Pests That Come With the Building, Not the Mess: What Actually Causes Infestations

Pests come with the building and not with the mess, and the simplest way to show it is to take the 2 kinds of building there are and find a city that is known for each. For the house standing on its own I am going to use Melbourne, where the older houses sit on timber stumps and the inspectors reported a 25% rise in homes with termite evidence back in 2019. For the block of units I am going to use New York, which went as far as appointing a rat czar in 2023 after 311 had logged close to 3.2 million rat sightings in a year. A clean kitchen in either city would change very little about what follows.

Three things seem to be behind most of the infestations I have read about, in both kinds of building:

• Gaps in the shell of the building, a crack in the slab, an unsealed pipe through a wall, a door with no sweep, a soffit vent with the mesh gone. A mouse gets through a gap the width of a pencil and a cockroach through less.
• Water sitting where it should not, a leaking pipe under the floor, ground that drains toward the house, a bathroom with no fan, and the basement leak that keeps coming back. Most pests need water before they need food, and fixing the water takes away the reason they settled.
• Everything a building shares, the plumbing risers, the gaps around conduit, the ceiling voids, the holes through the party wall. Your unit can be spotless and the problem is 3 doors down, coming through the gap behind the kitchen sink pipe.

Wiping the counters and keeping the cereal in jars is hygiene, and it has to be done, but it is a 10 minute job and the other thing could be a framing bill in the thousands if it has gone on long enough unseen.

Which Pests Come Through The Building And Which Come From The Kitchen

The 2 groups need 2 different responses, so they are listed apart. The building let these in:

• Termites. They come in where soil touches timber, through a crack in a slab, through the joint where brick meets frame, and a colony may have been eating a beam for years before anyone has seen a thing. By the time the damage shows, the framing often has to be replaced.
• Mice and rats. They follow warmth and shelter, and they nest in wall cavities, ceiling voids and the space under the floor, having come in through a foundation gap, a broken vent, an unsealed pipe or an open weep hole in the brickwork. A clean kitchen above an unsealed subfloor vent will have mice in it.
• The ones from the ground, silverfish, earwigs, some ants. They come up through the slab or the subfloor, and it is the damp under the house that brings them.

And the ones your habits have a say in:

• Cockroaches, which sit between the 2 groups. The small light brown German cockroach lives on food and water and will go where those are. The larger dark Oriental cockroach lives on damp and comes up through drains and pipe gaps however clean the kitchen is.
• Pantry moths and weevils, which usually arrive inside the packet and spread when dry goods sit in open bags.
• Fruit flies, which are the fruit bowl and the drain, and go within days once those are dealt with.

If the problem is termites, rodents or anything coming up from the ground, cleaning harder will not touch it, the entry point or the water has to be found and fixed.

What A Pest Inspection Checks

A proper inspection is a walk around and under the building looking for the 7 numbered points on the drawing above, and it can be done without going anywhere near the kitchen. Outside:

• The foundation all the way round, for cracks and for soil or mulch piled up against timber.
• The weep holes in the brickwork, screened or open.
• Every pipe and cable coming through an outside wall, sealed or not.
• The roof edge, broken fascia, gaps in the soffit lining.
• Where the water goes after rain. Water pooling at the base of the wall has been behind more subfloor pest trouble than any other single thing I have come across.

Under the floor, if there is a way in, the timber is checked for mud leads, which are the covered tunnels termites build up a stump or a pier, for water damage and for rot, the vents are checked for blockage because a closed subfloor holds damp and damp brings termites faster than anything else, and the plumbing is checked for drips. Inside, the wall cavities around the kitchen, bathroom and laundry pipes, the roof space for droppings and chewed wiring, and a moisture meter on the walls next to the wet rooms.

Melbourne is where this list stopped being optional for a buyer. In June 2019 Domain reported that Jim’s Building Inspections had seen a 25% rise in Melbourne homes showing termite evidence, and the suburbs named were the newer estates cut into bush, Cranbourne, Pakenham, Werribee, Carrum Downs, with Professor Nathan Lo at the University of Sydney saying an infestation can take a couple of years to show after the clearing. I read through what a building and pest inspection in Melbourne covers and it is the list above, both halves in 1 report before settlement, the stumps and the clearance under the bearers for the building, the mud leads and the moisture readings for the pest. Hmm, so that is why the buyers there stopped skipping it.

