The Eaton Fire began January 7, 2025, and destroyed or damaged thousands of structures across Altadena and the surrounding foothills.

More than a year on, owners are spread across every stage of this process. Some are still clearing. Some are in plan check. Some are framing. What most have in common is that the permitting path they’re navigating doesn’t resemble anything they’d dealt with before.

This covers what makes an Altadena rebuild specific, and where the decisions that affect your timeline actually sit.

Altadena Is Unincorporated LA County

This one fact reorganizes everything downstream.

Altadena is not part of the City of Los Angeles. It’s not part of Pasadena. It’s unincorporated Los Angeles County, which means rebuild permits run through the County rather than LADBS.

In practice:

• LA County Regional Planning reviews zoning compliance, site plan accuracy, setbacks, height restrictions, and the like-for-like comparison against your original structure
• LA County Building and Safety handles structural and code review, issues plan check corrections, and clears the permit once those are resolved
• LA County Public Works administers the process
• The County’s electronic permitting system is separate from the City’s

Most of what’s been written about rebuilding in Pacific Palisades describes a different agency track entirely. Owners who apply those procedures to an Altadena property tend to discover the mismatch at intake, after they’ve already built expectations around it.

Two other agencies come up regularly here. LA County Public Health handles septic systems and wells, which are common in upper Altadena. And water service in parts of Altadena runs through private water companies rather than a single municipal utility, so utility coordination is its own step.

The One-Stop Permit Center

LA County established the Altadena One-Stop Permit Center as the intake point for rebuild permitting.

The Board of Supervisors later approved a motion creating a Unified Permitting Authority within that center, intended to establish a single point of accountability able to make permitting decisions across departmental boundaries and cut the bottlenecks between departments.

Each permit still routes to its originating agency. The center functions as the front door, and it offers consultation appointments.

Hours, appointment availability, and procedures have changed over the course of the recovery. Confirm current details with the center directly rather than relying on anything published earlier.

The Like-for-Like Decision

LA County defines a like-for-like rebuild as reconstructing a structure of the same size in the same location. That definition matters because like-for-like rebuilds access the streamlined pathway.

Expanding square footage, changing the footprint, moving the structure on the lot, or changing the use generally shifts the project to standard review, with the full zoning analysis and timeline that involves.

Some owners want the house they had back. Others don’t want to rebuild the same house at all, for reasons that are entirely their own. Both are legitimate. What matters is making that decision early and knowingly, while it’s still a design conversation rather than a redesign.

Chapter 7A Fire-Hardening

Rebuilds in fire hazard severity zones must meet California Building Code Chapter 7A requirements for wildfire exposure. These govern roofing assemblies, exterior wall materials, vent design and placement, window glazing, decking materials, and eave construction.

Most homes lost in the Eaton Fire predated these requirements. The replacement house has to meet them, and that affects material selection, detailing, and cost.

Treat it as a design input from the first sketch rather than a compliance item bolted on at the end. Retrofitting Chapter 7A compliance into a finished design is more expensive than designing to it from the start.

What the Timeline Looks Like

Permitting has been the phase that surprised owners most.

Planning review for a straightforward rebuild has generally run several weeks. Building and safety review adds more, depending on correction volume. The two run parallel, each on its own clock. Historic and hillside cases take longer than straightforward ones.

Correction rounds are normal and rarely one-and-done. A correction letter is not a sign that something has gone wrong with your project. It’s a standard part of plan check, and every project in the queue gets them.

The other constraint owners hit is contractor availability. Regional capacity across the LA Basin is stretched thin, with rebuilds in Altadena, Pacific Palisades, and Malibu all competing for the same licensed crews. Owners who lock in a contractor early are in a better position on schedule than those who wait for a permit first.

Reported permit figures and timelines have shifted throughout the recovery. Check current conditions with LA County rather than trusting numbers published at any single point, including here.

Practical Sequencing

Start design and permitting alongside insurance resolution. These run concurrently. Beginning design does not commit you to build, and waiting for a settlement before starting means the two clocks run end to end instead of together.

Confirm your pathway before design. Like-for-like or standard review determines what analysis the project needs.

