Efflorescence is the chalky white mineral deposit you see on concrete and masonry – foundation stem walls, slab edges, retaining walls, and crawlspace piers. It forms when water moves through the material, dissolves salts, then evaporates and leaves them behind. In San Diego homes it isn’t usually structural damage itself, but it is a reliable sign that moisture is getting where it shouldn’t.
What efflorescence actually is
Concrete, brick, block, and mortar all contain soluble salts. When liquid water passes through the material and reaches an exposed face, the water evaporates and the salts crystallize on the surface as a white, sometimes fuzzy, powder. That’s efflorescence. The takeaway for a homeowner is simple: where you see efflorescence, water has been moving through the masonry. The deposit is the residue; the moisture is the real story.
People often confuse it with mold. A quick field distinction: efflorescence is typically white to off-white, gritty or crystalline, sits on hard mineral surfaces like concrete and block, and often dissolves or wipes away with water. Mold is usually fuzzy or slimy, comes in green, black, gray, or brown, prefers organic material like wood framing, drywall paper, and cardboard, and tends to smear rather than dissolve. A general home inspector documents what is visible; confirming mold takes a specialist and, often, lab sampling – it is never called by sight alone.
Why San Diego homes get it
Our climate is dry, so it is easy to assume foundations stay dry too. They don’t. A few local patterns drive most of the efflorescence we see across the county:
- Irrigation and landscaping against the foundation. Daily drip lines, sprinklers hitting stucco, and planters built right up to the stem wall keep soil saturated against concrete that should be drying out. This is the single most common cause we find on inland and suburban homes.
- Expansive clay soils. Large parts of inland San Diego – Santee, El Cajon, parts of Poway and Scripps Ranch – sit on clay that swells when wet and shrinks when dry. Wet clay holds water against the foundation and feeds it through the concrete.
- Hillside and retaining-wall drainage. On the slopes of La Jolla, Del Mar, and the canyon-edge lots all over the county, retaining walls hold back saturated soil. Without working weep holes and drainage behind them, water pushes through the wall and blooms efflorescence on the visible face.
- Coastal humidity and rare heavy rain. Near the coast, humidity and marine moisture keep things damp longer. And when an atmospheric-river storm dumps two inches in a day on ground that hasn’t seen rain in months, water finds every crack and cold joint.
- Older construction details. Pre-1970s homes in North Park, Kensington, and the older parts of Chula Vista frequently lack a capillary break or vapor retarder under the slab, so ground moisture wicks straight up into the concrete.
Where it shows up – and what each spot tells you
Crawlspace piers and stem walls
In a raised-foundation crawlspace, efflorescence on the concrete piers or perimeter stem wall points to standing water, poor grading, or a missing vapor barrier on the soil. Damp crawlspaces also invite wood-destroying organisms and fungal decay in the joists above. This is exactly the kind of hidden-area finding a crawlspace inspection is built to catch, because most homeowners never go down there.
Slab edges and garage floors
On a slab-on-grade home, a white ring around the slab perimeter or salt deposits pushing up through a garage floor suggests ground moisture migrating through the slab. By itself it is usually a moisture-management issue rather than a failure, but where flooring is going down over that slab, it matters – moisture under vinyl, laminate, or glued hardwood causes adhesive failure, cupping, and odor. A concrete slab survey looks at the slab condition, moisture clues, and cracking pattern together so you understand what you’re dealing with.
Retaining walls and basement-style walls
Efflorescence streaking down a retaining or below-grade wall almost always means the drainage behind it isn’t working – clogged or missing weep holes, no gravel drain, or no waterproofing membrane. On a tall engineered retaining wall, persistent water pressure is worth taking seriously, and questions about wall stability or movement belong to a licensed structural engineer, not a general inspector.
When to worry, and when not to
Light, isolated efflorescence on a garage slab or an exterior block wall, with no cracking, no soft or damp framing, and no musty odor, is usually a cosmetic nuisance tied to manageable moisture. Plenty of perfectly sound San Diego homes show a little of it. You don’t need to panic.
Pay closer attention when efflorescence shows up alongside other signals:
- It keeps coming back after you clean it off – moisture is actively, repeatedly cycling through.
- It appears with cracks, especially horizontal cracks, stair-step cracking in block, or cracks that are wider at one end. Sizing up which cracks matter is its own topic – see our guide to foundation cracks in San Diego and when to worry.
- It comes with a musty smell, soft or stained framing, peeling paint, or buckling floors.
- It is heavy and widespread across a foundation wall or crawlspace rather than a small patch.
- You also see spalling – concrete flaking and crumbling – which means the moisture and salts are starting to break down the material itself.
That combination doesn’t automatically mean a failing foundation, but it does mean the moisture source needs to be found and fixed before it causes real damage.
What a home inspector can and can’t tell you
A general inspection is a visual, non-invasive assessment. During a buyer’s inspection, we document efflorescence wherever we find it – crawlspace, slab edge, garage, retaining walls – note the likely moisture path, and flag related conditions like grading, downspout discharge, and irrigation against the structure. Thermal imaging can sometimes reveal temperature differences consistent with moisture behind a surface, though it doesn’t “see” water directly and isn’t a substitute for a moisture meter or destructive investigation.
What a general inspector does not do: confirm mold (that needs a specialist and lab work), perform a termite or wood-destroying-organism report (that’s a licensed pest operator, though a damp crawlspace is a reason to get one), or judge whether a cracked, moisture-loaded foundation is structurally adequate (that’s a structural engineer). We tell you what we see, what it likely means, and who to call next.
Practical next steps
If you’re seeing white deposits at home, start with the cheap fixes: pull irrigation and planters back from the foundation, redirect downspouts away from the slab, regrade so soil slopes away from the house, and check that retaining-wall weep holes are open. If it’s persistent, widespread, or paired with cracking or odor, get eyes on it before it gets worse.
Whether you’re buying, selling, or just want to understand your own home, a professional inspection puts the efflorescence in context with everything else around the foundation. The Real Estate Inspection Company – led by InterNACHI Certified Professional Inspector and CSLB-licensed general contractor Joseph Romeo – inspects homes across all of San Diego County. Call (619) 752-4399 to schedule. Pricing depends on square footage, age, and access; see our fee schedule for details.
