A Story From the Field: The New Floor That Smells From Below

Khun Ton and Khun Nan are a couple in their early thirties. Last year they bought a second-hand townhouse on a soi off Machareon Road in Nong Khaem, Bangkok, and renovated the whole ground floor. The thing they were proudest of was the pale oak-look SPC flooring laid straight over the old ceramic tiles, chosen because the salesperson had described it as "one hundred percent waterproof". The kitchen at the back got glue-down vinyl tiles.

When the October 2026 floods came, water entered the house to a depth of about ten centimeters and stayed for three days. Once it drained, the couple mopped every corner. The SPC surface had not swollen or bubbled. It looked as if the floor had survived. A week later, though, a damp, musty smell began rising from the floor, especially first thing in the morning after the house had been shut up all night. In some places the planks gave a soft little dip underfoot. Along the skirting near the back door, damp spots kept appearing. In the kitchen, several vinyl tiles had started to curl up at the edges, and they could see brown, sticky glue oozing underneath.

"It's a waterproof floor. Why does it still smell?" Khun Nan asked us. The answer is that the planks may well be waterproof, but the water is not inside the planks. It is underneath them.

We hear versions of this question in almost every overlay-floor home we visit after a flood. The good news is that, handled in the right order, many of these floors can be saved, and the smell can be removed for good rather than just covered up.

Where the Water Goes Under Your Floor

Floors in this family are built in different ways, and each type traps water in a different place.

• Click-lock SPC and LVT floors are "floating" floors. They sit on a foam underlay, or have one bonded to the back of each plank, and are not fixed to the subfloor. During a flood, water flows in through the joints and along the edges by the walls, and pools between the planks and the concrete or old tiles beneath. When the flood recedes, the top surface dries, but the water underneath has no way out, because the planks above are so good at keeping water in.
• Glue-down vinyl tiles or planks are stuck to the concrete. Several days of standing water weaken the adhesive, the tiles lift at the edges, and water settles beneath them.
• Sheet vinyl can let water in at the edges and seams, where it spreads out in a wide patch under the sheet.
• The concrete slab or old tiles below absorb water into the concrete and grout lines, and release it very slowly.

The water trapped under your floor is not clean. It carries silt, sewage and organic matter. In a dark, damp, warm space like that, bacteria and mold grow fast, and the result is a musty or sour smell drifting up through the joints in the floor.

It helps to picture a floating floor as a lid on a shallow tray. Whatever water got into the tray stays there, warm and dark, until someone lifts the lid. No amount of mopping on top of the lid will change what is happening underneath.

Check It Yourself: Signs That Water Is Trapped Under the Floor

1. A strong musty smell in the morning or after the house has been closed, strongest close to the floor.
2. A soft dip or a faint squelch when you step on certain spots.
3. Damp marks along the skirting or at plank joints, particularly early in the day or on humid days.
4. Lifted edges or opening joints, or vinyl tiles curling with glue oozing out.
5. Black or green spots in the joints, a sign of mold growing from underneath.
6. Remove a length of skirting and lift one plank by the wall on a click-lock floor. If you see water or mud underneath, the whole flooded area needs attention. Ideally ask a flooring installer to do this so the locking tongues are not damaged.

If you tick two or more of these, it is very likely there is moisture sitting under your floor, and it will not go away on its own while the planks stay in place.

What Happens If You Leave It

• Health. Mold spores and odors rising from under the floor cause sneezing, a blocked nose, itchy eyes, and can trigger allergies and asthma. Young children who crawl and play on the floor are affected most. Trapped floodwater can also carry germs from sewage and rat urine, which is linked to leptospirosis.
• More damage to the floor. The underlay breaks down, the glue fails across a wider area, and planks begin to cup or open at the joints.
• Walls and furniture start to smell too. Moisture from under the floor rises into the lower walls, cabinets and beds standing on the floor.
• Higher costs. The longer you wait, the more planks that could have been reused become damaged and must be replaced.

This article is not medical advice. If anyone develops a fever, muscle pain, red eyes or other unusual symptoms after contact with floodwater, see a doctor.

Does It Have to Come Up? A Guide by Floor Type

Click-lock SPC or LVT with water underneath. Have an installer lift the planks across the area that flooded. Planks that are not warped and whose locking edges are undamaged can usually be cleaned and relaid. Foam underlay that soaked in dirty water should be replaced.

Glue-down vinyl tiles that have lifted. Loose tiles should come up, the old adhesive should be scraped off, the concrete should dry completely, and the floor should then be relaid with fresh adhesive.

Sheet vinyl. If water has spread under a large area, the sheet usually needs to be lifted so the subfloor can dry.

