What to Do When You Find Foundation Cracks in Your Bay Area Home

The Moment You Spot a Crack

You are walking through your crawl space, cleaning out the garage, or just glancing at the side of your house when you see it: a crack in the foundation. Your stomach drops. Is your home in danger? Is this going to cost tens of thousands of dollars? Should you call someone right now?

Take a breath. Foundation cracks are one of the most common issues in Bay Area homes, and not all of them are cause for concern. The key is knowing the difference between a cosmetic blemish and a structural warning sign, then taking the right steps based on what you find.

This guide will help you assess what you are looking at, understand why it happened, and know exactly what to do next.

Why Foundation Cracks Happen in the Bay Area

The Bay Area is particularly hard on home foundations. Several local factors combine to make cracks more common here than in many other regions.

Expansive Clay Soils

Large portions of the Bay Area, especially in the South Bay, East Bay, and Peninsula, sit on expansive clay soils. These soils absorb water during the rainy season and swell, then dry out and shrink during summer months. This repeated cycle of expansion and contraction pushes against foundation walls and creates stress fractures over time.

Homes in cities like San Jose, Fremont, Milpitas, and areas near the bay shoreline are especially affected. The soil literally moves beneath your house, season after season.

Seismic Activity

The Bay Area straddles several active fault lines, including the San Andreas, Hayward, and Calaveras faults. Even small earthquakes that you barely feel can contribute to cumulative foundation stress over decades. A magnitude 3.0 tremor might not knock anything off your shelves, but repeated microseismic events gradually weaken concrete and mortar joints.

Age of the Home

Many Bay Area homes were built in the 1940s through 1970s, when concrete mixes and reinforcement practices were less advanced than today’s standards. Older foundations often have less rebar, thinner walls, and concrete that has naturally degraded over 50 to 80 years.

Tree Roots and Drainage

Mature trees near the home can draw moisture from the soil, causing uneven drying and differential settlement. Poor drainage that allows water to pool against the foundation accelerates deterioration and increases hydrostatic pressure on basement walls.

Types of Cracks and What They Mean

Not every crack tells the same story. Here is how to read what your foundation is telling you.

Hairline Cracks (Under 1/16 Inch)

These thin vertical cracks are the most common type and are usually cosmetic. Concrete naturally shrinks as it cures, and nearly every foundation develops some hairline cracking over time. If the crack is vertical, less than 1/16 inch wide, and not growing, it is typically not a structural concern.

What to do: Monitor and document. Take a photo with a ruler for scale. Check again in 6 months to see if it has changed.

Vertical Cracks (1/16 to 1/4 Inch)

Wider vertical cracks can indicate minor settlement. In the Bay Area, this is often caused by soil movement rather than a deficiency in the foundation itself. These cracks may allow water infiltration into crawl spaces or basements.

What to do: Seal with appropriate filler to prevent water entry. Have a structural engineer evaluate if you notice the crack growing.

Horizontal Cracks

Horizontal cracks are more concerning. They typically indicate lateral pressure from soil pushing against the foundation wall. In the Bay Area, this often relates to expansive clay soils or poor drainage. Horizontal cracks in the upper third of the wall are especially serious, as they can indicate the wall is bowing inward.

What to do: Call a structural engineer promptly. Horizontal cracks rarely stabilize on their own and tend to worsen over time.

Stair-Step Cracks

These cracks follow the mortar joints in block or brick foundations in a stair-step pattern. They signal differential settlement, meaning one part of the foundation is sinking more than another. In the Bay Area, this often results from uneven soil conditions or poor compaction beneath the footing.

What to do: Schedule a structural engineer’s assessment. Stair-step cracks usually require some form of foundation stabilization.

Diagonal Cracks

Cracks that run diagonally from the corner of a window, door, or other opening may indicate that the foundation has shifted unevenly. If you also notice doors that no longer close properly or visible gaps between walls and trim, the settlement is likely active.

What to do: Do not delay. Contact a structural engineer for evaluation.

What to Do Step by Step

Step 1: Document Everything

Before calling anyone, photograph every crack you can find. Use a ruler or coin in the photo for scale. Note the location, direction, and approximate width of each crack. This documentation serves two purposes: it gives your engineer a starting point, and it creates a baseline for monitoring whether cracks are growing.

Step 2: Check for Related Symptoms

Walk through your home and look for secondary signs of foundation movement:

• Doors or windows that stick or will not close properly
• Gaps between walls and ceiling or floor
• Cracks in interior drywall, especially above door frames
• Sloping or uneven floors
• Gaps where exterior walls meet the chimney or porch

These symptoms, combined with foundation cracks, help a professional assess the severity of the issue.

