ADUs – A Simple Way to Increase Value and Space

Whether you’re a growing family that needs more space, or you are inviting your aging parents to live with you, or you want to generate extra rental income – an accessory dwelling unit (ADU) makes getting more space simple, efficient, and affordable.

Benefits of an ADU

Generate additional income by renting to tenants, provide a private space for family members, or create extra room for your family – there are many reasons to install an ADU. Not only that, but an ADU is an effective way to increase the resale value of your home.

With years of experience in the contracting industry and real estate market, our team knows how to move the pieces along to build an ADU within your budget and timeline.

ADU Interior

Process for Building an ADU in North County San Diego

With JDN Construction, you will receive detailed plans and timelines, as well as a realistic budget for your proposed project and ensure that you understand all aspects of the project before signing on the dotted line.

We’ll walk you through the design process of what needs to happen to move the project forward including obtaining permits and zoning approval where necessary. Zoning is an important consideration in these cases and we can look after all of the paperwork to help you build your ADU.

The Facts on Accessory Dwelling Units (ADUs)

ADU and JADU defined

An Accessory Dwelling Unit is a secondary living space for family, students, elderly, in-house healthcare workers, and more within a property lot. ADUs may be attached or detached spaces that should include its own living, sleeping, cooking, and bathing facilities. California homeowners can now add both an ADU and a JADU to their property. Although a Junior Accessory Dwelling Unit (JADU) may not exceed 500 sqft and must have its own separate entrance and kitchen.

Space considerations

Detached ADUs may be built up to 1200 square feet. Attached ADUs can start at 800 sqft, but cannot exceed 50% of the primary dwelling size. Jr. ADUs must be contained within the proposed living space, like a garage or spare bedroom.

Lot size:
Residential lots will not be subject to any minimum lot size for Accessory Dwelling Unit (ADU)s by ordinance or of the underlying zoning district.
– Per State Law AB-68

Setbacks for a detached new construction Accessory Dwelling Unit (ADU) shall be no more than 4 feet from the rear and side lot lines. No setbacks shall be required for Accessory Dwelling Unit (ADU)s and Junior ADUs converted from legally established existing space. Attached new construction Accessory Dwelling Unit (ADU)s and conversions from existing space to be expanded must comply with the setbacks of the underlying zone.
– Per State Law AB68

Building multiple ADUs

Current legislation permits one detached/attached ADU and one attached JADU for an existing single family residence. In order to build these two additions, your lot must have adequate water and sewage services. It also must meet fire safety standards, and your property must meet minimum setback code requirements.

Converting rooms into ADUs

If you are not building an entirely new unit, you may convert the garage or an existing room within your residence. Replacing a room with an ADU or JADU may be beneficial because you can build one that matches the original blueprint, staying well within regulation.

Pricing & Financing

Budget considerations

ADUs are a great investment if you want to increase your property value. Depending on the size and features included in the project, a helpful cost metric to follow would be $275 per sqft. For a 800 sqft 2BR detached ADU, the approximate total project cost is $220K. The cost can be broken down in two phases:

Typical pre-construction costs: 

  • Plans and permit: ($8-10K) Includes Architectural design, structural design, title 24 energy calcs and
    bearing soils report.
    (Special circumstances may require additional civil engineering, structural engineering and soil reports)
  • Permit fee cost ($5k+) Is the average cost.
    (Fee cost vary from city to city; additional fees may apply)

Typical construction costs: 

  • Construction/build out ($255 x sqf) Includes all material and labor for turn key build. Also
    includes $10k allowance for site prep and utility cost.

