Buying a House: Spotting Rodents During the Viewing

"We viewed it three times, we signed in June, and by September we could hear something running above the bedroom. The loft insulation had to be completely redone: 6,000 euros." A couple from Villiers-sur-Marne told us this story almost word for word last year. The seller had said nothing. And, legally speaking, they weren't necessarily obliged to.

That's the first thing to understand when buying a house in the Val-de-Marne: none of the mandatory property surveys covers rodents. The technical survey file (DDT) required by articles L. 271-4 and following of the French construction and housing code covers asbestos, lead, gas, electrics, termites in areas designated by the prefect, the risk statement, the energy performance certificate and the drainage system. Not rats, not mice, not stone martens, not pine processionary caterpillars in the cedar at the bottom of the garden. The buyer is therefore their own inspector — and typically has two forty-minute viewings to detect what a professional would spot in twenty.

This guide follows the order of a real viewing: the signs to look for, the questions to put to the seller, what you can do between the preliminary contract and the final deed, and the few cases where a hidden defect claim really can be pursued.

What an infestation really costs after the purchase

Before getting technical, let's talk budget, because that's what makes an inspection worth it.

These amounts are almost never covered by the buyer's insurance: damage predating the purchase, or stemming from maintenance, is excluded from multi-risk home policies. We set out the rare exceptions in our article on what home insurance covers in the event of rodent damage. In other words: everything you failed to see before signing, you pay for.

Outside: what you can see from the pavement

The viewing starts before you go in. Walk the entire plot, notebook in hand, and don't let the agent whisk you straight into the living room.

Traces on the ground

The brown rat (Rattus norvegicus), the dominant species in the Île-de-France region, is a burrowing rodent. It leaves very readable clues:

• Holes 5 to 8 cm across, with clean, smoothed edges, at the foot of a slab, under a garden shed resting on blocks, along a boundary wall or at the edge of a bank.
• Runs: compacted, grassless earth pathways 5 to 10 cm wide, between the hedge and the compost bin or along a low wall. A rat always takes the same route.
• Droppings: dark spindle shapes 1.5 to 2 cm long for the brown rat, 4 to 7 mm for the mouse.
• Stashed grain or pet kibble in a corner of the garage or under a step.

Also look at the compost bin and the chicken coop, now ubiquitous in suburban gardens since food waste separation became general practice on 1 January 2024 (the AGEC law, article L. 541-21-1 of the French environmental code). A plastic compost bin sitting directly on the soil, with holes at its base, is a strong signal: see our garden action plan for rats around the compost bin and chicken coop.

The façade and the roof

Look up, and take photos with the zoom. A small pair of compact binoculars makes the roof readable from the garden: lifted tiles at the verge, an open rafter end, a torn-off roof ventilation grille, loose chimney flashing. Also check for droppings or feathers in the gutters — pigeons and rodents often use the same access routes.

At ground level, inspect service penetrations: water supply, electrical conduit, air conditioning condensate drain, telecoms cable entry. A 6 mm gap is enough for a young mouse, 2 cm for a brown rat.

The neighbourhood and the setting

In the Val-de-Marne, the surroundings matter as much as the house. Check:

• proximity to a building site (works on Line 15 of the Grand Paris Express have displaced colonies in several areas of Champigny, Créteil and Saint-Maur);
• the presence of waste ground, a communal bin store, a market or a restaurant within a hundred metres;
• proximity to the banks of the Marne: floods drive rodents out of sewers and riverbank burrows into cellars and basements;
• the condition of the neighbouring plot: if this becomes an issue, read our article on your options when rats come from the street or a neighbouring plot.

A quick look at the local authority's website (municipal hygiene and health department, council newsletter) will tell you whether a rat control campaign has been carried out recently in the area.

Inside: the viewing, room by room

The loft, the most informative space of all

If you only do one thing, make it going up into the loft. Ask the agent explicitly at the very first viewing, and bring a powerful rechargeable torch — a phone light simply isn't enough under a roof.

What to look for:

• tunnels dug through glass wool or blown cellulose, insulation compacted into a hollow;
• droppings lined up along purlins and low walls;
• greasy smear marks (dark, shiny streaks) on timber near a hole;
• a persistent ammonia smell, typical of rodent urine;
• electrical cables with nicked sheathing, and PVC shavings on the floor;
• hazelnut shells, stones, feathers or prey remains, which point more towards a stone marten or an edible dormouse.

Our guide to rodents in lofts and blown insulation explains how to tell old activity from an ongoing colonisation. And if the seller mentions "some noises, but it's just birds", the article on noises in the loft — stone marten, dormouse or bat will give you something to cross-check against.

The cellar, the crawl space and the garage

In the 1900–1930 millstone houses common in Saint-Maur, Nogent and Joinville, the cellar and crawl space concentrate most of the risk.

Look for holes at the foot of walls, ungrilled air vents, a poorly sealed wastewater inspection cover, an unsealed pipe entry. A damp wipe run along the bottom of a wall brings greasy smears to light. Also check the level of damp marks: a basement that floods regularly after a river flood event is both a structural problem and a doorway for rodents. In these houses, service ducts and the crawl space are the real motorways.

