A Story from the Field: The Unit That Was Always Rented

Ek is thirty-eight and works in an office in central Bangkok. Several years ago he bought a twenty-eight square metre unit in a five-storey low-rise condominium in Bang Kapi, planning to rent it out as a long-term side income. The building has no lift, which makes the upper floors harder to let, but Ek's unit is on the ground floor. It is easy to walk in and out of, close to a bus stop and a short ride from the university, so it has never been empty for long. His tenants have mostly been final-year students and young graduates in their first jobs.

During the 2026 floods, water from the street flowed into the car park and the ground-floor lobby. Every ground-floor unit had around thirty centimetres of water inside for several days. Ek's tenant carried his belongings up to a friend's room on the fourth floor and went to stay with relatives. A week later he sent a short message: "I'd like to end the lease. The room smells really bad and I can't live there anymore."

When Ek went to look at the unit after the water receded, the first thing he noticed was the smell. A musty, drain-like odor hit him as soon as he opened the door. The laminate floor had swollen into waves. The bottom edge of the built-in wardrobe, made of particleboard, had puffed up and was speckled with grey mold. The mattress on its low bed base had soaked up water and was heavy to lift. The grout in the bathroom had turned into black lines, and dried mud was caked under the kitchen sink.

He spent a full day washing the floor himself, ran the air conditioner to pull out moisture, then took photos and posted a new listing. Two people booked viewings. Both stood at the door for less than five minutes, said "Let me think about it," and never replied. That was when Ek understood that a room that looks clean in photographs is not yet a room someone actually wants to live in.

He also realised that his situation was common. Up and down the soi, owners of ground-floor units in similar walk-up buildings were facing the same problem: tenants gone, rent stopped, monthly common fees and loan repayments still due, and viewers walking away the moment they smelled the room. Getting the unit back on the market was not about cleaning harder. It was about cleaning differently.

Why Ground-Floor Units in Low-Rise Condos Recover More Slowly Than Expected

Most low-rise condominiums in Bangkok are walk-ups of four to eight storeys. They usually have no lift, no raised parking podium, and ground-floor units that sit level with the car park or only slightly above the street. When a flood comes, these units are hit first and stay wet longest. These are the problems we see most often:

• Small, closed rooms. Units of twenty to thirty square metres often have windows on one side only. Air barely moves, so moisture lingers for weeks and the musty smell soaks into curtains, mattresses and wardrobes.
• Finishes that absorb water. Laminate flooring, particleboard or plywood built-in furniture and the lower part of gypsum partition walls all absorb water, swell and become an easy home for mold.
• Shared building drains. Ground-floor units sit at the end of the building's drainage system. During a flood, wastewater can back up through bathroom floor drains and kitchen sinks, leaving stains and a lingering sewer smell.
• Corridors and common lobbies. Even when the inside of a unit is clean, a corridor that still smells will put viewers off before they reach the door.
• No lift. Removing damaged furniture and bringing in new items means carrying everything up and down stairs or through narrow corridors. Ground-floor units have it easier than upper floors, but every job still takes more time and labour than in a high-rise with a service lift.

The Real Costs a Rental Owner Needs to Consider

The next tenant's health. Urban floodwater is often mixed with sewage and may carry bacteria such as E. coli and the bacteria that cause leptospirosis, traces of which can remain on floors and lower walls. Mold spores in a damp, closed room can trigger allergies, asthma, a blocked nose and a persistent cough. A tenant who keeps falling ill after moving in is unlikely to renew, and may well mention it in the online groups where people look for rooms.

Income lost every month. Each empty month is rent you do not receive, while the common area fee, loan repayment and utilities standing charges still have to be paid. The longer the unit sits, the further mold spreads and the higher the eventual repair bill.

Rent level and credibility. A unit that viewers feel "flooded and still smells" tends to attract lower offers, or gets skipped in favour of upper-floor units, even though the ground floor used to be the easiest unit in the building to let.

Fixtures and furnishings. Built-in wardrobes, flooring, mattresses, curtains and the appliances supplied with the unit all deteriorate if mold is left to spread, which means replacing more than was really necessary.

