Termites in Walls: What Termites Eat and What to Do

Termites do not eat brick, concrete or stone. Their food is cellulose: timber, engineered boards, paper, cardboard and natural-fibre cloth. A masonry wall is the route they take, through cracks, mortar joints and the holes left for pipes, to the door frames, skirting boards, built-in cabinets and wallpaper fixed to it. If you suspect termites in a wall, leave the mud tubes whole, photograph and date each spot, look at the other side of the wall, note any damp, and have the house surveyed before anything is sprayed.

Can termites live in a brick or concrete wall?

They travel through one and shelter in it, but they are not eating it. Subterranean termites need moisture, so to cross a dry, exposed surface they build mud tubes: covered runways of soil mixed with saliva and droppings. Those are the brown lines along the base of a wall that many households call a nest on the wall. Usually they are a route, and the main nest is under the floor, in the soil around the foundations or much further away.

A concrete building has more openings than it appears to. There are shrinkage cracks, joints between one pour of concrete and the next, the junction of floor and wall, mortar joints, and holes left for water pipes, electrical conduit and aircon pipes. A very narrow gap is enough for a worker termite.

What people say	What is happening
Termites bore through concrete	They cannot digest concrete or gnaw through a solid mass of it. Purdue University's extension publication on termites says that in a building on a concrete slab they get in through expansion joints, cracks and the openings left for electrical, water and drainage lines.
A concrete house cannot have termites	It can, wherever a crack, a construction joint, a service shaft or a hole through the floor is unsealed, above all where the base of a wall is often damp.
The grit by the wall is brick being eaten	It is usually soil the termites carried in to build tubes and seal their route. In weak render or old, crumbly mortar they may also pick out sand grain by grain to widen a passage. Either way, have it checked soon.
The wall is what gets damaged	The damage is in the wood and paper behind it: door frames, skirting boards, the backs of built-in cabinets, timber floors and documents stored against the wall.

What do termites actually eat in a house?

Termites eat cellulose, the substance that plant cell walls are made of. Anything made from a plant can become food if they can reach it, whether it has been sawn, pressed, ground or woven.

They also bite through things they cannot digest when those lie across their path: insulation foam, soft plastic, rubber and thin membranes. The list below covers only what they use as food.

Solid timber: door frames and architraves, skirting boards, stairs, beams and rafters, timber floors, furniture.
Engineered boards: the chipboard, fibreboard and plywood used for kitchen cabinets, wardrobes, shelves and partitions, and laminate flooring.
Paper and card: books, files, cardboard boxes, wallpaper and the paper facing of plasterboard.
Bamboo, rattan, sedge and straw: blinds, mats, baskets and other woven goods.
Natural-fibre cloth such as cotton, linen and jute, when it is stored for a long time somewhere damp, against a wall or on the floor.
Dead roots and stumps, timber stakes, and formwork boards left under the floor or in the garden.

When a wall has termites, what on it is being eaten?

The brick and mortar stay almost whole. What is eaten is the plant-based material fixed to the wall or built into it; what you see is the trace termites leave as they pass.

Wallpaper and the paste under it: eaten in patches, so the paper bubbles and tears at a touch.
Plasterboard walls and ceilings: the paper on both faces is eaten, leaving a crumbly core that breaks easily.
Skirting boards, beading and door architraves in timber or board: eaten from the face against the wall outwards.
Timber panelling, headboard walls and the backs of built-in cabinets: the hidden face goes first while the front still looks good.
Timber studs and battens buried in the walls of older houses.
Paint and filler: not food, but they blister because termites pack soil and carry damp in directly underneath.

Which materials and furniture are most at risk from termites?

No wood-based material is immune. Materials differ in how attractive they are and how long they hold out, and damp changes the picture: the same board lasts far longer in a dry, airy spot than pressed against a damp wall.

Material	Risk, and why
Paper, cardboard, books	Very high. Soft and easy to chew, usually stacked in the dark and seldom moved.
Chipboard and fibreboard	High, above all at unsealed cut edges and on the face against the wall. Board that takes up moisture swells, softens and is eaten faster.
Plywood	High. Termites tend to eat one thin layer of veneer after another and leave the glue lines.
Softwood, sapwood, low-grade timber	High. The pale sapwood from the outer part of the trunk has less natural resistance than the heartwood.
Bamboo, rattan, sedge	High, from termites and woodworm alike, especially untreated and in a damp place.
Plasterboard	The paper facing is eaten. The gypsum core is not food, but it loses its bond and weakens.
Dense heartwood and oily timbers	Lower, thanks to the tight grain and natural resistance. Still possible when the wood stays damp for long or includes some sapwood.
Treated timber, moisture-resistant board	Holds out better than the ordinary kind, depending on the factory treatment, and is weaker at fresh cuts and drill holes.
Plastic, wood-plastic composite, foam	Not food. Can be bitten through when it lies on the termites' route.
Concrete, brick, stone, glass, metal	Not eaten. Termites only pass through the gaps, joints and holes between them.

How do I tell that termites are inside a wall?

Look for small changes on the wall and on the timber fixed to it. The University of Kentucky describes termites as cryptic insects that can be active for years behind walls, floor coverings or insulation without being discovered, so a wall that looks sound proves little.

