Two Story Addition Structural Engineer in Brentwood: Complete Guide to Second Story Additions

**AAA Engineering Design** | Licensed California Structural Engineers | (949) 981-4448 | 8031 Main Street, Stanton, CA 90680

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Adding a second story to your Brentwood home is one of the most impactful investments you can make. Brentwood properties command premium values, and a well-engineered two story addition increases both square footage and resale potential dramatically. But vertical expansions are structurally demanding — your existing foundation, walls, and framing system were not designed to carry the added weight of an entire upper floor. You need a licensed structural engineer with proven experience in second story additions to ensure safety, code compliance, and a finished product that lasts.

AAA Engineering Design has completed hundreds of vertical addition projects across Los Angeles County and Orange County. Our Brentwood clients choose us for our rigorous load path analysis, creative shear wall solutions, and our track record of permit-ready structural packages that sail through LA City Building and Safety review.

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A two story addition structural engineer is a licensed professional engineer (PE) who designs and certifies the structural systems required to safely add a second floor to an existing single-story structure. The structural engineer handles load path analysis, foundation assessment, shear wall design, moment frame design when needed, and all stamped drawings required for building permits.

Every second story addition in Brentwood requires structural engineering. The California Building Code (CBC 2022) and Los Angeles Municipal Code both mandate stamped structural drawings for any work that adds living area above grade. Without a licensed structural engineer, the LA City Building Department rejects permit applications outright. The structural engineer's role is not just bureaucratic — the engineer ensures that the forces from the new upper floor travel safely down through walls, posts, beams, and footings into the ground. A structurally deficient second story addition can cause progressive collapse, excessive deflection, cracked finishes, sticking doors, and catastrophic failure during seismic events.

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Brentwood homeowners have access to a full range of structural engineering services for second story additions, tailored to the specific demands of LA's high-value residential construction market.

**Existing Structure Evaluation.** Before any design work begins, AAA Engineering conducts a thorough assessment of your existing structure. This includes reviewing original construction documents (when available), inspecting the foundation type and condition, evaluating existing wall framing, and assessing the roof-to-wall connection system. In Brentwood, where many homes date from the 1950s through 1980s, we frequently encounter post-and-beam framing systems, older concrete slab foundations, and raised wood foundations that require specific attention before a second story is added.

**Load Path Analysis.** The core of any second story addition is the load path — the route that gravity loads, lateral loads, and seismic forces take from the new roof down to the foundation. AAA Engineering's structural engineers map every load path in detail, identify where the existing structure lacks capacity, and design upgrades that efficiently transfer forces without requiring full gut renovations.

**Foundation Upgrade Design.** Most existing Brentwood homes have foundations sized for a single story. Adding a second story increases tributary loads on footings by 50 to 100 percent. Our engineers design continuous footings, spread footings, and drilled pier systems that bring foundation capacity up to CBC 2022 requirements for the combined structure.

**Shear Wall Design.** Lateral forces from wind and seismic events are resisted by shear walls. In a second story addition, shear walls must be positioned in both the new upper floor and the existing lower floor, aligned to transfer forces vertically to the foundation. AAA Engineering designs shear wall layouts that meet code requirements while minimizing disruption to your floor plan. We use California's Special Seismic Certification System (SEISMIC) software and ASCE 7-22 lateral force procedures for every project.

**Moment Frame Design.** When architectural requirements prevent shear wall placement — open-plan living areas, large windows facing the street — AAA Engineering designs steel moment frames or wood moment frames that provide lateral resistance without solid walls. Moment frames are common in Brentwood renovations where street-facing facades have extensive glazing.

**Holdown and Anchor Bolt Schedules.** Every shear wall panel requires specific holdown hardware and anchor bolts to tie the new structure to the foundation. AAA Engineering provides complete hardware schedules specifying Simpson Strong-Tie or equivalent hardware that meets LA City plan check requirements.