Only the surface got wet and water did not enter the joints. For example, an upstairs floor splashed by rain. A thorough wipe-dry and a period of watching may be enough.

Laminate wood-look flooring. Its core is high-density fiberboard, which usually swells permanently in water. Most laminate floors that flooded need replacing.

Before anything is relaid, ask the installer to check the moisture level in the concrete with a moisture meter. Concrete that looks dry may still hold moisture deep inside, and covering it too soon simply traps the moisture all over again.

Being clear about our role: World Health Disinfection (WHD) does not lift, lay or repair floors. Lifting planks, replacing underlay, scraping adhesive and relaying should be done by a flooring installer or an experienced contractor. WHD takes care of the window while the floor is open: disinfection fogging of the concrete and the room, and ozone treatment to reduce mold and musty odor, before the installer relays the floor, with a further ozone treatment after relaying if needed.

Why Mopping and Fragrance Never Finish the Job

• Mopping again and again with floor cleaner cleans the top surface only, and the mop water runs into the joints and adds more moisture underneath.
• Pointing fans at the floor dries the surface quickly, but air cannot reach the sealed space under the planks.
• Running silicone along the edges traps even more moisture underneath and makes lifting harder later.
• Pouring bleach into the joints does not spread evenly, speeds up the breakdown of glue and foam, and the fumes irritate the airways.
• Air fresheners and scented candles mask the smell for a while, but the source is still right under your feet.

The Right Order of Work: Flooring Installer and Disinfection Team

1. Photograph and note the water level, the smelly spots and the damaged planks.
2. The installer lifts the floor, setting aside planks that are still good and discarding the underlay and damaged pieces.
3. Clean off the mud and dry the concrete, opening the house for airflow and using fans and a dehumidifier.
4. WHD fogs and ozone-treats while the floor is open, disinfecting the concrete, wall edges and the room.
5. The installer measures concrete moisture to confirm it is dry enough to relay.
6. Relay the floor, cleaning and reusing good planks or using new ones, with new underlay.
7. A final ozone treatment if needed, to reduce installation and fresh adhesive odors before you move back in.

Following this order means each trade does its part once. The most common mistake we see is the floor being relaid in a hurry over damp concrete, which brings the smell back within weeks and means paying for the floor twice.

Nong Khaem Homes and Overlay Floors

A great many townhouses and housing-estate homes in Nong Khaem, around Phet Kasem Road, Machareon Road and Nong Khang Phlu subdistrict, have been renovated by laying SPC or vinyl directly over the original ceramic tiles. It is quick, affordable, and avoids breaking up the old floor. When floodwater gets in, though, an overlay floor holds water at two levels: between the new planks and the old tiles, and in the grout and concrete beneath the old tiles. Moisture lingers far longer than in an ordinary house. That is why lifting the planks so the floor can breathe is a step you cannot skip.

Many of these homes also have built-in kitchen cabinets and wardrobes standing on the floating floor. Moisture trapped beneath them spreads upward into the cabinet bases, which are often particleboard. When the installer lifts the floor, it is worth checking the bottom of these units too, and asking a carpenter about any that have swollen.

Do not forget the upstairs rooms either. Townhouses have an open staircase, and warm, damp air rising from a wet ground floor carries the musty smell up into the bedrooms. Families often notice it first on bedding, curtains and clothes in wardrobes, even though no water ever reached the second floor. Once the source under the ground floor has been dealt with, those upstairs rooms usually clear quickly, especially if they are aired well and included in the ozone treatment.

Finally, keep an eye on the floor drain and the area around the back door. In many Nong Khaem sois, water arrived through the kitchen first, so that is where the subfloor stays wettest and where the strongest odor tends to concentrate. If you only have the budget to lift part of the floor, start there.

Questions Worth Asking Your Flooring Installer

A good installer will be happy to answer these, and the answers tell you a lot about whether the job will last.

• "How will you lift the click-lock planks without breaking the tongues?" Planks are usually unclicked by lifting at an angle from the wall side. Forcing them flat can snap the locking profile and turn a reusable plank into waste.
• "Will you replace the underlay?" Foam that sat in floodwater should be thrown away. If the planks have a bonded backing, ask whether it can be cleaned or whether those planks need replacing.
• "How will you check that the concrete is dry?" Look for an answer that involves a moisture meter or a recognized test, not just "it looks dry".
• "Will you leave an expansion gap and how will you finish the edges?" Floating floors need a small gap at the walls, hidden by skirting. Sealing that gap shut with silicone traps moisture next time.
• "What should we do differently if it floods again?" In flood-prone streets, some families choose to keep a few spare planks, or to lay ceramic tile in the kitchen and entrance where water arrives first.

Keep the installer's written quote and the moisture readings together with your flood photos. They are useful records if you need to make an insurance or assistance claim.

