Rainy season home care on Koh Samui (October to December): mould, humidity and ants

In the wet season, the enemy is moisture that has nowhere to go. Keep the air moving, run a dehumidifier or the AC's dry mode in closed rooms, leave gaps behind wardrobes, keep food in sealed containers and wipe surfaces every day. Clean bathrooms and floors more often than in the dry months, because mould and mud build up faster.

If the villa stands empty while you are away, someone needs to open it up, air it and clean it on a schedule. A regular clean every week or two, with a photo report, is often the simplest way to come back to a home that smells fresh rather than damp.

Samui's weather follows a different pattern from much of Thailand. The heaviest rain usually comes with the northeast monsoon, roughly from October to December, and November is often the wettest month. Expect days of steady rain, short tropical downpours and long grey spells when nothing dries.

Humidity stays very high for weeks on end. Stone floors feel damp, towels never quite dry, and any corner without airflow becomes a breeding ground for mould. Homes near the sea also get salt in the air, and homes on hills or at the end of dirt roads get mud and red dust carried in on every pair of shoes.

None of this means there is anything wrong with your house. It simply needs a slightly different routine for a few months.

Mould rarely appears overnight. It starts small, in the same places every year.

• Shower silicone and grout. The first dark spots usually appear along the bottom edge of the shower and in grout lines that never dry out completely.
• Behind wardrobes and beds. Furniture pushed tight against an outside wall traps damp air, and the wall behind it and the back of the furniture go first.
• Inside wardrobes. Clothes, shoes and bags kept in a closed cupboard can develop a white bloom or a musty smell.
• Leather. Mould loves leather sofas, bags, belts and shoes. A white or green film on leather is a sign that the room is too damp.
• Teak and other wood. Teak furniture and doors can turn grey and spotty if they stay wet, especially on a terrace or in a bathroom.
• The top corners of ceilings. Dark dots in the upper corners, especially in cool bedrooms, show where cold air meets damp air.

How to prevent it

• Keep the air moving. Open the windows when it is dry outside, use the ceiling fans, and do not shut the bathroom door after a shower.
• Dry the air in closed rooms. A dehumidifier, or your air conditioner's dry mode, makes a real difference in bedrooms and wardrobes.
• Leave gaps. Pull wardrobes and beds a few centimetres away from outside walls, and do not cram cupboards full.
• Use moisture absorbers. Put silica gel sachets or moisture absorber boxes in wardrobes and drawers, and replace them when they are full.
• Dry surfaces after use. A squeegee over the shower glass and a quick wipe of the shower tray stop most mould before it starts.
• Clean early, with the right product. Small spots come off with a mould remover that suits the surface. Never mix cleaning products, and keep strong ones away from natural stone and teak.

When cleaning is not enough

If mould keeps coming back in the same spot, or a wall feels wet to the touch or the paint is bubbling, the problem is usually water getting in: through the roof, a pipe, a window seal, or rising damp. Cleaning removes what you can see, but the cause needs a repair person. On our cleans we photograph these spots and include them in the report, so you can call your maintenance contact.

Many villas on Samui stand empty for part of the year, and a closed villa in the rainy season is an ideal home for damp. Without airflow, the house soon starts to smell musty. Linen in the cupboards smells stale, mattresses absorb moisture, and bathroom drains can begin to smell.

What helps:

• Regular visits. Someone opens up the house, airs every room, runs the taps and flushes the toilets so the drain traps stay full, and cleans the bathrooms and floors.
• The AC or a dehumidifier on a timer, if you are comfortable leaving it running for part of the day.
• Linen and towels stored dry in sealed boxes or bags, not in a closed, damp cupboard.
• A photo report after every visit, so you can see the house from abroad and spot anything unusual early.

We clean while you are off the island and send room-by-room photos after every visit. Keys or a door code are handed over in a way agreed in advance.

Heavy rain floods ant nests outdoors, so the ants move inside in search of dry places and food. In the wet months you may see trails along skirting boards, around the sink and near the bin.

• Keep food sealed. Sugar, cereal, coffee, bread and pet food belong in closed containers or the fridge.
• Leave no crumbs. Wipe the kitchen counters and dining table after every meal, and do not leave dirty dishes overnight.
• Take the rubbish out every day. Use a bin with a lid and empty it often, especially when it has food waste in it.
• Block the way in. Trails start at gaps around doors, windows and pipes. Sealing them is a job for a handyman.
• Watch the terrace. Fallen fruit, leaves and pet bowls left outside draw insects towards the doors.

Regular cleaning stops ants and small insects from settling in. For a heavy infestation, termites, or anything that keeps coming back, call a pest control specialist.

In the wet season, feet bring in a mix of mud, red dust from dirt roads and beach sand. On stone and tiled floors this grit scratches the surface, and it leaves stains if it dries.

• Put a coarse mat outside every entrance and a soft one inside.
• Keep to a no-shoes rule indoors, with a shoe rack by the door.
• Sweep or vacuum before mopping, so the mop does not spread the grit around.
• Rinse the terrace and entrance steps after heavy rain, before the mud dries on.

On grey days, towels and sheets can hang damp on the line for a long time and start to smell. Use a tumble dryer if you have one, or dry them indoors under a fan or next to the dehumidifier, and do not put linen away until it is completely dry.

If the washing becomes a problem, a laundry with proper dryers is often the easiest answer for a few months. For hosts, the rainy season is when one set of sheets per bed is no longer enough, so keep two or three. There is more on rotating linen in our Airbnb turnover checklist.

Wind and rain bring leaves, twigs and flowers down onto terraces and balconies. Left where they fall, they stain stone, block drains and keep the surface wet, which makes it slippery and encourages mould on teak furniture.

• Sweep the terrace often and keep the drains clear.
• Wipe outdoor furniture and keep cushions indoors or under cover.
• Dry teak after storms and keep it out of standing water.

On a regular visit we sweep the area by the terrace door and wipe the terrace table and chairs. A full terrace or balcony clean is part of a deep clean.

Regular cleaning keeps the house in order through the rains. A deep clean resets it: grout and silicone, limescale, the inside of cupboards and wardrobes, behind the furniture and all the hard-to-reach places where mould and dust collect.

The two best times are at the start of the wet season, so the house goes into it clean and dry, and in late November or early December, after the heaviest rains and before the high season starts in late December. If you are coming back for the holidays, book it for just before you arrive. For a rental, book it before the first high-season guests.

Deep cleaning starts from 2,300 ฿ per visit. After that, regular cleaning from 1,000 ฿ maintains the result, and booking every two weeks takes 10% off each visit. Full prices are on the prices page.

The real problem with the rainy season is not the mould itself. It is not knowing about it until you open the door after three months away.

With regular visits, you get a room-by-room photo report after every clean. Every clean follows a written checklist and is checked against that checklist and the photos. If we missed something on the checklist, tell us within 24 hours and we will come back and put it right free of charge. You can read how this works on our quality control page. We work across the island, and you can check your area on the areas page.