room. It was way less than $350/sf, but that was a long time ago. So, Walter, i do not have experience. I recognize that it can take a long time to get a permit. Right now I'm doing the most preliminary legwork to see if I can even afford this. I was hoping that with the economic downturn, contractors might have lowered their rates some.

My neighbors know I'd like to do this, and are very supportive of my plans. I'm not planning anything huge. So I don't anticipate a big problem with the city, I'd like to stay within all planning guidelines. But as I said, I'm just starting this process.

I see ads in the paper for sunrooms. Are those cheaper? Does anyone have experience with them?

Posted by in the midst
a resident of Another Palo Alto neighborhood
on Apr 20, 2009 at 5:04 pm

You'll probably need an architect (unless you go with a design-build firm), and you'll definitely need a structural engineer. Look for those who have experience in Palo Alto, and the same is true when hiring a contractor. You want people who know the local building codes and what the inspectors get ornery about. Hiring professionals who know the codes and follow them upfront will save you many future headaches.

With a 95 year old house, plan on unexpected structural surprises. Building out has fewer surprises than building above or below.

We sailed through the permit process, probably because our architect has experience with the City and anticipated the problem areas quite successfully. The inspection process hung us up more than once. Beware of the Palo Alto inspector who missed his morning Wheaties. They're that fickle.

Posted by common sense
a resident of Midtown
on Apr 20, 2009 at 8:36 pm

An addition to a 95 year old house has alot of variance than building a new home on a blank lot. For example - how much of an electrical upgrade will you need? adding another room may require an upgrade of fuse box/circuit breaker box, rather than just adding another circuit.

If you are adding a 2nd story is the existing foundation strong enough to support it? the existing walls?

If you are in the flood zone, you may need to fill in your basement if the square footage you are adding exceeds a threshold. And if your mechanicals are located in the basement (water heater, furnace) then you'll need to relocated those....

The list goes on & on....

Posted by curious
a resident of University South
on Apr 20, 2009 at 9:19 pm

I'm not in the flood zone. And I would only put the second story over the addition, not over the current house, if I do a second story at all. I don't have that much money to put into this, so I need to keep it as simple as possible.

Posted by Not so expensive ... dont listen to snobs.
a resident of Southgate
on Apr 21, 2009 at 3:47 am

Putting an extra room in the backyard will cost you the most - since you will have to get the foundation work done. It is cheaper to put a new room above a one storey house.

Keep in mind the big cost items in any construction is really the bathrooms and kitchen. If you are only adding a room (no kitchen/bath) to an existing structure you can figure it will be in $100 per sq. foot. Assuming your have good foundation and support structure.

BTW: $350 is the high end of the spectrum.

Posted by Walter_E_Wallis
a resident of Midtown
on Apr 21, 2009 at 5:22 am

Walter_E_Wallis is a registered user.

An enclosed porch/sunroom neither heated nor cooled is a lower cost alternative. Check your ideas early on with the permit counter folk.

Posted by curious
a resident of University South
on Apr 21, 2009 at 7:47 am

Thank you for the thoughtful responses. I WAS thinking of a room in the backyard; my house is old and I don't think the foundation could easily support a second story. I would like at least a half bath, too. I'll have to contact a contractor, I'm hoping maybe I can get away with less than $350/sf if I keep it really simple.

Posted by vote for sunroom
a resident of Downtown North
on Apr 21, 2009 at 9:12 am

We added a sunroom using one of the vendors that sells sunrooms only. Easiest remodel/addition I've ever done (and I have completed one major addition plus remodeled almost every room in the house) and because the vendors only install sunrooms, they're fast and efficient. Ten years later, it's still everyone's favorite room in the house, seems much more spacious than it really is, and when we got a leak a few years ago, the vendor came out and fixed it, no cost.

So I highly recommend a sunroom both for value and use. You will not pay anywhere near $350/foot. The only caveat is location. Ours faces northeast so doesn't get much direct sun, but with a different orientation you could be miserable.

Posted by Monty
a resident of Woodside
on Apr 21, 2009 at 11:32 am

I am an architect practicing in Palo Alto for over twenty years. Your question has many variables that could add or reduce cost depending on conditions. Typical Palo Alto construction is much higher than the $350 per square foot cost that are being tossed out. It also depends on what you are doing. Kitchens and bathrooms are more expensive than bedrooms because of appliances, fixtures and plumbing needs. A ninety-five year old house may have lots of things that a remodel should address. How old is the wiring, is it knob and tube? How much electricity is provided, many old house have outdated electrical supply and a remodel could trigger an upgrade to the electrical service? If you add an addition on you need to look at the roof, if it's old it may be time to replace it. What is the condition of the gutters? Unintended consequences of remodel can add cost. Is there termite damage? Is the roof in need of replacing? How old is the plumbing, is it galvanized pipe or has it been upgraded to copper?

