How to Thoroughly Dehumidify Wooden Houses after Flood

The restoration work of California wooden villas after being hit by floods is a complex and time-consuming project that requires systematic handling of multiple key issues. The following is a detailed repair process and its main contents:

 

Check if the structure of the house is damaged

Before returning home after a flood, it is necessary to inspect the structural damage of the house in advance and ensure that it is in a safe condition before entering. Ventilate the room in advance and check for loose power cords and gas leaks.

If the above situation exists, please contact the professional company for repair in a timely manner and wait for the problem to be resolved before entering. In addition, do not enter the basement that has been flooded to prevent the risk of electric shock.

 

Remove stagnant water from the house

The most crucial thing for safe disposal of a room after a flood is to remove all accumulated water as soon as possible. If there is a large accumulation of water in the basement, it needs to be extracted in batches according to the situation to avoid structural damage and wall collapse that may occur if all the water is extracted in a short period of time.

If there are petroleum substances present on the surface of the accumulated water, it is necessary to contact professionals to remove them before removing the accumulated water.  

 

Thoroughly dry the house

Open all doors and windows to maximize the use of natural wind. Use industrial-grade LGR dehumidifiers (in sufficient quantity to cover all areas), operate continuously, and reduce indoor humidity to below 50% (ideally 30-50%). Use high-power fans (such as axial fans) to promote air circulation and blow towards damp walls, floors, attics, etc.

It is usually necessary to cut and remove gypsum boards that have been soaked in water for more than 24-48 hours or 30-60 centimeters above the water level (including parts that may be damp inside). Water will rise along the wall, damaging the insulation layer and accumulating.

Dismantle wooden flooring (solid wood, composite flooring), carpets, and liners that have been soaked in water. Inspect and handle the underlying flooring.

Insulation materials such as fiberglass and cellulose soaked in water must be thoroughly removed and replaced. They cannot be effectively dried and are excellent culture media for molds.

If water seeps into the bottom of the cabinet, it is usually necessary to remove the bottom cabinet, inspect and dry the wall and floor structures.

Use a hygrometer to monitor the moisture content of wood (which should be reduced to below 15%, preferably close to the local equilibrium moisture content) and indoor humidity. The drying process may take several weeks or even longer, and the next step should not be rushed.

 

Professional evaluation and detailed examination

Hire a professional mold testing company to conduct air and surface sampling, evaluate the degree and type of mold contamination (especially whether there are toxic molds). Develop a professional remediation plan.

Check all wooden structural components (beams, columns, wall studs, floor joists, subfloor, roof trusses, etc.) for signs of decay, softening, deformation, cracking, termite or fungal erosion.

Use a humidity detector and visual inspection.

A certified electrician shall conduct a comprehensive inspection of all wires, sockets, switches, distribution boards, and electrical appliances. Floods can cause damage to wire insulation and corrosion of connection points, posing a serious fire hazard. The power supply can only be restored after a thorough inspection, cleaning, drying, or replacement of damaged parts, and passing the test.

Check whether the water supply pipe, drainage pipe, and sewage pipe are cracked, blocked, or contaminated. Check whether the water heater, boiler, and other equipment are damaged by water ingress.

Pipeline systems, furnaces, air conditioning units, etc., may be contaminated or damaged by floods and require professional cleaning, disinfection, or replacement.

 

Cleaning, disinfection, and mold removal

According to the evaluation report, it will be executed by a professional company! Usually includes: physical isolation of contaminated areas (negative pressure isolation), thorough removal of moldy materials that cannot be cleaned (such as severely moldy gypsum boards, wood), and cleaning of all surfaces with a HEPA vacuum cleaner.

Thoroughly scrub and treat all hard surfaces with specialized disinfectants/fungicides registered with the Environmental Protection Bureau (follow instructions to ensure safety). Clean again with a HEPA vacuum cleaner. Perform final cleaning on all processed areas. After completion, perform another test to verify the cleaning effect.

Disinfect all hard surfaces (frame wood, subfloor, concrete, etc.) with EPA-approved disinfectants (such as diluted bleach solution or other specialized disinfectants) to kill bacteria and viruses. Pay attention to ventilation and safety.

 

Structural repair and reconstruction

Replace damaged structural timber: Based on the assessment of the structural engineer, replace beams, columns, wall studs, floor support beams, etc. that have decayed, softened, or lost their load-bearing capacity. This is the foundation for ensuring the long-term safety of the house.

Replacing sub floor/slab: Remove and replace damaged sub floor (usually plywood or OSB board).

Repair/reinforce foundation: If there are problems with the foundation, professional reinforcement or repair is required.

Rebuild the wall: install new insulation materials (waterproof or closed cell foam spray insulation materials are recommended), new gypsum board (moisture-proof gypsum board is considered), and make steam barrier.

Install new flooring: Install new base and surface flooring (solid wood, composite flooring, ceramic tiles, etc.). Consider materials that are more water-resistant in areas prone to moisture.

Repair/replace doors and windows: Check if the door and window frames are deformed or damaged, and replace them if necessary. Ensure good sealing.

Interior decoration: painting, installation of skirting boards, cabinets (if new installation is required after removal), countertops, etc.

 

System recovery and testing

Electrical system restoration: Electricians complete all repair work, conduct comprehensive testing, and ensure safety before restoring power supply.

Pipeline system restoration: Repair or replace damaged pipelines, test for smooth water supply and drainage without leakage. Turn on the faucet and drain the stagnant water from the pipeline until the color of the drinking water becomes colorless and odorless.

HVAC system restoration: Clean or replace pipelines, repair or replace equipment to ensure normal operation. It is advisable to raise the water temperature of the water heater to 60 ℃ and open the hot water tap to release the stagnant water in the hot water pipeline for 1 hour to completely remove the pollution in the hot water pipeline.  

 

The restoration after a flood is a huge project that requires patience, meticulous planning, and professional execution. In California, addressing mold issues and ensuring structural safety (while also considering earthquake resistance) are the core challenges of restoration work. It is essential to prioritize safety and health, and seek professional assistance.