Crawl-space assessment
Is there a cripple wall, how tall is it, what is the sill and foundation condition, and how much clearance is there to work.
Foundation Repair / Earthquake retrofitting
Earthquake retrofitting for raised wood-frame houses
Many older Los Angeles houses sit on a raised foundation with little or nothing tying the wood frame to the concrete. A seismic retrofit adds that connection — and, where short cripple walls hold the house up, braces them so they are less likely to collapse in an earthquake.
Discuss a seismic retrofitOverview
The California Residential Mitigation Program describes two common versions: bolt-only, where the frame sits directly on the foundation wall, and brace-and-bolt, where short cripple walls stand between the foundation and the floor. What is under your house decides which applies.
A retrofit improves how the house stays on its foundation in shaking. It does not level floors, close cracks or stop settlement. If the foundation itself is damaged or moving, that needs to be understood first, because bolting a frame to a failing foundation does not solve the problem.
Who this helps
- Owners of raised wood-frame houses with a crawl space, especially older houses
- Owners who see no anchor bolts or plates along the sill when they look in the crawl space
- Owners planning a remodel who want structural work done while access is open
- Owners exploring the state Earthquake Brace + Bolt program — eligibility and participating-contractor rules are set by the program
01
What the work can include
Actual scope and methods depend on the site evaluation and the approved design.
Anchorage
Anchor bolts or foundation plates connecting the sill to the concrete, at the spacing and type the plan specifies.
Cripple-wall bracing
Structural sheathing nailed to the cripple-wall studs, with venting and blocking per the plan.
Related repairs
Replacing deteriorated sill sections or posts found during the work, when the plan or engineer allows them to be handled together.
A
The three connections, in plain language
In shaking, the ground moves the foundation first. Whatever ties the house to it decides whether the house moves with the foundation or slides and drops off it.
Foundation bolting
Steel bolts or approved plates that fasten the wood frame to the concrete below. Without them, the house may rest on the foundation by weight alone.
Sill anchorage
The sill plate is the flat board lying on top of the foundation wall. Anchoring means fastening that board to the concrete so the frame above cannot slide off.
Cripple-wall bracing
Cripple walls are short stud walls in some crawl spaces, between the foundation and the first floor. Bracing them with structural panels keeps them from folding over sideways.
Bolt-only and brace-and-bolt, side by side
Conceptual schematics for understanding only. They are not construction details: hardware, spacing, panels and nailing come from the approved plan for the actual house.
B
Three different situations — three different rule sets
These are often lumped together as "seismic retrofit". They differ in construction, standard, and whether the work is voluntary or ordered.
| Situation | What it looks like | Typical work | Standard or rule | Voluntary or required |
|---|---|---|---|---|
| Raised single-family house | A wood house over a crawl space, with or without cripple walls | Bolt-only, or brace-and-bolt where cripple walls exist | CRMP describes EBB retrofits under the California Existing Building Code, Chapter A3, for light wood-frame houses · source | Voluntary for the owner, unless a local authority or project says otherwise |
| Living space over a garage | An older house with a room above a garage and its large door opening | Strengthening garage walls (panels, steel columns or proprietary walls, beams, hold-downs, clips) plus any crawl-space retrofit | CRMP describes ESS retrofits using FEMA P-1100 plan sets; an engineer may still be needed · source | Voluntary for the owner |
| Multi-unit soft-story building (City of LA) | Older multi-story wood-frame apartments or condos with tuck-under parking or open fronts | Engineered strengthening of the weak story | LADBS mandatory program under City Ordinances 183893 and 184081 · source | Required for buildings in scope once LADBS issues an order, with deadlines set by the ordinance |
Age alone does not make a house eligible for a program or require a retrofit. Whether a building is in scope is decided by the program or the building authority, using their own criteria.
C
From first look to closed permit
- 01
Evaluation
Look at what is actually under the house: foundation type and condition, sill, cripple walls, access, moisture.
- 02
Plan determination
Decide whether an approved standard plan fits the house or an engineer must design the retrofit. Damaged concrete, tall or unusual walls and hillsides usually point to an engineer.
- 03
Permit
The permit is issued by the building authority for the address — LADBS inside the City of Los Angeles, other cities and the County elsewhere.
- 04
Work
Installation follows the plan; anything found that the plan does not cover is raised before it is changed.
- 05
Inspection
The authority's inspector checks the work at the stages the permit requires.
- 06
Closeout
Final inspection, permit finaled, and the plan, permit card and photos kept together for the owner's records.
About grant programs
- CRMP runs Earthquake Brace + Bolt (EBB) for raised houses and Earthquake Soft-Story (ESS) for living space over a garage.
- Registration opens for limited periods, and eligibility depends on location (ZIP code), the house, ownership and occupancy, and available funding.
- Grant-funded work must be done by a contractor listed in CRMP's contractor directory; EBB also allows qualified owner-builders, ESS requires a directory contractor.
- Houses in a FEMA Special Flood Hazard Area may have additional flood-insurance and recording conditions for larger FEMA-funded grants.
KB Remodeling does not claim to be a CRMP directory contractor, FEMA-trained or certified, or program-approved. We do not promise grant approval, reimbursement or any insurance discount.
