An out-of-state buyer touring a "teardown opportunity" on a quiet Brentwood street this spring assumed the math would work the way it does almost everywhere else in the country: buy the lot, clear the old house, build something larger and newer in its place. Their architect ran the zoning numbers before they wrote an offer. The existing house was 4,200 square feet. What the city would actually let them build on that same 7,500 square foot lot today was closer to 3,375 square feet. Tearing down would have made the house smaller.
That is not a quirk of one address. It is the predictable result of a citywide zoning change that most buyers, and more than a few agents, have not fully absorbed. If you are comparing a fixer or a rebuild candidate against a move-in-ready home anywhere in Brentwood, this is the number you need before you fall in love with either one.
The rule that changed what "bigger" means
Los Angeles adopted the Baseline Mansionization Ordinance in 2008 after a wave of complaints about oversized new construction crowding out older single-family streets. The original version let R1 lots build up to 50 percent of lot area, with a 20 percent bonus available for certain design features, which meant a well-designed new home could reach roughly 60 percent of the lot.
In 2017, the city tightened it. Ordinance No. 184,802 dropped the base allowance to 45 percent of lot area, eliminated the 20 percent design bonus entirely, and cut the garage space that does not count toward total square footage from 400 square feet down to 200. The Brentwood Homeowners Association's own explainer walks through the arithmetic on a typical 7,500 square foot lot: under the old rules, you could build 4,500 square feet. Under the current rule, the cap is 3,375.
That gap matters because a large share of Brentwood's housing stock, particularly homes on the smaller lots under 10,000 square feet where City Planning focused these changes, predates 2017. Those houses are frequently larger than what the same lot would be allowed to build today. In zoning terms, they are legally nonconforming. They are grandfathered in at a size the current code would never approve from scratch.
| Lot size | Allowed under pre-2017 BMO (50% + 20% bonus) | Allowed under current BMO (45%, no bonus) |
|---|---|---|
| 7,500 sq ft | ~4,500 sq ft | ~3,375 sq ft |
What renovation preserves that demolition throws away
This is the part that reshapes the buy-versus-rebuild decision. Renovating a nonconforming home preserves its existing footprint. You can gut it, reconfigure it, modernize every system inside it, and keep the square footage the current code would no longer let you build. Demolish it, and you reset to today's smaller limit. The two paths do not produce the same house, and the difference has nothing to do with construction budget. It is entirely a function of when the original permit was pulled.
On hillside parcels, a second layer applies. The Baseline Hillside Ordinance caps cumulative grading, meaning cut and fill combined, at 500 cubic yards plus 5 percent of lot size, and it also governs building height, setbacks, and retaining wall size. Anything crossing 250 cubic yards of earthwork also triggers a separate grading bond requirement. For canyon and hillside pockets like Mandeville Canyon, where a slope of 15 percent or more puts a lot under BHO jurisdiction, this is often the first constraint a project runs into, well before floor area becomes the limiting factor. Checking the "Hillside Area" field on the city's ZIMAS zoning lookup before you write an offer is not optional due diligence on these lots. It is the whole ballgame.
None of this means renovation is automatically cheaper. Per square foot, renovation typically runs 20 to 40 percent more than equivalent new construction. But that comparison only means something once you know the two paths are producing different sized buildings in the first place. A buyer pricing a renovation against a rebuild without first running a nonconformity analysis is comparing numbers that describe two different houses.
The newer friction: what the mansion tax does to the exit
Zoning caps what you can build. A separate, more recent cost affects what happens when you try to sell it. Los Angeles voters passed Measure ULA, the transfer tax on property sales above $5 million within city limits, and its effect on the high end of the market has been more than theoretical. A 2026 RAND analysis, cited in a Los Angeles zoning guide from Benson Construction Group, estimates the tax has reduced sales of properties above that threshold by roughly a third.
That threshold sits squarely inside the price range a finished spec home on a Brentwood teardown lot is likely to land in once construction, permitting, and carrying costs are added to the purchase price. It is not a zoning rule, but it functions like one for anyone weighing whether a ground-up rebuild pencils out. A statewide ballot initiative aimed at repealing or restructuring the tax has qualified for the November 2026 ballot, and the City Council is reportedly weighing its own amendments, including an exemption for new construction, for potential placement on the same ballot. Until voters act, the tax applies as written, and it is one more reason developers are pickier than the "land scarcity" headline suggests about which Brentwood lots they will actually option.
What the 2026 numbers are actually telling you
Read on its own, Brentwood's price data looks contradictory. Over the three months ending June 2026, the median sale price came in at $2.3 million, down 21.7 percent from the same period a year earlier. In the same window, the median price per square foot rose 7.9 percent to $989. A falling median alongside a rising per-square-foot number is not a market losing value. It is a market where the mix of what is selling has shifted, with fewer of the large, expensive, ground-up rebuilds changing hands and more mid-size homes making up the transaction count. Given how the BMO cap and the ULA threshold both push against exactly that category of project, a thinner slice of big spec rebuilds reaching the market is not a coincidence.
The rest of the market has not softened. Brentwood inventory sat at a three-year low earlier in 2026, and roughly 62 percent of single-family sales closed above list price, with an average sale-to-list ratio of 101.8 percent. New construction, meanwhile, made up less than 3 percent of annual sales, a figure land scarcity alone does not fully explain once you account for how much harder the zoning and tax math has made the rebuild path.
What this means if you are comparing a teardown to a move-in-ready home
Before you let a "bring your architect" listing shape your offer strategy, get the nonconformity analysis done. Pull the original permits from LADBS, check the parcel's zoning and hillside status on ZIMAS, and calculate what the lot would actually support under today's code. If the existing house already exceeds that number, you are not looking at a blank canvas. You are looking at a structure whose size may be worth more standing than rebuilt.
If the numbers do favor a rebuild, price the ULA exposure into your total cost picture from the start, not after the design is finished. And if you are the one selling a nonconforming home, understand that its legally protected square footage, not its age or finishes, may be your strongest selling point to the next buyer's architect.
Frequently asked questions
Does Measure ULA apply to me if I am buying a $3 million home? The tax applies to the sale, based on the sale price, so it is the seller's cost at closing rather than the buyer's. It only applies once a transaction crosses the $5 million threshold, so a $3 million purchase falls outside it, but it becomes relevant fast if renovation or new construction on that property is likely to push a future resale above that line.
Can I add onto my existing nonconforming home instead of tearing it down? In many cases yes, though any addition still has to work within the total floor area the property is already grandfathered at, and a licensed professional should confirm your specific parcel's allowance before you commit to a design.
How do I check if my lot falls under the Baseline Hillside Ordinance? Look up the parcel on the city's ZIMAS mapping tool and check the "Hillside Area" field under the zoning tab. A slope of 15 percent or greater generally triggers BHO review in addition to the standard BMO floor area limits.
If you are weighing a Brentwood teardown against a finished home, or trying to figure out what your own nonconforming property is actually worth in this market, Pence Hathorn Silver can walk the zoning and pricing math with you before you write an offer. Schedule a free consultation and get the numbers first.
