Cost to install LA french drain?

$4K–$12K typical perimeter drain.

Basement waterproofing in LA?

$15K–$35K for a full interior-exterior system.

Bay hillside drainage cost?

$10K–$30K. Engineering + permit + excavation.

$20K–$55K for interior membrane + sump + exterior regrade.

California Drainage & Waterproofing.

LA drainage — french drains, area drains, downspout extensions, sump pumps. Hillside homes get engineered solutions.

Bay drainage — hillside saturation, basement intrusion, foundation perimeter drains. Engineer-designed, permitted, warrantied.

Los Angeles

$4K – $35K

Surface french drain bottom; full basement system top.

Timeline — 3–7 days for typical drainage system.

Los Angeles Drainage & Waterproofing →

San Francisco Bay Area

$6K – $55K

Bay hillside + heavy rain lift cost.

Timeline — 5–10 days including hillside coordination.

San Francisco Bay Area Drainage & Waterproofing →

Scope — what we deliver.

Site assessment
Engineering if needed
Permit
Excavation + install
Backfill + test

Permits look different in LA vs the Bay.

Los Angeles — permit notes

Permit if connecting to public storm.
Engineering on hillside.
Discharge to street legal in LA.

Bay Area — permit notes

Permit + stormwater compliance.
Engineering common.
Discharge regulations vary by city.

How we think about drainage & waterproofing.

Exterior work is moisture management, full stop. Roofing, siding, stucco, decks, and concrete all exist to move water away from the building before it has time to soak in. We detail every transition — roof-to-wall, wall-to-deck, deck-to-door — as if it will see a hose test, because in winter it will.

California climates are deceptively hard on exteriors. UV is brutal. Marine air corrodes fasteners. Wildfire embers land on debris in valleys. We default to WUI-compliant materials (Class A roofing, ⅛" mesh vents, ignition-resistant siding) on every exterior job, even where it's not yet required — it's $2–6K extra and it's the difference between a saved house and a lost one.

The schedule, written out.

Week 0
Inspection + scope
Roof + flashing inspection, moisture probe of siding, deck post + ledger check, photo documentation.
Week 1–2
Permits + material procurement
Permit (most cities require for re-roofs, additions, decks > 30" off grade); material delivery scheduled around rain forecast.
Week 2–4
Tear-off + dry-in
Selective demo, sheathing inspection, replace rotted decking, install underlayment + flashing.
Week 4–6
Install
Roof, siding, stucco scratch + brown + finish, deck framing + decking, concrete forms + pour.
Week 6–7
Trim + paint + seal
Trim, paint, sealant on penetrations, deck stain or color.
Week 7–8
Inspection + warranty
Final inspection, manufacturer warranty registration, owner walk.

Materials & assemblies.

Component	Default spec	Why
Roofing	30-yr architectural shingle, standing-seam metal, or single-ply TPO/PVC for low-slope	Standing-seam metal wins lifetime cost in most CA climates.
Underlayment	Synthetic underlayment + peel-and-stick ice-and-water at valleys and penetrations	30-lb felt is no longer the right baseline.
Siding	Fiber cement (Hardie), engineered wood (LP SmartSide), or stucco with weep screed and 2-layer WRB	WRB layering is what controls 90% of stucco failures.
Deck framing	PT lumber for posts, joists, ledger; stainless or coated fasteners; flashing at ledger	Galvanized fasteners on PT lumber corrode in 5 years.
Decking	Composite (Trex, TimberTech), thermally modified hardwood, or kiln-dried IPE with hidden fasteners	Composite is the lowest-maintenance default for CA sun.
Concrete	4000 psi mix, #4 rebar @ 16" o.c., proper expansion + control joints	Cracks come from poor jointing, not from the mix.

Hidden costs we flag up front.

Line item	Range	When it hits
Sheathing replacement	$8–$22/sqft	tear-off reveals rot or delaminated OSB
Deck ledger flashing repair	$1.5K–$6K	ledger was nailed, not bolted with flashing
Stucco crack repair (full re-skim)	$6K–$18K	1980s synthetic stucco has reached end of life
Tree removal / overhead clearance	$1.5K–$8K	roof or wall access requires it
Permit (re-roof + structural)	$300–$2.5K	many cities now require for re-roof + decks

cheaper alternatives

What we'd consider — and what we wouldn't.

Overlay re-roof (shingle over shingle)
30% cheaper but voids most warranties + traps moisture; never on a building you plan to keep.
EIFS over stucco
Better thermal but historically a moisture-management nightmare — only with rainscreen detail.
Pressure-treated decking
60% cheaper than composite but requires re-staining every 2 years to last.

pitfalls — takeover-job patterns

Mistakes to avoid.

Skipping the moisture probe of stucco before scope-of-work — a 'paint job' turns into a $25K re-skim
Mounting a deck ledger to siding without flashing — #1 source of catastrophic deck failure in CA
Not detailing kick-out flashing at roof-to-wall — drives water behind the siding for years
Installing concrete without proper joint spacing — random cracking that no patch will hide

Drainage & Waterproofing — Los Angeles.

Drainage & Waterproofing — Bay Area.

In short.

Cost to install LA french drain?: $4K–$12K typical perimeter drain.
Basement waterproofing in LA?: $15K–$35K for a full interior-exterior system.
Bay hillside drainage cost?: $10K–$30K. Engineering + permit + excavation.
Wet SF basement fix?: $20K–$55K for interior membrane + sump + exterior regrade.

Stay in the same trade

Related exterior construction services.

Same service, other region

Drainage & Waterproofing across California.

Authority sources

Drainage & Waterproofing — official California resources.

Primary sources we cross-reference on every project — agencies, utilities, and code bodies whose decisions actually move your permit and budget.

FEMA flood map service center
FEMA
California stormwater resources
California State Water Board
CSLB license lookup
California Contractors State License Board
Verify any contractor's license, bond, and complaint history before signing.
California Building Standards Commission
BSC
Authoritative source for the California Building Code (Title 24).

Ready to scope a California drainage & waterproofing project?

Send us the address. We’ll pull zoning, setbacks, and feasibility before you spend money on drawings — and the inquiry routes straight to the California desk.

Talk to the California desk →