A Guide to San Diego's Pre-Approved ADU Plans

You may have heard that San Diego County and the city of Encinitas are making floor plans for accessory dwelling unit (also known as ADUs, guest houses, second units, casitas, granny flats) available to the public. Read on to decide if permit-ready plans are the right choice for your ADU project.

What are the “pre-approved” or “permit-ready” ADU building plans?

San Diego County, Encinitas and Del Mar have produced several granny flat plans to make it easier for homeowners to begin the process of adding an ADU to their property. Encinitas ADU plans are part of what is called the Permit-Ready Accessory Dwelling Unit (PRADU) Program.

Some of the San Diego County and PRADU plans have been reviewed by building departments previously, though there is not a clear definition of “permit ready.” In our experience, pre-approved plans are typically not the final choice for people we speak with about their ADU projects. This is due to design constraints and minimal – if any – real cost savings on the overall project.

Can I submit pre-approved plans as-is?

No; all of the pre-approved plans are only about 80% complete and will always require property-specific modification and documentation. In addition to the building plans, your project will still require Title 24 energy calculations, truss calculations, storm water plan, and a site plan (also called a plot plan).

The site plan must show the property layout with the footprints of all existing and proposed structures, electrical services, fences, walls, gates, setbacks, parcel area, easements, driveways, slopes, drainage for storm water and other features. When applicable, grading plans, septic design and other plans and calculations must be created and also submitted with the pre-approved plans in order to obtain a building permit.

Additionally, most homeowners would need to make at least some amendments to the ADU floor plan. For example, a door or window may need to be moved due to site layout or constraints. ANY change means you will still need to pay for plans to be drawn up, plus then the plan is no longer “pre-approved.” Unfortunately it’s not as simple as just “editing” the county plan… a new set would need to be drawn up, meaning these changes could increase the plan cost by $2-4K.

Does using pre-approved ADU save money?

It’s probably not cheaper overall to use a pre-approved plan. Keep in mind that 90-95% of the costs of your ADU project are in construction. It’s important to note that the standard plans were not designed with a strong eye toward value as far as construction costs. Most pre-designed plans put out by the county or other entities have not been evaluated by a builder or value-engineered (e.g. designed to require less material and to be labor-intensive). As a result, the few thousand dollars you may save on plans could quickly evaporate in significantly higher build costs.

For instance, most San Diego area standard ADU plans aren’t designed with trusses (much more efficient to build), “wet” walls may not be combined (which results in more expensive plumbing costs), and foundations may be over-engineered and complex (with unnecessary bearing walls and interior footings). The standard plans from jurisdictions have also not used standard sized windows and doors, or optimized around standard size shower & tub inserts. This means you’re losing cost savings, and in some cases, facing supply chain issues for more custom sizes. In our SnapADU plans, we have worked with our material suppliers to ensure a good supply of our standard door and window sizes.

Do I need an architect if I use a pre-approved plan?

While you are not required to have to have an architect design & stamp your ADU plans, you will need to have a drafter produce the site plan, title 24 calculations, and any required structural calculations. This is assuming no changes to the floor plans themselves as discussed above.

Is using ADU pre-approved plans faster?

Maybe. Pre-approved plans are sometimes put into an expedited queue, though in some instances the pre-approval queue is just as long as the standard queue. Also, if for any reason the pre-approved plan has a deviation (e.g. because you wanted to move a window or a door), the plan will end up in the standard queue.

Our experience is that the overall approval times are comparable with any other ADU plan, which is typically between 10-16 weeks for municipalities in Greater San Diego. This may be because a time-intensive part of the review process involves reviewing the property-specific specs, not necessarily the floor plan itself. Also, we have been seeing enormous queue times in the City of San Diego; the pre-check process alone was taking 25 business days as of July 2022. Overall, most of the time devoted to a city dealing with your plans lies in factors outside of the plan of the ADU structure itself.

Also, it can save time if you select any build-ready plan, since there will be less time dedicated to creating the floorplan, elevations, and construction details from scratch. Even with custom floor plans, we recommend that clients pick a plan that is closest to what they envision and make modifications from there to expedite the design process, saving both time and money.

Has SnapADU built any of the standard ADU plans?

Yes, we have built several of the County and PRADU standard plans – you can check out our ADU projects here. We are happy to deliver what our clients want built. In many cases though, we find that the San Diego County Standard Plans and Encinitas PRADU plans may not end up providing the best overall value for the client.

Often we’ll end up producing semi-custom plans for clients by starting with a plan that most closely represents what they are looking for, then tweaking the layout. This typically ends up costing $2500 more in architecture design fees vs. using a standard plan, though we can easily save that much by ensuring the plans are designed for an efficient build so we can stay on your budget. Also, many clients feel the nominal additional design cost is worth it to design something that will be exactly fit to their needs and will best utilize the available space for the ADU.

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