Guaranteed minimum by zone
- R1
- 25% of lot size
- RS
- 23%
- RE9 · RE11
- 20%
- RE15 · RE20 · RE40
- 18%
- RA
- 13%
- Absolute floor
- 800 sq ft
Baseline Hillside Ordinance · Los Angeles
Baseline Hillside Ordinance:
the slope sets the size.
In the Los Angeles hills your buildable square footage is not a number in the zoning code. It is a calculation run band by band across your own topography — and until a surveyor maps it, nobody can honestly tell you what your lot will carry. Here is the arithmetic, and the three places it usually breaks.
First Question
Two conditions, both required.
The Baseline Hillside Ordinance lives at LAMC § 12.21 C.10. It reaches a lot only when both of the following are true.
One: the zone. The lot is zoned R1, RS, RE or RA. Multifamily and commercial zones are outside it entirely.
Two: the map. The lot is designated Hillside Area on the Department of City Planning Hillside Area Map. This is a published map, not a judgement about how steep your driveway feels. Parcels that look flat are inside it and parcels on visible slopes are sometimes outside it.
Get either half wrong and every number that follows is wrong. It is the first thing we check on any hills address, before anyone draws anything.
Adopted 2011 and substantially amended by Ordinance 184,802 (effective 17 March 2017), with later amendments by Ordinances 187,712 and 187,930. Figures on this page are drawn from the current codified text.
The Method
Your lot is six lots, and each one has its own ratio.
The ordinance divides your parcel into six slope bands, applies a different floor area ratio to each, and adds the results. Steep ground earns less floor area than gentle ground, and anything at 100 per cent slope or above earns none at all.
| Slope band | R1 | RS | RE9 | RE11 | RE15 | RE20 | RE40 | RA |
|---|---|---|---|---|---|---|---|---|
| 0 – 14.99% | 0.45 | 0.45 | 0.40 | 0.40 | 0.35 | 0.35 | 0.35 | 0.25 |
| 15 – 29.99% | 0.45 | 0.40 | 0.35 | 0.35 | 0.30 | 0.30 | 0.30 | 0.20 |
| 30 – 44.99% | 0.40 | 0.35 | 0.30 | 0.30 | 0.25 | 0.25 | 0.25 | 0.15 |
| 45 – 59.99% | 0.35 | 0.30 | 0.25 | 0.25 | 0.20 | 0.20 | 0.20 | 0.10 |
| 60 – 99.99% | 0.30 | 0.25 | 0.20 | 0.20 | 0.15 | 0.15 | 0.15 | 0.05 |
| 100%+ | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
Multiply the square footage sitting in each band by that band’s ratio, then add the six results. That sum is your maximum Residential Floor Area. A 10,000 square-foot R1 lot that is half gentle and half steep does not get 0.45 across the whole thing — it gets 0.45 on the gentle half and 0.30 on the steep half, and the difference is roughly 750 square feet of house.
The map is not optional. A Slope Analysis Map must be prepared, stamped and signed by a registered civil engineer or licensed land surveyor, at a scale of at least one inch to 100 feet with contours no coarser than 10 feet and two-foot intermediates. The Director of Planning approves the calculated floor area before you may apply to Building and Safety. This is a real step with a real timeline, and it is the one most owners have not budgeted for.
The Floor Under the Floor
If the slope math leaves you nothing, there is a backstop.
On genuinely severe ground the band calculation can produce a figure too small to build. The ordinance guarantees a minimum instead: a flat percentage of lot size, or 800 square feet, whichever is greater. You may use the guaranteed minimum in place of the slope band result.
When it actually bites
Less often than people hope, and in one specific situation. In R1 every slope band except the last carries a ratio above 0.25, so the band method normally wins. The guarantee only takes over when real area sits at 100 per cent slope or steeper, because that ground earns a ratio of zero.
A 7,000 square-foot R1 lot with 60 per cent of its area above 100 per cent slope earns roughly 980 square feet by the band method. The guarantee pays 1,750. On a cliff parcel that gap is the difference between a project and a view lot.
Run both calculations regardless. The ordinance lets you take the better of the two, and which one wins is not obvious until the surveyor returns the band areas.
Height
Measured plumb, from the ground beneath it.