The CSIRO guide to termites puts a number on the clearance, at least 400 mm under the bearers, and wants the cladding to finish 100 mm above the soil, and it says plainly to inspect before buying and at least once a year after that.

Why An Apartment Is A Different Problem

You can do everything right inside your own unit and still get the pests from someone else’s, because in a block the entry paths belong to the building. In a house you own all of the shell, seal the gaps, fix the damp, keep the subfloor dry and most of the paths are closed. In a block the paths are the plumbing stack, the conduit between units, the gap at the top and bottom of the party wall, the garbage room, the storage cages in the basement, and no tenant controls any of them.

Rats are the clearest case, which is why New York is the city for this section. On April 12, 2023 Mayor Adams introduced Kathleen Corradi as the city’s first director of rodent mitigation, the rat czar, after 311 had taken almost 3.2 million rat sightings in a year, and his words were:

“Rats are smart, they are resilient.”

“We needed a maestro.”

The first mitigation zone was Harlem, $3.5 million and 33 staff.

The rats in those buildings have been coming up through the sewer connections, into the pipe chases between floors, and out through the gaps behind toilets and kitchen sinks that were never sealed when a 1920s building was plumbed, and a block that old may have dozens of those gaps. Keeping your apartment clean does nothing about the rat using a chase 4 floors below you.

Bedbugs are the other one that no single unit can beat, they move through shared walls, through the gap behind an outlet, along a baseboard crack, and 1 infested unit can have reached its neighbors within weeks.

I looked at what an NYC pest control company lists for co-ops and apartment buildings, and it is garbage chute fogging, drilling the wall voids, rodent proofing the building, ladder work to nests on the outside, and none of those is a job you could book for 1 unit. In a block the treatment is the building, and treating 1 apartment at a time usually moves the pests next door until the treatment wears off.

When Each Pest Shows Up In The Year

Having picked 1 city from each half of the world, the calendar has to be read twice. The usual advice is that pests come indoors when it gets cold, and that is about half right, the 2 risky windows are spring and autumn.

Spring is termite season. The winged ones swarm after rain, September to November in Melbourne and March to May in New York, and small winged insects at a window or a light fitting in those months mean a mature colony is close. That is the month to go under the house. Summer is the cockroaches and the ants, heat speeds the breeding and a German cockroach population can double in about 6 weeks of warm weather, so the ant trail that was a few scouts in spring is a line across the kitchen by midsummer.

Autumn is the column on the drawing to read twice. Mice and rats scout buildings in autumn for somewhere to winter, and the gap they find in October is the one they will use until March. Sealing the gaps in autumn, before they have found them, does more than a winter of traps after they have moved in. Winter kills none of it, the termites stay active underground, the cockroaches stay warm indoors, and the rodents that got in during autumn are nesting in the walls, so the damage is accumulating where no one looks.

Which is the trouble with a once a year pest check. The structural points want looking at every 3 or 4 months, and the water points want looking at by season, because what leaks in summer and what pools in winter after rain are different things.

What To Check And When

Every 3 or 4 months:

• Walk the foundation for new cracks, soil against timber, and drains that have stopped draining.
• Make sure the subfloor vents have not been buried under garden soil or leaves.
• Look at every pipe through an outside wall and reseal anything that has cracked or pulled away.
• Run the bathroom and kitchen fans and check they vent outside, because a fan that vents into the ceiling is a damp ceiling.

Once a year:

• Get into the roof space with a flashlight, for droppings, chewed wiring, nesting material, and daylight showing through the eaves.
• If there is a subfloor, look at the framing for mud leads on the stumps or bearers and for water damage.
• Check the door sweeps and seals and replace any that have worn through or gone flat.

Before you make a final buying decision, get the combined building and pest report before settlement. Why I say this is because termite damage to framing can run into tens of thousands and it does not show on a walk through. After heavy rain, look for water standing against the foundation and for new damp marks low on the inside walls or under the floor.

Most of what keeps the serious pests out is the same work that keeps water out of the structure, and this is also the elderly people trick, discuss it with your grand ones and they will suggest the same as well. Once a year under the house with a flashlight, and yes, every 3 or 4 months around the outside with the pipe seals and the vents on the list, and after a big rain a look at where the water went. The crumbs can wait until after that, but the gaps cannot.