Foundation types you will see
Slab on grade. The most common type in tracts built from the 1960s onward. The slab itself is mostly hidden under flooring, so inspectors look for clues: cracks in the garage slab, cracked tile, sloping floors and gaps at baseboards.
Raised foundation with crawlspace. Common in older homes. The inspector enters the crawlspace when it is accessible and checks the perimeter footing, piers, posts, girders, floor joists, moisture, and the connections between the house and the foundation.
Hillside and stepped foundations. Caissons, grade beams and retaining walls carry hillside homes. They are only partly visible and often call for a specialist.
Reading cracks
| What you see | Usually means | Next step |
|---|---|---|
| Hairline cracks in a garage slab | Normal curing shrinkage | Monitor |
| Diagonal stucco cracks at window corners | Settlement or shrinkage | Seal and monitor |
| Cracks wider than 1/4 inch | Movement | Structural engineer |
| One side of a crack higher than the other | Differential movement | Structural engineer |
| Stair-step cracks in block walls | Settlement or lateral pressure | Structural engineer |
| Doors and windows sticking in several rooms | Frame distortion | Evaluate with other clues |
Southern California factors
- Expansive clay soils swell when wet and shrink when dry. Poor drainage close to the house makes this worse.
- Hillside grading in many Orange County and San Diego communities created cut-and-fill lots. Fill can settle over time.
- Earthquakes test the connection between the house and its foundation. Older raised homes may lack anchor bolts or cripple wall bracing.
- Landslide areas exist in parts of coastal Orange County and San Diego. The Natural Hazard Disclosure report tells you whether the property is in a mapped zone.
Inside the crawlspace
Typical findings include earth-to-wood contact, which invites rot and termites; standing water or a damp soil surface; missing or rotted posts; plumbing leaks; and debris. Inspectors also note whether anchor bolts are visible along the sill plate and whether cripple walls have plywood bracing.
Drainage comes first
Many foundation issues start with water. Downspouts that dump next to the foundation, soil that slopes toward the house and over-watered planters all add moisture to the soil under the footing. Fixing drainage is often the cheapest and most effective repair. See exterior and drainage.
Common questions
When should I hire a structural engineer?
When the inspector reports cracks wider than about a quarter inch, vertical offset across a crack, sloping floors, doors that stick across several rooms, or retaining walls that lean. An engineer can tell you whether the movement is historic or active and what a repair would involve.
Are stucco cracks a foundation problem?
Usually not. Stucco cracks at the corners of windows and doors are common as the building settles and the stucco shrinks. A pattern of cracks that keeps growing, or that lines up with floor or slab cracks, deserves a closer look.
What is a post-tension slab?
Many newer Southern California tracts use post-tensioned slabs with steel tendons tightened after the concrete cures. They resist cracking from expansive soils. Never cut or core-drill one without locating the tendons first; a stamp in the garage often warns about this.