Financing options

Common solutions are:

  • Home Equity Line of Credit (HELOC) or Home Equity Loan: Banks will lend up to 80% of your current home value. Both types of loans require home equity. HELOCs are more flexible in a sense where you withdraw funds as needed, only paying interest on an outstanding balance. Home Equity Loans will send a one-time payment in cash after closing the loan.
  • Renovation Loan: Appraisals are based on “As-Completed” value of the property, meaning they will lend funds based on the value after the ADU is completed. Most banks will loan up to 95% of the As-Completed value.
  • Cash-out refinance: Replacing your existing mortgage, this new home loan will be more than what you currently owe except the difference can be cashed out to fund your ADU building project. This requires home equity with a limit of 80-90% for the cash-out opportunity. If your home is estimated at $1M after the ADU and you currently owe $500K, you will earn a $800-900K loan with a cash-out opportunity of $300-400.

How we can help in the financing phase
We will work with you and your lender to supply the necessary paperwork, plan information, and budget details to submit for loan documentation. Most lenders we have worked with required intended floor plan and full breakdown of construction costs by trade before appraisal. Please give us a call if you wish to include us in future correspondence with your lender.

What material and finishes are typically included?

The average ADU build will have the following finishes:

  • Exterior are typically stucco with Dash finish. (sand & Santa Barbara smooth to be additional cost)
  • Interior drywall is typically smooth skiptrowel finish.
  • Concrete walk ways and patio typically are broom finish.
  • Roof finishes typically match the existing house, tile or asphalt composition singles.
  • Cabinets are all plywood box construction, typically prefinished with soft close hinges and drawer glides.
  • Windows are typically Milgard Trinsic series white vinyl or equal.
  • Countertops material is quartz or granite with 4” – 6” backsplash.
  • Flooring is typically vinyl plank.
  • Ceiling height is typically 9’
  • Interior doors are typically standard height of 6’8”
  • Exterior doors are typically fiberglass or wood.
  • Plumbing fixture allowance for midgrade quality fixtures.

These are typical finishes; however, we can install any and all desired finishes that the budget will


ADU construction timeline expectations

Projects are completed over a span of 5 – 6 months, starting from obtaining the permits to completion of your ADU.

A standard timeline for an ADU project:

  • Planning & Permitting 1st month: Once the proposal is signed, we start designing and prepare to submit plans to the city. We handle all correspondence between the city to ensure the building process stays on track with the agreed timeline.
  • Budget Consultation 1 week: We will help refine your budget to achieve your desired design plans. A final cost estimate is approved before the construction process begins.
  • Buildout 14-18 weeks: After receiving the permits and final plan, construction will start within the week. We will directly oversee the process and provide you with progress updates on your project.

Pre-approved ADU building plans

San Diego County and the city of Encinitas have “permit-ready” standard ADU building plans. Each package includes the required permits needed for the desired unit.

Pre-approved plans and their benefits

The appeal of these plans is the expedited process to obtain the permits. Additionally, it can reduce architectural costs as there will be no need to customize the plan. However, amendments like changing door or window placement to accommodate your specific site will change the status from pre-approved plan to a standard customized plan.

Rentals & Investments

Can I add an ADU on a short term rental?

ADUs may be rented out with a minimum of a 30-day contract. JADUs require owner-occupancy as they are not your typical standalone units; however, owner-occupancy is not required for “standard” ADUs.

Can I build an ADU in a duplex?

Yes, you are permitted two detached ADUs for a structure of two or more residential dwellings attached to each other. Per every four residential units, you can convert an existing living space (garage, storage rooms, attics, basements, etc.) into an ADU or JADU.

What to Expect Working With JDN Construction

Do you offer free consultations?

Yes, we would love to answer any questions you have about your project needs. Our experts will work closely to ensure your design dreams will become a reality with us. We know the options are endless and overwhelming, so we make it our mission to help build the right ADU of your dreams.

What locations do you serve?

We are based in North San Diego County, serving Oceanside, San Marcos, Escondido, Vista, Fallbrook, Rancho Santa Fe, Cardiff, Del Mar, Solana Beach, Carmel Valley, Rancho Bernardo, and other surrounding areas.

What does the onboarding process look like?

If you do not have plans drawn before working with us, we will work hand-in-hand with our architects to craft the ideal design plan for you. We pride ourselves in being involved every step of the way so you don’t have to.

Contact Us to Get Started