Living in the House While the Floor Is Up

Most families in Nong Khaem cannot move out while the work is done, so it helps to plan the days. Move daily life upstairs where possible, and keep young children off the exposed concrete, which may still carry flood residue until it has been cleaned and disinfected. Store the planks that will be reused somewhere dry and flat, stacked so they do not bend. Keep windows open on dry days and run a dehumidifier at night with the doors closed. On the day of ozone treatment, plan to be out of the house for the period the team advises, take pets with you, and move houseplants outside. When you come back, the team will already have ventilated the space.

The whole process usually feels slower than people expect, mainly because of drying time. But a few extra days of patience at this stage are what stop the musty smell from coming back in a month.

The Solution: Disinfection Fogging and Ozone Treatment While the Floor Is Open, With WHD

The best moment to disinfect is when the installer has lifted the planks, because the concrete and wall edges that were covered are finally exposed to disinfectant and ozone. WHD uses our disinfection fogging service with CHEMGENE HLD4H disinfectant, delivered through an ULV fogger that covers the concrete, the grout lines of the old tiles and the lower walls. This is followed by our ozone treatment service to reduce mold spores and break down the odor molecules absorbed into the room.

How the Service Works

1. Survey. We look at the water level, the floor type, the strongest odor spots and the moisture in the lower walls.
2. Preparation advice. We coordinate with your installer on which areas to lift and agree on timing.
3. Disinfection fogging. We fog CHEMGENE HLD4H across the exposed concrete, wall edges, under built-in cabinets and high-touch surfaces.
4. Ozone shock treatment. We close up and run the ozone generator for a period suited to the area. No people, pets or plants may be inside.
5. Ventilation. We open the house to air it and tell you when it is safe to return.
6. Re-check. We assess odor after the service and can treat again after the floor is relaid if you wish.

Ozone safety. Treatment is carried out only in unoccupied spaces. The team controls the dose, removes or covers sensitive electronics, artworks and natural rubber items before starting, and the space is always ventilated before anyone goes back in.

10 Reasons Nong Khaem Families Choose WHD

1. We are clear that lifting and laying floors is the installer's job, and help you get the timing right.
2. We work while the floor is open, the moment when disinfectant can reach the source.
3. We use CHEMGENE HLD4H for surface disinfection.
4. ULV mist reaches grout lines and wall edges a mop cannot.
5. Ozone treatment reduces musty odor absorbed by walls and furniture around the room.
6. A follow-up ozone treatment after relaying helps reduce installation odors.
7. Controlled ozone dose, with care for electronics.
8. Suitable for homes with young children who crawl and play on the floor.
9. Can be combined with residential ozone disinfection for upstairs rooms that picked up the smell.
10. Practical moisture-control advice so the smell does not return in the rainy season.

Before and After

Customer Voice (Example Scenario)

"We thought a waterproof floor meant we were fine. The team explained that the water was sitting under the planks and suggested we get the flooring installer to lift them first. While the floor was up, they came in to fog and ozone-treat. Once the installer relaid it, the musty smell never came back, and we were able to reuse most of our SPC planks."

— Khun Ton and Khun Nan, townhouse off Machareon Road, Nong Khaem (example scenario from the field)

Frequently Asked Questions

Q: SPC is waterproof, so why lift it?
A: The planks are waterproof, but floodwater runs through the joints and pools beneath them, where it cannot evaporate. That causes musty odor and mold. Lifting lets the subfloor dry and be disinfected.

Q: Can the original SPC planks be reused?
A: If they are not warped and the locking edges are undamaged, they can usually be cleaned and relaid. Let a flooring installer lift and assess them, and replace any underlay that soaked in floodwater.

Q: Can you ozone-treat without lifting the floor?
A: It can reduce the smell in the room to some extent, but if water is still trapped under the planks, the smell will return. We recommend lifting and drying first.

Q: Does WHD lift or lay floors?
A: No. Flooring work should be done by a flooring installer. WHD provides disinfection fogging and ozone treatment.

Q: How long does the concrete need to dry?
A: It depends on how long water stood, the slab thickness and the weather. Have the installer measure moisture before relaying, rather than judging by the surface.

Q: Do you serve Nong Khaem and nearby areas?
A: Yes. We serve Nong Khaem, Bang Khae, Phasi Charoen, Thawi Watthana and other areas of Bangkok and its surrounding provinces. Contact us on LINE @whd268.

Floor Lifted? Don't Relay It Before It's Disinfected

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

Related Links

• Residential ozone disinfection
• Ozone odor and chemical residue removal
• Master Ozone Generator
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Health reference: World Health Organization (WHO): Floods · Department of Disease Control, Thailand