Step 3: Hire a Structural Engineer

A licensed structural engineer is the right professional for this job, not a foundation repair company. Repair companies have an inherent incentive to recommend work; an independent engineer gives you an unbiased assessment.

Expect to pay $500 to $1,500 for a residential foundation evaluation in the Bay Area. The engineer will inspect the cracks, assess the overall structural condition, and provide a written report with recommendations.

Step 4: Get a Geotechnical Report If Recommended

If the structural engineer suspects soil-related issues, they may recommend a geotechnical investigation. A geotechnical engineer tests the soil beneath and around your foundation to identify its composition, bearing capacity, and moisture behavior. This report costs $2,000 to $5,000 and is especially valuable in Bay Area neighborhoods with known soil challenges.

Step 5: Evaluate Repair Options

Based on the engineering reports, your repair options may include:

• Epoxy or polyurethane crack injection ($2,000-$5,000): For sealing non-structural cracks and preventing water infiltration
• Carbon fiber reinforcement ($5,000-$10,000): Strips bonded to foundation walls to resist further bowing or cracking
• Helical piers or push piers ($10,000-$25,000+): Steel piers driven to stable soil or bedrock to lift and stabilize a settling foundation
• Underpinning ($15,000-$30,000+): Extending the foundation deeper to reach more stable soil layers
• Partial or full foundation replacement ($30,000-$80,000+): Necessary when the existing foundation is too deteriorated to repair

All pricing is approximate, reflects 2026 Bay Area market conditions, and is subject to change. Every project is unique. Final costs are determined on a project-by-project basis during our design phase.

How to Prevent Foundation Problems

While you cannot control earthquakes or soil composition, you can reduce the stress on your foundation.

Manage Drainage

Water is the single biggest controllable factor in foundation health. Ensure gutters and downspouts direct water at least 4 to 6 feet away from the foundation. Grade the soil around your home so it slopes away from the building, dropping at least 6 inches over the first 10 feet.

Control Moisture Levels

In the Bay Area’s dry summers, the soil around your foundation can shrink dramatically. Some homeowners use soaker hoses during extended dry periods to maintain consistent moisture levels in the soil near the foundation. The goal is to prevent the extreme wet-dry cycles that stress concrete.

Maintain Trees and Vegetation

Large trees within 15 to 20 feet of your foundation can draw significant moisture from the soil, causing differential settlement. If you cannot remove the tree, install a root barrier to redirect root growth away from the foundation.

Address Cracks Early

Small cracks sealed promptly stay small. Left open, they allow water infiltration that accelerates deterioration through freeze-thaw cycles (yes, even in the Bay Area during cold winter nights) and ongoing soil movement.

When to Call a Professional

Call a structural engineer right away if you observe any of the following:

• Cracks wider than 1/4 inch
• Horizontal cracks in foundation walls
• Stair-step patterns in block or brick foundations
• Cracks accompanied by bowing or leaning walls
• Water actively flowing through a crack
• Interior symptoms like sticking doors, sloping floors, or wall cracks
• Any new cracks appearing after an earthquake

For minor hairline cracks with no secondary symptoms, monitoring every 6 to 12 months is reasonable. But when in doubt, the cost of an engineer’s assessment ($500-$1,500) is a small price for peace of mind.

How Foundation Issues Affect Remodeling Plans

If you are planning a remodel and discover foundation cracks, addressing them first is not optional. Any addition, second story, or structural modification to your home depends on a sound foundation. Building new construction on a compromised foundation is like building on sand.

Here is how foundation issues typically intersect with remodeling:

• Second-story additions place significant new load on the foundation. Existing cracks may need reinforcement before the foundation can support the additional weight.
• Kitchen and bathroom remodels that open walls often reveal hidden foundation issues that were not visible from the exterior.
• Room additions require new foundation work that must tie into the existing system. If the existing foundation has problems, the new and old sections may settle at different rates.

A design-build firm that handles both structural assessment and construction can coordinate these overlapping scopes efficiently.

Why Custom Home Design and Build

At Custom Home, we see foundation issues regularly in Bay Area homes. Our two-phase design-build process is designed to catch these problems before they become expensive surprises.

During Phase 1 (Design), we conduct a thorough structural evaluation of your home. If foundation concerns are identified, we bring in structural and geotechnical engineers before finalizing any design or pricing. This means foundation repairs are scoped and budgeted as part of your project, not discovered as a change order mid-construction.

Because we manage both design and construction, we coordinate foundation work seamlessly with the rest of your remodel. There is no finger-pointing between separate architects, engineers, and contractors. One team, one plan, one budget.

If you have noticed cracks in your foundation and are considering a remodel, start with a conversation. We will help you understand what you are dealing with and how to move forward with confidence.

Schedule a free consultation to discuss your project and get expert eyes on your foundation.