Alteration + new area · Los Angeles
Home additions that connect new space to the house you already have.
An addition is not a small new house attached to an old one. The useful question is where new area can join the existing structure without creating unresolved circulation, structural or building-system conflicts.
Concept imagery · Not represented as completed RSA work
Project fit
When an addition is the right project
A sound starting point when
- The existing house has useful structure and rooms worth retaining.
- A defined expansion can solve the space problem without reorganizing the entire residence.
- The lot and review path can accommodate added floor area, height and construction access.
Compare another path when
- If changes reach most rooms and systems, compare a whole-home remodel.
- If the existing structure cannot support the program, compare a ground-up custom home.
- If the goal is an independent dwelling, use the ADU pathway rather than treating it as an ordinary addition.
Scope decisions and deliverables
Existing-condition record
Document the legal floor plan, structure, roof, levels, utilities and the connection area before assuming what can stay.
Deliverable
Measured existing-condition plan and permit-history question list.
Expansion direction
Compare rear, side and second-story options against setbacks, lot coverage, circulation, daylight, privacy and construction impact.
Deliverable
Option comparison with the reason one direction advances.
Old-to-new coordination
Resolve foundations, lateral system, roof drainage, waterproofing, heating and cooling, electrical and plumbing at the connection.
Deliverable
Coordinated permit set identifying retained and new work.
Occupied-home strategy
Decide whether the house can be occupied, what must be isolated and when services will be interrupted before construction sequencing is set.
Deliverable
Access, protection, temporary-service and decision schedule.
Deliverables table
Existing-condition record
- Decision it supports
- Which legal rooms, structure, levels, roof forms and services can anchor the addition design.
- What remains open
- Concealed framing, foundations and service capacity remain open until investigation resolves them.
Expansion option comparison
- Decision it supports
- Whether a rear, side or upper-level direction best fits the property and homeowner priorities.
- What remains open
- Agency or consultant confirmation not yet received stays marked as a dependency.
Old-to-new coordination set
- Decision it supports
- How retained and new structure, envelope, drainage and building systems connect.
- What remains open
- Field conditions that cannot be verified without opening the building are not represented as known.
Phasing and scope basis
- Decision it supports
- What can be isolated, when services are interrupted and what the construction proposal includes.
- What remains open
- Temporary work, allowances and occupancy assumptions remain separately visible until agreed.
What changes the scope
The legal plan or permit history does not match the house on site.
- Scope effect
- The retained-area basis and approval path may change before addition work can be defined.
- How it is resolved
- Reconcile the record with the responsible jurisdiction instead of designing from an unverified plan.
Investigation finds inadequate foundation, lateral capacity, roof support or a difficult connection.
- Scope effect
- Structural work can extend beyond the new room or floor area.
- How it is resolved
- Update engineering and identify the affected existing work before revising the proposal.
Added area requires electrical, heating/cooling, sewer, water or drainage upgrades.
- Scope effect
- Equipment, routes and utility coordination expand beyond the visible addition.
- How it is resolved
- Add the system work to the coordinated drawings and state any capacity confirmation still pending.
The owner changes occupancy, access or finish-continuity requirements.
- Scope effect
- Protection, temporary services, sequencing and work in retained rooms may change.
- How it is resolved
- Revise the phasing basis and identify the added retained-area work before construction starts.
Proposal readiness
An addition proposal needs a verified connection—not only a square-foot target.
Can be defined now
- Measured retained and new work shown separately.
- The selected expansion direction and design basis.
- Consultant, permit and construction responsibilities.
- Protection, access and known service-interruption assumptions.
Must remain explicit
- Concealed conditions at the connection.
- Unconfirmed utility and equipment capacity.
- Agency corrections not yet received.
- Selections or temporary-work decisions still pending.
Decision Room
Turn this project path into a working brief.
Use the same scope logic from this page to compare assumptions, record unresolved conditions and prepare better questions.
Compare paths
If changes reach most rooms and systems, compare a whole-home remodel.
Identify cost drivers
Accurate records for the existing house and any prior additions.
Prepare the permit path
Address, parcel number and any prior permit documents.
Site and design dependencies
- Accurate records for the existing house and any prior additions.
- Structural investigation at the proposed connection.
- Setbacks, lot coverage, height and any design or historic review.
- Electrical, heating/cooling, sewer and water capacity for added area.
- Access for demolition, excavation, material delivery and weather protection.
What to prepare
- 1Address, parcel number and any prior permit documents.
- 2Existing plans or a list of rooms and conditions that must remain.
- 3The problem the added area must solve, not only a target square footage.
- 4Known drainage, foundation, roof or utility issues.
- 5Whether the home must remain occupied during the work.
Questions that shape the decision
- Is an addition reviewed as new construction or an alteration?
- It contains both: newly created area and work where it connects to the existing building. The drawings should identify new, altered and retained work clearly; the responsible agency determines the applicable review for the actual scope.
- When should we consider a second story?
- When ground-level setbacks or open-space priorities constrain expansion, but only after the existing foundation, lateral system, access and temporary weather protection are studied. It is a structural and sequencing decision, not just a floor-plan choice.
- What should be documented before design?
- The legal existing plan, levels, roof and foundation conditions, utility locations, connection area and known permit history. Unknown concealed conditions should stay explicit until investigation resolves them.
Primary sources
- California Building Standards Commission
Current California building-code publications and effective dates.
- California Energy Commission — 2025 Building Energy Efficiency Standards
Energy requirements for newly constructed buildings, additions and alterations under the 2025 standards.
- Los Angeles City Planning — application forms
Official forms for City Planning entitlements and administrative clearances. Building permits are a separate review, and another city or LA County may be the responsible agency.
- City of Beverly Hills — Permit Center Plan Review & Permitting Guide
City guide identifying pre-application consultation for larger projects and the documents used to start plan review. It applies only when Beverly Hills is the responsible jurisdiction.
- City of Beverly Hills — residential submittal requirements
City checklist for residential drawings, surveys and project-specific items. It states that projects vary and may require additional information.
Useful next steps
- Build an addition budgetUse this page to resolve the next decision before fixing the scope.
- Compare contractor proposalsUse this page to resolve the next decision before fixing the scope.
- Follow the project processUse this page to resolve the next decision before fixing the scope.
- Compare whole-home remodelingUse this page to resolve the next decision before fixing the scope.
RSA location
Based in Beverly Hills, serving Greater Los Angeles.
Your next step