Resolve site conditions early. Debris clearance, soil testing, septic evaluation, and geotechnical work all precede or run alongside design.

Identify every clearance the parcel requires. Fire, public health, water utility, grading, and historic preservation review where it applies. A building permit can’t be issued while any one of them holds.

Submit complete. Intake staff check completeness before a package reaches a plan checker. An incomplete submission doesn’t enter the queue — it waits.

Fee Relief

LA County has committed to fee waivers and reductions for fire rebuild permits. Eligibility and policy have developed over the course of the recovery.

Confirm current fee policy with the One-Stop Permit Center before you build it into a budget.

How We Approach Altadena Work

We’ve completed more than 1,500 projects across Los Angeles County over more than ten years, and we’ve submitted plans across virtually every building department in the county, including unincorporated LA County.

Our method begins with diagnosis. Before design starts, we identify every overlay, ordinance, specific plan, and review body that touches the parcel, and give you a real read on what the property allows.

On a rebuild, that means settling four things before design commits: the applicable pathway, the fire-hardening requirements, every parallel clearance the property needs, and any site-specific constraints. Getting those wrong isn’t a drafting error. It’s weeks of review time.

We call this inspector-led design. Our principal spends part of every week reviewing buildings as a working code inspector, so our plan sets are organized around what a plan checker will actually ask.

The Bottom Line

An Altadena rebuild runs through LA County, not LADBS. The like-for-like decision shapes your review path. Chapter 7A applies regardless of what the original house was built to. Clearances from health, fire, and utility agencies proceed alongside the building permit, and any one of them can hold it.

Recovery programs and procedures continue to develop. Verify current requirements directly with LA County and the Altadena One-Stop Permit Center.

Rebuilding in Altadena? Design 1 Studio Inc. provides a free initial consultation covering pathway, site conditions, and the permitting requirements affecting your parcel. Call +1 626-214-8651.

Unpermitted work does not resolve itself. It waits.

It surfaces when you sell. When you refinance. When an appraiser measures the house, and the number doesn’t match the record. When a city inspector notices that what’s standing on the lot isn’t what the file says should be there.

Owners usually arrive at that moment expecting the worst. In our experience at Design 1 Studio, the practical position is better than they assume. Most unpermitted work in Los Angeles County can be legalized. The process is defined, the path is well established, and the outcome is usually a permit rather than a demolition order.

What it isn’t is automatic. Legalization requires documenting what actually exists, evaluating it against current requirements, and carrying an application through permit and inspection. That takes real work.

But it’s work with a known endpoint, which is more than can be said for leaving it alone and hoping the question never gets asked.

What Counts as Unpermitted Work

Unpermitted work is construction completed without a building permit. In LA County it commonly takes these forms:

• Additions to the house built without a permit
• Garage conversions to habitable space
• Enclosed porches and patios
• Converted attic or basement space
• Second dwelling units built outside the permitting process
• Structural, electrical, or plumbing alterations performed without inspection

Unpermitted does not automatically mean unsafe or poorly built. Some unpermitted additions are well constructed and would meet code with minimal modification. Others carry structural, electrical, or plumbing deficiencies. The only way to know is evaluation against current code requirements.

What unpermitted work always means is a legal and financial liability. It affects property value, insurability, and the ability to sell or refinance.

The Legalization Process

Step One: As-Built Documentation

Someone has to document what actually exists. We survey the existing construction and prepare as-built drawings recording dimensions, materials, structural conditions, and electrical and plumbing configurations.

This step gets underestimated constantly. Unpermitted construction usually departs from any drawing that was ever produced — often from any drawing that ever existed. Assumptions carried forward from here become errors that surface at plan check, months later, at the worst possible time.

We measure. We don’t assume.

Step Two: Code Compliance Analysis

We evaluate those as-built conditions against current building code, zoning requirements, and local jurisdiction standards. The analysis sorts everything into three buckets: what complies, what doesn’t, and what has to change.

Zoning belongs in this step, and owners often don’t expect it. An addition can be built well, meet every structural requirement, and still sit inside a required setback. Or exceed the allowable floor area for the lot. Or break a height limit.

