A Story from the Field: The Old Wooden Building Everyone Loves

Khru Somsak is the homeroom teacher for Mathayom 1, the first year of lower secondary, at an opportunity expansion school in Phrom Buri District, Sing Buri. In Thailand, an opportunity expansion school is a rural primary school that has extended its classes up to Mathayom 3 so that village children can continue their education close to home. This one teaches everything from kindergarten to Mathayom 3, with fewer than two hundred students, most of them children of local rice farmers.

The building everyone is most attached to is the old two-story wooden classroom block. Its ground floor holds three secondary classrooms. The floor is made of wooden planks laid over timber joists, raised only a little above the ground. The walls are overlapping wooden boards, and the windows are wooden shutters that swing open to let the breeze through. Generations of students from the subdistrict have studied in these rooms.

During the 2026 floods, the school closed early. Water filled the crawl space under the building and rose about a hand span above the ground-floor planks, where it sat for several days. When the water receded, Khru Somsak and his colleagues came back to inspect the building. The classroom doors were hard to open because the wood had swollen. Some floorboards had cupped and warped. A damp, musty smell mixed with mud hit them before they even stepped inside. The wooden student desks had white mold growing on the legs and underneath the tops. The display boards of student work along the lower walls had turned to pulp, and wet mud still sat in the crawl space beneath the building.

The second semester was only a few weeks away. At the staff meeting, the director asked whether the ground-floor classrooms would be ready in time. Several teachers worried about students with allergies and asthma. One suggested simply painting over everything to get it done. Khru Somsak knew that wood still wet inside would bring the problem right back. He wanted a plan that would make this beloved building genuinely safe to use again.

Why Flooded Wooden Classrooms Need Different Care From Concrete Buildings

1. Wood Absorbs Water and Releases It Slowly

Wood is porous. After several days underwater, water penetrates deep into the timber. The surface may look dry within a few days, but the inside stays damp for a long time. That hidden moisture is what keeps mold growing and what causes musty odors that simply refuse to go away.

2. A Low Crawl Space Is an Invisible Source of Moisture

In a wooden building raised only slightly above the ground, the crawl space has very little airflow. Mud and standing water under the floor send humidity up through the gaps between the planks all day long. Unless the crawl space is dealt with, the classroom above will stay damp.

3. Students Spend Many Hours a Day in the Same Room

Secondary students sit in the same classroom for six or seven hours a day. If the air carries a high load of mold spores, students with allergies or asthma may sneeze, feel congested, cough or have trouble breathing. That affects both their health and their concentration. For Mathayom 3 students preparing for end-of-year exams and the move to upper secondary or vocational school, a stuffy, musty classroom is an extra burden they do not need.

4. Mud and Standing Water Carry Disease Risks

Teachers, janitors and older students who help clean the school come into contact with mud and standing water, which can carry many kinds of bacteria, including those that cause leptospirosis through cuts in the skin. Everyone should wear boots and gloves, and students should not work in a crawl space that still has standing water.

5. Small Schools Have Small Budgets

Most opportunity expansion schools have few teachers and no budget to replace an entire wooden floor or wall system at once. Doing the essential work in the right order helps the school spend wisely and still open the semester on time.

Why the Usual Fixes Fall Short

• Painting or varnishing straight away: paint and wood finishes seal moisture inside the timber. Mold keeps growing underneath, and the coating soon peels or blisters.
• Pouring bleach on wooden floors: it can stain the wood and adds another round of moisture to the floor. The fumes also bother students.
• Locking the rooms until term starts: a sealed wooden room that is still damp is a perfect mold incubator.
• Cleaning only the floor surface and ignoring the crawl space: the mud below keeps sending moisture and smells upward.
• Air fresheners and perfume sprays: they mask the odor for a few hours and are not suitable for rooms with allergic students.

The Right Order of Work: Dry First, Then Disinfect and Ozone-Treat

1. Clear the crawl space: remove mud and debris from under the building, open the vents so air can move, and drain any standing water.
2. Wash and ventilate: wash mud off floors and walls, then open every window and door on dry days. Use fans to push air out of the building, not toward rooms that are already clean.
3. Inspect the timber structure: ask a carpenter to check joists, beams and warped floorboards, and to look for signs of termites, which often follow damp wood.
4. Sort contents: paper display boards, foam boards and pulped student work should be photographed for the record and discarded. Move wooden desks and chairs out to dry in a shaded, breezy area.
5. Disinfection fogging and ozone treatment: once the wood surface has started to dry and the mud is gone, the professional team comes in.
6. Paint or varnish: this is the last step, only after the carpenter confirms the wood is dry enough. For some sections that may be after the semester has started.

Following this order is the single most important decision a school can make after a flood. It prevents the most common and most expensive mistake, which is sealing wet wood under a fresh coat of paint and then paying to strip and repaint it a few months later.

How to Tell Whether the Wood Is Drying

Teachers do not need special training to keep an eye on drying progress. A few simple checks over several days give a good picture.