The owner's time. Most owners of rental units have full-time jobs. They cannot sit in the unit every day or spend weekend after weekend deep cleaning. Getting the job done properly in one round is almost always better value.

Why Washing the Unit Yourself and Running the Air Conditioner Is Not Enough

• Mopping with ordinary floor cleaner. It makes the floor look clean, but it does not disinfect grout lines, skirting boards or the lower walls that have already soaked up water.
• Running the air conditioner day and night. It lowers humidity in the air, but if the evaporator coil or drain pan has been contaminated, the unit can blow musty air and mold spores straight back into the room. Have an air-conditioning technician inspect and clean it first.
• Air freshener sprays and scented candles. They mask the smell for an hour or two. When a viewer comes on another day, the original smell is back.
• Painting over mold stains. If the wall is not truly dry, mold will push the paint off within a few weeks, and the new tenant will be the first to see it.
• Treating only the inside of the unit. If the corridor, stairwell and neighbouring units have not been dealt with, odors drift back in under the door and through the windows.

The Solution: Restore the Unit with WHD Disinfection Fogging and Ozone Treatment

World Health Disinfection (WHD) provides disinfection fogging and ozone treatment for condominium units, apartments and condo common areas after floods. We take single-unit jobs for individual owners, as well as multi-unit jobs arranged by a juristic person or a group of owners together.

Disinfection fogging with CHEMGENE HLD4H. Our team uses CHEMGENE HLD4H, a professional-grade disinfectant, applied with ULV equipment that produces a very fine mist. It reaches grout lines, skirting boards, the space under the sink, the area around drains, lower walls and the inside of built-in wardrobes left open for treatment.

Ozone treatment for the whole unit. In a small room, ozone spreads evenly into every corner. It helps reduce airborne mold spores and breaks down the molecules behind musty, sewer-like and muddy odors that have settled into curtains, cabinets and walls. A compact condo unit can be closed off completely, which makes it particularly well suited to ozone treatment.

How We Work in a Ground-Floor Condo Unit

1. Survey the unit and its surroundings. We check how high the water rose, which materials are damaged, the condition of the bathroom drains and whether the corridor outside also smells.
2. Advice on stripping out and sorting. Mattresses, warped laminate and particleboard that has swollen and started to crumble should come out first. Disinfection works best on surfaces that are clean and starting to dry.
3. Coordination with the juristic person. We confirm the work date and time, the route for carrying equipment through the building, and whether the common corridor outside the unit should be treated at the same time.
4. ULV disinfection fogging. Bathroom, kitchenette, floors, lower walls and the inside of cabinets.
5. Ozone treatment. The unit is closed, and dose and time are set to suit its size. Televisions and sensitive electronics are covered or moved out beforehand.
6. Ventilation and re-check. Doors and windows are opened so the ozone can break down into oxygen. We re-check odors and mold spots and tell the owner when it is safe to go back in.

Working with the Juristic Person So the Job Goes Smoothly

In a condominium, an owner is responsible only for the inside of their own unit. Corridors, stairwells, the car park and shared drainage are the responsibility of the condominium juristic person. Talking early makes a big difference to the outcome.

• Give notice in advance. Send a message or fill in the building's contractor-entry form according to its rules, with the company name, date, time and scope of work.
• Ask about the shared drains. If several ground-floor units have the same sewer smell, the cause may be the building's drainage system or inspection chambers, which the juristic person should have a plumber check.
• Invite neighbouring owners. Ground-floor units that flooded together can be treated on the same day. That reduces odors migrating from one unit to the next and means the building office only has to coordinate once.
• Suggest treating the common corridor. The juristic person may consider booking disinfection fogging for common areas on the ground floor, which helps the whole building look ready to welcome residents back.

Getting the Unit Ready to List Again

Once the unit has been disinfected, ozone-treated and repaired, the next step is to give prospective tenants confidence.

