Why do two similar Sherman Oaks homes command very different prices? In many cases, it comes down to city rules that limit how big you can build and how construction happens on sloped lots. If you plan to buy, sell, or expand in Sherman Oaks, understanding these size and hillside rules can protect your budget and help you set realistic expectations.
In this guide, you’ll learn what the Baseline Mansionization Ordinance, Baseline Hillside Ordinance, and Hillside Construction Regulations mean for your property, how they affect value, and the smart steps to take before you commit to a plan. Let’s dive in.
BMO and BHO, in plain English
Baseline Mansionization Ordinance
The Baseline Mansionization Ordinance limits how large a house can be on single-family lots. The focus is on the size of the home compared with the lot and how bulk and massing appear from the street. The goal is to preserve neighborhood scale and avoid oversized additions that change the character of a block.
In practice, BMO affects how much new square footage you can add, where upper floors can sit relative to the first floor, and how the building envelope presents from the street. It is administered by the City of Los Angeles Department of City Planning and used by plan checkers during permitting.
Baseline Hillside Ordinance
The Baseline Hillside Ordinance applies to designated Hillside Areas. In Sherman Oaks, that includes many parcels near the Santa Monica Mountains foothills and canyon edges. The rules go a step further than BMO to address grading, retaining walls, how homes sit on slopes, and visual impacts.
If your lot is in a Hillside Area, expect stricter controls on site disturbance, maximum building envelope, and sometimes height or story limits measured from natural grade. The intent is to protect terrain, manage stormwater and slope stability, and reduce the visual prominence of large homes on hilltops and ridges.
Hillside Construction Regulations
Hillside Construction Regulations translate policy into construction requirements. They cover grading permits, geotechnical and structural documentation, cut-and-fill limits, and special inspection pathways. For hillside projects, you will likely need a geotechnical report, engineered foundations or retaining walls, and more coordination with city reviewers.
Where these rules apply in Sherman Oaks
Sherman Oaks includes both flat neighborhoods and hillside pockets. Many hillside parcels fall under BHO and HCR, while flat single-family areas are primarily under BMO. The key is parcel-specific verification. Two neighboring homes can be treated very differently.
Use the City’s zoning and parcel map to confirm overlays and zoning before you plan a remodel. The Zoning Information and Map Access System, often called ZIMAS, shows whether a parcel is in a Hillside Area, along with zone details that trigger BMO or BHO. Always verify at the parcel level rather than relying on assumptions about a block or tract.
How size limits are set
Floor area and massing
Both BMO and BHO limit floor area relative to lot size. This establishes the maximum legal size of a home without discretionary approvals. Planners look at total building volume, how additions are counted, and the relationship of new space to existing non-exempt floor area. If your plans push the baseline maximum, you may need to redesign or pursue a more complex review.
Height and stories
Height and story limits can be assessed from natural grade, especially on hillside lots. This helps reduce towering facades and visual bulk from the street or valley below. If you are planning a second story or roof deck, expect reviewers to check how height relates to topography and designed stepbacks.
Setbacks and stepbacks
To soften the look of larger homes, standards often require upper-floor stepbacks or increased setbacks. These elements can affect room sizes, bedroom placement, and the location of stairs or corridors. Early design thinking can save time by anticipating these requirements rather than forcing last-minute changes.
Grading and retaining walls
On hillside lots, grading and retaining walls are tightly controlled. Large earthwork operations typically trigger more review and more detailed geotechnical documentation. Retaining walls above certain heights require engineered design and specific permits. Expect inspectors to look closely at cut-and-fill volumes, drainage, and slope stabilization.
Lot coverage and landscape
To manage runoff and neighborhood character, rules may limit impervious surfaces and require landscape features that support drainage. Bioswales, permeable paving, and targeted planting can help meet these standards. Your architect and civil engineer will coordinate to prove compliance in plan check.
What counts as an addition
When you add square footage, reviewers compare your total to the allowed maximum. Some remodeling that does not increase floor area is treated differently from new living space. Features like covered patios, mezzanines, or converted attics can be counted in different ways depending on the specifics, so you will want a clear plan set and a confirming zoning read before you finalize budgets.
ADUs on flat and hillside lots
State ADU law expands options for accessory units, but it does not eliminate safety and site requirements. In hillside contexts, ADUs must still meet grading, setback, geotechnical, and construction rules. Siting an ADU in a tight or sloped yard can be challenging, and foundation solutions can add cost. Treat early feasibility as a must rather than an option.
Nonconforming conditions
If a home already exceeds today’s baseline size, additions may be limited or blocked unless you pursue discretionary relief. Each case depends on permit history and the nature of the nonconformity. Plan on a property-specific review and request any available permit records before you commit to a design.
Permit pathways and what to expect
Smaller, code-compliant projects often qualify for ministerial approval. Projects that exceed baseline standards or require significant grading can shift into discretionary review, which may involve public notice and hearings. That adds time and uncertainty.