Those are land use problems, not construction defects, and they get resolved differently. Sometimes they’re the harder half of the project.

Step Three: Plan Preparation

We prepare plans documenting existing conditions and specifying the modifications required for compliance, then submit them to the building department as a permit application to legalize the work.

Step Four: Permit and Inspection

The building department reviews the plans and issues a permit. Inspections verify the work meets code. Required modifications get completed and re-inspected until it passes.

One thing to expect: inspecting existing construction sometimes means opening walls or ceilings. An inspector can’t sign off on framing, wiring, or plumbing they can’t see. Plan for it rather than being surprised by it halfway through.

The ADU Pathway

If the unpermitted work is a second dwelling unit, a separate and often more favorable path may apply.

California’s Assembly Bill 2533, effective January 1, 2025, expands the state’s amnesty framework for unpermitted ADUs and JADUs built before January 1, 2020. It requires jurisdictions to provide a legalization process, prohibits denial based solely on code violations absent a genuine health or safety risk, and applies habitability standards rather than full current-code retrofit requirements. The categorical disqualifier is classification as substandard under Health and Safety Code Section 17920.3.

The City of Los Angeles operates AB 2533 alongside its Unpermitted Dwelling Unit Ordinance, Ordinance 184,907, effective 2017, which requires legalized units under that local pathway to provide at least one low or moderate income unit per UDU. LADBS accepts AB 2533 applications without that covenant.

Determining which pathway applies to a specific unit is part of the analysis, and it materially affects what the owner is obligated to provide.

Questions Owners Ask

Will the city penalize me? In most cases the building department’s primary interest is bringing the work into compliance rather than penalizing the owner. There may be fees, and some jurisdictions assess double permit fees for unpermitted work. The process is designed to resolve the issue. Verify current fee policy with your jurisdiction.

Does everything need to be demolished? No. Demolition is typically a last resort, required only when the work fundamentally cannot meet code. Most unpermitted work can be legalized with modifications ranging from minor to moderate.

What if the previous owner did the work? The current property owner is responsible regardless of who performed it. Purchasing a property with unpermitted additions transfers the obligation.

Can I sell without addressing it? Disclosure obligations apply in California real estate transactions. Unpermitted work is increasingly flagged by assessors, appraisers, and buyers’ agents, and it affects financing and negotiation.

How long does it take? It depends on the scope of the work, the modifications required, the jurisdiction, and the correction rounds at plan check. A firm answer requires evaluating the specific property.

Why This Is Worth Doing Before You Have To

Owners who start legalization on their own timeline have options that owners in an active transaction do not. There is time to evaluate, to sequence modifications, and to work through plan check without a closing date applying pressure.

Owners who discover unpermitted work thirty days before a sale closes are managing the same process under conditions that remove most of the flexibility.

How Design 1 Studio Handles This Work

We’ve prepared as-built documentation, code compliance analysis, and legalization plans on properties across Los Angeles County over the past decade. More than 1,500 projects total, and we’ve submitted to virtually every building department in the county — LADBS, the San Gabriel Valley cities, South Bay and coastal jurisdictions, the Westside, and unincorporated LA County including Altadena and Hacienda Heights.

That range matters more on legalization work than most owners expect. Every jurisdiction handles unpermitted construction differently — what they’ll accept as as-built documentation, how they treat fees, which department signs off first. A process that works in Alhambra isn’t the process in Santa Monica.

What you get from us is an honest read. What the existing work actually is. What it takes to legalize it. Whether the path is workable at all.

Where a structure can’t reach compliance, we say so. That’s not a pleasant conversation, but it’s a cheaper one than the alternative.

Conclusion

To bring unpermitted work up to code, you document what exists, evaluate it against current requirements, prepare plans specifying the modifications needed, and carry the application through permit and inspection. If the work is a pre-2020 second unit, the AB 2533 amnesty framework may apply and change the requirements meaningfully.

The problem does not improve by waiting. It becomes more urgent when a transaction is pending.

Carrying unpermitted work on a Los Angeles County property? Design 1 Studio Inc. provides a free initial consultation covering existing conditions, applicable pathways, and a realistic assessment of the work required. Call +1 626-214-8651.

