Building an ADU in California

Building an ADU in California

Is building an ADU in California worth it? How much does it cost to build an ADU in California? We are happy to answer any questions and discuss any concerns you may have.

The construction of ADUs is on the rise in California as more people than ever before look to add livable space to their property. (We cover the benefits of an ADU extensively in this article, here.)

Perhaps you as the reader are fully aware of the trend and the benefits, but you are stuck on how to actually get one built. In this article, we will outline the roadmap and walk through the step by step process of building an ADU in California (or anywhere for that matter).

Building an ADU | Budget

Before you can start to build your personalized ADU, you sit down and forecast your budget. This can be particularly difficult at the present, with lumber prices at an all time high and inflation pushing up the cost of all goods and services generally. What may have cost $150,000 or $175,000 a few years ago, is now well over $200,000. 

As a piece of the budget exercise, consider both what you can pay for outright and also what you would be able to finance. We cover the financing of an ADU in this article, here. Many banks are specializing in ADU financing. It is becoming easier than ever to be able to finance the construction of an income generating real estate asset. As a rule of thumb, you should have at least 20% of the cost of a project in cash, or $50,000 for a $250,000 unit. Some banks will actually help finance the entire amount. It is always wise to have a fund set aside for issues that might arise, which could increase the project cost.

Feasibility Study & Civil Engineering

Alright, now you’ve decided on a budget. You’ve got $45,000 or so set aside, and you have a bank that is willing to finance your $225,000 unit (we sell these, check one out!) outright. Now you need to see if building an ADU in your California backyard is possible. Enter the feasibility study.

Most reputable contractors will conduct a feasibility study before entering into a contract. At Cedar ADU, we come out within one week of initial contact and will review your property, confirming that the setbacks and zoning requirements are all set. 

As an aid, when building an ADU in California, most homeowners should plan on having at least a 5 foot distance between the proposed ADU and the property line, and at least a 10 foot distance from the house. This can vary from jurisdiction to jurisdiction, but this is a general guide which should satisfy most local requirements. What this means is that a 20 foot by 30 foot rectangular ADU (let’s make it easy on ourselves and have it be a perfect rectangle), would need a backyard that’s 1400 square feet.

In addition to setbacks and zoning requirements, the ADU builder should also look into any easements on your property. Occasionally, a property will have an easement that runs through the property, making it difficult to build an ADU. This is definitely best discovered earlier than later.

Finally, as a piece of the feasibility study, and as a portion of the civil engineering, the placement of the utilities should also be considered. Unless you are looking to build a dark, bathroom-less shed, you’ll want to make sure that the ADU can be hooked up to the sewer line, have running water, and electricity. Here at Cedar ADU, we will walk you through the sitemap of your property. We will also propose the best placement of your ADU as it relates to utility hookups.

Design Session

Alright, are you still with us? Wonderful. Now that you have set a budget AND determined that an ADU is feasible, you’ll want to make sure that you are building something you will actually like. Afterall, when you look out at the back of your property, you will be seeing this unit everyday.

In the design session, the ADU builder will sit down and map out what your unit will look like. From the external siding, to the flooring, to the little knobs on the bathroom cabinets. Any ADU builder worth his or her salt will have the entire design planned out before the unit goes for permits.

Building an ADU | Obtaining Permits

Let’s be honest, this is probably the most daunting part of building an ADU. Many people have asked us about and expressed concern over the permitting process. The driving force behind these concerns is uncertainty more than anything. Admittedly, permitting can be a difficult process. Going with a builder who will handle permitting from start to finish with you (like Cedar ADU) will greatly reduce this burden. An experienced ADU builder has gone through the permitting process a number of times and has a great checklist for what needs to be ready.


You did it. Everything you have done to prepare to build an ADU in California (or elsewhere) has led to this moment. You are now past the permitting stage which has taken anywhere from one day to several months. What’s next on the docket is to prepare the site for the foundation and to prepare the utilities. Usually, there is likely some level of excavation that needs to be done. It is followed up with pouring concrete for a slab or stem wall foundation. The utility hookups can come before or after, depending on the savviness of your engineers.

Once the foundation is ready, it’s time to actually put up a structure. This is where many ADU providers differ. Your run-of-the-mill general contractor likely will frame the building using the traditional stick build method. Next up is your crane in, “I promise this is not a manufactured home, it’s modular, prefab!” type builders. As skillful as some of these builders are, all joking aside, just watch out for craning and powerline disconnection fees! Usually a crane will show up and deliver the unit to the slab. In case you have an enormous side yard that fits a truck, a semi will show up. The last major option are builders that have a priority system that goes up quickly in a backyard.

These different builders will all put the finishing touches on the structure, following the design plan laid out earlier in the process. 


Building an ADU may seem like a daunting process but 80% of the battle is the planning and preparation. It makes all the difference having a qualified, experienced builder act as a guide through the whole process. It is even better to find an ADU developer that can deliver a turnkey ADU, completely hassle-free. If you noticed, we are a bit biased. But we seriously think you should give Cedar ADU a call and see what they have to say!