Woodworm Treatment Cost by Scope
Prices below are for professional spray or gel treatment by a PCA-member or BWPDA-registered company, including survey and written guarantee. Timber replacement costs are quoted separately.
| Scope | What Is Included | Typical Cost Range |
|---|---|---|
| Woodworm survey only | Inspection, moisture readings, written report | £75-£150 |
| Single room (floor or ceiling timbers) | Spray treatment + guarantee (up to 20m²) | £250-£500 |
| Roof space / loft timbers | Spray treatment of rafters, joists and timbers | £300-£600 |
| Ground floor — suspended timber floor | Treatment of joists and underside of boards | £400-£700 |
| Whole house — 2-bed property | All affected timber throughout | £1,000-£1,800 |
| Whole house — 3-4 bed property | All affected timber throughout | £1,500-£2,500 |
| Timber replacement (per joist/rafter) | Remove and splice or replace a damaged member | £150-£400 each |
| Antique furniture treatment | Targeted injection/gel treatment | £100-£300 per item |
2026 UK averages. London and South East 15-25% higher. Prices include VAT at 20%.
Signs of Active Woodworm Infestation
Woodworm can be difficult to distinguish from historic (inactive) damage. Look for these indicators of a live infestation:
- Fresh exit holes: Small, round holes (1-2mm diameter for common furniture beetle) with clean, sharp edges and light-coloured frass (fine dust) around them. Old holes have darkened, rounded edges.
- Live frass: Fine, gritty powder beneath or around affected timber, particularly in spring and early summer when adult beetles are emerging.
- Weak or crumbling timber: In severe cases, structural timbers feel soft underfoot or crumble when probed with a penknife — a sign of extensive internal galleries.
- Adult beetles: Small brown beetles (3-5mm) found near windows or on sills in late spring/early summer, as adults emerge through exit holes to mate.
- Species identification: The common furniture beetle (Anobium punctatum) is responsible for most UK woodworm problems. Deathwatch beetle (in hardwood structural timbers) and house longhorn beetle (mainly Surrey and surrounding areas) are more serious and rarer.
Treatment Options: Spray, Gel and Replacement
The standard treatment for woodworm is a penetrating insecticidal spray — typically a permethrin-based solution — applied to all accessible timber surfaces. The chemical penetrates the wood and kills larvae as they feed. Treatment is most effective when applied in late winter or early spring, before adult beetles emerge. Most contractors also offer boron-based treatments as a lower-toxicity alternative.
Gel treatments are used for furniture, joinery or areas where overspray is undesirable — the gel is applied directly to exit holes and absorbed into the timber over time. They are slower-acting than spray but equally effective for isolated items.
Where timbers are structurally compromised — typically where more than 30-40% of the cross-section is damaged — chemical treatment alone is insufficient. Replacement or splicing of the affected joist, rafter or floorboard is necessary. This structural carpentry work is quoted separately and typically costs £150-£400 per member, excluding any associated floor or ceiling making-good.
A quality woodworm treatment guarantee runs for 20-30 years and should be backed by an insurance-backed guarantee (IBG) — so it remains valid even if the contractor ceases trading. Check that the IBG is issued by a recognised scheme such as QANW or Guarantee Protection Insurance (GPI).
What Affects the Cost of Woodworm Treatment?
- Extent of infestation: A single affected floor costs far less than whole-house treatment across multiple floors and roof timbers.
- Accessibility: Treating timbers in a sealed suspended floor or a tight roof space with no boards takes longer and costs more than open-access timbers.
- Species of beetle: Deathwatch beetle infestations in oak structural timbers or longhorn beetle in roof timbers can cause severe structural damage requiring significant timber replacement — costs can run into thousands for large or historic properties.
- Timber replacement requirements: Replacing structurally damaged joists or rafters is a carpentry and structural task that adds substantially to the bill.
- Damp conditions: Woodworm thrives in damp timber — if the root cause of elevated moisture is not resolved (poor ventilation, damp ingress), reinfestation is likely. Treating the underlying damp is essential and may add to the total cost.
- Location: Contractors in London and the South East charge 15-25% more than the national average.
- Guarantee level: Some contractors offer 10-year guarantees; reputable companies offer 20-30 years with an IBG. The longer guarantee may cost slightly more but provides greater security.
Pitfall: Treating Inactive Woodworm Unnecessarily
Many properties — particularly those built before 1960 — show historic woodworm exit holes that were treated decades ago and present no live infestation. Paying for chemical treatment of inactive woodworm is wasteful. Before instructing a contractor, get an independent survey to confirm activity, or look yourself for the signs of live infestation listed above. A survey costing £75-£150 can save you from unnecessary expense.
Budget Before You Buy
Our planner helps you set a realistic refurbishment reserve before you buy — if a survey flags woodworm, factor in both treatment costs and any associated structural timber replacement to arrive at a confident offer figure.