Before anyone can say what is wrong with a foundation, someone has to say what kind of foundation it is. That sounds obvious. In practice it is easy to skip, and it matters: a raised floor on a concrete stem wall, a house on posts and pads, a brick perimeter wall from the 1920s, and a post-tensioned slab each fail differently, get inspected differently, and fall under different retrofit rules.
La Jolla’s housing is old enough that you see all of them. Census figures for ZIP Code Tabulation Area 92037 (American Community Survey 2024 5-year, table B25034) count 19,688 housing units, and 12,924 of them were built before 1980. That is roughly two-thirds. The ZIP area does not match the community-plan boundary exactly, and the census never records foundation type, so nobody can turn those numbers into “most La Jolla homes have a raised foundation.” What they do say is that a large share of houses here went up decades before the current code edition, so their foundations reflect older practice.
This post is a field guide to the types. If you already know you have a raised floor and want a list of things to watch, use our older La Jolla raised foundations post instead. If you want the company overview first, start at the La Jolla Structural home page.
Knowing the foundation type is not a diagnosis. It tells you which questions to ask, which specialist answers them, and which repair or retrofit paths are even on the table.
How to read the house from the outside
You can often narrow it down from the yard, without tools.
- Screened vents low on the exterior walls, a crawl hatch, and a floor a step or more above the yard point to a raised floor over a crawl space.
- A floor at about the same level as the patio, no vents, and a garage floor that runs straight into the house point to slab-on-ground.
- A concrete wall that steps down in stages along a sloping side yard usually means stepped footings, which the residential code calls for when a footing bottom would otherwise slope more than 1 in 10 (CRC R403.1.5).
- Tall exposed posts or framed walls on the downhill side, with open or enclosed space under the house suggest a hillside system.
- Brick, block, or stone where you expected concrete at the base of the wall deserves a closer look, covered below.
Some houses show two of these at once. FEMA’s retrofit guidance treats a raised house combined with a slab portion as its own configuration.
Raised perimeter foundation on a concrete stem wall
This is the type most people picture for an older California house. A continuous concrete footing and stem wall run around the perimeter; a wood sill plate sits on top; floor joists span over a crawl space; interior girders rest on posts and pads.
FEMA P-1100 (October 2019, prepared by the Applied Technology Council for the California Earthquake Authority and FEMA) splits this group in two. In one version, short wood stud walls called cripple walls stand between the stem wall and the first floor. In the other, the floor framing sits directly on a taller stem wall with no cripple wall. FEMA defines a crawlspace dwelling as one where the under-floor space is mostly unoccupied, the tallest cripple wall is no more than 7 feet, and the average grade slope is no steeper than 1 vertical in 5 horizontal.
What matters for an older one:
- Reinforcement and anchorage were built to the rules of the day. The current California Residential Code requires reinforcing steel in footings and stem walls in Seismic Design Categories D0 through D2 (R403.1.3) and half-inch anchor bolts no more than 6 feet apart along the sill (R403.1.6). An older stem wall was built to whatever applied when it was poured. Do not assume it matches today’s detail, and do not assume it doesn’t.
- Cripple walls are the seismic question. California’s Existing Building Code lists unbraced cripple walls and sills not connected to the foundation as structural weaknesses (CEBC Appendix A, §A303.1). Our cripple wall bracing basics and seismic bolt-and-brace overview posts cover the retrofit side.
- The crawl space is where problems show first. Moisture, decay at bearings, and settled pads are all raised-floor issues. Repair options live on our raised foundation repair page, and the step-by-step is in the raised foundation repair process.
The California Residential Mitigation Program’s Earthquake Brace + Bolt grant uses 1980 as its cutoff: a house must be built before 1980 and have a raised foundation or crawl space, among other criteria. That is a program rule, not a code history lesson, and it says nothing about whether any one address qualifies.
Posts on pads, and sills on dirt
Inside a raised house, posts on concrete pads holding up girders are normal. The concern starts when posts on isolated pads carry the perimeter walls too, with no continuous footing around the outside.
