If your home has Mission Bay flood damage from this week's record tides, the next few days matter more than the next few months. Fast drying limits mold, good documentation protects your claim, and a little planning before you rebuild can keep you from paying for the same repair twice.

This guide is written by a licensed San Diego contractor for homeowners in Mission Bay, Mission Beach, and other low-lying coastal neighborhoods. It covers what to do right now, why saltwater damage behaves differently from a plumbing leak, and the permit rule that can change the scope of your repair.

What happened around Mission Bay

On Monday morning, October 26, an extreme high tide overtopped the city's sand berms in Mission Beach and sent seawater down boardwalks, alleys, and streets, into garages and yards (FOX 5). At least one Mission Bay resident reported water reaching the first floor of his home (10News). On Tuesday, NOAA's tide gauge at Broadway Pier peaked at 8.52 feet, and some of the water around Mission Bay appears to have pushed up through the storm drain system rather than over the berms (Times of San Diego).

There was no storm behind it. A Kelvin wave, a slow pulse of warm ocean water linked to this year's El Niño, is raising sea level along the coast. Scripps scientists estimate these waves can push tides roughly 6 to 17 inches above normal (FOX 5). The National Weather Service has a Coastal Flood Warning in effect for the San Diego County coast through Thursday afternoon (NBC 7), and researchers expect more Kelvin waves this season (NPR).

Your first 48 hours

1. Document before you clean

   Take wide photos and video of every affected room, then close-ups of the waterline on walls, cabinets, doors, and appliances. Measure the water height from the floor. Keep damaged items until your adjuster has seen them or approved disposal, and save every receipt for pumps, fans, and temporary housing.

2. Call your insurance agent and check your flood coverage

   Standard homeowners policies generally exclude flood, including tidal flooding. Coverage usually comes from a separate flood policy through the National Flood Insurance Program or a private carrier. Report the loss quickly and ask what documentation they need before work begins.

3. Get the water out and the structure dry

   A water mitigation company will extract water, open wet cavities, and set dehumidifiers and air movers. The EPA's guidance is to dry water-damaged materials within 24 to 48 hours to prevent mold growth (EPA). That guidance is written for clean water. Seawater that came through streets and storm drains should be treated as contaminated, which means soaked porous materials like carpet, pad, insulation, and drywall usually need to come out rather than be dried in place.

4. Don't close the walls too soon

   Surfaces can feel dry while the framing, bottom plates, and slab are still wet. Ask for moisture readings that show materials are back to normal before any new drywall, flooring, or cabinets go in. Sealing in moisture is how a flood repair turns into a mold remediation job a year later.

Why saltwater damage is different

A burst pipe leaves clean water that evaporates. Seawater leaves salt. Salt stays in drywall, insulation, wood, and concrete after the water is gone, and it keeps pulling moisture out of the air. In a coastal home with naturally humid air, that means materials can stay damp longer and stucco or concrete can show white efflorescence for months.

Salt is also hard on metal. It corrodes nails, screws, and framing connectors, electrical terminals and breakers, appliance control boards, and HVAC components. In practice, a saltwater repair usually involves:

• A flood cut that removes drywall and insulation above the visible waterline, set by moisture readings rather than guesswork.
• Cleaning and rinsing framing before it dries, plus a check of bottom plates, sill plates, and connectors for corrosion or decay.
• Replacing submerged electrical devices, including outlets, switches, and GFCIs, and having the panel inspected if water reached it.
• Evaluating appliances and equipment that sat in water: water heaters, furnaces or air handlers, washers, and dryers.
• Inspecting flooring and subfloor or slab, especially under cabinets and built-ins where water hides.

The cheapest time to make a home more flood-resilient is when the walls are already open.

Before you rebuild: the 50% rule

If your home sits in a FEMA Special Flood Hazard Area, federal floodplain rules apply to the repair. When the cost to restore a damaged building equals or exceeds 50% of the building's market value before the damage (land not included), the home is considered "substantially damaged." It then has to be brought into compliance with current floodplain standards, which can mean elevating or floodproofing before you rebuild (San Diego County).

What that means for you:

• Look up your flood zone on the FEMA Flood Map Service Center before you sign a repair contract.
• Get a detailed, itemized scope. The permitting agency reviews repair costs against your building's value, so a vague estimate creates delays. A design-build contractor handles design, engineering, and permits under one team, which keeps that paperwork consistent.
• Plan the whole repair at once. Splitting work across permits doesn't make the rule go away, and planning together avoids tearing out new work later.

Rebuild it better than it was

With more Kelvin waves expected this season, putting back the same carpet and paper-faced drywall invites the same damage. Since the lower walls are already open, this is the moment to consider tile or sealed concrete instead of carpet, cement board and closed-cell foam in the lower wall, outlets and equipment moved higher, and a backwater valve on drain lines. FEMA classifies materials like cement board and closed-cell foam insulation as flood damage-resistant (FEMA Technical Bulletin 2).

We cover these upgrades room by room in our guide to flood-resilient remodeling for San Diego coastal homes.