You bought an older La Jolla house with a raised foundation, and the seller’s paperwork says nothing about earthquakes. Or a previous owner mentioned years ago that the house was bolted. Either way, you want to know whether anything is already down there.
This post is a recognition guide. It shows what retrofit hardware can look like from a crawl space, how it differs from original construction, and what to photograph so someone qualified can review it. It doesn’t explain how a retrofit works (our bolt-and-brace overview does that) and it doesn’t tell you whether what you find is adequate. Seeing hardware isn’t the same as a verified retrofit.
Safety first: look from the hatch if you’re unsure
Crawl spaces can hold sharp debris, exposed wiring, pests, and tight clearances. If you aren’t equipped and comfortable, look and photograph from the access opening with a strong flashlight, or have the visit done by someone who goes under houses for a living. Never go in alone.
Know which kind of foundation you’re looking at
The Earthquake Brace + Bolt program, run by the California Residential Mitigation Program, describes two raised-foundation layouts:
- Cripple walls. EBB describes them as “short (4 feet or less) walls between the wooden frame of the house and the foundation.” You’ll see short stud walls sitting on the concrete, with the floor framing on top.
- Stem wall only. Where the wood frame of the house sits directly on the foundation, which EBB calls a stem wall, the program describes a bolt-only retrofit instead.
Knowing which one you have tells you what to look for. Our cripple wall bracing basics post covers the vocabulary in more depth.
What to look for: anchorage to the foundation
The connection between the wood sill (the board lying on the concrete) and the foundation is where much of the visible hardware sits. EBB puts it this way: large anchor bolts “or foundation plates are used to bolt the wooden frame of the house to the concrete foundation, to strengthen the connection between the two.”
Original anchor bolts. Some houses were built with bolts set in the concrete when it was poured. You’ll see a nut and washer on top of the sill, with the bolt coming up from below. The 2025 California Residential Code describes this kind of anchorage for new construction, including “minimum 1/2-inch-diameter (12.7 mm) anchor bolts” and “A nut and washer shall be tightened on each anchor bolt.” Seeing nuts on the sill tells you bolts exist. It doesn’t tell you their size, spacing, or depth, or whether they were added later.
Retrofit bolts. Bolts added after construction are drilled through the sill into the existing concrete. From the crawl space they can look similar to original bolts. Clues that a bolt may be a retrofit include large or square plate washers, bolt tops that look newer than the surrounding wood, or a fresh-looking drill pattern. None of those clues is proof.
Foundation plates. Steel plates or brackets fastened along the side of the sill and the side of the concrete can be a retrofit sign, especially where there isn’t room to drill from above. EBB’s photo caption for a bolt-only retrofit says: “Note the metal foundation plates (bolting) around the perimeter of the foundation.” Look for a repeating pattern along the perimeter.
What it isn’t: hold-down straps at a single corner, joist hangers, or random metal straps on floor framing may be original or unrelated to seismic work. Photograph them anyway and let a reviewer decide.
What to look for: braced cripple walls
If you have cripple walls, bracing means sheathing on them. EBB describes it plainly: “plywood or OSB sheathing is attached along the cripple walls to strengthen the structure between the house and the crawl space.”
Signs to note:
- Panels on the inside face of the cripple walls, rather than bare studs.
- How continuous it is. Panels on one wall but not others, or short sections only, is worth recording.
- Nailing. Rows of nails along the panel edges are typical of structural sheathing. You can photograph them; you can’t judge their spacing or adequacy from a photo.
- Vent holes cut in the panels, which can be cut so the crawl space keeps its ventilation.
- Condition. Water stains, delamination, rot at the bottom edge, or termite damage can matter as much as whether the panels exist.
The California Earthquake Authority’s discount criteria for retrofitted homes state: “If the house has cripple walls, they all must be braced in accordance with California Building Code (CBC) standards.” That’s an insurance-discount rule, not a building-code verdict, but it shows why some panels and all walls braced aren’t the same thing.
Don’t forget the water heater
EBB lists water heater strapping as part of its program and says “EBB requires that the water heater be properly strapped and braced.” Straps around the tank are easy to see and worth a photo, though they say nothing about the foundation.
Paperwork that tells you more than hardware
Hardware shows what’s there. Paper tells you how it got there:
- Permit history. The City of San Diego’s Development Services records can show whether seismic or foundation work was permitted at the address. Our permit basics post explains how that works.
- EBB verification. CEA notes that if a retrofit “was completed through the Earthquake Brace + Bolt program,” the homeowner can “provide a valid Brace + Bolt verification number” on its form.
- CEA’s Dwelling Retrofit Verification (DRV) form. CEA refers to inspections conducted using the DRV instructions for its premium discount. If a previous owner had one done, ask for a copy.
- Seller disclosures or contractor invoices that mention bolting or bracing.
What to photograph and record
- A wide shot from the hatch in each direction, so the layout is clear.
- Close-ups of any bolts, plates, or brackets, with a tape measure in frame for scale.
- Each cripple wall: bare, partly sheathed, or fully sheathed.
- Panel edges showing nailing, and any vent holes.
- Stains, rot, cracks in the concrete, or pest damage near the hardware.
- The water heater straps.
- A rough sketch of where each item is around the perimeter.
That set of photos makes a seismic evaluation faster and gives a reviewer something concrete to work from.
What you can’t tell from looking
Visible hardware doesn’t confirm that bolts are embedded deep enough, that the concrete is sound enough to hold them, that sheathing is nailed correctly, or that the whole load path is complete. A house can have some retrofit pieces and still have gaps. Whether existing work is adequate is a judgment for a qualified evaluator, and when design questions come up, a structural engineer.
Cost factors, not prices
We don’t publish prices. Things that shape the effort and cost of reviewing existing retrofit work include: crawl space height and access; the length of the perimeter; whether there are cripple walls or only a stem wall; condition of the sill, framing, and concrete; whether records exist; and whether an engineer’s review or a plan set is needed for any added work.
Where we fit
We’re a foundation and structural repair company serving La Jolla citywide. On a visit we can document what’s under your house and explain what we see on our seismic retrofit and raised foundation repair pages. We aren’t engineers, and we don’t certify retrofits. We work with verified contractors and coordinate with licensed engineers as needed. This post is general education, not an assessment of any property.
Next step
If you want to know what’s already under your house, request a Free Quote for an on-site look anywhere in La Jolla, or call (650) 739-6537. Bring any photos and paperwork you’ve found.
Sources (accessed October 25, 2026)
- California Residential Mitigation Program, Earthquake Brace + Bolt, “The Earthquake Brace + Bolt Retrofit”
- California Earthquake Authority, “Get a Discount” (retrofit discount criteria and DRV form)
- 2025 California Residential Code, Section R403.1.6 Foundation anchorage
- City of San Diego Development Services, Records