The kitchen, the utility room and the cupboards

Open the base units. Pull out the dishwasher and the trim panel behind the oven if you can. The classic signs:

• gnawed skirting board seals, nibbled corners of chipboard panels;
• punctured bags of flour or rice in a store cupboard;
• black marks around the waste pipe entry under the sink;
• bait blocks or traps left in a corner — the single most telling clue of all. A bait station under the sink means there has been a problem, and no one will write that in the listing.

Photograph everything, systematically. A set of reusable mouse traps still sitting in a garage is worth more than any verbal admission.

Smells, sounds and small details

If possible, view the property late in the day or early in the morning: rodents are crepuscular and nocturnal, and scratching behind a partition or in the ceiling is easier to pick up in the quiet. Be wary of an over-scented house, air fresheners everywhere, windows wide open in the middle of October: it isn't proof, but it is a question worth asking.

The questions to ask the seller — in writing

Verbal answers count for nothing in a dispute. Send your questions by email to the agency or the notaire, and keep the replies.

Have you observed the presence of rodents (rats, mice) or other pests in the property, the loft, the cellar or the garden over the past five years? Has any treatment been carried out? By which company, on what date, with what invoices and what intervention report?

Also ask for:

• invoices from any rat control company and the completion report;
• the date the loft insulation was installed and its invoice;
• a history of claims made to the insurer (a claims record can be requested);
• for trees: whether there are pines on the plot and whether nests have recently been removed, since the pine processionary caterpillar is classified as a species harmful to human health by decree no. 2022-686 of 25 April 2022.

A written answer of "no known problems" that turns out to be false changes the legal picture entirely.

Hidden defects and misrepresentation: what you can actually claim

This is the question that always comes up. The honest answer: it's possible, but demanding.

Article 1641 of the French civil code defines a hidden defect as a fault that makes the item unfit for its purpose, or so reduces its usefulness that the buyer would not have bought it — or would have paid less — had they known. For an infestation to qualify, four conditions must be met:

1. A defect predating the sale. A colony established for years, proven by the age of the damage (mineralised insulation, long-gnawed timber), not a mouse that got in in November.
2. A hidden defect. If the holes were visible at the foot of the garage wall, the judge will find that you could have seen them: that is an apparent defect, and your claim is barred.
3. Sufficient severity. A few droppings won't do. A roof structure and insulation needing complete replacement, a documented health risk — yes.
4. No enforceable exclusion clause. Almost every private preliminary contract contains a clause excluding the hidden defects warranty. It is valid… unless the seller acted in bad faith or is a property professional (Cass. civ. 3e, settled case law). Hence the vital importance of written questions: a seller who denied by email a treatment for which an invoice exists moves into misrepresentation (article 1137 of the civil code), and the clause falls away.

The time limit: two years from discovery of the defect (article 1648 of the civil code). In practice, get a professional assessment quickly, and keep dated photos, quotes and the intervention report. The ADIL of the Val-de-Marne and a property law solicitor are the right people to help you judge whether an action is worth pursuing.

Between the preliminary contract and completion: the useful window

You have a ten-day cooling-off period after notification of the preliminary contract (article L. 271-1 of the CCH), then generally two to three months before the final deed. That is the period in which to act.

• Negotiate an additional viewing with a professional of your choosing. Nothing forbids it, and a seller who refuses without reason is already telling you something.
• Commission a voluntary pest survey. It isn't mandatory but costs a fraction of the first repair quote, and it carries weight in a negotiation.
• Insert a conditional clause or a clause making the seller responsible for treatment: this is accepted more often than people think, especially on a property that has had few viewings.
• Plan for handover day: a sealing kit with fine stainless steel mesh, some metal wool for pipe penetrations, and expanding foam plugs for ducts will let you block off the obvious access points before you even move in. For rental inventories, we've set out the inspection protocol to follow before signing.

The three weeks after moving in

A house left empty for several months is a house that rodents have quietly taken over. As soon as you arrive:

1. Do a full tour with a torch, loft and cellar included, before storing anything.
2. Don't take boxes up to the attic without opening them first: the moving box is a classic vector.
3. Set out a few discreet detectors: flour dusted on the floor reveals footprints overnight, and non-toxic glue traps placed along walls work as movement detectors (never outdoors, never within reach of a pet).
4. Store pet kibble and bird seed in rigid plastic airtight storage containers rather than in their original bags.
5. Seal up before you treat. As long as the access points are open, you're simply swapping one colony for another.

Finally, a reminder that, under the European biocidal products regulation and ANSES decisions, anticoagulant rodenticides sold to the public are limited in concentration and must be used in a secured bait station. Badly placed, they poison cats, hedgehogs and birds of prey far more reliably than they resolve a structural infestation.

Get an inspection before you sign

A house in the Val-de-Marne sells for €350,000 to €600,000. A targeted inspection before signing, or a pest survey within the preliminary contract window, represents less than a thousandth of that amount and avoids the nasty surprise of the first autumn invoice.

If you're viewing a property in Champigny-sur-Marne, Saint-Maur-des-Fossés, Créteil, Vitry-sur-Seine or Nogent and have doubts after your tour of the loft, contact us to arrange a pre-purchase inspection, or take a look at our coverage areas and our prices. If you've just moved in and can already hear something running above the ceiling, our emergency line is the right call: the earlier the intervention, the less it costs.