Woodworm, Japanese knotweed and asbestos are the three findings most likely to make a buyer’s stomach drop halfway through a survey report. They’re also, in the great majority of cases, findings with a bounded and fairly ordinary cost attached — not the deal-breakers they’re often taken for. In 2026, professional woodworm treatment typically costs £500–£1,000, a Japanese knotweed herbicide programme runs £1,000–£3,000 for a domestic-scale infestation, and asbestos removal on a single item — a garage roof, a shed, a textured ceiling — averages £800–£3,000.
But it depends heavily on what’s actually there, not just what the word on the page says. “Woodworm” on a report can mean long-dead flight holes in a joist nobody will ever see again, or an active infestation still working through a roof timber. “Japanese knotweed” can mean a manageable clump by the fence, or growth close enough to a structure to warrant a proper risk assessment. “Asbestos” can mean an intact cement garage roof that’s safer left alone than removed, or loose lagging round a hot water pipe that needs a licensed contractor before anyone goes near it. The number on the quote follows from which of those you’ve actually got.
I diagnose these findings for a living. I don’t treat timber, spray herbicide or strip asbestos myself, so I’ve no reason to talk any of them up or down. What follows is 2026 pricing for all three, cross-checked against current UK trade cost guides, what actually drives the number, and — more useful than the invoice — whether the finding on your report needs the full treatment at all.
The short answer
Figures below were checked on 4 August 2026 against 2026 cost guides from Checkatrade, MyJobQuote, The Asbestos Register and specialist Japanese knotweed contractors, cross-referenced against each other rather than taken from a single source. As with most trades in this series, London and the South East — Dom’s patch included — trend above the national figures quoted here.
| Finding | Typical cost (2026) | What it covers |
|---|---|---|
| Woodworm treatment | £500–£1,000 | Professional spray/injection treatment of an average room or loft (25m²); up to £2,000+ for severe or whole-property cases |
| Knotweed — herbicide programme | £1,000–£3,000 | PCA-accredited treatment plan with insurance-backed guarantee, small-to-average domestic infestation |
| Knotweed — full excavation | £4,000–£20,000+ | Dig-and-remove, needed only for redevelopment or the most severe cases |
| Asbestos removal | £800–£3,000 | A single item — garage roof, shed, water tank or textured ceiling; average around £1,600 |
None of these are figures worth spending before you know which category you’re actually in, which is what the rest of this covers, finding by finding.
What drives the price
Extent and access. Across all three, the number scales with how much material is affected and how hard it is to reach — a loft with restricted access costs more to treat than an open one, and a knotweed infestation against a boundary wall costs more to dig out than one in open ground.
Accreditation and the guarantee. A PCA-accredited knotweed contractor or a licensed asbestos removal firm costs more up front than an unaccredited outfit, but the insurance-backed guarantee or licence is usually what makes the property mortgageable and insurable afterwards — the paperwork is often the point, not just the treatment.
Whether it’s licensed work. For asbestos specifically, the Health and Safety Executive splits work into licensed and non-licensed categories. Sprayed coatings, pipe lagging, loose-fill insulation and asbestos insulating board are usually licensed work, needing a specialist contractor, 14 days’ notice and medical surveillance. Intact, undamaged asbestos cement — the material behind most garage roofs and sheds — is often non-licensed work if handled carefully, which is a meaningfully cheaper job.
Region. London and the South East trend above the national figures quoted here, in line with most trades in this series.
Woodworm: is it even still active?
The single most useful question on a woodworm finding isn’t “how much to treat it” but “is there anything left to treat.” Flight holes left by common furniture beetle can sit in a joist or floorboard for decades after the insects that made them are long gone. The signs of an active infestation — pale, fresh bore dust (frass) rather than old and discoloured, clean-edged exit holes rather than weathered ones, or actual beetles in season — are what a competent surveyor looks for before recommending treatment at all. A lot of what gets flagged on older timber, particularly in lofts and under suspended ground floors, is historic and inactive, and spending £500–£1,000 on a guarantee-backed chemical treatment for it is money that buys reassurance rather than a repair.
Where an infestation genuinely is active, damp is very often the reason it took hold in the first place — common furniture beetle strongly favours timber with elevated moisture content. Dealing with the damp source, not just spraying the timber, is usually the more durable fix, and where a section of timber is structurally compromised rather than just cosmetically holed, replacing that piece can be cheaper and more reliable than treating around it.
