How to Price Woodworm Treatment: Labour, Materials and Margin Guide

Quick Answer: Woodworm treatment in the UK prices at £8-£18/m² for a spray treatment of accessible timber, with typical whole-loft or single-room jobs at £400-£900 and full-house treatments at £1,500-£3,500. The cost is driven less by the chemical than by access — lifting floors, clearing lofts, and replacing structurally weakened timber. A pre-treatment survey (£150-£350, often refunded against the job) should always precede a quote, because identifying the species and whether the infestation is active changes everything.

Summary

"Woodworm" is the catch-all term for several wood-boring beetles, the Common Furniture Beetle (Anobium punctatum) being by far the most frequent in UK housing. Pricing woodworm work badly is easy because customers see flight holes and assume the worst, while the real questions are: which species, is it active, and is the timber still structurally sound? The answers determine whether the job is a £400 spray or a £4,000 partial re-timbering.

The biggest professional error — and the biggest reputational risk — is treating for the sake of treating. Many "woodworm" call-outs are old, inactive infestations where the beetles left years ago. Spraying dead holes earns a quick fee but a chartered surveyor or buyer's structural engineer will see through it. The correct approach is to survey, identify activity (frass colour, sharp-edged holes, bore dust), and only treat live infestation — then deal with the moisture conditions that allowed it.

This guide separates the survey, the chemical treatment, the access works (which dominate the cost), and the structural repairs that some infestations demand. It covers the common UK species, the dangerous ones (House Longhorn and Death Watch Beetle), and the moisture-control work that prevents recurrence. For related damp and decay work see damp proofing pricing guide, dry rot treatment pricing guide and damp survey pricing guide.

Key Facts

Survey and treatment costs

Access and ancillary costs

Regulatory and standards

Quick Reference Table

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Scope Method Typical Cost Notes
Single room floor Spray + lift boards £400-£800 Most common domestic job
Loft / roof timbers Spray accessible £350-£700 Clear loft first
Whole house Spray throughout £1,500-£3,500 Vacate during treatment
Structural timber Boron paste / gel £12-£25/m² Deep penetration
Active + decay Treat + replace timber £2,000-£6,000+ Engineer may be needed
Death Watch Beetle (oak) Specialist survey + treat £1,000-£5,000+ Listed/period buildings

Add access (floor lifting £15-£35/m²), structural repair (£40-£90/lin m), and a £180-£350 skip on any job with timber replacement.

Detailed Guidance

Identify the species before quoting

The species sets the whole strategy. Quoting a one-size spray for every flight hole is how money is lost — and how genuinely dangerous infestations get missed.

WOODWORM IDENTIFICATION
│
├─ Round holes ~1-2mm, lemon-shaped frass ──> Common Furniture Beetle
│                                              (standard spray treatment)
│
├─ Round holes ~3-4mm, mostly sapwood ──────> Powderpost Beetle
│                                              (hardwoods, often new timber)
│
├─ Holes ~3mm in oak/old hardwood,           
│   "tick" sound in spring ─────────────────> Death Watch Beetle
│                                              (period/listed — specialist)
│
└─ Oval holes ~6-10mm, softwood,             
    bun-shaped frass, blistered surface ─────> House Longhorn Beetle
                                               (NOTIFIABLE in some areas —
                                                structural, urgent)

House Longhorn Beetle (Hylotrupes bajulus) is the serious one — it destroys structural softwood and is geographically concentrated (historically north-west Surrey). In some areas Building Regulations require pre-treated timber because of it. Death Watch Beetle attacks old oak and is the bane of listed buildings; it needs a conservation-aware specialist, not a domestic sprayer.

Active vs inactive — the honest test

Only active infestation needs treating. Signs of activity:

Inactive signs: greyed, dusty holes; holes painted over with no new dust; frass that is old and discoloured. A surveyor who recommends full treatment for obviously dead holes is either inexperienced or selling. Be the trade who says "this is historic, you don't need it" — it builds the reputation that wins the structural jobs.

The chemical treatment

Modern treatments are water-based permethrin micro-emulsions (low odour, occupant-friendly) for surface spray, and boron (disodium octaborate) pastes or rods for deep structural penetration. Application:

The chemical is cheap relative to the access. A whole loft might be £40-£80 of product but £400-£600 of clearing, masking, spraying, and reinstating.

Access — the real cost

You cannot treat what you cannot reach. Suspended timber floors must have boards lifted (and relaid) to spray joists and undersides — £15-£35/m². Lofts must be cleared of stored items and insulation pulled back. Boxed-in timber, behind-plaster wall plates, and built-in furniture all add labour. Quote access explicitly and survey it carefully; "treat the floor" without lifting it is not a real treatment.

Structural repair and the underlying moisture

Beetle larvae thrive in damp timber. Treating the beetle without fixing the moisture invites recurrence — and often the moisture (a leaking gutter, failed DPC, blocked sub-floor vents) has already caused rot. Where timber is structurally weakened, options are sister-joisting (£30-£60/lin m), splice repairs, or full replacement (£40-£90/lin m + treated C16/C24 timber). A structural engineer's sign-off may be needed for floor or roof members — budget £350-£600 for an engineer's visit and calculation if load-bearing timber is failing.

Guarantees and the PCA

Customers — especially those treating before a sale — often want an insurance-backed guarantee (typically 20-30 years) that a mortgage lender will accept. These are issued by PCA-member firms and underwritten by GPI/QANW-type schemes. The guarantee adds cost and administration but is frequently the actual reason for the job. Price it as a separate line and be clear it covers re-treatment, not the underlying moisture defect.

Frequently Asked Questions

Do I always need to treat woodworm?

No. If the infestation is inactive — old, greyed holes with no fresh frass and no live beetles — treatment is unnecessary and treating it is poor practice. Many mortgage-driven "woodworm" referrals turn out to be historic. The correct response is a survey, an honest activity assessment, and treatment only where activity is confirmed. Fixing damp conditions is often more important than spraying.

How long does woodworm treatment take to work?

Surface spray kills emerging adults and larvae near the surface; deeper larvae are killed as they tunnel toward the treated zone, so full kill can take through the next flight season (up to a year). This is why new flight holes can appear after treatment — they are existing larvae emerging, not a treatment failure. Set this expectation with the customer in writing.

Is woodworm treatment safe for the household?

Modern water-based permethrin treatments are low-toxicity and low-odour, but the space must be vacated during application and ventilated afterward per the manufacturer's re-entry guidance. Fish tanks must be covered and isolated (pyrethroids are highly toxic to fish), and bats — which are legally protected — must be ruled out of any loft before spraying. If bats are present, work must stop and Natural England be consulted.

Why does the survey cost extra?

A proper timber survey identifies the species, confirms activity, locates the moisture source, and assesses structural condition — the four things that determine whether you need a £400 spray or £4,000 of repairs. Reputable firms refund the survey fee against the works. A "free survey" is usually a sales visit incentivised to find a problem.

Regulations & Standards