Hillside projects typically require more documentation, including a geotechnical report, grading plans, and structural engineering for foundations and retaining walls. This increases pre-permit time and design cost. Build that into your timeline so you do not face surprise delays once you are under contract with a contractor.
How size rules shape value
Buildable potential and price
In Sherman Oaks, buyers and appraisers consider both current living area and realistic room to grow. If BHO or HCR constraints limit expansion, a home’s highest and best use may be close to its current size. That can cap upside compared with similar properties on flat lots with more baseline room to add.
Scarcity and comps
In mixed areas, maxed-out homes sometimes sell at a premium because buyers understand that further expansion will be difficult. On the flip side, a smaller home on a highly constrained hillside lot may trade lower than a similar home where expansion is feasible. Proper valuation means reviewing not just recent sales, but also the remaining allowable floor area and the complexity of achieving it.
Cost and timing expectations
Hillside work often carries a higher per-square-foot cost due to geotechnical studies, engineered foundations, retaining walls, and erosion control. Permitting timelines can run longer as well. Buyers who plan to add bedrooms or a second unit should budget for added design, permit, and construction layers from the start.
Seller preparation in Sherman Oaks
Disclosures and records
If you plan to list, gather information on zoning overlays, past permits, and any unpermitted work. Buyers will ask, and being proactive builds trust. If your property is in a Hillside Area or has prior approvals, document that clearly for your agent.
Pre-market feasibility
A quick zoning check and a consult with a local architect or planning professional can clarify what is feasible. If there is straightforward ADU potential, highlight it in marketing. If expansion is limited, set expectations honestly and position the home’s strengths rather than promising future square footage that is unlikely to be approved.
Buyer due diligence checklist
- Run a parcel check in the City’s ZIMAS tool to confirm zoning, Hillside Area status, and overlays.
- Pull permit history and check for violations or unpermitted work through the Los Angeles Department of Building and Safety record search.
- Confirm whether the lot is within mapped Hillside Areas, fault zones, or special flood or fire hazard zones.
- Obtain lot dimensions and, for sloped sites, a topographic survey or site plan.
Involve the right professionals
- Architect familiar with LA’s BMO, BHO, and HCR for an initial feasibility opinion.
- Geotechnical engineer for hillside parcels to confirm slope stability and likely grading scope.
- Contractor experienced in hillside work for cost estimating.
- Land-use attorney or planning consultant when discretionary approvals may be needed.
- Appraiser with Los Angeles hillside experience to understand market impacts.
Typical documents and timeline
- Parcel map and existing site survey with topography.
- Geotechnical report for grading and structural design.
- Grading and drainage plans plus structural and retaining wall designs.
- Architectural plans showing stepbacks, height, and massing to demonstrate compliance.
- Pre-permit feasibility can take weeks to a few months. Permit package preparation often takes several months. Ministerial reviews may finish in weeks or months. Discretionary approvals can take many months and carry risk.
Common pitfalls and gray areas
- ADU interactions are complex. State law creates rights, but hillside safety and grading limits still apply. Local interpretation can vary.
- Nonconforming structures require case-by-case review, especially if you hope to reconfigure or rebuild.
- Variances and other discretionary approvals are not guaranteed and can draw neighborhood input that affects outcomes. Avoid designing to the exception if a by-right path exists.
Your next step
If you are weighing a remodel, an ADU, or a sale in Sherman Oaks, start with a quick zoning and permit history check, then talk with an architect who knows LA’s hillside and mansionization standards. From there, you can calibrate budget, timeline, and pricing strategy with your agent.
When you want a grounded view of value and market positioning, plus introductions to trusted local experts, connect with Sean Curts & Associates to Request a Free Home Valuation. We help you set a clear plan, whether you plan to expand, sell as-is, or buy with future improvements in mind.
FAQs
How do I check if a Sherman Oaks property is under BMO or BHO?
- Use the City’s ZIMAS map to verify zoning and whether the parcel is in a Hillside Area. A quick review by a planning consultant or architect can confirm how the rules apply to your lot.
Can I add square footage if the house already exceeds today’s baseline?
- Additions are reviewed against current allowed totals. If the structure is nonconforming, expansion is often limited and may require discretionary relief that is not guaranteed.
Do these rules stop me from rebuilding after a disaster in Sherman Oaks?
- Rebuilding rights depend on the ordinance and permit history. Some paths exist to rebuild, but safety upgrades or compliance with certain standards may be required. Contact Planning and LADBS early.
Do state ADU laws override hillside limits in Sherman Oaks?
- ADU laws create opportunities, but hillside safety, grading, and objective standards still apply. Expect similar technical hurdles for ADUs on sloped lots.
How much do BMO and BHO affect home value?
- There is no single number. Impact depends on remaining allowable buildable area, the cost and timeline to realize it, and comparable sales. In constrained areas, scarcity can raise prices for maxed-out homes or lower prices where improvement potential is limited.
