Are San Diego’s Pre-Approved ADU Plans Right for You? The Real Deal on ADUs

share Share

21 min read

Thinking about adding an ADU to your San Diego property? Discover the pros and cons of pre-approved vs. custom ADU plans, and learn why the cheapest option isn’t always the best choice for your home and future.

Architect reviewing San Diego pre-approved ADU plans with drafting tools and coffee


Hey there, San Diego homeowner! Thinking about adding an ADU to your property?

You’ve probably heard about the city’s pre-approved ADU plans.

These permit-ready plans sound great, right? Save time, save money, get your ADU up fast.

But hold up. Is it really that simple?

We’ve helped tons of folks like you add an ADU to their property. And we’ll share a secret, there’s more to the story.

Let’s break it down, no fluff, just the facts.

What Are Pre-Approved ADU Building Plans?

The City of San Diego’s standard ADU plans are designed to make building accessory dwelling units easier. That’s cool.

They’ve got these pre-approved floor plans. Basically, ready-to-go designs.

The idea? Pick a plan, and you’re halfway there.

But here’s the thing – it’s not always that easy.

These set of plans are approximately 85% complete, but that missing 15% can be crucial.

The Good Stuff About Using Pre-Approved ADU Plans

  • They’re free. That’s right, no cost for the plans.
  • Faster start. You skip the whole design phase.
  • City-approved. They’ve already got the thumbs up on the basics.

Pre-approved ADU plans are available to homeowners within the County of San Diego. Some ADU floor plans even allow for one ADU and one JADU on the same property, maximizing your space.

Sounds sweet, doesn’t it?

For some homeowners, especially those with straightforward lots and simple needs, these plans can be a real game-changer.

They can jumpstart your ADU project and potentially save you thousands in design fees.

But Wait, There's More: Challenges of Pre-Approved Plans for Your ADU Project

Here’s where using pre-approved granny flat plans becomes challenging:

  • One size doesn’t fit all. Your lot’s unique. These plans? Not so much.
  • Changes cost you. Want to move a window? That’ll slow things down.
  • Hidden costs. You still need site plans, calculations, all that jazz.

We had a client in La Mesa, let’s call him Joe. He thought he’d save big with a pre-approved plan.

Guess what? By the time we adapted it to his sloped lot, he’d spent more than a custom design would’ve cost.

This isn’t uncommon. Many homeowners don’t realize that pre-approved plans often need significant modifications to fit their specific property.

These plans to make changes can eat into your budget and timeline, sometimes negating the initial benefits of using a pre-approved plan.

Custom ADU Plans: The Other Option for Building Your Accessory Dwelling Unit

Now, let’s explore the process of building an ADU with custom ADU design options.

Yeah, they cost more upfront. But hear us out:

  • Fits like a glove. Designed for your specific lot and needs.
  • Matches your style. Blends with your house, not some cookie-cutter design.
  • Future-proof. Plan for what you’ll need down the road.

Custom plans allow for creative solutions. We once designed a custom ADU with a Junior Accessory Dwelling Unit on the first ADU floor that worked for both scenarios. This kind of flexibility just isn’t possible with pre-approved plans.

The Real Cost Breakdown: Pre-Approved vs Custom ADU Building Plans

Pre-approved plans: $0 for the plan, but $$$ for adjustments.

Custom plans: $$$ upfront, but often cheaper in the long run.

Why? Because we nail it the first time.

Let’s break it down further:

  • Design fees. Pre-approved plans might save you $8,000-$25,000 initially.
  • Site-specific adjustments. For pre-approved plans, this could cost $5,000-$15,000 or more. With custom plans, it’s often included.
  • Permit fees. About the same for both.
  • Construction costs. Can be higher for pre-approved if the design isn’t efficient for your specific lot.

The cost of building an ADU is worth considering, as an ADU is a great investment in your property and future. While pre-approved plans seem cheaper at first glance, the total project cost often evens out or even tips in favor of custom designs.

Time: It's Not Just About Speed When Building an ADU in San Diego

Pre-approved plans aim to make the permitting process faster, but it’s not always a streamlined route.

But if you need changes, you’ll need to obtain a building permit all over again, putting you back in line with everyone else.

Custom plans take more time upfront but can sail through approvals faster.

Here’s a typical timeline:

  • Design phase. Pre-approved: 1-2 weeks | Custom: 4-8 weeks
  • Approval process. Pre-approved: 4-8 weeks | Custom: 6-10 weeks
  • Construction. About the same for both, usually 3-6 months

Remember, these are ballpark figures. Every project is different, and unexpected issues can arise with both pre-approved and custom plans.

What's Right for You? Choosing Between Standard and Custom ADU Plans

Ask yourself:

  • Is your lot pretty standard?
  • Do you just need a basic ADU?
  • Are you on a super tight budget?

If you said yes to all three, maybe pre-approved plans work for you.