Before a retrofit visit: what to gather
An assessment checklist, not instructions to do structural work yourself. Do not enter a crawl space that is wet, tight or has exposed wiring.
- Where the crawl-space access is, and anything stored or blocking it
- Photos you already have of the underside of the house, with dates
- Year built and any permits or plans you hold, including past retrofit or foundation work
- Whether there is a room over the garage, and whether the house is on a hillside
- Cracked, crumbling or patched concrete you have noticed, and where
- Water heater and gas meter locations, and any moisture or pest notes
- Any CRMP registration or program correspondence, if you applied
Official references
Common triggers
- No visible anchor bolts or plates at the sill
- Short wood walls between the foundation and the first floor in the crawl space
- A home purchase, insurance question or remodel that prompts a structural review
- Cracked or crumbling foundation concrete — a signal to evaluate before retrofitting
Options
- Bolt only
- Where the floor framing sits directly on the foundation wall, anchorage alone is the usual retrofit.
- Brace and bolt
- Where cripple walls exist, they are braced with sheathing and the sill is bolted to the foundation.
- Standard plan or engineered plan
- Some building authorities offer prescriptive standard plans for qualifying houses. Taller cripple walls, hillside houses, damaged foundations or unusual framing usually need an engineer's design.
Limits and what this is not
- A retrofit does not make a house earthquake-proof; it reduces specific known weaknesses.
- Retrofit does not repair settlement, cracking or drainage problems.
- Houses on slabs, hillside stilts or with major foundation deterioration fall outside a simple brace-and-bolt approach.
- We do not claim participation in, or eligibility for, any grant program; check the program's own rules.
02
Contractor, engineer and city inspector
| Aspect | Contractor evaluation (KB) | Licensed engineer | City or county inspection |
|---|---|---|---|
| Question answered | What is visible and what practical next step fits | What is causing it and what the design should be | Does permitted work match the approved plans |
| When | Before anything is decided | When movement, capacity, soil or design is in question | At permit stages during construction |
| Relied on for | Planning and pricing a defined scope | Professional engineering judgment and drawings | Code compliance of the inspected work |
On this project
Whether a standard plan or an engineered design applies is decided with the building authority for the address; the City of Los Angeles, for example, publishes standard plans through LADBS, while other cities have their own procedures. When an engineer is needed, they design the retrofit and may observe it. The city or county inspector checks the work at the stages the permit requires. Our crawl-space look is a contractor evaluation, not an engineering assessment.
Permits →03
Typical sequence
- 01
Crawl-space look
We check access, cripple walls, sill condition and the visible foundation.
- 02
Plan path
Standard plan if the house qualifies; otherwise an engineer's design.
- 03
Permit
The permit is obtained from the authority for the address before work starts.
- 04
Work and inspection
Anchorage and bracing are installed and inspected; access panels and vents are restored.
Access and disruption questions
- Is there an access hatch, and how much headroom does the crawl space have?
- Are there utilities, ducts or insulation in the way that must be moved and replaced?
- Is there moisture, debris or pest damage under the house?
- Most retrofit work happens beneath the floor; noise and access interruptions inside the house are usually limited, but not zero.
Questions homeowners ask
How do I know whether I have cripple walls?
Look through the crawl-space access: short wood-stud walls standing on the concrete under the floor are cripple walls. If the floor framing rests directly on the concrete, there are none. We can confirm during a visit.
Does brace-and-bolt work correct settlement?
No. Brace-and-bolt strengthens the connection between a raised wood-frame house and its foundation; settlement repair addresses movement or damage in the foundation itself. If both concerns exist, evaluate the foundation's condition before choosing the retrofit plan. Rooms over a garage follow a different assessment path, explained in the seismic resource on this page.
Can you retrofit a house on a slab?
Slab houses are usually already connected differently and fall outside the brace-and-bolt approach. Other seismic issues, if any, need an engineer's review.
Will the city require a permit?
Generally yes. The authority for your address decides which plan and inspections are required.
Will a retrofit fix settlement or uneven floors?
No. Bolting and bracing improve the connection between house and foundation in shaking. Settlement, sloping floors and drainage problems are separate and need their own evaluation.
What if the foundation concrete is cracked or crumbling?
That has to be understood first. Anchors need sound concrete to hold. Deteriorated sections may need an engineer, repair or partial replacement before — or as part of — a retrofit.
Can we stay in the house during the work?
Usually, since most work happens under the floor or in the garage. Expect noise, access needs and occasional utility interruptions; garage work for living-over-garage houses can take the garage out of use for a time.
Who handles the permit?
On a contracted project we coordinate the permit with the authority for the address, using a standard plan where it applies or the engineer's drawings where it does not. The owner signs where the authority requires.
How do you get into a tight crawl space?
Through the existing access where possible. If access or headroom is too limited, a new access opening may be needed — that is part of the plan discussion, not a surprise.
What documentation will I have afterwards?
The approved plan, the permit with its inspection sign-offs, and photos of the work before it is covered. Programs such as EBB or ESS have their own documentation rules.
KB Remodeling · CSLB #1066105
Discuss a seismic retrofit
Tell us what you are seeing and the city. No street address is needed to start.