Brown mud tubes, between a chopstick and a finger in width, running along the base of the wall, up a corner, round a door frame or across the back of a cabinet.
Paint or wallpaper that bubbles or ripples as if damp, and feels hollow behind when pressed lightly.
A door frame or skirting board that gives a dull thud when tapped, or a wooden door that suddenly sticks and is hard to close.
Soil dropping out of mortar joints, cracks, power sockets or service boxes.
Shed wings lying in heaps by window sills, lamps and the base of walls in the swarming season.

Signs in the rest of the house: Our guide to termites in Saigon houses goes room by room and tells winged termites from flying ants.

How do I mark out the affected area before the survey?

There is time to do this properly: the University of Kentucky points out that termites damage wood fairly slowly, so a few more days spent choosing a plan do not usually make the damage much worse. Five steps make the survey more accurate:

Leave every mud tube as it is. An intact tube shows which way the termites are travelling and where bait could be placed if it is needed.
Photograph each spot with an object beside it for scale, and note the date you found it, the room and the floor.
Check the adjoining rooms, the far side of the same wall and the storey below, where you can get to them.
Move books, papers, clothes and loose wooden items out of the area, without clearing away or washing the tubes themselves.
Write down every damp place: seepage stains, a leaking pipe, an overflowing gutter, water that stands at the base of a wall after rain.

What should I not do to termites in a wall?

Most quick fixes deal with the termites in sight and leave the nest working. According to the University of Kentucky, retail do-it-yourself products rarely get rid of a termite infestation that is already established in a house.

Quick fix	Why to hold back
Spraying insecticide on the mud tube	It kills only the termites in the tube at that moment. The colony can move to a route that is harder to find, which hinders baiting later.
Breaking a tube open to see if they are alive	The tube is what the surveyor reads the direction of travel from. A photograph and a mark beside it are enough.
Salt, kerosene or boiling water in a wall gap	Nothing shows that any of them destroys a nest. Kerosene is a fire risk, above all near sockets and buried wiring, and water adds the moisture termites prefer.
Painting or filling over the damage at once	It hides the traces while termites may still be feeding underneath. Wait until the treatment provider confirms that activity has stopped; with bait that takes weeks of monitoring.
A shop-bought product on one small spot	If you do use one, pick a product with a valid registration number in Vietnam and read the label. Keep it from children, pets and food, mix it with nothing else, and stop once termites show up in several places.

What UpClean does about termites in walls, and how to book a survey

Ask for a survey when damage shows in more than one item, when eaten wood has soil in it, when you cannot tell termites from woodworm, or before you replace cabinets or relay a floor where termites have been. UpClean's survey is free, and the written plan and all-inclusive quote that follow state how far a wall or floor will be disturbed.

UpClean's own pest-control technicians carry out the treatment. Up specialists, UpClean's identity-verified and trained staff, cover the furniture, stay with each working point and wipe down at the end. Each damaged item is photographed as found, which gives you something to show whoever repairs the joinery. UpClean has declared its eligibility to provide pest-control services as required by regulation; the declaration and product information are available on request.

Afterwards you receive an Up Report, a record sent by WhatsApp or Zalo with the treated locations, photographs and the follow-up dates. To book, send pictures of the wall to 0968 726 135 on WhatsApp or Zalo, or phone between 7:00 AM and 8:00 PM, seven days a week. Enquiries, quotes and the Up Report can all be in English. The specialist's name and photo reach you before the visit, which is what building management needs if your building asks residents to register outside staff.

Termite control: What the service includes and the areas covered.
Woodworm treatment: For small round holes and very fine powder with no soil.
Pre-construction termite protection: For a house being built or heavily renovated.
Book a survey: Send the request online.

Frequently asked questions

Do termites eat concrete or brick?+

No. Termites eat the cellulose in wood, paper and plant-based materials. They only pass through cracks, expansion joints and pipe penetrations in concrete to reach the wood behind it.

Is the line of soil on my wall a termite nest?+

In most cases it is a mud tube, which is a covered route. The main nest is usually under the floor, in the soil around the foundations or somewhere else, and locating it is part of the survey.

Does the wall have to be broken open to treat termites inside it?+

Not always. Many cases need only small holes drilled at the base of the wall or in a door frame, which are filled afterwards, and bait hardly touches the wall at all. The plan states how much the wall will be disturbed before work starts.

Do kitchen cabinets or a door frame eaten by termites have to be replaced?+

Not necessarily. Have the termites stopped first, then judge how sound the wood is: tap it, press a screwdriver tip into a hidden face and see whether screws and hinges still hold. A damaged back panel or the foot of a frame can be replaced alone; parts that are hollow throughout should go. Stairs, beams and rafters carry load and need someone qualified in structures.

How fast do termites eat wood?+

There is no general figure: it depends on the species, the size of the colony, the kind of wood and the moisture. On the whole they eat fairly slowly, and serious damage usually follows a long time undetected. That leaves time for a careful survey, but is no reason to wait once you have seen signs.

Is it termites, woodworm or damp rot?+

Termite-damaged wood usually keeps a whole surface and is hollow in layers along the grain, with damp soil inside if the termites are subterranean. Woodworm leaves small round holes and very fine powder. Damp and mould discolour the wood and turn it soft or fibrous, with no tunnels. Decaying wood often attracts both insects, so one item can carry several traces.

Termites in walls: do they eat brick and concrete, what do they eat, and what to do before a survey