The CEBC names this directly. Its list of structural weaknesses includes “a perimeter foundation system that is constructed only of wood posts supported on isolated pad footings,” perimeter foundations that are not continuous, and sill plates or floor framing sitting directly on the ground without a code-conforming foundation. Small exceptions exist, such as short single-story extensions and porches.
Look for it under porches, enclosed porches, and early additions, where a few posts on blocks may have stood in for a poured footing. FEMA P-1100’s crawlspace criteria allow a post-and-pier perimeter to be retrofitted with cripple walls, and they also require a continuous perimeter foundation, or a retrofit that creates one. Translation: discontinuous perimeters usually turn into foundation work, not just bracing.
Brick, block, or stone perimeter walls
Some older California houses sit on unreinforced brick, unreinforced concrete block, or stone. We know of no survey counting how many La Jolla homes do. Age alone won’t tell you; looking at the stem wall from the crawl or the yard will.
Two authoritative documents treat these walls carefully:
- The CEBC lists a perimeter foundation “constructed of unreinforced masonry or stone” as a structural weakness and requires a registered design professional to evaluate unreinforced masonry or partial perimeter foundations (§A304.2.2). Where the code official approves, the foundation can be strengthened according to that evaluation instead of being replaced.
- FEMA P-1100’s prescriptive plans are off the table if any part of the foundation is unreinforced masonry or stone. Its commentary also says that in many cases an unreinforced brick foundation, and possibly stone, “may be deemed acceptable without replacement,” especially where only shear anchors are added, if the engineer finds no significant defects or deterioration.
That second point is worth holding onto. A masonry foundation is a reason for an engineered evaluation. It is not an automatic replacement order.
Conventional slab-on-ground
Slab-on-ground houses, additions, and garages sit on concrete poured on the ground with thickened or turned-down edges acting as the footing. There is no crawl space and no cripple wall. The CRC has its own reinforcement detail for these turned-down footings in high seismic categories (R403.1.3.3).
For retrofit purposes, the CEBC’s prescriptive cripple-wall chapter does not apply to buildings or portions built on slabs on grade. Slab questions tend to be about movement: settlement, heave, and concrete shrinkage. Our slab settlement vs soil movement post explains how to tell those apart, and slab foundation repair covers repair options.
Post-tensioned slab
A post-tensioned slab looks like any other slab from the living room. Inside it, steel tendons are tensioned after the concrete cures. The California Building Code points designers to the Post-Tensioning Institute’s DC10.5 standard for post-tensioned slabs on expansive soils (CBC §1808.6.2), and the residential code sends foundations on expansive soil to that same CBC section (CRC R403.1.8).
Why it matters to an owner: don’t drill, saw, or core a slab until you know whether it is post-tensioned. A stamped warning in the garage slab is a common marker; the Post-Tensioning Institute recommends one. A missing stamp proves nothing. Repair literature from the International Concrete Repair Institute describes locating tendons with non-destructive testing such as ground-penetrating radar before any coring, and says cutting tendons calls for engineering analysis. Plumbing reroutes, remodel trenches, and new anchors are the usual moments this matters.
Hillside systems
On slopes, foundations change shape. Common pieces include stepped continuous footings, drilled piers or caissons tied together with grade beams, uphill retaining stem walls, and tall cripple walls or open post-and-beam framing on the downhill side.
FEMA P-1100 has a separate category for these. It defines a hillside dwelling as one where the tallest cripple wall or open post exceeds 7 feet and the average grade slope is steeper than 1 vertical in 5 horizontal, among other conditions. Those houses are assessed and retrofitted under their own chapter. The CEBC’s prescriptive provisions stop at cripple walls 4 feet tall; anything taller needs a registered design professional. Brace-and-bolt plans built for flat lots are generally the wrong tool here.
The residential code also has setback rules for buildings on or near slopes steeper than 1 vertical in 3 horizontal (CRC R403.1.7), with alternate setbacks allowed when a qualified engineer shows they work. For the planning maps and observation cues, read Mount Soledad hillside foundation considerations. Repair framing is on hillside foundation repair.