• Finish repairs before taking photos. Replace the warped flooring, repair cabinet edges, repaint only when the walls are genuinely dry, and fit a new mattress and curtains.
• Air the unit before every viewing. Most viewers make up their minds based on the smell in the first five minutes.
• Be honest about the flood. If a viewer asks, explain that the unit took on water and describe what was done to restore it. Transparency builds far more trust than avoiding the question.
• Keep records. Save before-and-after photos and the service receipts. They are useful for insurance claims and for explaining the work to tenants.
• Add simple care notes to the new lease. For example: open the windows regularly, do not dry wet laundry inside, and tell the owner promptly about any new mold spot.

Checklist: High-Risk Spots in a Ground-Floor Condo Unit After a Flood

• ☐ Bathroom floor grout, around the toilet and the floor drain
• ☐ Under the kitchen sink, the cabinet below the counter and the waste pipe
• ☐ The bottom edge of built-in wardrobes, the back panel against the wall, and under the bed base
• ☐ Laminate or vinyl flooring and the skirting boards around the room
• ☐ Gypsum or plastered walls from thirty to fifty centimetres above the floor
• ☐ Curtains, mattress, pillows and fabric sofa
• ☐ The air conditioner, drain pan and drain line (have a technician inspect and clean them)
• ☐ Low sockets and the breaker panel (have an electrician check before switching on)
• ☐ The corridor outside the unit and the gap under the door

Strip Out, Restore or Replace? A Simple Guide for Common Condo Finishes

Owners often ask which parts of a flooded unit can be saved. The answer depends on how long the water stayed and how wet the material became, but these general guidelines help with planning:

• Laminate flooring. If the boards have swollen, lifted at the joints or warped into waves, they usually need replacing. Water trapped beneath laminate cannot dry properly and becomes a hidden source of musty odor.
• Vinyl or tile flooring. Tiles can usually be cleaned and disinfected. Pay close attention to grout lines. Click-lock vinyl may need lifting to check whether water is trapped underneath.
• Particleboard built-ins. Particleboard that has swollen rarely returns to its original shape and loses strength. Damaged panels, kick plates and drawer bases are generally replaced. Solid wood or plywood components in good condition can often be cleaned, dried and kept.
• Gypsum partition walls. If the lower part of a gypsum wall has soaked up water, the affected section is commonly cut out and replaced once the cavity has been inspected and dried.
• Mattresses and fabric sofas. Items soaked by floodwater are usually best discarded. Items that were only exposed to damp air may be cleaned, and our dust mite removal service can help with those that are still usable.
• Curtains. Washable curtains can be laundered thoroughly and dried in the sun. Heavy blackout curtains with foam backing often hold odors and may be better replaced.

Whatever is kept, the order of work matters: strip out what cannot be saved, clean, disinfect and ozone-treat, let the structure dry, then rebuild. Reversing the order traps moisture and odor behind new finishes.

A Practical Timeline from Flood to New Lease

Days 1 to 7: Assess and document. Photograph the damage before anything is thrown away. Contact the juristic person about the building's condition and drains. Have an electrician check sockets and the breaker panel. Remove the mattress, soaked textiles and any flooring that has clearly failed. Open the windows whenever it is safe and dry outside.

Days 7 to 14: Disinfect and deodorize. Once the unit is cleared and surfaces have begun to dry, book disinfection fogging and ozone treatment. If neighbouring owners agree, schedule all ground-floor units on the same day, and ask the building office whether the corridor can be included.

Days 14 to 30: Repair and refurnish. Replace flooring, repair or replace built-ins and repaint when the walls are dry. After finishing work, a second, lighter ozone treatment can help reduce the smell of new paint and adhesive before viewings.

Day 30 onward: List and maintain. Take fresh photos in daylight, air the unit before every viewing and keep your records ready. After the new tenant moves in, check in after the first month to ask whether they have noticed any damp or odor.

Every unit is different, so treat this timeline as a guide rather than a promise. Walls in a unit that stood in water for a week will take longer to dry than walls in a unit that was wet for a day.

