Woodworm in Property, Is It Active, Is It Serious, and What Does Treatment Cost?

What is Woodworm?

"Woodworm" is the collective term for the larval stage of wood-boring beetles. The most common species in UK properties is the Common Furniture Beetle (Anobium punctatum), though the House Longhorn Beetle (Hylotrupes bajulus) and Death Watch Beetle (Xestobium rufovillosum) are also found, the latter particularly in older hardwood structural timbers.

The larvae tunnel through timber, feeding on the wood for a period of two to five years before pupating and emerging as adult beetles through the characteristic flight holes visible on timber surfaces. The Property Care Association (PCA) is the authoritative body for the assessment and treatment of wood-boring insect infestation in the UK.

How to Identify Woodworm

The most visible sign of woodworm is the presence of small, circular flight holes left by emerging adult beetles. However, not all flight holes indicate an active infestation, old flight holes from a previous infestation that has since died out are common and do not necessarily require treatment.

The critical question is always whether the infestation is active. Fresh, cream-coloured frass (bore dust) falling from or below flight holes is the clearest sign of current activity. Old frass is typically grey or dusty in appearance. Adult beetles emerge between May and August, this is the best time to inspect for new emergence holes.

Is It Serious?

The severity of a woodworm infestation depends on the species, the extent of the damage, and the type of timber affected.

• **Common Furniture Beetle** in softwood joists and floorboards is very common in pre-1960s properties and is often of limited structural significance unless widespread. PCA guidance notes that many old infestations have self-resolved as the timber has dried out.
• **House Longhorn Beetle** is more destructive and is notifiable to your local authority under the Infestation Control Regulations in certain areas of Surrey and the Home Counties. It can cause significant structural weakening of roof timbers.
• **Death Watch Beetle** affects large hardwood structural members, typically oak, in historic buildings. Treatment can be complex and costly.

PCA Guidance on Treatment

The PCA recommends that treatment should only be carried out where there is evidence of active infestation. Treating old, inactive woodworm is unnecessary and wastes money. A PCA-qualified surveyor should confirm activity before any treatment is specified.

Where treatment is warranted, options include:

• **Permethrin-based insecticidal fluid** applied by brush or spray to accessible timber surfaces, the most common residential treatment
• **Boron-based treatments**, low toxicity, effective for accessible timbers
• **Fumigation**, used in severe or inaccessible infestations, carried out by specialist contractors

A PCA-member contractor will provide a treatment guarantee, typically 20–30 years, which can be assigned to new owners on sale.

Woodworm and Property Transactions

Woodworm is a commonly noted finding in RICS surveys of older properties. Buyers should:

• Establish whether any observed infestation is active (recent frass, new holes)
• Obtain a PCA specialist report if the RICS surveyor recommends further investigation
• Request disclosure of any previous woodworm treatment and check whether a guarantee is in place and assignable
• Treat a confirmed active infestation as a negotiating point, obtaining quotes from two PCA-member contractors before exchange

Property Passport UK records a property's age and construction data sourced from public datasets, which can help buyers identify whether a property falls into the age range, typically pre-1960s, where woodworm in softwood joinery and structural timbers is most commonly encountered.