Building demolition or strip-out: exterminate rats before you start breaking

The jackhammer went into the basement slab on a Monday morning. By Wednesday, the caretaker of the adjoining building was reporting three rats in the bin room. By Friday, a ground-floor shop forty metres away closed for two days for emergency treatment. Three weeks later, two condominium buildings on the same street had each signed a rat-control contract, and the managing agent of one of them was sending a registered letter to the project client.

Nobody had treated the building for rats before knocking it down. The tender documents mentioned a strip-out, asbestos removal, a lead survey, a soil study. Not a single line about pests.

This is the most common gap in deconstruction projects across the Paris region. A building that has stood empty for eighteen months — bare walls, services cut off — is almost always a rodent reservoir: nobody moves through it any more, the cellars are no longer inspected, and the waste stacks are still connected to the sewer network. The day the partitions are opened up, the colony is not destroyed — it is evicted, and it heads for the neighbouring buildings.

This article describes what rat control prior to a demolition, strip-out or major refurbishment must include: the survey, the non-negotiable lead times, who bears responsibility, and the documents to demand before the first bucket hits the wall.

Skip, bins and drums piled up in an alleyway against a building wall

Why a demolition site relocates rats instead of killing them

Vibration and dust drive them out, they don't kill them

A brown rat (Rattus norvegicus) lives within a restricted territory, often less than fifty metres around its burrow, provided food, water and shelter are all available there. When vibration, dust and sudden openings remove the shelter, the animal does not stay: it uses the routes it already knows, namely the sewer collectors, electrical ducts and old adjoining cellars.

The classic outcome on a Haussmann-era block in the Paris region:

The field rule is simple: treat before opening up, not during. A campaign launched mid-demolition arrives too late, because the population has already left the baiting zone.

The strip-out is the most dangerous phase

The strip-out — removal of finishes, partitions, equipment and suspended ceilings — is the moment when everything comes to light: nests in mineral wool, runs in timber floors, food caches in crawl spaces. It is also the moment when site workers are most exposed to dried droppings being put back into suspension.

The INRS classes exposure to rodent droppings among the biological risks on demolition and renovation sites, with leptospirosis, hantavirus infection and salmonellosis at the top of the list. The demolition contractor's occupational risk assessment document must mention this risk as soon as the building shows signs of infestation.

The pest survey: the document missing from 80% of files

What it must establish

A pre-works pest survey is not a ten-minute walk-round with a torch. It must produce:

• a dimensioned building plan, floor by floor, locating all signs of activity (droppings, smear marks, gnawing, burrows, runs);
• an assessment of pressure by zone (low, medium, high) and the dominant species: brown rat in basements and services, house mouse on the upper floors and in ducts;
• an inventory of the connection points with adjoining buildings and the public network: inspection chambers, floor gullies, waste stacks, telecom ducts, abandoned shafts;
• any other pests present: German and oriental cockroaches in damp ducts, bed bugs in flats that have been vacated but not cleared, pigeons and their parasites in open roof spaces;
• dated photographs and a GPS or addressed record of the intervention points.

This document serves two purposes. Technically, it sizes the campaign. Legally, it establishes the baseline: if it shows high pressure before works, it justifies the budget requested from the client; if it shows low pressure, it protects the project against later claims from neighbours.

Who commissions it

The client. In practice, depending on the project:

• Social landlord demolishing a block as part of an urban regeneration scheme: the survey forms part of the preliminary studies, in the same way as the asbestos and lead inspections.
• Condominium undertaking a major refurbishment including a cellar strip-out: decision at the general meeting, quotation attached to the notice. The mechanism is the same as for a maintenance contract — see our article on how to get a rat-control contract approved at a general meeting.
• Developer buying an empty building: the clause must appear in the demolition contract as a separate item, not buried in "miscellaneous allowances".

Making the demolition contractor responsible for rat control without a distinct priced item is the surest way never to see it carried out.

Brown rat held gently in open hands against a black background

The protocol: three weeks minimum before the first bucket

Phase 1 — Knock-down baiting (D-21 to D-7)

The aim is not to "put down bait" but to reduce the population before it is disturbed. A serious contractor installs secured, numbered bait stations at high density in basements, plant rooms and surrounding areas, with inspections every three to four days.

Two technical points that make all the difference:

• Consumption must be measured, not merely noted. A record stating "bait consumed" with no quantity makes it impossible to track the decline curve. The report must quantify, station by station, visit by visit. Our inspection criteria are set out in the article on the rat-control service report.
• Second-generation anticoagulants take 4 to 10 days to act. That is a pharmacological fact, not a commercial buffer: bait laid the day before the project starts has no effect whatsoever. ANSES also points out that these products fall under the Biocidal Products Regulation and that professional use requires Certibiocide certification.

Phase 2 — Mechanical trapping and proofing (D-7 to D0)

In areas where baiting is prohibited or risky — close to schools, parks or water points, or where cats and pigeons are present — mechanical trapping takes over. Steel snap traps laid in quantity along the identified runs give a verifiable result and recoverable carcasses, which avoids odours inside partitions once work has begun.