Hillside height is an envelope — a plumb line from the grade directly below to the roof above it, taken at every point along the exterior walls. There is no averaging across the building. A house that steps down a slope is measured at each step.
Height districts 1, 1L and 1VL
- Roof slope ≥ 25%
- 33 ft (R1, RS, RE9)
- 36 ft (RE11–RA)
- Roof slope < 25%
- 28 ft (R1, RS, RE9)
- 30 ft (RE11–RA)
A pitched roof buys you five feet. In 1XL the ceiling is 30 feet; in a Single Story district it is 22 feet pitched, 18 flat, and one storey.
Three things that cut it shorter
The encroachment plane. In R1 a plane rises from 20 feet above the lower of existing or finished grade along the required front and side setbacks. It slices the upper corners off the envelope you just calculated.
Substandard Hillside Limited Streets. Within 20 feet of the front lot line nothing may exceed 24 feet, measured from the centreline of the street — not from your grade.
What you get back. Unenclosed cantilevered balconies with visually permeable railing may project five feet past the envelope, and a Zoning Administrator can approve up to 45 feet overall. If 40 per cent of the block already exceeds the limit, the prevailing height may govern instead.
The Part That Decides Cost
Grading is capped. Caissons are not.
This is the provision that separates a hillside project that pencils from one that does not, and it is the one least understood by owners arriving with a flat-lot design.
The by-right cap
- R1
- 1,000 cu yd
- RS
- 2,200
- RE9
- 2,400
- RE11
- 2,800
- RE15
- 3,200
- RE20
- 4,000
- RE40
- 6,600
- RA
- 3,600
Read the R1 row twice. The ordinance states a formula of 1,000 cubic yards plus 10 per cent of lot size — then caps each zone by this table. In R1 the cap equals the base, so the 10 per cent is not available by right at all. It becomes a discretionary request to a Zoning Administrator. Most of the Hollywood Hills is R1.
What does not count against it
Cut and fill for deepened foundation systems — caissons and piles — is exempt, provided the scheme does not involve freestanding retaining walls. So are water storage tanks, required stormwater retention, driveway cut and fill up to 500 cubic yards, remedial grading recommended in an approved geotechnical report, and fill derived from cut under the main building footprint up to half that cut.
That exemption is the whole argument for building on caissons in the LA hills. It is not only a geotechnical decision — it is an entitlement decision. A cut-and-fill scheme on a steep R1 lot can exhaust 1,000 cubic yards before the foundation is in, while a caisson scheme reaching the same floor area may never touch the cap.
Import and export have their own limits — and their own hours
Earth may move only between 9:00 a.m. and 3:00 p.m., Monday to Friday. Combined import and export is capped at the by-right quantity above — and at 75 per cent of it where the lot fronts a Substandard Hillside Limited Street. On a narrow canyon road that six-hour window and the reduced cap drive the haul schedule, and the haul schedule drives the programme.
New slopes no steeper than 2:1, and permits in order
All newly graded slopes must be no steeper than two horizontal to one vertical unless Building and Safety’s Grading Division determines otherwise. And no grading permit issues until the building permit is approved — so you cannot start moving dirt while the house is still in plan check.
The Rest of the Envelope
Parking and setbacks, where the plan usually gives.
Parking
Two spaces, inside a private garage, not in the required front yard. A single space suffices only on a nonconforming lot 40 feet or less wide with no alley — and that exception disappears if the lot fronts a Substandard Hillside Limited Street.
On those substandard streets, a combined floor area above 2,400 square feet triggers one more space per additional 1,000 square feet or fraction, to a maximum of five on site. Those extra spaces need not be covered and may sit in the front yard. On a narrow lot, parking is frequently what caps the house — not floor area.
Setbacks
Front yard is 20 per cent of lot depth, capped at 20 feet in R1, RS and RE9 and 25 feet elsewhere. Side yards start at five feet in R1 and seven in RS. Rear is 15 feet in R1.
Two modifiers do the real work: one additional foot of side yard for every 10 feet of height above the first 18, and a required plane break — five feet deep, ten feet long — on any side wall over 14 feet tall running more than 45 feet. Tall narrow houses pay for their height in width.