Mixed systems after additions
Remodels can leave an older house with more than one foundation. A 1940s raised core might carry a 1970s slab family room and a later garage conversion. FEMA’s crawlspace configurations explicitly include a cripple wall or stem wall foundation in combination with a slab-on-ground foundation.
The line where two systems meet is a place evaluators look carefully, because the two parts were built at different times, on possibly different soil preparation, to different rules. That is a reason to inspect the junction, not proof that something there moved. If part of the house was built on fill or expansive soil, City of San Diego Information Bulletin 141 (April 2026) requires a geotechnical report by a registered design professional with plans for buildings supported on those soils. An old report from a past addition can tell you a lot.
What the type tells you, and what it doesn’t
| Foundation type | What usually gets examined first | Where to read more |
|---|---|---|
| Raised stem wall, with or without cripple walls | Crawl moisture, posts and pads, sill anchorage, cripple wall bracing | Raised foundation repair |
| Posts on pads at the perimeter, or sills on soil | Continuity of the perimeter, decay, whether new footings are needed | Raised foundation repair |
| Unreinforced brick, block, or stone | Condition of the masonry and mortar; engineered evaluation | Foundation inspection |
| Conventional slab | Movement direction, cracks, drainage at the edges | Slab foundation repair |
| Post-tensioned slab | Tendon location before any cutting; movement | Slab foundation repair |
| Hillside systems | Piers, grade beams, tall cripple walls, slope and drainage | Hillside foundation repair |
The type does not tell you whether anything has failed, whether a retrofit is required, or what a repair costs. Two houses with the same foundation type can be in very different shape.
Records help more than guesses
Original plans and permit history can confirm a type faster than a crawl. Our seller foundation documentation checklist explains how City of San Diego records requests work and where older paper records live. A prior geotechnical or engineering report, if one exists, often names the foundation system outright.
Cost factors, not prices
We don’t publish repair totals. What moves scope on an older house is mostly tied to type: crawl clearance and access for raised floors; how much of a perimeter is discontinuous; whether masonry needs testing and engineered strengthening; tendon location work on post-tensioned slabs; slope, pier depth, and access on hillside lots; geotechnical reports where fill or expansive soil is involved; permits; and whether additions bring a second system into the job. Our what drives foundation repair cost post goes further.
When to get the foundation identified properly
Ask for an evaluation when you are buying an older house, planning a remodel that will cut into a slab or touch the perimeter, seeing cracks or floor movement you can’t explain, or unsure whether you have brick, stone, or posts where you expected concrete. A foundation inspection starts with confirming the system. Where load path, masonry strength, or slope stability is in question, we coordinate with licensed engineers as needed.
Next step
If you want to know what is actually under your house and what that means for repair or retrofit, we evaluate homes anywhere in La Jolla. Request a Free Quote, or call (650) 739-6537. Our companion post, the coastal lot foundation checklist, covers the site side: overlays, hazard maps, soil, and drainage.
Sources (accessed October 14, 2026)
- U.S. Census Bureau, American Community Survey 2024 5-year, table B25034 (Year Structure Built), ZCTA 92037, via Census Reporter
- California Residential Mitigation Program, See If You Qualify (Earthquake Brace + Bolt criteria)
- 2025 California Existing Building Code, Appendix A, Chapter A3, Sections A301.2, A303.1, A304.2.2
- FEMA P-1100, Vulnerability-Based Seismic Assessment and Retrofit of One- and Two-Family Dwellings, Vol. 1 Prestandard (October 2019): definitions, Tables 4.1-1 and 4.1-2, Commentary C.4.4.4
- 2025 California Residential Code, Sections R403.1, R403.1.3, R403.1.5, R403.1.6, R403.1.7, R403.1.8
- 2025 California Building Code, Section 1808.6.2 (PTI DC10.5 for post-tensioned slabs on expansive soils)
- International Concrete Repair Institute, Concrete Repair Bulletin, May/June 2013, “Creating Openings in Unbonded Post-Tensioned Structures”
- City of San Diego Information Bulletin 141, Soil Bearing Capacity (April 2026)