But if you want something that really fits your needs, custom might be the way to go.

Consider long-term factors too. Will your needs change in the future? Are you planning to rent out your ADU? These considerations might push you towards a custom design that can adapt to your changing needs.

Real Talk: Why We Often Recommend Custom Plans for Your San Diego ADU

Look, we’re not here to knock the city’s pre approved plans. They’re trying to help, and they are an immense benefit to homeowners who need them.

But in our experience, most folks end up happier with custom.


  • It’s yours. Designed for you, not some generic homeowner.
  • Better value. Often adds more to your property value.
  • Fewer headaches. We catch problems before they happen.

A detached ADU fits like a glove, designed for your specific lot and needs. We can incorporate energy-efficient designs, smart home features, and even plan your future ADU to accommodate what you’ll need down the road.

Wrapping It Up: Making the Best Choice for Your ADU in San Diego

So, are San Diego’s pre-approved ADU plans the right choice for your project?

Maybe. For some homeowners, they’re a great fit. But for most? Custom plans often win out in the long run.

Here’s the bottom line: whether you’re leaning towards pre-approved plans or a custom design, the key is to make an informed decision. Your ADU isn’t just an addition to your property – it’s an investment in your future and a contribution to San Diego‘s housing solution.

Remember, every property is unique, and so are your needs. What works for a neighbor in Carlsbad might not be the best fit for someone in Pacific Beach. That’s why expert guidance is crucial.

We get it – this is a big decision. You’re not just building an ADU; you’re creating new opportunities and potentially changing the way you live. It’s exciting, but it can also feel overwhelming.

That’s where we come in. Whether you’re near the sandy shores of Carlsbad or the bustling streets of Pacific Beach, we’re here to help. As the best ADU builders in Carlsbad, we’re committed to making your ADU project a success, no matter which route you choose.

Why not take the first step? Schedule your free consultation with us today. Let’s sit down, discuss your vision, and figure out the best path forward – together. Your dream ADU is waiting. Let’s build it.

FAQs: Your Guide to Pre-Approved and Custom ADU Plans in San Diego

Yes, but it might kick you out of the “pre-approved” fast track. The City of San Diego’s standard ADU plans are designed to simplify the process of building, but plans to make changes can complicate things. Minor modifications to the floor plan might be okay, but significant alterations could require a full review. Remember, additional documentation must be submitted with the pre-approved plans to ensure compliance with local regulations. The dwelling unit checklist summarizes all the information you are required to provide.

Upfront, you might save $8,000-$25,000 on design fees. However, the cost is worth considering carefully. You’ll still need a complete set of plans and site-specific calculations, which can eat into those savings. Pre-approved San Diego ADU plans aim to make the permitting process more affordable, but the total cost might end up similar to a custom design when you factor in necessary modifications. Remember, a complete ADU can significantly increase your San Diego housing value.

While the basic pre-approved plan doesn’t require an architect, you might need one for site-specific changes. You’ll definitely need someone to create site plans, handle Title 24 energy calculations, and manage other technical aspects. This could involve an architect, engineer, or specialized drafting service. Even with pre-approved plans, you’ll need to provide required structural calculations specific to your site.

The timeline can vary. Pre-approved plans can save a few weeks initially, but if changes are needed, you might lose this advantage. The ADU design process typically takes 4-8 weeks for custom plans, while both pre-approved and custom plans usually require 4-10 weeks for approval. Construction generally takes 3-6 months. Remember, pre-approved ADU plans in San Diego went into effect to streamline the process, but individual circumstances can affect timelines.

Not always. County standard pre-approved plans work best on flat, rectangular lots with few constraints. Sloped lots, unusual shapes, or other quirks might require custom plans. Don’t forget that you’ll need to submit grading plans along with your ADU application, regardless of whether you use pre-approved or custom plans. Pre-approved plans may not be suitable for all dwelling unit in areas with unique zoning or environmental considerations within the County of San Diego.

Not necessarily. Pre-approved plans meet all building codes and are designed to help streamline the process. However, they might not be optimized for your specific site or needs. Custom plans often make better use of your specific lot and can incorporate features important to you. Whether you choose a detached accessory dwelling or an ADU attached to your main house, the plans should fit your needs.

It depends. Pre-approved plans are designed to be generally appealing, but they might not match your home’s specific style. While these plans that you can use offer convenience, designing an ADU from scratch allows for complete customization. Consider whether you want one ADU and one JADU, or if you’re planning to build within an existing structure. The ADU guide provided by the city can help you understand your options.

Most pre-approved plans are for full ADUs. JADUs have different requirements and are usually conversions of existing space. You’ll likely need a custom plan for a JADU. The checklist guidance explains the requirements for both ADUs and JADUs, so be sure to review this carefully when deciding which option is best for adding an ADU to your property.


Get more stories from us in your inbox.

    More Blogs

    Share via

    Facebook Gmail Twitter WhatsApp