Rats in the basement — what to do

If droppings have been seen in the basement, movement can be heard or there is a sharp smell, the rats are most likely already nesting there rather than just visiting.

Why rats choose the basement

A basement combines everything they need: warmth from the heating substation, damp, darkness and pipe runs to travel along. The sewer is a direct route for the brown rat from the street mains into the building.

How to judge how serious the problem is

A few fresh droppings by a wall mean a visit. Droppings in several places, grease marks along the walls, gnawed cardboard packaging and a smell mean a nest — and that is a different scale of treatment.

What to do first

Do not sweep droppings up dry — the dust goes into the air. Use a damp cloth and gloves. Do not plug holes with expanding foam before the inspection: rats gnaw through it, and you lose the information about their runways.

When the problem is the whole building's problem

In an apartment block the basement is a communal space. If the rats are there, treating a single flat upstairs will give no result — the source is what has to be treated.

Inspecting a basement step by step

Start the inspection at the heating substation — it is warm and damp there, and there are almost always unsealed openings around the pipe entries. Work along the line where the wall meets the floor with a torch — rodents travel along vertical surfaces, not across the middle of a room. If there is a gap between a pipe and the concrete that your thumb fits into, that is enough for a rat to squeeze through. Open the inspection hatches and look into the sewer stack shaft — in older Riga buildings the cast iron joints are often loose, and that is exactly where an entry point forms. Then the storage cages, the ventilation openings and the outside door thresholds — if there is more than two centimetres between the bottom of the door and the floor, that is an open doorway. Photograph every find straight away — it will be easier later to compare whether movement is continuing.

How to tell a nest from a route through

A common mistake: someone finds a few droppings and concludes a colony is living in the basement, when in fact it is only a route through. A route through is marked by a long, linear band of tracks along a wall, individual droppings scattered evenly, and greasy dark rub marks on the wall render roughly five to ten centimetres above the floor. In a nest the droppings are concentrated in a small area — in a corner or under a shelf — and next to them is gnawed soft material: cardboard, mineral wool, fabric fibres, packed into a bowl shape. Added to that is a sharp ammonia smell, which a route through does not have. The practical significance is considerable: a route through means the source is outside your basement and the whole building has to be worked on, while a nest means breeding is taking place on the spot and action has to start immediately.

Why holes must not be sealed before treatment

Logic says: find the hole, concrete it up, problem solved. In practice this is precisely the action that drives rats into the flats. A basement colony forages along several routes. If you close all the lower exits in one day the animals do not disappear — they look for an alternative direction, and the only direction left is upwards, through the sewer and heating duct shafts. The result is that a few days later residents on the first and second floors start hearing scratching behind the kitchen wall. The correct order is the reverse: bait points are put in first and the population brought down, bait consumption is watched over two to three weeks, and only once consumption has stopped does the physical sealing take place. If you close up earlier, you wall the animals inside the building.

Clearing up droppings safely

Rodent droppings and urine contain pathogens that can get into the air along with dust. So never sweep dry in a basement and never use a vacuum cleaner — both send fine particles into the air in an enclosed, poorly ventilated space. The correct method is the wet one. Put on rubber or nitrile gloves and a respirator, and open the doors and windows for at least half an hour. Thoroughly dampen the contaminated area with a sprayer using soapy water or a bleach solution and let it stand for five to ten minutes. Pick the material up with paper towel, put it in a bag you can tie, and that bag into a second one. Wipe the surface down with a damp cloth. Wash the gloves before taking them off, then your hands.

What residents should store differently

Storage cages in an apartment block basement are the main reason rodents stay in a building after treatment. Cardboard boxes are not a storage container — they are ready-made nesting material, and so is old textile: blankets, outdoor clothing, offcuts of carpet, mattresses. Move anything you want to keep into rigid plastic boxes with lids. Store potatoes and onions in closed containers or on a metal mesh shelf, not in sacks on the floor. Do not leave sacks of animal feed in the basement at all. Leave at least thirty centimetres of clear floor along the walls so that inspection is possible and there are no hidden corridors to travel along. Tyres, furniture carcasses and building rubble that have stood in a corner for years have to go — nests are most often underneath them. It is worth agreeing this with the whole stairwell at once — one neglected cage sustains all the rest.

How to approach the building manager properly

The basement, the heating substation and the stairwell are communal spaces, and their upkeep is the responsibility of the building manager, not of an individual flat owner. The cost of treatment is therefore usually met from the building's maintenance funds. To make sure a request does not go unanswered, write it with concrete facts: date, room, exactly what you saw or heard, attach photographs and state how many flats are already affected. A vague sentence about something running about in the basement gets deferred; a request with photographs and five signatures usually does not. Ask the residents' representative to collect neighbours' signatures — a collective request changes the priority. If there is no answer within two weeks, submit the request again, asking for written reasons and a planned deadline for action.

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