There are a lot of unpermitted second units in Los Angeles County. Converted garages. Backyard cottages. Mother-in-law suites. Enclosed spaces that quietly became dwellings decades ago and have been occupied ever since.

For years, the owners of those units faced a bad choice. Leave the unit undisclosed and carry the liability, or attempt legalization under rules that were inconsistent, expensive, and often ended in a demolition order.

California changed that. Assembly Bill 2533, authored by Assemblymember Juan Carrillo and signed September 28, 2024, took effect January 1, 2025. It expands the state’s ADU amnesty program, and for owners of pre-2020 units, it opened a path that didn’t reliably exist before.

What AB 2533 Actually Does

The law requires jurisdictions to create a legalization process that provides permits for previously unpermitted ADUs and JADUs, unless the unit is substandard under Health and Safety Code Section 17920.3.

Four provisions carry the weight:

• Eligibility now reaches units built before January 1, 2020. Earlier frameworks stopped at January 1, 2018. AB 2533 moved the date, bringing units built between 2018 and 2020 into eligibility.
• Cities cannot deny a permit based solely on code violations. Denial requires that the violation create a genuine health or safety risk. That reverses the old dynamic, where any deviation from current code could block legalization outright.
• Health and safety standards govern, not full current-code compliance. Local agencies apply habitability standards rather than requiring the unit to be retrofitted to every provision of current building code. This is the change that makes legalization financially possible for a lot of owners.
• Applicants are not penalized for having an unpermitted unit. The framework is built around bringing units into compliance, not punishing the people who come forward.

The one categorical disqualifier is classification as substandard under Section 17920.3, which covers serious safety hazards.

Who Qualifies

You may be eligible if:

• The ADU or JADU was built or converted before January 1, 2020
• The unit is not substandard under Health and Safety Code Section 17920.3
• The unit sits on a parcel with an existing primary dwelling

What doesn’t disqualify you: having no permits at all, an active code enforcement case, or an existing Notice of Violation. Those are the exact situations the law was written to resolve.

One Important Limit

This is amnesty for a pre-existing inventory. It is not forward-looking permission.

Building an unpermitted unit today creates no eligibility for future amnesty. What it creates is code enforcement exposure, retroactive fees, full current-code retrofit costs, and insurance gaps — with none of the AB 2533 protections attached. If you’re considering a new ADU, permit it.

Local Implementation Varies, and in LA It Matters

State law sets the floor. Jurisdictions keep real flexibility in how they implement, and in Los Angeles that flexibility has teeth.

The City of Los Angeles runs AB 2533 alongside its pre-existing Unpermitted Dwelling Unit Ordinance, adopted as Ordinance 184,907 and effective in 2017. The UDU Ordinance is a parallel local pathway, and it requires legalized units to provide at least one low or moderate income unit per UDU. LADBS accepts AB 2533 applications without that affordability covenant.

Read that twice if you own a property in the City of LA. Two pathways exist. They carry materially different obligations, and choosing the wrong one commits you to a covenant you may not have needed to accept.

Unincorporated LA County and each incorporated city administer their own implementation. Confirm current requirements with whichever jurisdiction has authority over your parcel before anything gets filed.

What the Process Requires

Legalization generally runs in four steps.

• As-built documentation. We survey the existing construction and prepare drawings recording what was actually built — dimensions, materials, structural conditions, electrical and plumbing configurations. Everything downstream rests on this being accurate.
• Code compliance analysis. We evaluate those as-built conditions against applicable health and safety standards, zoning requirements, and local jurisdiction standards. The analysis sorts the unit into three categories: what complies, what doesn’t, and the required modifications.
• Plan preparation and submission. We prepare plans documenting existing conditions and specifying the modifications needed for compliance, then submit them as a permit application.
• Inspection and correction. Inspectors assess the unit and identify necessary corrections. Modifications get completed and re-inspected until the work passes. On final inspection and release of all department holds, the unit is legalized.
• Expect that inspection to require opening walls or ceilings in places. An inspector can’t verify framing, wiring, or plumbing they can’t see, and anticipating that is easier than being surprised by it.

