Woodworm is the larval stage of wood-boring beetles that tunnel through timber, causing hidden structural damage. Common signs include small round exit holes, powdery dust called frass, and weakened or crumbling wood. Left untreated, woodworm can compromise floor joists, roof timbers, and load-bearing structures — particularly in older properties with damp or poor ventilation.

What Is Woodworm?

Despite its name, woodworm is not actually a worm. It refers to the larvae of several species of wood-boring beetles that lay their eggs in the cracks and crevices of untreated or damp timber. When the eggs hatch, the larvae bore into the wood and feed on it from the inside — often for several years — before emerging as adult beetles.

The term ‘woodworm’ is commonly used across the UK to describe infestations caused by beetles including:

• Common Furniture Beetle (Anobium punctatum) — the most widespread species in UK homes
• Deathwatch Beetle (Xestobium rufovillosum) — typically found in older hardwood structures
• House Longhorn Beetle — capable of causing severe structural damage
• Powderpost Beetle — attacks hardwoods, common in older properties
• Woodboring Weevil — strongly associated with damp or decaying timber

Each species attacks different types of timber and requires a specific treatment approach — which is why professional identification matters.

The Woodworm Life Cycle: Why Larvae Are the Real Problem

Understanding the life cycle of wood-boring beetles explains why woodworm damage is so often discovered late — and why it is so easily underestimated:

• Egg: Adult beetles lay eggs in the grain, cracks, or existing exit holes of timber, typically between April and September.
• Larva: The hatched larvae immediately begin boring into the wood, creating tunnels known as galleries as they feed. This larval stage can last between 3 and 5 years — and all visible damage occurs invisibly beneath the timber surface during this time.
• Pupa: The mature larva pupates just beneath the timber surface before transforming into an adult beetle.
• Adult: The adult beetle chews through the timber surface, leaving the characteristic small, round exit hole. It mates, lays eggs in new timber, and the cycle begins again.

Key point: By the time you see exit holes on the surface, the infestation may already have been active for several years. Early professional inspection is the only reliable way to assess true severity.

How to Spot Woodworm: 6 Warning Signs in Timber

Early identification is the most effective way to limit damage. Look out for the following warning signs:

• 1. Small round exit holes — typically 1–2mm in diameter, with clean, sharp edges indicating recent beetle emergence
• 2. Fine powdery dust (frass) — bore dust found around or beneath timber is a strong indicator of active larvae
• 3. Weakened, crumbling, or brittle wood — timber that collapses under light pressure has likely been significantly compromised from within
• 4. Visible tunnels beneath the surface — often apparent when timber is cut or broken open
• 5. Live or dead beetles near timber — particularly in the emergence season between April and September
• 6. Structural sagging or movement — in floors, roof structures, or beams, suggesting that load-bearing timber has been compromised

How do I know if woodworm is active or old?

Old exit holes tend to have darkened, rounded edges and are free of fresh dust. Active infestations produce frass that is light in colour — cream or yellowish in tone — and may appear freshly scattered around or beneath the affected timber. If you are unsure, a professional survey is the only reliable method of confirmation. Visual inspection alone can be misleading, and older holes do not guarantee the infestation is inactive.

Which types of wood are most at risk from woodworm?

Wood-boring beetles strongly prefer sapwood — the younger, outer layer of a tree — over heartwood, which is denser and less nutritious for larvae. Softwoods such as pine and spruce (common in floorboards, roof timbers, and joinery) are particularly vulnerable. That said, certain species such as the Deathwatch Beetle specifically target old hardwoods like oak and chestnut, often found in historic buildings and churches.

What Causes Woodworm? The Role of Damp and Moisture

Woodworm infestations are strongly linked to moisture. Timber with a moisture content above approximately 20% becomes significantly more attractive to egg-laying beetles — and more hospitable for larvae to thrive. In dry, well-ventilated timber, infestations are far less likely to take hold or spread.

Common causes of high timber moisture content in UK properties include:

• Poor ventilation in subfloor voids, roof spaces, or cellars
• Condensation build-up on cold surfaces in poorly insulated properties
• Leaking pipes, gutters, or roof defects allowing water ingress
• Damp basements or ground-floor timbers in contact with soil
• High indoor humidity in properties without adequate air circulation
• Rising damp from the ground affecting floor joists and subfloor structures

This is why addressing moisture is not simply part of treatment — it is the single most important factor in preventing reinfestation.

Is Woodworm Dangerous? Structural & Health Risks Explained

Yes — woodworm can be genuinely dangerous, primarily in structural terms. Infestations in load-bearing timber, including floor joists, roof timbers, and wooden beams, can lead to serious structural compromise over time, resulting in:

• Sagging or bouncing floors
• Weakened load-bearing elements
• Roof structure instability
• Costly structural repairs or full timber replacement
• Issues arising during property surveys or mortgage applications

The risk is highest in older London properties where roof and floor timbers have been exposed to intermittent damp over decades, and where infestations may have gone undetected for years.

Is woodworm harmful to humans or pets?

