Are Pre-Approved ADU Plans Worth It?
A ready-made ADU plan can be one of the better-value ways to add a backyard unit — or a false economy that needs so much reworking you would have been better starting fresh. Which one it is comes down almost entirely to your lot. Here is how to tell.
What "worth it" actually depends on
The value of a stock ADU plan is not fixed. It rises when the plan fits your lot closely and the design work it saves is work you would otherwise pay for. It falls when your site forces so many changes that you end up paying for a near-custom design on top of the purchase. So the honest answer to "is it worth it?" is "it depends on the fit" — and the fit is knowable before you buy.
Where a ready-made ADU plan tends to pay off
- Regular, buildable lots — reasonably flat, conventionally shaped, with clear room for a detached unit or a straightforward conversion.
- A close match — you like one of the available layouts enough that only minor adjustments are needed.
- A desire to move sooner — starting from a drawn design can shorten the design phase, though it does not change your jurisdiction's review process.
- Comfort with the extras — you understand that site-specific engineering and local details are added separately.
Where it usually isn't worth it
- Hillside or steep lots — slope, grading, and access tend to drive the design, and a flat-lot plan rarely transfers.
- Tight or irregular lots — unusual shapes, tight setbacks, or easements can force a redesign.
- Particular requirements — if you have specific needs for layout, accessibility, or how the unit relates to the main house, custom often wins.
The earlier journal entry on six things to check before you design an ADU is a good lot-readiness checklist to run first.
Remember what a plan does not include
Even a well-matched ADU plan still needs the site-specific layer — a foundation for your soil and slope, utility connections, and any jurisdiction-required details. Budget for that from the start so the plan's price is not mistaken for the project's price. Our note on what changes still need an architect explains the usual dividing line.
And the "pre-approved" question
If a plan is marketed as "pre-approved," find out what that means in your case. Some California cities and counties run their own pre-reviewed ADU plan programs, which are separate from a designer's ready-made plans and specific to the jurisdiction. Confirm with your local planning and building department whether any such program applies to your address. The LA and OC ADU permitting overview points to the official sources.
A ready-made ADU plan is worth it when the lot fits the plan — not when the plan has to be bent to fit the lot.
Kevin Cohen Design is preparing a collection of ready-made ADU plan sets. You can join the early-access list on the plans page, or explore custom ADU design and build if your lot calls for it.
General information only, not legal, engineering or code advice. Rules differ by city and change over time, so confirm the details for your property with your local building and planning departments and with qualified professionals.