Why Owners Do This

• Property transactions. Unpermitted work surfaces during a sale or refinance. Appraisers, lenders, and buyers’ agents flag discrepancies between recorded square footage and what’s standing on the lot.
• Unpermitted structures create coverage complications.
• Tenant and landlord clarity. A permitted unit sits inside landlord-tenant law without the ambiguity an unpermitted one carries.
• Property value. A legalized unit is a documented asset. An unpermitted one is an undisclosed liability that transfers to whoever buys the property next.

Questions We Get

Will the city penalize me for coming forward? The framework is structured against that outcome. AB 2533 prohibits penalizing applicants for having an unpermitted unit and prohibits denial based solely on code violations absent a health or safety risk.

Will I have to demolish it? Demolition is a last resort, generally reached only where the work fundamentally cannot meet health and safety standards. Most unpermitted work can be legalized with modifications ranging from minor to moderate.

What if the previous owner built it? The current owner is responsible regardless of who did the work. Buying a property with unpermitted construction transfers the obligation to you.

Does unpermitted mean unsafe? No. Some unpermitted units are well-built and meet standards with minimal modification. Others carry real structural, electrical, or plumbing deficiencies. Evaluation against applicable standards is the only way to know which one you have.

What about units built after January 1, 2020? Those fall outside AB 2533 and follow the standard legalization path, which is a different and generally more demanding process.

How We Approach Legalization

We’ve prepared as-built documentation, code compliance analysis, and legalization plans on properties across Los Angeles County over more than a decade. We’ve been designing ADUs since 2017 and have completed hundreds of ADU projects.

The work starts with an honest evaluation of the unit and the parcel. We identify which pathway applies, what the jurisdiction specifically requires, and what modifications the unit will need to pass. You get a real number and a real assessment before you commit to anything.

Where a unit can’t reach compliance, we say so. We’d rather tell you that at the start than produce drawings that were never going to move.

The Bottom Line

AB 2533 gives owners of pre-2020 unpermitted units a defined, health-and-safety-based path to legalization that earlier frameworks didn’t reliably provide. Eligibility is broad. Denial grounds are narrow. The process is built around compliance rather than penalty.

Implementation varies by jurisdiction, and in the City of Los Angeles, the interaction between AB 2533 and the UDU Ordinance deserves attention before an application is filed. Programs and procedures continue to develop, so verify current requirements directly with your jurisdiction.

The problem doesn’t improve by waiting. It gets urgent when a sale is pending.

Have an unpermitted unit on your Los Angeles County property? Our first consultation is free. We’ll look at the unit, tell you which pathway applies, and give you a straight assessment of what legalization takes. Call +1 626-214-8651.

We get this question often, and the short answer for most Accessory Dwelling Unit projects in California is no. But the longer answer is where the useful information lives, because a handful of conditions change it, and in our experience misreading those conditions is expensive.

Do you need an architect for an ADU? For a typical detached or attached woodframe ADU on a standard LA County lot, California law does not require one. For an ADU on a hillside parcel inside a Specific Plan area, inside an HPOZ, or on a lot where the unit count pushes past statutory limits, the picture changes, and that’s the conversation we’d rather have with you before you’ve committed to a design.

The Statute That Governs the Answer

California Business and Professions Code Section 5537 exempts specific building categories from the requirement that a licensed architect prepare the plans. The exemption covers single-family dwellings of woodframe construction not more than two stories and basement in height, and multiple dwellings containing no more than four dwelling units under the same construction and height limits.

Nearly every standard ADU sits inside that exemption. A detached backyard unit, a garage conversion, a JADU carved out of existing space, an attached unit sharing a wall with the primary dwelling, all typically woodframe, all typically single story or two, all within the four-unit ceiling.

The Structural Portion Is a Separate Question

Section 5537 subsection (b) requires that any portion of an exempt structure deviating from substantial compliance with conventional woodframe framing requirements in Title 24 be prepared by or under the responsible control of a licensed architect or registered engineer, and carry that licensee’s stamp.

This is why the honest answer to “do you need an architect for an ADU” is rarely a clean no. You generally need licensed engineering for the structural scope even when the architectural design does not require an architect. Foundation design, framing, lateral systems, and hillside conditions routinely bring an engineer in.