At the same time, anything that can be closed off on the party-wall side is sealed: stainless steel grilles over floor gullies, blocking of abandoned shafts, installation of stainless steel mesh plugs in through-ducts. This is the only point in the project when those spots are accessible.

Phase 3 — Monitoring during the works (D0 to completion)

A preliminary campaign with no follow-up loses all meaning after three weeks. The contract must provide for:

• inspection visits throughout the demolition period, monthly as a minimum, weekly on projects in dense urban settings;
• a monitoring record displayed in the site welfare facilities, available to the health and safety coordinator and the labour inspector;
• a reporting procedure for site workers: who to alert, and within what timeframe;
• suitable protective equipment for strip-out phases — disposable FFP3 masks, waterproof handling gloves, single-use coveralls — and a standing instruction never to dry-sweep droppings.

Phase 4 — Disinfection of contaminated areas

When the strip-out exposes nests, urine-soaked insulation or accumulations of droppings, cleaning and disinfection must be carried out before work continues: wetting down, removal in sealed bags, virucidal and bactericidal disinfectant. The detailed protocol is set out in our article on disinfection after a rodent infestation, and the items to require in a quotation are described in the one devoted to disinfection quotations for commercial premises.

Responsibilities: who answers for the neighbour's rats

The departmental sanitary regulations apply to the site

The departmental sanitary regulations in the Paris region require owners and occupiers to keep premises clean and to carry out any necessary rat-control operations. An empty building awaiting demolition is still a building: its owner is responsible for it, including for whatever comes out of it.

In practice, neighbours have three levers:

1. Report to the municipal hygiene and health department (SCHS) or to the ARS depending on the municipality, with dated photographs and a statement from the caretaker.
2. Formal notice to the client by registered letter, citing the departmental sanitary regulations and quantifying the costs incurred. The structure of such a letter is set out in our article on the effective formal notice in the face of inaction.
3. Liability action for abnormal neighbourhood nuisance, a regime that does not require any proven fault. A pest controller's report establishing the chronology — site opened on such a date, first sightings a fortnight later, no prior rat control — makes up the bulk of the case.

The weak point of a client facing a claim is not the infestation itself, it is the absence of an initial survey. Without a baseline record before works, they cannot demonstrate that the rodents did not come from their property.

For neighbouring managing agents and landlords: anticipate, don't endure

A demolition permit is displayed on site and can be consulted at the town hall. As soon as a project of this kind opens up within a hundred metres, the right sequence for a managing agent or property manager is as follows:

• a precautionary letter to the client requesting the pest survey and the prior rat-control protocol, copied to the municipal hygiene department;
• a baseline record of their own property: inspection of cellars, bin rooms, refuse chutes and plant rooms, with dated photographs — this is the document that will establish that the infestation came later;
• temporary reinforcement of the system: more stations in the basement for the duration of the works, weekly monitoring of the bin room, sealing of floor gullies;
• informing occupants by notice, with instructions to report all sightings centrally to the caretaker.

The same infestation-displacement mechanism is at work during road works and façade renovations; we described it in the article on rats that turn up three weeks after a neighbouring site starts work.

What the "rat control" item in a demolition contract must contain

A priceable, verifiable and enforceable item includes at the very least:

Two wordings to reject systematically: the lump-sum "rat control included" with no breakdown, and the clause that relegates pest control to "site allowances". The method for comparing bids is developed in our article on analysing a rat-control tender, and the drafting of the tender document in the one on the specification for a pest-control service.

The most expensive mistakes

Treating after the basements have been opened up. The population has already left. You pay for a campaign that no longer protects anything, and the neighbourhood absorbs the infestation.

Forgetting flats that have not been cleared. A building emptied of its occupants but not of its furniture is a reservoir for bed bugs and cockroaches. Furniture removed without treatment carries the infestation to waste facilities, reuse channels and sometimes to rehousing accommodation. An inventory of remaining furniture must appear in the survey.

Neglecting the surrounding areas. A fenced site with welfare facilities, a canteen and skips creates its own food source. Site bins with lockable lids in the break area, emptied daily, remove half the problem. Food scraps left behind a site cabin sustain a population that baiting will never offset.

Assuming the sewer network has been treated. Rat control in public collectors is the responsibility of the network operator and follows its own schedule. It does not cover the building's private connections, which are precisely the entry routes. The inspection chambers and gullies of the building being demolished must be treated and sealed under the private contract.

Documenting nothing. With no layout plan, no quantified records and no before-and-after photographs, the client has no means of proving that it acted. A site file containing the survey, visit reports and the final certificate is worth more than three invoices.

In summary

A demolition or strip-out in a dense urban setting is as much a rat-control operation as a civil engineering one. The sequence that works comes down to six points: a pest survey within the preliminary studies, a distinct priced item in the contract, a knock-down campaign started twenty-one days before the basements are opened up, sealing of connections with adjoining properties, monitoring maintained throughout the works, and disinfection of areas contaminated during the strip-out.

For a client, this represents a negligible fraction of the deconstruction budget. For the condominiums and businesses on the block, it is the difference between a noisy building site and two years of infestation. If you manage property close to a project of this kind, ask for the pest survey before the first bucket hits the wall — and arrange a service quotation or a monitoring contract for your own building for the duration of the works.