• Look at the color: wet wood is darker. As it dries, the color lightens and becomes more even. Dark patches that do not fade suggest moisture is still trapped.
• Feel the surface: press the back of your hand against the floor and lower walls. Wood that still feels cool and clammy compared with a dry area is still damp.
• Use your nose: the musty smell should become weaker day by day with good ventilation. If it stays the same or gets stronger, something underneath, often the crawl space, is still wet.
• Watch the boards: cupped floorboards often flatten partly as they dry. Boards that stay badly warped may need to be replaced by a carpenter.
• Use a moisture meter if one is available: many local carpenters own an inexpensive wood moisture meter and can take readings to confirm when painting is safe.

The Solution: Chemgene HLD4H Disinfection and Ozone Treatment by a Professional Team

World Health Disinfection provides a professional disinfection fogging service using CHEMGENE HLD4H through ULV foggers, which reach the gaps between floorboards, the undersides of desks, wall corners and the crawl space. We also provide an ozone shock treatment service for classrooms that can be closed up, reducing airborne mold spores and breaking down musty odor molecules.

Timing matters as much as technique. The team schedules work for weekends or school holidays, treats the rooms that are driest first, and leaves rooms that are still damp for a second visit rather than forcing everything into one day. That way the school can open the rooms that are ready on time and bring the remaining rooms back into use a little later, without compromising on safety.

Step-by-Step Process at a School

1. Survey with the director and teachers: check how high the water reached, which rooms have mold, the crawl space, the computer room, the science room and the canteen.
2. Advice on preparation: the order of cleaning, ventilation and sorting contents.
3. Move or cover equipment: computers, projectors, televisions and sound systems should be moved out or completely covered. Chemicals in the science room should first be checked and stored safely by the responsible teacher.
4. Disinfection fogging: mist is applied in classrooms, on wooden floors, walls, desks and chairs, restrooms and in the crawl space.
5. Ozone treatment: classrooms are sealed one at a time or zone by zone, and the ozone generator runs for a time suited to the room size. No people, pets or plants may be inside during treatment.
6. Ventilation: every wooden shutter is opened to air the room. The team confirms when it is safe to go back in.
7. Re-check: the team inspects odors and mold spots with teachers and schedules a follow-up if some timber is still damp.

Ozone Safety

• Work is done on days without students, and rooms must be ventilated properly before anyone re-enters.
• Potted plants teachers use to decorate classrooms, and any animals kept at school, must be moved out before treatment.
• Electronics and rubber items should be removed or covered. The team controls the ozone dose to suit each room.

Why Old Wooden School Buildings Are Worth Saving

After a flood it is tempting to see an old wooden classroom block as a liability. In fact, these buildings have real strengths. Solid hardwood that has stood for decades is often sturdier than the plywood and particleboard used in many newer fittings. Wooden shutters and high ceilings give natural cross-ventilation that helps rooms dry once the crawl space is cleared. And for a rural community, the building itself carries memories: parents and grandparents of today's students sat in the same rooms.

Wood also tolerates a flood better than people expect, as long as it is allowed to dry properly. The damage usually comes later, from moisture trapped under paint, from mud left in the crawl space, or from termites drawn to damp timber. A careful recovery plan protects both the students' health and the community's investment in the building.

Involving Older Students Safely

Mathayom students often want to help restore their school, and their energy is valuable. The key is to give them tasks that are safe and meaningful.

• Good tasks for students: carrying dry furniture to drying areas, wiping desks once the mud is gone, photographing and listing damaged items, sorting textbooks into wet and dry groups, and making posters to explain the recovery plan to younger children.
• Tasks to leave to adults: working in the crawl space, shoveling mud, handling moldy boards and pulped paper, anything involving electrical equipment, and any work in the science room.
• Protective gear: students who help should wear gloves and masks, work in short shifts, and wash their hands before eating.
• Keep sensitive students away: those with asthma or severe allergies should take on tasks outside the affected rooms.

Handled this way, the cleanup becomes a lesson in community responsibility as well as in practical science.

Keeping Good Records for Reporting and Budget Requests

Public schools report flood damage to their educational service area office and may need documentation to request repair budgets. A few simple habits make that process smoother.

• Photograph every room before cleaning, during cleanup and after treatment, from the same angle each time.
• List discarded items such as display boards, damaged desks and textbooks, with approximate quantities.
• Keep the carpenter's notes on warped boards, damaged joists and any termite findings.
• Keep the service description and dates of disinfection and ozone treatment provided by the team.

A clear record also helps the next time water rises, because the school will know exactly which rooms flooded, how high and what worked.

