Most owners who consider an addition in Del Mar have lived with the house for a while. They know which room is too small, where the light falls in the afternoon, and how much they’d like a bedroom upstairs with a glimpse of the water. What they often haven’t considered is what the existing foundation was designed to carry, and whether it can carry more.
These notes are meant for that early stage, before drawings are finished and before anything goes to the City.
First, which jurisdiction
It’s worth saying plainly because it trips people up. The City of Del Mar is a small incorporated city with its own design review, zoning and building departments. Carmel Valley and Del Mar Heights share the name and the ZIP code feel, but they sit within the City of San Diego, which has different rules and a different process. Everything below about design review applies to the City of Del Mar. If your home is in Carmel Valley, our Carmel Valley foundation repair page is the better starting point.
How Del Mar reviews additions
The City’s resident handbook on design review lays out the path. A few points matter for the structural side:
- Minor projects may qualify for Administrative Design Review, where the Planning Director makes the decision after a 10-day notice period. If someone objects, the project goes to the Design Review Board.
- Larger projects go to a regular Design Review Board hearing.
- Repairs that keep a structure’s outer dimensions the same are generally exempt from design review, though building permits may still apply.
- Neighbors are notified. Owners within 300 feet receive notice at least 10 days before a hearing.
- Story poles go up 15 days before the hearing and must be certified by a licensed land surveyor or civil engineer 10 days before.
- Other permits tie in. The Board can also act on related permits such as a Land Conservation Permit for grading, a Coastal Development Permit and a Tree Removal Permit. An application is held incomplete until certain separate approvals, such as a Floodplain Development Permit, are obtained.
Floor area ratio, setbacks, lot coverage and height limits live in the City’s zoning code, and Del Mar has a dozen residential zones. A designer will work through those numbers. The structural questions sit alongside them.
None of this comes with a predictable outcome or schedule, and we don’t suggest otherwise. The City and, where applicable, the Coastal Commission make those determinations.
Coastal and flood considerations
Two outside rules can change the scope of an addition, sometimes significantly.
California’s coastal regulations, at 14 CCR 13250, describe which improvements to existing single-family homes are exempt from a coastal permit and which aren’t. Improvements on a lot within 50 feet of the edge of a coastal bluff are among those that are not exempt. On property between the sea and the first public road, or within 300 feet of the inland extent of a beach, an increase of 10 percent or more in internal floor area, or an increase of more than 10 percent in height, also requires a permit.
On the flood side, federal rules at 44 CFR 59.1 define substantial improvement as work whose cost equals or exceeds 50 percent of the structure’s market value. In a mapped flood zone, crossing that line can mean the whole building must come up to current floodplain standards, not just the new part. For homes in North Beach, that can reshape a project entirely. Our earlier note on North Beach cottages goes into this further.
The structural questions
With the process in view, here are the questions we’d want answered before an addition is drawn in detail.
What are the existing footings, and what were they sized for? Many older Del Mar homes sit on shallow continuous footings designed for a single story of wood framing. A second story adds weight that has to reach the soil somewhere. Sometimes the existing footings are adequate. Sometimes they need to be enlarged or supplemented, and sometimes new footings carry new posts that bypass the old walls.
What’s the soil like? A geotechnical report describes the soil, any fill, groundwater and recommended foundation types. Del Mar has terraces, sandstone, canyon slopes and lagoon-edge ground, and these behave differently. A report done for the original house, if one exists, is a useful start but may not reflect current standards.
How will new meet old? Where an addition extends the footprint, the new foundation meets the existing one. If the two settle differently, a crack can open at that line. The connection detail, and whether the new foundation is designed to match or separate from the old, matters.
Where does the load go? Every new beam, post and shear wall has to deliver its load down to a footing. In older homes, the path isn’t always obvious, and remodels over the decades may have removed walls that once carried weight.
Is the existing structure tied down? Adding a story raises seismic and wind forces. Hold-downs, anchor bolts and shear walls that were fine for one story may need upgrading for two.
What condition is the existing foundation in? Cracks, settlement, moisture or deterioration are better found before design than during construction. Our foundation inspection page describes what a pre-design review covers.
A sensible order of work
- Confirm the jurisdiction and zone.
- Gather existing records: original plans, permits, any prior soils report.
- Have the existing foundation and framing reviewed.
- Commission a geotechnical report if the project calls for it.
- Let the architect and engineer develop the design with those findings in hand.
- Then begin the design review process.
Owners who reverse steps three and five sometimes find that a design approved in concept needs rethinking once the foundation is understood.
How we help
We review existing foundations and framing ahead of addition design, and we coordinate with licensed engineers as needed for structural design and with geotechnical professionals for soils. Our design review foundation projects page explains how we support work that passes through Del Mar’s process. Cost depends on the size and age of the home, access to the crawl space or slab, the scope of the planned addition and the records available, and we explain those factors once we’ve seen the house. We serve the whole City of Del Mar, including for owners who live elsewhere much of the year.
If you’re early in planning an addition and want to understand what your foundation can support, ask for a Free Quote.