Summarised from LAMC § 12.21 C.10 as currently codified. Height districts, specific plans, HPOZ overlays, Very High Fire Hazard Severity Zone requirements and Coastal Zone jurisdiction all layer on top and can govern instead. This is a screen, not a legal opinion, and it is not a substitute for counsel or a licensed surveyor.
Why Us On This
We build in the hills. That is the whole answer.
Most of what is written about the Baseline Hillside Ordinance is written by people who have never taken a caisson scheme through plan check. Our hillside work includes The Pyramid MCM, The Apex HH, The Hideaway HH, The Treehouse HH and The Mulholland Residence.
Those projects are why the grading section above leads with caissons rather than with the cap. On a steep lot the foundation strategy decides the entitlement, the entitlement decides the schedule, and the schedule decides whether the project is worth doing.
The streamlining statutes will not help you here. SB 79 is paused across most of the city and excludes fire hazard severity zones; the city’s Low-Rise programme excludes Hillside Areas outright; and AB 1751 excludes high and very high fire hazard severity zones. For most hills parcels the Baseline Hillside Ordinance is the path, not the fallback.
Ground-up homes we build carry the TDG Builder Warranty under California SB 800. Remodels and conversions do not.
Good Questions. Straight Answers.
Before you draw anything.
How do I know if my lot is in a Hillside Area?
It is a published designation on the Department of City Planning Hillside Area Map, and it does not always match intuition. Flat-looking parcels fall inside it and some visibly sloped parcels fall outside. Zoning alone is not enough either — the lot must be zoned R1, RS, RE or RA and mapped as Hillside Area. Send us the address and we will confirm both in the same reply.
Can I work out my square footage before paying a surveyor?
You can get a useful estimate from county contour data, and we do this routinely as a first pass. What you cannot do is use it. The ordinance requires a Slope Analysis Map stamped by a registered civil engineer or licensed land surveyor, and the Director of Planning must approve the resulting floor area before Building and Safety will take an application. Treat the desktop number as a go or no-go, not as a design brief.
Why does my architect keep talking about caissons?
Because cut and fill for deepened foundations — caissons and piles — is exempt from the grading cap, provided the scheme avoids freestanding retaining walls. On a steep R1 lot the by-right allowance is only 1,000 cubic yards, which a conventional cut-and-fill pad can consume entirely. Going deep rather than wide is frequently the only way to reach your permitted floor area without a discretionary application.
Is the 1,000 cubic yards really the same as the base amount in R1?
Yes, and it catches people out. The ordinance states a formula of 1,000 cubic yards plus 10 per cent of lot size, then caps each zone separately. For R1 that cap is 1,000, so the additional 10 per cent is not available as of right — it has to be requested from a Zoning Administrator. Larger-lot zones such as RE40 fare much better at 6,600 cubic yards.
What is a Substandard Hillside Limited Street and why does it matter so much?
It is a defined roadway classification in LAMC § 12.03, and fronting one changes four things at once: a 24-foot height ceiling within 20 feet of the front lot line measured from the street centreline, import and export cut to 75 per cent, the loss of the narrow-lot parking exception, and additional parking required above 2,400 square feet. In the canyons this classification often matters more to feasibility than the slope does.
Does SB 9, SB 79 or AB 1751 override any of this?
Generally not in the hills. SB 79 is paused across most of Los Angeles and excludes Very High Fire Hazard Severity Zones; the city’s replacement Low-Rise programme excludes Hillside Areas by definition; and AB 1751 excludes high and very high fire hazard severity zones. See how the statutes interact — but on a typical hills parcel the Baseline Hillside Ordinance is the governing framework.
Can I exceed the height limit?
Sometimes. A Zoning Administrator may approve up to an overall 45 feet. Separately, where 40 per cent or more of the existing dwellings fronting both sides of your block already exceed the limit, the average of those taller houses may become your permitted height without a discretionary application. Establishing prevailing height is a survey exercise, and it is worth doing before you assume the table binds you.
Do you take on hillside projects for owners, or only your own developments?
Both. We develop our own sites and we build for owners on theirs — see Develop With TDG. If the lot does not work and you would rather not carry it, we also buy directly; see Sell Your Lot. On a hills parcel we will tell you plainly which of the three we would choose.
Send us the address.
We’ll confirm whether the ordinance applies, run a first-pass slope band estimate, and tell you what the lot realistically carries — before you commission a survey.