**Permit Package Preparation.** Our permit packages include structural calculations, foundation plans, framing plans, shear wall schedules, connection details, and all required code compliance notes. We coordinate with your architect and contractor throughout the LA City plan check process.

Our residential structural engineering services cover the complete range of single-family and multi-family vertical addition projects in Brentwood and across LA County. For properties requiring seismic upgrades alongside the addition, our seismic retrofitting services provide comprehensive lateral system upgrades.

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The engineering process for a two story addition follows a defined sequence that reflects California's demanding code requirements and LA City's plan check procedures.

**Step 1: Initial Site Assessment (Week 1).** AAA Engineering visits your Brentwood property to conduct a field investigation. We measure existing structural members, inspect the foundation type and condition, check soil conditions where accessible, and document the current structural system. This assessment typically takes 2 to 4 hours on-site and produces a written condition report.

**Step 2: Geotechnical Review (Weeks 1-2).** For most Brentwood properties, we require a soils report from a licensed geotechnical engineer before completing foundation design. Brentwood sits in the Santa Monica Mountains transition zone, with variable soil conditions ranging from competent alluvial deposits to expansive clay zones. The soils report defines allowable bearing pressure, lateral earth pressure parameters, and seismic site classification.

**Step 3: Structural Design (Weeks 2-4).** With site data in hand, AAA Engineering's structural engineers develop the complete structural design. This includes gravity system design (beams, columns, floors, roof), lateral system design (shear walls or moment frames), foundation upgrade design, and connection details. We size every structural member using SAP2000, ETABS, or manual calculations verified by a second engineer.

**Step 4: Construction Document Preparation (Weeks 4-6).** Our CAD technicians produce permit-ready structural drawings coordinated with the architectural drawings. Plans include foundation plan, floor framing plan, roof framing plan, shear wall schedule, hardware schedule, and full structural details. All drawings carry the wet stamp and signature of a California PE.

**Step 5: Plan Check Submittal (Weeks 6-10).** We submit the complete permit package to LA City Building and Safety. LA City typically takes 4 to 8 weeks for initial plan check review. AAA Engineering responds to all plan check corrections promptly, typically within 1 to 2 weeks of receiving comments.

**Step 6: Permit Issuance and Construction Support.** Once permits are issued, AAA Engineering provides construction support services including responding to contractor RFIs, reviewing shop drawings for structural hardware, and performing structural observation visits at key construction milestones (foundation forms, framing completion, shear wall nailing prior to drywall).

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Brentwood presents a specific set of structural engineering challenges that distinguish it from other LA neighborhoods and require specialized knowledge.

**Seismic Zone 4 Demands.** Brentwood lies within 15 miles of multiple major fault systems, including the Santa Monica Fault, the Malibu Coast Fault, and the Verdugo Fault. The 1994 Northridge earthquake caused significant structural damage in Brentwood and neighboring Pacific Palisades, with several unreinforced masonry and soft-story structures suffering partial collapse. Current CBC 2022 requirements mandate seismic design for Site Class C or D soils, which is the dominant condition in Brentwood. AAA Engineering designs all second story additions to meet or exceed CBC 2022 seismic provisions.

**Variable Soil Conditions.** Brentwood's soil profile varies significantly across the neighborhood. Hillside properties near Mandeville Canyon and Rustic Canyon frequently encounter expansive Topanga formation soils and decomposed granite. Flatland properties near San Vicente Boulevard and Barrington Avenue typically sit on Pleistocene alluvium with better bearing capacity. AAA Engineering's foundation designs account for site-specific soil conditions documented in the required geotechnical report.

**Hillside Construction Complexity.** Many of the most desirable Brentwood properties sit on slopes. Second story additions on hillside lots present additional structural challenges: cut-and-fill foundations with differential settlement potential, retaining wall loads that interact with the building foundation, and irregular diaphragm shapes that complicate shear wall design. Our hillside engineering services address these specific challenges with specialized design approaches including grade beams, caissons, and stepped foundations.