We recently worked on a remodel to a los altos hills home where there was nearly a$100,000 of cost associated with deficiencies in the existing structure. I would consult with an architect trained to look at these sorts of issues. They should very early be able to get a handle on this and provide you with some ballpark numbers but tossing out figures to help steer you is worth what you are paying for it, nothing. You need to explore this further to get a handle on what your remodel would cost and that means expending some money to get an answer you an take to the bank.

Posted by Walter_E_Wallis
a resident of Midtown
on Apr 21, 2009 at 5:24 pm

Walter_E_Wallis is a registered user.

Never connect new wiring to old. Set a new service if you need it, and back feed the old. Replacing all the wiring on a house over 40 years old can get you an insurance reduction. If you can get permission to pump sewage rather than require gravity flow, you have more flexibility of location. A second floor would definitely require a new foundation and might make your house uninhabitable for a while. Definitely get a local architect.

Posted by observer
a resident of Another Palo Alto neighborhood
on Apr 21, 2009 at 5:27 pm

I agree that $350 a sq ft is really low. The low cost housing being built in P.A. is costing over $1000 per sq ft.

You could probably build it for $350/sq ft for the foundation and framing it in and maybe a roof, not counting fees etc to the city.

A big enlargement could require the entire house be brought up to code on many issues: insulation, windows, ---

Bids for work from outside this area or the bay area would probably be lower. Contactors in P.A. charge based on it is in wealthy P.A.

Posted by curious
a resident of University South
on Apr 21, 2009 at 7:33 pm

What!?! (isn't that a great punctuation mark? It's called an interrobang). $1000/sf? I don't think so. That would translate to a 1000 sf house costing $1 million in construction costs alone, and I don't see that happening with the new houses I see popping up, even in Palo Alto.

It's been interesting, following the replies to this thread. So far I've got suggestions from $100 - $1000 per sf. I guess the advice here is worth every penny I paid for it! ;)

Posted by Outside Observer
a resident of another community
on Apr 21, 2009 at 8:38 pm


Given all that you've heard here, are you still considering an addition?

If so, please keep posting as you proceed. I, and I think many others in Palo Alto would welcome a home owner's perspective, if you do decide to go forward.

Posted by Sarah
a resident of South of Midtown
on Apr 21, 2009 at 9:59 pm

[Post removed by Palo Alto Online staff.]

Posted by palo alto mom
a resident of Embarcadero Oaks/Leland
on Apr 21, 2009 at 10:26 pm

[Post removed by Palo Alto Online staff.]

Posted by curious
a resident of University South
on Apr 21, 2009 at 10:46 pm

Does anyone have advice on architects vs design/build places? Any recommendations for a design/build company? It seems that by having both functions under one roof, you'd have less chance of having communication problems which can crop up.

Posted by PA resident
a resident of Southgate
on Apr 22, 2009 at 9:50 am

Look into prefabs for an addition, they are really affordable.
Web Link

Posted by in the midst
a resident of Another Palo Alto neighborhood
on Apr 22, 2009 at 10:04 am

RE communication problems, that's a good point. When we were interviewing architects it seemed that they all had their own favorite builders that they preferred working with. You might interview the team if you go this route.

We hired an architect and found we didn't like any of the 3 preferred general contractors. We found a contractor on our own who happened to be a design-build guy and of course we immediately regretted paying the architect fees when we could have gone straight to this contractor. In hind sight, it wasn't necessarily a waste of money even though we modified the architect's plans. An architect can provide sanity checks and oversight along the way, which may well justify their fees if you anticipate tricky situations.

When we observed the dynamics of the architect and preferred contractors together, they did have good communication as you suggest. However, we also felt like outsiders to our own project. With the introduction of an unfamiliar contractor, the communication between the architect and builder was rather sparse but we felt like the architect was working on our side. Had we gone directly to the design-build guy, we'd have missed the insights and occasional advocacy we received from the architect.

As you're seeing from the posts, there's no one right answer. You're smart to do your homework on what the issues and tradeoffs will be for your particular case and comfort.

Posted by pat
a resident of Midtown
on Apr 22, 2009 at 11:03 am

We recently completed a big project. We wanted to use the same contractor we worked with years ago because he is absolutley trustworthy, does fantastic work, and sticks to his schedule. Our architect had not worked with him before and wanted to interview him. We thought that was a good thing, because it's a team effort.