When an ADU Project Does Require an Architect

We look for these conditions early, because each one moves a project outside the Section 5537 exemption:

• More than four dwelling units. The exemption covers multiple dwellings containing no more than four units. Multi-ADU strategies on a lot that already holds a duplex or triplex can cross that line, and the count is easy to lose track of when a project grows during design.
• Three or more stories. The statute permits two stories and a basement. Two-story ADUs stay exempt. A third level does not, and we’ve seen owners add one late in design without realizing what it triggers.
• Construction outside woodframe. The exemption is written specifically for woodframe construction. Steel, concrete, and masonry systems fall outside it regardless of the building’s size.
• Framing outside conventional limits. Subsection (b) requires that any portion deviating from substantial compliance with conventional woodframe framing requirements in Title 24 be prepared by, or under the responsible control of, a licensed architect or registered engineer, carrying that licensee’s stamp. Long spans, irregular geometry, and unusual load paths commonly land here.
• Commercial occupancy conversion. Converting a commercial structure to residential use brings change-of-occupancy analysis that sits outside the residential exemption entirely.

What Actually Determines Whether Your ADU Gets Approved

Here is the part owners underestimate. The licensure question is usually the easy one. The approval question is harder, and it turns on the parcel rather than the professional.

Zoning and Overlay Analysis

Before a floor plan means anything, someone has to establish what the lot allows. That means identifying the base zone and every layer sitting on top of it: overlay zones, specific plans, hillside ordinance boundaries, preservation overlays, coastal zone designations, and any zoning administrator determination affecting the property.

Plans fail plan check when this step is skipped or done superficially. The designer checked the base zone but missed an overlay or a specific plan that changes the development standards. The plans were drawn around the wrong parameters, and every downstream decision inherits the error.

Ministerial Versus Discretionary Review

Most ADU applications in California move through ministerial review. State law requires local agencies to act on a complete ADU application within 60 days. Ministerial review measures the project against objective standards, and a compliant project must be approved.

Discretionary review works differently. A board, commission, or planning officer evaluates the project against subjective standards including massing, neighborhood character, architectural compatibility, and historical context. An ADU inside an HPOZ, a Specific Plan area, or a scenic corridor can land in that environment, and code compliance alone will not carry it.

Hillside Conditions

Slope changes everything about an ADU. Grading quantities, retaining wall design and setbacks, drainage, access, and the Baseline Hillside Ordinance floor area and height limits in City of Los Angeles hillside areas all come into play.

We work across the City of LA hillside areas, including one ADU at the toe of a slope where prior firms said the retaining wall setbacks made the project impossible. The setbacks were real. The reading of them was wrong. The project was approved as designed.

Your Realistic Options

Option One: Pre-Approved Standard Plans

LADBS operates a Standard Plan Program in which private licensed architects and engineers prepare ADU designs that LADBS pre-approves for compliance with the Building, Residential, and Green Codes. When an applicant selects an approved Standard Plan, LADBS reviews site-specific factors including zoning compliance and foundation requirements.

This route removes the design step for owners whose lot and program fit an available plan. It does not remove the site-specific review, and it does not help on parcels with unusual conditions or discretionary review requirements.

Option Two: A Building Designer

A building design firm prepares custom construction documents within the Section 5537 exemption and coordinates the licensed engineering the project requires. This is the common path for custom ADUs on lots where a standard plan does not fit.

Option Three: A Licensed Architect

Appropriate when the project falls outside the exemption, or when an owner wants that specific professional relationship.

Questions Owners Ask

Will using a building designer slow down plan check?

What affects plan check is the completeness and accuracy of the submitted set, not the title of who prepared it. Correction cycles come from zoning errors, classification mistakes, and incomplete documentation.

Does a garage conversion need the same analysis?

Yes. Conversions carry their own issues around existing conditions, foundation adequacy, fire separation, and egress. The existing structure has to be evaluated, not assumed.

What about an unpermitted unit already on the property?

That is a legalization question governed by separate provisions, including California’s amnesty framework for units built before January 1, 2020. It runs on a different track from new ADU construction.

