A Guide to ADU Types: Detached, Attached, and Beyond
Detached, attached, conversion, or JADU? Here is a plain-English guide to the main ADU types for Pasadena homeowners, and how to figure out which one fits your lot.
Why the ADU style you choose shapes everything
The image most people have of an ADU is a small detached cottage in the backyard. That is one type, though it is not the only one, and the type you choose shapes the cost, the timeline, the permitting, and how the unit suits your property. Picking the right type for your lot and your goals is the first real decision in any ADU project.
California acknowledges several distinct accessory dwelling unit categories in its law, each carrying its own rules and trade-offs. Learning them ahead of time helps you have a productive conversation about what is possible on your lot, instead of fixating on a single image of what an ADU should be.
We design and build all of these types ourselves, so steering you toward any single option serves us nothing. Below is the honest breakdown of how they compare.
Detached ADUs
A detached ADU is a standalone unit, separate from the main house, usually placed in the backyard or to the side. It is the most private and flexible option, since it functions as its own small home with its own entrance, and it tends to add the most value and rental appeal because of that independence.
What you give up with a detached unit is simplicity, because it is new construction from scratch: a dedicated foundation, full framing, a roof, and new utility hookups. As a result it is generally the most demanding and expensive type, and it depends on having enough land and proper access.
For homeowners able to handle the space and the budget, a detached ADU is frequently the most satisfying choice, exactly because it is a real, independent dwelling rather than a carved-out part of the existing house.
- A standalone home with a private entrance
- The most versatile option, with rental upside
- New foundation, frame, roof, and full utilities
- Best with ample lot area and easy access
- Commonly the most extensive build
Conversions plus attached ADUs
An attached ADU shares at least one wall with the existing home, built as an extension off the main structure. It can be more economical than a fully detached unit because it leans on the existing foundation and structure in part, while still providing a separate living space with its own entrance.
With a conversion ADU, you turn underused space into a unit, usually a garage and occasionally a basement or another part of the home. The existing shell makes this one of the more affordable ways to add an ADU, though the actual cost depends on the condition of what you are converting and what it takes to make it a legal dwelling with proper insulation, systems, and egress.
If a detached build is not a fit for your lot or budget, both attached units and conversions are excellent choices. The best fit rests on your existing structure, your space, and the purpose you have in mind for the unit.
Exploring the Junior ADU (JADU)
A junior accessory dwelling unit, or JADU, is a smaller kind of unit built inside the existing single-family home, most often by converting a bedroom or a similar space. JADUs have a smaller size cap than a standard ADU and their own set of rules, which include an efficiency kitchen and, often, an owner-occupancy condition.
A JADU draws homeowners for its cost and simplicity. As it is created within existing conditioned space, it can be one of the most affordable ways to add a compact, legal rental or family unit, and current rules sometimes allow it beside a separate ADU on the same lot.
The limitations are matters of size and configuration: a JADU is small by design and forms part of the main home rather than a separate structure. Yet for the right homeowner, it is an affordable way to add a compact unit that can earn income or house family.
Aligning the type with your lot
The right type depends on the answers to a few questions. How much lot area and access are there? What is your budget? Are you looking for a fully independent unit or a smaller space carved out of the home? And what is the purpose: to house family, to generate rent, or to add flexible space for the future?
We walk your property and talk through all of it, then recommend the type or types that genuinely fit. A large lot with good access and a real budget may point to a detached unit; a tight lot or a tighter budget may point to a conversion or a JADU. There is no universally correct type, only the right one for your situation.
Designing around your lot's actual limits from the outset is how we keep the project buildable and the budget honest, regardless of type.
Common questions about the different ADUs
A recurring question is whether a homeowner can build a second ADU. Under current California rules, many single-family lots can pair a standard ADU with a JADU, though the particulars turn on the lot and the local code, which we confirm for your property. When the conversation shifts to rental income, a detached unit usually fetches more for its privacy, while a conversion tends to be the lower-cost option.
People regularly ask if the type affects timing. It does: a conversion of sound existing space is usually quicker than ground-up detached construction, thanks to a large part of the structure already being in place. We share a realistic timeline for the specific type at the consultation.
In a free consultation we address all of these for your particular lot, since the right type is the one matched to your property and your objectives, rather than a blanket recommendation.
From detached to attached to conversion to JADU, each type has its place, and the best fit comes down to your property, your budget, and the unit's intended use.
If you are weighing the options in Pasadena, call 626-659-9417 for a free design consultation and an honest read on what fits your property.
Give us a call at 626-659-9417 and we will lay out your options.