**Older Construction Vintage.** A large percentage of Brentwood's single-family housing stock dates from the 1950s and 1960s. These structures were built under older building codes that did not require engineered shear walls, holdowns, or anchor bolts at modern standards. Before adding a second story, AAA Engineering assesses existing lateral resistance and designs the necessary upgrades so the combined structure meets current code.

**Neighboring City Comparisons.** Pacific Palisades properties face similar seismic and slope challenges to Brentwood, plus elevated wildfire risk that affects material selection. Santa Monica has its own building department with slightly different plan check requirements than LA City. Beverly Hills Building and Safety is known for thorough plan check review, and West LA properties under LA City jurisdiction follow the same code as Brentwood. AAA Engineering is familiar with all of these jurisdictions and their specific requirements.

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Structural engineering fees for a two story addition in Brentwood range from $5,000 to $15,000, depending on project complexity, size, and the extent of foundation and lateral system upgrades required.

For more detail on structural engineering cost factors, visit our structural engineering services guide. Our permit engineering services include full coordination with LA City Building and Safety to minimize plan check delays.

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Selecting the right structural engineer for your Brentwood second story addition determines whether your project proceeds smoothly or gets stuck in expensive delays and revisions.

**Verify California PE Licensure.** Every engineer who signs and stamps structural drawings for a Brentwood project must hold a current California Professional Engineer (PE) license in Civil or Structural Engineering. Verify the license at dca.ca.gov. Unlicensed drawings are rejected immediately by LA City Building and Safety.

**Check Los Angeles Building Department Experience.** LA City Building and Safety has specific requirements for structural calculations format, load combinations, and drawing standards that differ from other California jurisdictions. Engineers who primarily work in Orange County or San Diego may not be familiar with LA City plan check procedures, which leads to repeated correction cycles and permit delays. AAA Engineering handles hundreds of LA City permits annually.

**Evaluate Second Story Addition Portfolio.** Ask to see completed permit packages and project photos from comparable second story additions. An experienced engineer should show you projects with similar scope — existing structure evaluations, foundation upgrades, shear wall design — with successful permit outcomes.

**Assess Communication and Responsiveness.** Second story additions involve close coordination between the structural engineer, architect, contractor, and owner. Choose an engineer who responds to emails within 24 hours, attends pre-construction meetings, and provides written responses to contractor RFIs during construction.

**Understand the Full Scope of Services.** Some engineering firms quote low fees but charge separately for plan check responses, construction support, and revisions. AAA Engineering provides all-inclusive fee quotes that cover design, calculations, drawings, plan check support, and standard construction support.

**Beware of Bargain Engineering.** In Brentwood, structural engineering represents 2 to 5 percent of total project construction cost. A second story addition typically costs $400,000 to $900,000 in total construction. Cutting corners on structural engineering to save $3,000 is false economy — inadequate structural design leads to permit rejections, contractor change orders, and structural deficiencies that devalue the property and create liability.

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Brentwood second story addition projects encounter predictable structural challenges that an experienced engineer anticipates and designs around from the start.

**Inadequate Existing Foundation Capacity.** The single most common issue in Brentwood second story additions is an existing foundation that lacks bearing capacity and depth for the added loads. Pre-1960 slab-on-grade foundations in Brentwood are frequently 4 inches thick with minimal reinforcing — inadequate for the increased loads from a second story. AAA Engineering evaluates existing foundation capacity through soil testing and structural calculations, then designs continuous footings, grade beams, or drilled piers to supplement or replace inadequate sections.

**Missing or Inadequate Shear Walls.** Many Brentwood homes from the 1950s and 1960s have minimal lateral bracing. Adding a second story doubles the seismic weight and increases lateral demands dramatically. Finding locations for code-compliant shear walls in an existing floor plan — without destroying the architectural program — requires creative structural solutions. AAA Engineering uses perforated shear wall design, wood structural panel segments, and steel moment frames to provide required lateral resistance within the existing floor plan.