How Design 1 Studio Handles ADU Projects

We’ve been designing ADUs since 2017 and have completed hundreds of ADU projects across Los Angeles County. We handle detached units, garage conversions, junior ADUs, two-story units, and multi-ADU strategies.

Our approach begins with diagnosis. Before a floor plan is drawn, we identify every overlay, ordinance, specific plan, and review body that touches the parcel, so you get a clear read on what the property will and will not allow. On a Topanga property in the Santa Monica Mountains Coastal Zone, that analysis established the proposed ADU could not survive the GSA limits and Coastal Zone overlay. We wrote the analysis the owner needed before any drawings were produced. That is also part of the work.

The Bottom Line

Do you need an architect for an ADU? Usually not. Under California Business and Professions Code Section 5537, plans for woodframe residential buildings up to two stories and basement, containing four or fewer dwelling units, may be prepared without a licensed architect. Most ADUs sit comfortably inside those limits. You will generally still need licensed engineering for the structural scope, and subsection (b) requires an architect or registered engineer to stamp any portion that departs from conventional woodframe framing under Title 24.

The more consequential question is whether whoever prepares your plans has read your parcel correctly. The licensure question is usually settled in a sentence. The zoning, the overlays, and the review path take real work, and that is where projects stall.

Considering an ADU in Los Angeles County? Our first consultation is free. We’ll evaluate the property, identify the constraints that apply, and give you a clear read on feasibility before you commit to a design. Call +1 626-214-8651.

You’re planning a home addition, an ADU, or a ground-up house in Los Angeles County. Someone tells you to hire an architect. Someone else says a building designer can handle it. A third person tells you the city won’t accept plans unless an architect stamps them.

Only one of those is reliably true, and it isn’t the third one.

The architect vs building designer question is one of the most common sources of confusion we encounter, and it costs people money in both directions. Some owners hire a licensed architect for a project that never required one. Others hire an unqualified drafter for a project that legally required a stamp.

The difference isn’t a matter of opinion or reputation. It’s written into California law. Once you understand the statute, the decision gets a lot simpler.

The Legal Line: Business and Professions Code Section 5537

California regulates the practice of architecture through Business and Professions Code Chapter 3. Section 5536 makes it a misdemeanor for an unlicensed person to prepare plans for a building, with one qualifier that changes everything: except for the buildings described in Section 5537.

What the Exemption Covers

Under subsection (a), the chapter does not prohibit any person from preparing plans, drawings, or specifications for:

• Single-family dwellings of woodframe construction, not more than two stories and basement in height
• Multiple dwellings containing no more than four dwelling units, woodframe, not more than two stories and basement in height

Read that carefully, because it covers an enormous share of residential work in LA County, including single-family homes, duplexes, triplexes, fourplexes, detached ADUs, and second-story additions.

Woodframe, within two stories plus basement? California law does not require a licensed architect to prepare the plans.

The Exception Inside the Exemption

Subsection (b) adds a condition that matters. If any portion of an otherwise-exempt structure deviates from substantial compliance with conventional woodframe framing requirements in Title 24, the building official must require that portion to be prepared by, or under the responsible control of, a licensed architect or registered engineer carrying that licensee’s stamp and signature.

In practice, the structural scope routinely goes to a licensed engineer even when the architectural design doesn’t require an architect. That’s normal, expected, and built into how most residential projects in LA County get assembled.

What a Licensed Architect Is

A licensed architect in California has completed an accredited education path, a documented experience requirement, and the Architect Registration Examination, and holds a current license from the California Architects Board. The stamp is legally required on categories of buildings the Section 5537 exemption doesn’t reach.

Projects That Require an Architect or Engineer

• New commercial buildings and additions to existing commercial buildings
• Structures exceeding two stories and a basement
• Multi-unit residential buildings with more than four dwelling units
• Assembly, educational, factory, hazardous, and institutional occupancy groups
• Structural alterations outside conventional framing limits
• Steel, concrete, or masonry construction outside the woodframe exemption

If your project sits in any of these categories, the question is already answered by statute. You need the licensed professional.