What Prospective Tenants Notice in the First Five Minutes

From the viewer's side, the decision is fast and mostly sensory. Knowing what they notice helps you prioritise.

• The smell at the door. A musty or drain-like smell is the single biggest reason viewers leave. This is where ozone treatment and good ventilation make the most visible difference.
• The bathroom. Black grout, a smelly floor drain or stains around the base of the toilet suggest that the unit is not hygienic, even if everything else looks fine.
• The bottom of the wardrobe and walls. Viewers who know the area flooded will look low. Swollen edges and stains are a clear sign that the problem has not been dealt with.
• The air conditioner. A musty blast when the air conditioner is switched on can undo all your work. Have it cleaned before the first viewing.
• The corridor. If the corridor smells, viewers assume the unit will too. This is why cooperation with the juristic person matters.

10 Reasons Condo Owners in Bang Kapi Choose WHD

1. Ozone treatment for condo units suits small rooms that can be fully closed, reducing musty odors throughout.
2. ULV disinfection fogging reaches grout lines, the space under the sink and the inside of cabinets.
3. We use CHEMGENE HLD4H, a professional-grade disinfectant.
4. Single-unit jobs are welcome, ideal for individual rental owners.
5. We help plan the work with the juristic person and neighbouring units.
6. Our team carries equipment by stairs in buildings without a lift.
7. Ozone dose is controlled, and electronics are covered before treatment.
8. Clear advice on which materials to strip out and which can be restored.
9. A dust mite removal service for mattresses and sofas that are still usable.
10. A mosquito spraying service around buildings with standing water.

Before and After Restoring a Ground-Floor Unit

Customer Voice (Example Scenario)

"I thought washing it myself and running the air con would be enough, but viewers stood at the door and left. Once I pulled out the flooring and mattress, had the team disinfect and ozone-treat the unit, and then did the repairs, the smell I used to get when opening the door was gone. I told the new tenant straight out that the unit had flooded and what had been done. He appreciated that and signed the lease."

— Ek, condo unit owner in Bang Kapi (example scenario)

Frequently Asked Questions

Q: Can I book a service for one unit of just over twenty square metres?
A: Yes. We handle small condo units for individual owners, and if neighbouring owners are interested, their units can be treated on the same day.

Q: Do I need permission from the juristic person?
A: You should always notify the building according to its rules, because the team will use common corridors, and a notice should be placed on the door during ozone treatment.

Q: Should treatment be done before or after repairs?
A: In general, strip out damaged materials first, then disinfect and ozone-treat, then repair and repaint once the walls are dry. After finishing work, another ozone treatment can reduce paint smell and any remaining mustiness before the tenant moves in.

Q: How long after ozone treatment can I go back in?
A: It depends on the size of the unit and how well it can be ventilated. The team will tell you when it is safe after the re-check.

Q: What should I do about an air conditioner that was exposed to damp?
A: Have an air-conditioning technician inspect and clean the coil, drain pan and drain line before regular use. The room itself can be ozone-treated with the unit switched off.

Q: Upper-floor units weren't flooded but smell musty. Do they need treatment too?
A: If the smell is coming from the stairwell or shared drains, the juristic person should deal with the source on the ground floor first. If a unit still smells afterwards, our team can assess it and ozone-treat that unit individually.

Q: Will ozone damage the furniture and appliances I supply to tenants?
A: Dose and time are controlled for the size of the room. Sensitive electronics, artworks and items with natural rubber parts are covered or removed beforehand as a precaution.

Get Your Ground-Floor Unit Rented Again

We serve condo units, walk-up low-rise condominiums and apartments in Bang Kapi, Khlong Chan, Hua Mak and nearby areas.

Book Ozone Treatment – Click Here

View Disinfection Service – Click Here

Call 065-556-6294 · LINE @whd268 · worldhealthdisinfection@gmail.com

Related Links

• Residential ozone disinfection
• Ozone treatment for odors and chemical residue
• CHEMGENE HLD4H disinfectant spray, 750 ml
• All articles
• External sources: WHO: Floods and health and Thailand Department of Disease Control