No. Woodworm poses no direct health risk to humans or pets. The beetles do not bite, sting, or transmit disease. However, dust and debris from heavily infested timber can irritate airways in sensitive individuals, and heavily compromised structures present a physical safety risk. Modern professional treatments use water-based, low-odour formulations that are safe once dry, though adequate ventilation during application is always recommended.

Can Woodworm Affect a Property Survey or Mortgage?

Yes — and this is one of the most common reasons homeowners and buyers seek urgent treatment. Surveyors carrying out RICS home surveys are required to flag active or historic woodworm infestations, particularly where structural timber is involved. Mortgage lenders may then require a specialist report, or insist on a professional treatment guarantee, before proceeding with the loan.

An untreated or unresolved infestation can delay or derail a property transaction entirely. Having a professional woodworm survey completed — with a documented treatment guarantee in place — is the most straightforward way to satisfy lender and surveyor requirements and keep a sale on track.

How to Prevent Woodworm: Moisture Control & Timber Protection

Long-term woodworm prevention centres on reducing the conditions that make timber attractive to beetles in the first place. Key steps include:

• Improve ventilation in subfloor voids, loft spaces, and cellars — ensure air bricks are clear and airbricks are functioning
• Address all sources of damp — leaking pipes, rising damp, roof defects, or bridged damp-proof courses
• Treat exposed or unfinished timber with a boron-based preservative following professional treatment
• Monitor timber in vulnerable areas (roof, floors, outbuildings) annually for early signs
• Keep indoor humidity below 60% where possible, using dehumidifiers in damp-prone spaces
• Seal cracks and joins in timber to reduce egg-laying opportunities during the active season (April–September)

Properties in London — particularly Victorian and Edwardian terraces — often have subfloor ventilation issues that go unaddressed for years, making periodic professional inspection especially worthwhile.

DIY vs Professional Treatment: What You Need to Know

Over-the-counter woodworm treatments are available from DIY stores and are surface-applied. While they can deter beetles from laying eggs on treated surfaces, they have significant limitations:

• They do not reach larvae deep within structural timber — where the real damage is occurring
• They do not identify the species, which matters because treatment requirements differ significantly between species
• They do not address moisture — the root cause of the infestation — meaning reinfestation is likely
• They do not provide the guarantee documentation required by surveyors and mortgage lenders

Professional treatment is strongly recommended in the following situations:

• Structural timber is affected (floor joists, roof timbers, load-bearing beams)
• The infestation appears widespread, or has been present for several years
• A property survey has flagged woodworm as a concern requiring evidence of treatment
• A treatment guarantee is required for mortgage or insurance purposes
• Previous DIY treatment has not resolved visible signs of activity

Professional Woodworm Treatment in London: What to Expect

At Damp and Mould Solutions Ltd, our woodworm treatment process follows a structured, evidence-based approach:

Step 1 — Woodworm Survey

Our CSRT-certified surveyors assess the full extent of the infestation, identify the species involved, measure timber moisture levels, and distinguish between active and inactive signs. This survey forms the basis of an accurate, tailored treatment plan.

Step 2 — Targeted Treatment

Depending on the species, severity, and timber type, we apply the most appropriate method:

• Surface insecticide treatments (permethrin-based, water-based solutions) — eliminates larvae and emerging adult beetles
• Deep injection treatments — penetrates thick or structural timber in severe infestations
• Boron-based treatments — provides long-lasting protection and prevents reinfestation

Step 3 — Timber Repair Where Required

Where timber has been significantly weakened, we repair or replace affected sections to restore structural integrity.

Step 4 — Moisture Control & Long-Term Prevention

We address the root cause by improving ventilation, reducing damp, and advising on ongoing timber protection to prevent recurrence.

Typical treatment costs in London range from £1,450 to £2,500, depending on the size of the infestation, species, and extent of damage. A professional survey ensures accurate pricing and avoids unnecessary work.

Suspect woodworm in your property? Damp and Mould Solutions Ltd are CSRT-certified woodworm treatment specialists in London with 15+ years’ experience. We provide comprehensive surveys, targeted professional-grade treatment, and long-term guarantees. ☎  Call: 020 4542 6114✉  Email: info@dampandmouldsolutions.co.uk Book your woodworm survey today and protect your property for the long term.

FAQ

How do I know if woodworm is active?

Fresh frass (light-coloured, powdery bore dust), clean-edged exit holes, and live or recently dead beetles between April and September are the most reliable indicators of an active infestation.

When is woodworm most active?

Adult beetles emerge and lay eggs between April and September. This is the best time to spot new exit holes and confirm whether an infestation is currently active.

Is woodworm covered by home insurance?

Typically no. Woodworm infestation is usually classified as a maintenance issue rather than an accidental event, meaning it is generally excluded from standard home insurance policies.

Does woodworm affect property value?

Yes — particularly if structural timber is affected or if the infestation is flagged in a surveyor’s report. A professional treatment guarantee significantly mitigates the impact on valuation and sale progression.

Can woodworm spread from furniture to structural timber?

In principle, yes — adult beetles emerging from infested furniture can lay eggs in nearby structural timber if conditions are suitable (damp, untreated wood). Isolating infested furniture items and treating promptly reduces this risk.