**Split-Level and Irregular Geometry.** Brentwood's hillside properties frequently have split-level floor plans with irregular diaphragm shapes. Irregular diaphragms concentrate shear forces at re-entrant corners and discontinuities, requiring detailed analysis that exceeds simplified code procedures. AAA Engineering performs 3D diaphragm analysis for irregular floor plans to ensure accurate load distribution.

**Soft Story Conditions at First Floor.** Some Brentwood homes have large garage openings or extensive glazing at the front facade, creating a soft story condition where the first floor has substantially less lateral stiffness than the second floor. CBC 2022 requires specific analysis and mitigation for soft story conditions. AAA Engineering addresses soft story issues through steel moment frames at the garage level or moment-resistant columns alongside the large openings.

**Neighbor and View Impact Concerns.** Brentwood homeowners are protective of views and neighborhood character. Second story additions that impact neighboring views trigger discretionary review processes that extend project timelines. AAA Engineering coordinates structural design with architectural massing early in the project to avoid structural systems that constrain building height or setback.

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AAA Engineering Design is the structural engineering firm Brentwood homeowners trust for second story additions that are safe, code-compliant, and buildable.

**Proven LA City Permit Track Record.** We have prepared and successfully permitted hundreds of second story addition structural packages through LA City Building and Safety. Our familiarity with LA City plan check reviewers' preferences and requirements means fewer correction cycles and faster permit turnaround.

**In-House Full-Service Team.** AAA Engineering's team includes licensed structural engineers, CAD technicians, and permit expediters working under one roof. You get seamless coordination between structural design, drawing production, and permit processing — no handoffs between separate firms.

**Brentwood-Specific Expertise.** We understand Brentwood's soil variability, seismic exposure, hillside construction challenges, and the high standards of LA City Building and Safety. Our designs reflect the specific conditions at your Brentwood address, not generic templates.

**Early Involvement Saves Money.** AAA Engineering works best when involved before architectural design is finalized. Early structural input shapes the architecture toward structurally efficient solutions — regular shear wall locations, logical load paths, minimized transfer beams — that reduce both engineering fees and construction costs.

**Fixed-Fee Transparency.** We quote fixed fees for defined scopes of work. No surprises, no hourly billing that runs open-ended. You know your engineering cost before the project begins.

**Post-Construction Support.** After your second story addition is complete, AAA Engineering maintains your project file. If you need structural documentation for refinancing, sale, or future renovations, we provide it efficiently and affordably.

Our foundation engineering services and structural engineering services are available throughout Brentwood and the greater LA area. Learn more about second story addition engineering in our residential structural engineering guide.

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**Jennifer M. — Brentwood (Mandeville Canyon)** "We added a 1,800 SF second story to our 1963 ranch house on Mandeville Canyon Road. AAA Engineering evaluated the existing slab, designed new continuous footings under the bearing walls, and created a shear wall layout that preserved our open-concept kitchen. LA City plan check approved on second submittal. The contractor said the structural drawings were the clearest he had worked from in 20 years. Highly recommended."

**Robert T. — Brentwood (San Vicente Corridor)** "Our 1955 post-and-beam house needed a complete foundation upgrade to support the second story we wanted. AAA Engineering's structural assessment identified exactly which footings needed deepening and where we needed new grade beams. Their calculations were thorough and the plan check went smoothly. We are living in our completed addition now — solid, quiet, no movement at all. Worth every penny."

**Sarah and David K. — Pacific Palisades** "We live just over the hill in Pacific Palisades but chose AAA Engineering based on a neighbor's recommendation. The hillside conditions here are challenging — cut-and-fill foundation, steep lot, expansive soils. AAA designed a stepped foundation system with drilled piers that our soils engineer signed off on immediately. The second story went up without a single structural issue. AAA Engineering is our go-to for any future work."

