Why R1 rules reward keeping the house
When the City Council updated the single-unit standards in 2019, one stated goal was to encourage owners to retain existing homes, and today's code reflects it. Under Table 9.07.030 of the Santa Monica Municipal Code, a new two-story house in the R1 district is held to a floor area ratio of 0.45, while an existing structure with an addition may reach 0.55. On parcels under 5,000 square feet, the code converts those ratios into fixed caps, with a limit on how much of the area can sit upstairs.
The higher ratio applies only to projects that do not result in a demolition as the city defines it. On a 5,000 square foot lot, the gap between those two ratios works out to about 500 square feet of floor area. Keeping enough of the original structure is often the single most valuable design decision on a Santa Monica remodel.
When a remodel becomes a demolition
Under Chapter 9.25, a demolition occurs when more than 50 percent of the exterior wall elements are removed, or stop serving as a necessary structural part of the building, at any time over a five-year period. Wall elements include studs, columns, cripple walls and their footings, and windows and doors, and the share is measured horizontally around the perimeter, story by story. For a structure over 40 years old that is on the city's Historic Resources Inventory, removing more than 25 percent of the street-facing walls can be enough.
Before a permit is issued for work that removes over 40 percent of the exterior walls, a registered structural engineer must certify that the walls shown to remain are sound and will not need to come out, and the owner and contractor sign an affidavit acknowledging the definition and its penalties. We plan the framing sequence and the structural design so retained walls stay in place, because losing them midway can change the permits and the allowable size of the project.
Height, setbacks and the second story
R1 homes are limited to two stories. On parcels up to 20,000 square feet, the maximum height is 28 feet, with no wall above 23 feet except gables and dormers that meet the stepback rules, and any part of the building above 23 feet must stay inside a 45-degree plane drawn inward from the side setback. A second story also needs front and side upper-story stepbacks, each adding up to at least 1 percent of the parcel area unless the whole upper floor is set back far enough to make them unnecessary.
Upstairs outdoor space is capped too: an individual balcony, terrace or deck may not exceed 3 percent of the parcel area or 300 square feet, whichever is less. Older homes with side setbacks that no longer conform get one helpful exception. A one-time addition of up to one story and 14 feet in height may continue along the existing nonconforming side setback, provided it stays at least 4 feet from the property line and runs no more than 15 feet in length.
When the Architectural Review Board is involved
A remodel in the R1 district that conforms to the development standards is generally not subject to architectural review. One exception is a parcel with a grade difference of 12.5 feet or more between the front and rear property lines, where the Architectural Review Board reviews a new residence or an addition of 50 percent or more.
The board can also approve certain departures from the standards, such as reduced aggregate side setbacks, upper-story stepbacks that do not meet the table, larger balconies or decks, and some street-facing garage door and front porch designs, if it makes findings about the site's special circumstances and the effect on neighbors. If the house is on the Historic Resources Inventory, the board also considers whether the change respects its historic character and the Secretary of the Interior's Standards. That route adds time, so we only pursue it when it clearly improves the design.
Landmarks, structures of merit and the 40-year rule
Santa Monica's Landmarks Commission oversees designated landmarks, structures of merit and historic districts. Altering a landmark or a building in a designated historic district requires a Certificate of Appropriateness. For a structure of merit, alterations generally do not need one, though reviewing bodies take the designation into account and demolition does. The California State Historical Building Code applies to alterations of designated buildings, which can give some flexibility with older construction.
Even an undesignated house can be affected. When a demolition permit is filed for a building whose original permit is more than 40 years old, the application goes to the Landmarks Commission, and a designation application may be filed within 75 days. If an application is filed, no demolition permit can issue until the designation is decided. Because partial removals can count as demolition, we check the inventory and the age of your house before the scope is set.
Permits, the coastal zone and the work week
Building permits are handled by the city's own Community Development Department, with plans submitted and corrected electronically. As of 2026, Santa Monica has a certified coastal Land Use Plan but not a complete Local Coastal Program, so the Coastal Commission itself issues coastal development permits in the city's Coastal Zone. The city and the Commission signed an agreement in 2026 aiming to finish the program by the end of 2027, so we confirm early whether your project needs a coastal permit or exemption.
Construction is not allowed before 8 a.m. or after 6 p.m. on weekdays, before 9 a.m. or after 5 p.m. on Saturdays, or at any time on Sundays and listed holidays. We plan demolition, deliveries and inspections around those hours, and you receive a written scope and price before work begins.