Pest control is usually treated as a facilities problem: something that happens to a building years after the design team has moved on. But for one of the UK’s fastest-growing infestation risks, the die is largely cast at specification stage.

Clothes moth and carpet moth numbers have climbed steadily for over a decade, with heritage bodies recording some of the highest levels since monitoring began. The insects’ success is, in an uncomfortable way, a design story. Modern buildings, warm year-round, well sealed, generously carpeted and full of quiet voids, are close to ideal moth habitat. And the difference between a building that suffers recurring infestations and one that never does often comes down to decisions made in the spec, the fit-out and the handover.

Here’s what the design and construction side should know about a pest the industry rarely thinks about.

Why modern buildings suit moths so well

The species doing the damage, the common clothes moth and the case-bearing carpet moth, need three things: keratin-based fibres to feed their larvae, warmth to breed, and undisturbed darkness to do it in.

Contemporary buildings deliver all three:

• Continuous heating has removed the winter die-off that once limited populations to one or two generations a year. At a steady 20 degrees, breeding runs year-round
• Wool floor coverings, specified for acoustics, feel and sustainability credentials, are the carpet moth’s primary food source. Larvae graze from room edges and under fixed furniture, precisely where damage goes unseen
• Voids everywhere: suspended floors, raised access flooring, boxed services, built-in joinery and skirting gaps offer harbourage that no vacuum cleaner or surface treatment will ever reach
• Airtightness keeps conditions stable, and modern cleaning regimes rarely disturb edges, corners or the floor beneath fixed furniture

None of this argues against warm, well-sealed, wool-carpeted buildings. It argues for knowing the tenant you’re designing in alongside the ones you’re designing for.

The specification decisions that matter

A handful of choices at design and fit-out stage largely determine a building’s moth exposure.

• Fibre selection is the big one. Moth larvae digest keratin; they cannot digest man-made fibres. A 100% synthetic carpet is effectively moth-proof, while an 80/20 wool blend is a food source. That doesn’t make wool wrong, its acoustic, environmental and quality arguments stand, but it makes the choice consequential. Sensible middle paths exist: synthetics in high-risk, low-visibility areas such as hotel bedrooms, corridors and residential rental stock, with wool reserved for spaces that will be inspected and maintained properly.
• Detail the edges. Damage concentrates where carpet meets skirting and under fixed elements. Tight, well-finished perimeter details, sealed skirting junctions and accessible edges make both inspection and treatment feasible. Gaps behind skirting and beneath built-in wardrobes are larval safe rooms.
• Think about void access. Where infestations establish in floor voids or behind boxed services, treatability depends on access panels that fit-out either provided or didn’t. The same access arguments made for M&E maintenance apply to pest management; the trades just never sit in the same meeting.
• Storage design in residential schemes. Built-in wardrobes over carpeted floors, with dark, unventilated interiors, are classic infestation origins. Hard flooring inside built-in storage, ventilation and lighting all reduce the risk at essentially zero cost when specified early.

The construction-phase risk nobody briefs

Refurbishment projects carry a specific and underappreciated moth risk: disturbance and inheritance.

Stripping out an older building with a historic infestation scatters larvae and eggs precisely when dust, temporary works and stored materials make monitoring impossible. Retained carpets, stored furniture and soft strip-out arisings can reseed a finished scheme. And furnished show flats, hotel FF&E and staged interiors routinely import natural-fibre goods that have sat in warehouses for months.

The mitigations are cheap and procedural:

• Survey older buildings for existing infestation before strip-out, especially where wool carpets are being lifted
• Quarantine or treat retained textiles and furniture before reinstatement
• Inspect FF&E deliveries containing wool, feather or silk components on arrival
• Run pheromone monitoring traps through the fit-out and defects period, a few pounds per floor, catching problems while they’re still snagging items rather than claims

That last point deserves emphasis on handover. An infestation surfacing during the defects liability period, in a hotel, BTR block or high-end residential scheme, becomes an argument about origin that nobody can win cleanly. Dated monitoring records from practical completion onward settle it before it starts.

When a building already has them

For completed buildings, the response discipline matters as much as the design, because moth biology punishes half-measures. Eggs, larvae, pupae and adults are present simultaneously; surface treatment kills the visible generation while the next matures in the voids, and the infestation returns on a six-week schedule that gets misread as reinfestation rather than incomplete treatment.

Established problems in occupied buildings justify bringing in moth control professionals at the survey stage rather than after a failed in-house attempt, particularly in London’s period conversions and dense residential stock, where infestations travel between units through shared voids and the true extent is reliably larger than the visible damage. A proper survey maps the spread before anyone commits to a treatment plan, and options now include whole-room heat treatment, which eliminates every life stage in one chemical-free session, a meaningful advantage in occupied residential and hospitality settings.

Where the infestation centres on textiles and storage, or has already survived one round of treatment, specialist treatment for moth infestations is the higher-percentage call than a generalist contract. Single-pest specialists succeed on exactly the details that building-level treatments miss: species identification, treatment of stored textiles and concealed harbourages, and follow-up visits timed to intercept eggs that survived the first pass. For managing agents, the specialist’s documentation also feeds directly into service-charge justification and dilapidations files.

A small line in the spec, a large line in the accounts

The financial asymmetry is what makes this worth a design-stage conversation. The preventive measures, fibre choices, edge details, storage ventilation, monitoring traps through handover, cost between nothing and trivial. The failure modes are not trivial: wool carpet replacement at £30 to £60 per square metre across a floorplate, recurring treatment cycles in multi-unit buildings, FF&E write-offs in hospitality, and defects-period disputes with no clean answer.

Moths will keep thriving in the buildings Britain now constructs; the warmth and the wool aren’t going anywhere. Whether they thrive in your buildings is, to a surprising degree, a specification decision. Design the harbourage out, monitor through handover, and escalate properly on first evidence, and the industry’s least-discussed pest stays that way.