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Ready to start your Brentwood two story addition? AAA Engineering Design provides structural engineering services for residential and commercial projects across Southern California.

**Phone:** (949) 981-4448 **Address:** 8031 Main Street, Stanton, CA 90680 **Service Area:** Brentwood, Pacific Palisades, Santa Monica, Beverly Hills, West LA, and all of Los Angeles County

Call us to schedule a site visit and structural assessment for your two story addition project.

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**Q: Does every two story addition in Brentwood require a structural engineer?** A: Yes, every second story addition in Brentwood requires stamped structural drawings from a California-licensed PE. LA City Building and Safety rejects permit applications for vertical additions without structural engineering documentation. The structural engineer is responsible for ensuring the existing structure can support the added loads and that the combined structure meets CBC 2022 seismic and gravity requirements.

**Q: How long does structural engineering take for a Brentwood second story addition?** A: Structural design and drawing preparation typically takes 4 to 6 weeks from site visit to permit submittal. LA City plan check adds another 4 to 8 weeks. Total time from engineering start to permit issuance is typically 10 to 16 weeks for a standard project. Complex projects with multiple plan check correction cycles can take 5 to 6 months.

**Q: Will I need a soils report (geotechnical investigation) for my second story addition?** A: Almost always yes. LA City Building and Safety requires a geotechnical report for projects that increase structural loads on the foundation. The soils report provides allowable bearing pressure, liquefaction assessment, and seismic site classification data that the structural engineer uses to design the foundation. Geotechnical investigation typically costs $2,500 to $5,000 and takes 2 to 4 weeks.

**Q: What happens if my existing foundation is inadequate for a second story?** A: AAA Engineering designs foundation upgrades as part of the second story addition project. Typical upgrades include deepening existing footings, adding new continuous footings under bearing walls, installing drilled pier systems, and strengthening existing slab sections. Foundation upgrade construction costs vary from $25,000 to $100,000+ depending on the extent of work required.

**Q: Can I add a second story to a post-and-beam house in Brentwood?** A: Yes, post-and-beam construction is common in Brentwood and is fully capable of supporting a second story with appropriate upgrades. AAA Engineering evaluates existing posts, beams, and connections for adequacy under the new loads, then designs reinforcement or replacement of inadequate members. Post-and-beam foundations frequently require upgrading — the original footings under posts are often sized only for single-story loads.

**Q: What is a soft story condition and does it affect my second story addition?** A: A soft story is a floor level with substantially less lateral stiffness than adjacent floors — typically caused by large garage openings, extensive glass, or open-plan spaces at the ground level. California's CBC 2022 requires analysis and mitigation of soft story conditions for all new and significantly remodeled structures. If your existing Brentwood home has a large garage opening at the front, AAA Engineering designs moment frames or other lateral systems to eliminate the soft story condition as part of the second story addition.

**Q: How does shear wall design affect my floor plan?** A: Shear walls are the primary lateral force-resisting element in wood-frame second story additions. They require solid wall segments at least 2 to 4 feet wide, located at the building perimeter and interior. AAA Engineering works with your architect to locate shear walls at positions that provide required lateral resistance while preserving your desired floor plan. When the floor plan cannot accommodate shear walls — large open spaces, extensive windows — we design steel moment frames that provide lateral resistance without solid walls.

**Q: How much does a second story addition cost in total in Brentwood?** A: Total construction cost for a Brentwood second story addition typically ranges from $400 to $600 per square foot of added area, or $400,000 to $900,000 for a 1,000 to 1,500 SF addition. Structural engineering fees of $5,000 to $15,000 represent 1 to 4 percent of total project cost. Foundation upgrades, if required, add $25,000 to $100,000 to construction costs. Architectural fees, permits, and contractor overhead add another 20 to 30 percent above direct construction costs.

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