10 Reasons Schools Choose Professional Disinfection and Ozone Treatment

1. Mist that reaches between floorboards and under the building: ULV fogging covers far more than hand wiping.
2. Fewer mold spores in classrooms: ozone treatment improves the air for students who sit there all day.
3. Wood's musty odor reduced at the source: no need for perfume.
4. A disinfectant used in hygiene work: CHEMGENE HLD4H suits many surface types.
5. Help with the right order of work: no wasted budget on repainting.
6. Zone-by-zone work: rooms that are ready can be used first.
7. Confident teachers and parents: clear steps that can be explained.
8. Semester opens on schedule: students do not need to be moved elsewhere.
9. Aftercare guidance: including use of the Chemgene 750 ml spray on high-touch points.
10. Mosquito control on school grounds: playing fields and crawl spaces with standing water can be supported by our mosquito fogging service.

Before and After

A Teacher's Voice

"I am glad we did not rush to paint over everything like some people suggested. The team advised us to clear the crawl space and get air moving first, then did the disinfection and ozone room by room. When term started, the kids stopped complaining about the smell, and the students with allergies in my class could sit through lessons normally."

— Khru Somsak, Mathayom 1 homeroom teacher at an opportunity expansion school, Phrom Buri (illustrative scenario)

Do Not Forget the Canteen, Restrooms and Kindergarten Rooms

Beyond the wooden building, an opportunity expansion school has other spaces students use every day, and they also need to be ready before term begins.

• Canteen and kitchen: discard any ingredients touched by floodwater, wash dishes, compartment trays and dining tables, and check the water tank and drinking water filter. Kitchen staff and the teacher in charge of school lunch should inspect together.
• Student restrooms: clear mud from restrooms and floor drains, make sure wastewater is not backing up, and include them in the disinfection fogging.
• Kindergarten classrooms: young children sit and play on the floor, so replace any mats or carpets that soaked in floodwater, and ventilate these rooms longer than others after ozone treatment.
• School library: remove wet books first. Disinfectant should never be sprayed directly onto books.

Before term starts, the school should update parents through each class's LINE group, explaining what has been done with before and after photos, and asking parents to tell teachers about any student with allergies or a chronic condition so teachers can keep an eye on them during the first weeks.

Caring for Wooden Classrooms After Term Begins

• Have the daily student duty team open every shutter in the morning and close them when rain comes.
• For the first weeks, avoid leaving bags and books against the lower walls or directly on the wooden floor.
• Check floors and walls weekly. If dark spots or a musty smell return, students should tell a teacher.
• Wipe desks, door handles and stair rails regularly.
• Inspect the crawl space after heavy rain and make sure no water pools there, as it can breed dengue mosquitoes.
• Paint or varnish once a carpenter confirms the timber is dry enough, possibly during the next school break.

These habits also double as a practical lesson for students about how buildings, moisture and health are connected, something many of them will need when they help repair their own homes after future floods.

Frequently Asked Questions

Q: The wooden floor is still damp. Can it be disinfected right away?
A: Clear the mud and ventilate first so the wood surface starts to dry. The team will assess readiness during the survey.

Q: Does ozone treatment dry the wood?
A: No. Ozone helps with odor and airborne spores. Drying wood depends on ventilation and time.

Q: Do moldy wooden desks have to be thrown away?
A: Solid wood desks that are not rotten can usually be cleaned, dried and disinfected. Plywood desks that have swollen or delaminated should be replaced.

Q: Can the team work in the science room with its chemicals?
A: The responsible teacher should first check and store chemicals safely. The team then works in the agreed areas.

Q: Can the whole school be done in one day?
A: It depends on the number of rooms and how ready each area is. The team may work zone by zone so rooms that are ready can be used first.

Q: What about termites after the flood?
A: Damp timber can attract termites. Ask a carpenter or pest control specialist to inspect joists and wall bases, and treat termites separately if found.

Q: How long after ozone treatment can students return?
A: Once the team has ventilated the room and confirmed it is safe. Because treatment is scheduled on days without students, rooms normally have a full extra day of fresh air before classes resume.

Q: Should we treat the second floor too?
A: If water did not reach it, the upper floor usually needs only good ventilation and routine cleaning. However, humidity rising from below can carry musty odors upstairs, so the team will check it during the survey and advise.

Q: Which areas do you serve?
A: Phrom Buri, Mueang Sing Buri, In Buri, Bang Rachan, Tha Chang and nearby districts.

Get the Old Wooden Classrooms Ready for Students Again

Services for schools, learning centers and wooden buildings in Sing Buri Province

View Disinfection Service – Click Here

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

Related Articles and Links

• Ozone treatment for odors and chemical residue
• Master Ozone Generator
• Mosquito fogging service
• All articles
• External sources: WHO: Floods and health and Thailand Department of Disease Control

#SchoolDisinfection #PostFloodDisinfection #OzoneTreatment #MoldRemoval #MustyOdorRemoval #Chemgene #DisinfectionService #PhromBuri

Keywords: wooden classroom disinfection after flood, school ozone treatment, opportunity expansion school, wooden school building, moldy school desks, musty odor removal, Phrom Buri, Sing Buri 2026