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Planning for a second story addition in the Bay Area

August 18, 2021

2021 is the best time to build an ADU

The rising property prices in the Bay Area coupled with the efforts of California state officials to streamline the building of ADUs (additional dwelling units), construction of various ADUs are becoming more and more popular. City governments are also making an effort to encourage its residents to build legal ADUs. Major cities like San Jose, Fremont, and Danville are even recommending builders and architects with pre-approved ADU plans. All that being said, if you’ve always wanted or needed an ADU but don’t have the space in your yard for a detached structure, your option is either to convert your garage into an ADU or build an ADU on top of your property.

In this article, we’ll go over tips and common questions when planning for a 2nd story addition.

Am I allowed to build a 2nd story addition on my property?

The short answer is yes. Assembly Bill 670 which was adopted on Aug 30th, 2019 essentially voids restrictions on ADUs as long as your ADU plans comply with 65852.22 of the Government Code

But remember that just because you’re allowed to do it doesn’t always mean your city will make it easy for you. City building departments can still deny you a building permit if your ADU designs don’t comply with the aesthetic of surrounding structures. So if you’re envisioning an ADU built on top of your current property, take a look around the neighborhood and see if anyone else has done it. If so, this means the precedent has been set and if your ideas are anything like that of your neighbor, you shouldn’t have a problem acquiring permits.

Can I build a 2nd story addition on my property?

Most people will build a 2nd story addition above their garage or living room. The question of whether you can build depends on what loads the walls and foundation were designed for when the property was built. It is unlikely that the builder who built your home anticipated a second story addition so your home is likely unable to bear a 2nd story addition. But not to fear, there is a solution to this.

The solution is retrofitting or in other words, strengthening the walls and foundation to be able to handle the added weight of another livable floor and a roof. Retrofitting requires your builder to acquire a set of plans from a local licensed structural engineer. Plans for structural retrofitting for a 2nd story addition typically run $10,000 to $20,000 depending on the size of the addition. 

How much does it cost to do a 2nd story addition on my property?

2nd story additions typically cost $400 per square foot for labor and rough materials, not including the cost of permits, engineer plans, and the finish materials you choose to put in the end. The good news is that you should be able to calculate the entire cost of the project as long as you know how large this addition will be.


To get a rough idea of how much your project will cost, you’d get a quote from an engineer for the plans based on the square footage, get a quote from a builder based on the square footage, and then get quotes from flooring, countertop, and cabinet companies for the finish materials. 

If you’re not sure what the dimensions of your cabinets will be or how much counter-space you’ll have, we recommend investing the money into getting pre-construction 3-D designs. This is a service that will create 3D floor plans for your addition. With these plans, you’ll know exactly how much finish materials you’ll need.

Can I finance a 2nd story addition on my property?

You most likely can. There are a variety of loan products available for home renovation projects. The most popular loan product we’ve seen our clients use for home additions are HELOC products. So if you inherited your home or if your home recently appraised for higher than what you bought it, you’ll likely have some equity to tap into.

The second most popular loan product we come across are ARV (after renovation value) loan products like those offered by Renofi. These loan products allow you to leverage both the equity your property already has and the equity it will have once the renovations are completed.

To learn more about what financing options are available to you, visit our financing page.

How do I get started designing my 2nd story addition?

The best place to get started are with 3D pre-construction designs or architect plans.  3D preconstruction designs are a fraction of the cost of architectural plans and will allow you to get a quote from an architect for plans, a builder for construction, and materials from vendors. The other benefit is you’ll be able to visually see what your addition will likely look like when built.

Alternatively, you can bypass getting 3D pre-construction designs and go straight to an architect but you won’t be able to compare the pricing of architects since they’ll likely ask you to commit a down-payment so they can start preliminary drawings to give you a price on the final set of plans.

How large can I make this 2nd story addition?

The size limit will depend on what your city will allow and what the square footage of the original property was. Size limits for additions are typically calculated as a percentage of the main structure.

Luckily, there is a quick solution to this. Call your local building department, give them your address and ask them how large of a 2nd story addition you can build. They’ll likely refer you to the planning department and they’ll be able to give you a concrete number.

How do I get permits for my 2nd story addition?

To get permits for a 2nd story addition, you’ll need a set of architectural plans to submit to the city building department. There will be other permits that your builder will need to get during the construction part so if you’re working with a good builder, they should be able to apply for all the permits for you granted that you provide the plans.

If you’re looking for a hands off solution, firms like ours handle the entire process from 3D design or architectural plans to the construction. If you’d like to get started with building a 2nd story addition and want someone to talk you through the process, you can book a phone call with us.

How long will it take to add a 2nd story addition?

Assuming that no dry rot, termites, or other major structural problems are discovered, the construction of a 1,000 sq ft addition will typically take 6 to 7 months. That’s roughly 4.6 days per square foot.

Building an ADU or 2nd story addition is a major financial investment that will definitely raise the value of your home. The challenge is staying within budget so you come out profiting from the investment. Our blog posts are biased towards our services at HQR but we do recommend reading through the review of the firms you’re looking at for a more unbiased perspective. That will give you a clear idea if the service they provide is consistent and of high quality.

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