What a Building Designer Is

A building designer prepares construction documents for projects inside the Section 5537 exemption and coordinates licensed engineering for the portions that require a stamp.

The discipline sits close to the construction document, the plan check counter, and the field. That proximity is the substance of the difference. A practice organized around permitting spends its working hours on:

• Zoning analysis, overlay identification, and development standard verification
• Site planning, setbacks, height envelopes, and floor area calculations
• Complete construction document sets coordinated across structural, mechanical, electrical, and plumbing
• Plan check submission, correction response, and resubmission through permit issuance
• Discretionary review preparation for HPOZs, Specific Plans, and design review boards

We operate as a building design firm rather than an architecture practice, and that’s a deliberate choice. Our drawings are documents that get buildings built, not portfolio pieces.

Three Ways Owners Get This Decision Wrong

Mistake One: Assuming a Stamp Solves Zoning

A stamp certifies that a licensed professional took responsibility for the documents. It does not certify that the project complies with a Specific Plan, sits correctly inside a hillside ordinance envelope, or accounts for an overlay zone.

Plans get rejected at plan check for reasons that have nothing to do with who signed them:

• Incomplete zoning research
• Wrong building type classification
• Overlooked overlay zones
• Unfamiliarity with a jurisdiction’s submittal requirements

A stamped set with the wrong setback assumption fails exactly the same way an unstamped one does.

Mistake Two: Treating Every Project as Exempt

The exemption has hard edges. Owners get into trouble when a project quietly crosses one:

• A fifth dwelling unit added to a four-unit plan
• A third story added during design development
• A change of occupancy converting a residential structure to commercial use
• Framing that departs from conventional woodframe tables

Any of those moves a project out of the exemption. The time to catch it is during pre-design diagnosis, not at plan check.

Mistake Three: Choosing by Title Instead of Project Fit

The more useful question isn’t which title someone holds. It’s whether they’ve permitted your project type, in your jurisdiction, recently.

A designer fluent in LADBS submittal requirements may be unfamiliar with Sierra Madre’s design review process. Every city in LA County maintains its own plan check expectations, submittal requirements, and local code amendments.

A Practical Way to Decide

Work through these in order:

1. Identify construction type and height. Woodframe, two stories plus basement or less? You’re likely inside the exemption.
2. Count the dwelling units. Four or fewer keeps the residential exemption available.
3. Confirm the occupancy. Commercial, assembly, and institutional occupancies fall outside it.
4. Check the framing. Anything departing from conventional woodframe requirements pulls in an engineer for that portion.
5. Map the review path. Determine whether the parcel triggers discretionary review through an HPOZ, Specific Plan, hillside ordinance, historic commission, or coastal overlay.

Step five is where projects most often stall. Ministerial review measures a project against objective standards, and compliant plans must be approved. Discretionary review puts the project in front of a board evaluating massing, neighborhood character, and compatibility.

In that environment, code compliance is the floor. Not the approval.

How We Approach It

We’ve completed more than 1,500 residential and commercial projects across Los Angeles County over more than ten years. A substantial share arrived already in trouble — plans rejected at plan check, correction cycles that kept growing, or a designer who ran out of answers.

Our operating principle is inspector-led design. Our principal spends part of every week reviewing buildings as a working code inspector, and that perspective shapes how we draw and organize plans.

Before design begins, we identify every overlay, ordinance, specific plan, and review body touching the parcel, so you get a real read on what the property allows.

We also state plainly what we don’t promise. Some projects survive discretionary review and some don’t. When a parcel can’t accept what an owner wants, we say so before drawings are produced.

Answering the Question

The architect vs building designer decision comes down to four things: project scope, construction type, occupancy, and the review path your parcel triggers.

For woodframe residential work up to two stories and four units, California law leaves the choice to you. Beyond those limits, the statute decides.

What doesn’t vary is the requirement that whoever prepares your plans understands the jurisdiction, reads the zoning correctly, and organizes documents for the person reviewing them.

Working through a residential or commercial project in Los Angeles County? 

Our first consultation is free. We’ll diagnose the parcel, the jurisdiction, and the review path before any design work begins. Call +1 626-214-8651.