It all turned out extraordinarily well. The architect now recommends the contractor and vice versa.

The architect we used on our first project years ago cared only about the structure. When it came to tiles, paint, etc., we were on our own. I guess we could have hired an interior designer, but that would have added yet another voice to the project.

Our current architect was involved with every detail and that was extremely helpful! She opened our eyes to ideas and suppliers that we never would have known about.

A house is not just a structure. A good architect will talk to you about light (natural and artificial) and many details that you (or a contractor) might not think about. He/she will also understand your budget and stick to it. Ditto a good contractor.

We were fortunate to work with two extraordinary professionals. The project was completed on time and in budget and we're really happy with the result!

Posted by Neal
a resident of Community Center
on Apr 22, 2009 at 11:27 am

Don't forget your property taxes will go up accordingly. If your project costs $50,000 you'll have the thrill of paying an additional $500 each year.

Posted by Crescent Park Dad
a resident of Crescent Park
on Apr 23, 2009 at 11:07 am

Items to consider that have not been mentioned so far --- all to do with planning:

- In Palo Alto, a 1-story addition is the easiest way to get through the planning process. 1-story addition = no neighborhood review.

- 2nd story additions require time for neighborhood reviews. This can get messy. If you must do a 2nd story addition, then do your best to follow the guidelines issued by the planning department.

- Do your best to work within the codes, set backs, etc. set out by the city. Every waiver or exception will extend your review time.

- Strike up a cordial working relationship with the city planners, public works, etc. They are great people and can provide tons of free advice. Go in with a bad attitude and you're going to be less successful in your remodel efforts.

- For any addition or remodel: Talk to your neighbors before you start! Let them know what you're doing - get them on your side.

- Working with contractors: If you have specific expectations, make sure they are in writing. Even such things as a daily clean up of the work site should be in writing.

- Old home remodels reveal big surprises. Budget 10-20% funds for termite damage, dry rot, bad electrical, bad plumbing, foundation rework, etc. And also realize that you will come across new projects that fall under the heading, "While we're at it"...

- Will you need to move out of your home during the remodel? Then budget for lodging, moving expenses, storage and so on.

- Very few remodels go perfectly as planned. Allow for extra time and extra budget.

Posted by Paul Owens
a resident of College Terrace
on Apr 27, 2009 at 2:12 pm

I own and operate Owens Construction and do quite a lot of work in Palo Alto. I would be happy to give you a free consultation and answer all your questions, no obligations and no pressure. Call or email if you like, 650.888.2666 [email protected]
I have over 23 years of residential remodel and new construction experience, absolutely love working in Palo Alto (great people, beautiful architecture) and you are welcome to pick my brain for free!
Paul Owens, Owens Construction.

Posted by homeowner
a resident of Midtown
on Apr 29, 2009 at 11:41 pm

We are planning to improve our bath in ~60 yr old house in Palo Alto. It is a very small space and there really is no scope for us to do anything but cosmetic improvement.

I learnt that in spite of the scope of the project the city requires quite elaborate documentation of the project as permit application and is asking to get a plumbing, electrical, building and demolition permit.

Can someone who has recently completed a recent project clarify why all these permits are needed? Is there a $$ limit below which permit may not be needed?

Posted by Ron Plumber
a resident of Barron Park
on Jan 5, 2017 at 6:56 pm

I'm reading this thread that's nearly 7 years old. Curious, did you do your addition? If so, what was the final cost?


Posted by Mary
a resident of Old Palo Alto
on Jan 5, 2017 at 8:23 pm

"Can someone who has recently completed a recent project clarify why all these permits are needed?"

The rigorous permitting requirements in Palo Alto and most all of California are due to the prevailing progressive ideology that most people who run the government have. People who run the government think that the average citizen need expert help in living their lives and that everyday decisions need to be made by government experts. And too, they enjoy exercising control over citizens.

I have a relative in Austin in the building business who used to build in Los Altos/Palo Alto. To get a permit for a new house takes an average of 3-4 days in Austin. Smaller projects are handled over the counter. The building codes are somewhat stricter in California (mostly for energy and water saving), but the biggest difference is in the attitude of those who administer the Codes. In California cities like Palo Alto the building bureaucrats have the attitude that their job is to thwart you whenever they can and to delay you to the maximum extent possible when they can't stop your project entirely. In Austin, city workers think their job is to help you build your project according to the code. They help instead of hinder you.

The attitude in PA probably suits those who would like to keep building to a minimum though it would be better - and more honest - if the city would just enforce a strict zoning code. They wouldn't put up with what the average homeowner has to do to remodel his house in Austin.

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