Can I build a Granny Flat On My Property In San Diego?

Granny flats or ADU’s are the new trend in 2021. We have seen our amount of leads or homeowners nearly triple from 2019 to present times. Local San Diegans are aware of the shortage of housing that just does not seem to let up. The dilemma of limited supply also is creating a near untouchable real estate market for the average middle class person who does not already own. Many realtors and housing experts also attribute the recent pandemic as a source of supply issues. Homeowners are staying put, working from home and have no plans of leaving if they already are invested with a mortgage. With the surge of real estate prices and supply so low, Granny flats are an obvious answer to create more wealth, space or just simply housing solutions by using your existing property. So, what are the stipulations and qualifications to build an ADU on your San Diego property? Let’s walk through some of the common questions we receive.

Above is the S&P/Case-Shiller U.S. National Home Price Index – The trend is up with not sign of reversal.

Granny Flat Design & Sizes

California has really made it much easier to build granny flats with Assembly Bill No. 68 but here are some basic granny flat design restrictions/considerations for San Diego in 2021.

What size can a granny flat be?

See the example table below directly from the San Diego county website.

  • Maximum size is up to 50 percent of the existing house footprint or simply a maximum of 1,200 square feet
  • Minimum size is 150 square feet.
  • Your ADU must adhere to the with the main property’s setback. If you have an ADU that is two-stories, it must be placed five feet from both the side and rear lot lines.
Square Footage of Existing single-family residence (SFD) Maximum Allowed Square Footage for Detached ADU Maximum Allowed Square Footage for Attached ADU (up to 50% of SFD)
1,450 sq. ft. 1,200 sq. ft. 725 sq. ft.
1,800 sq. ft. 1,200 sq. ft. 900 sq. ft.
2,000 sq. ft. 1,200 sq. ft. 1000 sq. ft.
3,000 sq. ft. 1,200 sq. ft. 1,200 sq. ft.
4,500 sq. ft. 1,200 sq. ft. 1,200 sq. ft.

For more in depth design regulations read the San official documents here.

Design Consideration 1 – Transition Exterior

Outdoor fire pit close to structure for more fun!

Now getting into more design specifics a general rule of thumb, for granny flat designs in San Diego is that you want to consider the transition of existing architecture to your new granny flat building. In other words, if you currently have Spanish Colonial architecture you would want to carry the same look and feel vs doing a modern look or craftsman style. You would want to use matching exterior to synchronize everything.

Design Consideration 2 – Utilize Outdoor Space

If you are building a stand alone ADU you should absolutely use the outdoor space or backyard to your advantage. San Diego weather is nice all year, so look at the outdoor space as potential extra living room space. An extended deck, fire pit or open doors that let the sun in are great design ideas to capture more of the paradise weather and feeling less confined to a small living footprint.

Pricing For Your Granny Flat

Construction costs in general should NEVER be templated, generic pricing. There are too many specifics involved with your property, your design specifications and even down to the amenities and products you choose to go with. For example, if you opt for ceramic roofing tiles vs asphalt shingles there is going to be a price difference. Ceramic roofing lasts about 3x as long as asphalt shingles and also the cost to install and rough product pricing is much higher.

All things considered to give a good price range for 2021, homeowners should consider (with caution, see above) to pay anywhere from $275-$500 per sq. foot for your granny flats.

Getting Council Approval For A Granny Flat

As with any construction in San Diego you will be required to obtain a Building Permit to ensure that the new house meets all the zoning, building, health & safety codes. Depending on whether or not you live in an incorporated or unincorporated area of San Diego that will dictate the process. The simplified, standard council approval for a granny flat is:

  1. Understand the fee estimates you will need to pay.
  2. Prepare plot plan and bring building plans to Building Plan Pre-Submittal Review (BPPR) counter and obtain BPPR
    approvals (Zoning, Building, Land Development, and DEH).
  3. Schedule appointment for project submittal & complete the Building Permit Application (form PDS #291)
  4. Return to your meeting and submit building plans and permit application. Allow at least one hour for project submittal.
  5. Pay plan check fees
  6. Plans are reviewed by County staff for compliance with codes and ordinances and
    correction lists are generated by the following County specialties (as required):
     Engineer (Structural)
     Planner
     Electrical, Plumbing, and Mechanical
     County Fire Marshal (if not in fire district)
  7. Pick up plans and correction lists from the Building Division counter.
  8. Prepare a thorough response list to each correction list describing where and how all
    correction items were addressed on the plans
  9. Return corrected plans, old plans, correction list(s), and response list(s) for recheck.
  10. Return signed-off correction lists and stamped, approved plans to the Building Division.
     Submit evidence that all conditions of approval for permit issuance have been satisfied.
  11. Permit is issued and construction may begin.

Above is a simplified version as there are miscellaneous fees and processes depending on the county you are located. Please note, due to the pandemic the county has been very delayed in their processing at this time in August 2021.

Map showing incorporated vs unincorporated areas of San Diego.

So, there you have it, this article should get you on your path to building your next ADU or Granny flat in San Diego. If you are seeking a more detailed granny flat guide we have this resource for you as well:

Contact Us if interested in any of our services at: 619-726-7692.


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