Remodel when the house has enough space but the wrong layout. Add on when you need more space that's part of the main home. Build an ADU when you need a separate living unit — for family, rental income, or future flexibility. The right answer depends on your lot, your budget, and how you'll use the space in ten years.
Side-by-side comparison
| Remodel | Room addition | ADU | |
|---|---|---|---|
| Best when | Space is enough; layout, light, or condition is the problem | You need more room in the main house — a bedroom, suite, or larger kitchen | You need a separate unit — family, rental, or flexibility |
| Adds square footage | No | Yes | Yes, as a separate unit |
| Separate entrance and kitchen | No | No | Yes |
| Permit path | Building permit; preservation-zone guidelines if exterior changes | Building permit; zoning limits; formal design review for major additions in preservation zones | State law requires a decision within 60 days of a complete application (Gov. Code §66317) |
| Solar PV required? | No | No — additions follow the Energy Code's addition rules | Yes for new detached ADUs unless an exception applies; no for attached ADUs and conversions |
| Property tax | Depends on scope — ask the assessor for your project | Only the new addition is reassessed | Only the new ADU is reassessed |
| Disruption to daily life | Highest — work happens inside the house | Medium — depends on where it attaches | Lowest for a detached ADU |
Five questions that usually decide it
- Who will use the space? Your own household points to a remodel or addition. Someone who needs independence — a parent, an adult child, a tenant — points to an ADU.
- Do you need a separate kitchen and entrance? If yes, it's an ADU.
- How much yard are you willing to give up? A second-story addition or a garage conversion keeps the yard; a detached ADU uses it.
- How will you use it in ten years? An ADU can change from family to rental and back. An addition stays part of the house.
- Is the existing house in good shape? If the foundation, electrical, or plumbing need work anyway, a remodel or addition can fix them at the same time.
Why we can give you a neutral answer
Most companies sell one of these. ADU companies sell ADUs; remodelers sell remodels. We design and build all three, so in the first consultation we can compare them for your lot and budget — and recommend the one that makes sense, not the one we happen to sell.
Details on each: Remodeling · Room additions · ADUs
More questions
If your parents want independence — their own kitchen, entrance, and routine — an ADU usually works better. If they need daily help and want to be part of the household, a ground-floor addition with an accessible bedroom and bathroom can be the better fit. We design both and can compare them for your lot.
Per square foot, remodeling existing space is usually less than building new space, because the foundation, roof, and walls already exist. But if the remodel can't deliver the room you need, an addition may be the better value. We price options side by side during design.
Both are new construction, and in both cases only the new construction is reassessed under Proposition 13; the existing house and land keep their assessed base value.
Yes, and it's often more efficient: one design, one permit set, and one construction period. It also lets you fix older systems in the existing house while walls are already open.