Japanese knotweed: the real cost is the mortgage, not the herbicide
RICS moved away from the old “seven-metre rule” in 2022, replacing the blanket automatic flag for any knotweed within 7m of a building with a more proportionate, distance- and risk-based assessment — broadly, growth beyond about 3m from a boundary or structure no longer triggers an automatic report to a lender in the way it once did. In practice this means a modest, well-managed clump doesn’t derail a sale the way headlines from a decade ago suggested it would.
What most lenders still want, and what most of the £1,000–£3,000 herbicide programme actually buys, is a PCA-accredited treatment plan with an insurance-backed guarantee — usually 5 or 10 years — in place before completion. That guarantee, not the spraying itself, is what a surveyor and a lender are really looking for in the paperwork. Full excavation and off-site disposal, at £4,000–£20,000 or more for a domestic garden, is rarely necessary for an ordinary case; it’s the route for redevelopment sites, tight completion timelines, or infestations too established or close to a structure for herbicide alone to be a credible option.
Asbestos: the risk is disturbing it, not living with it
Most domestic asbestos finds — a cement garage or outbuilding roof, an old water tank, a textured ceiling coating, vinyl floor tiles — are more dangerous to remove badly than to leave alone. Intact material that isn’t damaged, drilled or being demolished generally isn’t releasing fibres, and encapsulation (sealing it in place, from around £30 per m²) is often a cheaper and lower-risk answer than full removal, particularly for a roof that’s otherwise sound.
Where removal genuinely is the right call — the roof is being replaced anyway, or the material is damaged or in a location it can’t practically be sealed in — a £200–£600 management survey confirming exactly what’s present and whether it’s licensed or non-licensed work is worth commissioning before a removal quote, rather than after. It’s a far smaller outlay than jumping straight to a £2,000+ removal job that turns out not to have been necessary.
What I’d watch for in a quote
- Chemical treatment proposed with no evidence of live infestation — fresh frass or clean exit holes, not just the presence of old ones.
- A knotweed contractor with no PCA membership and no insurance-backed guarantee on offer — a treated garden that’s still unmortgageable afterwards has solved nothing.
- Asbestos “removal” quoted where testing alone, or encapsulation, would resolve it more cheaply and with less disruption.
- No written scope specifying the area treated or removed, the method used, and — for asbestos — whether it’s licensed or non-licensed work.
- Guarantee terms left vague. Ten years is standard for both a knotweed treatment plan and most asbestos or timber-related structural guarantees, and it should survive the contractor going out of business.
- No independent survey first — relying on the same firm that wants the job to also confirm you need it.
Questions I get asked
How much does woodworm treatment cost? In 2026, treating an average room or loft (around 25m²) typically costs £500–£1,000, rising above £2,000 for severe or whole-property infestations. Basic spot spraying is cheaper, around £150–£350, and a pre-treatment survey is usually £80–£250. A large share of “woodworm” findings on a survey are long-dead flight holes needing no treatment at all — worth confirming before paying for any of the above.
How much does Japanese knotweed removal cost? A PCA-accredited herbicide treatment programme with an insurance-backed guarantee, the usual route for a domestic-scale infestation, typically costs £1,000–£3,000 in 2026, more for larger or harder-to-access growth. Full excavation and removal, needed only for redevelopment or the most severe cases, runs £4,000–£20,000 or more for a garden-scale job. It’s the treatment plus a valid guarantee that satisfies most lenders, not excavation.
How much does asbestos removal cost? Removing a single domestic item — a garage roof, shed, water tank or textured ceiling — typically costs £800–£3,000 in 2026, averaging around £1,600, with a minimum call-out of £150–£250. A single garage roof is usually £600–£1,500. Much intact, undamaged asbestos is safer encapsulated or left alone than removed, so a £200–£600 survey confirming what you actually have is worth doing before booking any removal work.
Do I have to declare woodworm, knotweed or asbestos when selling my house? Japanese knotweed has its own question on the standard TA6 property information form, and answering it inaccurately can lead to a claim after completion, so known knotweed should always be declared with treatment records if you have them. Woodworm and asbestos aren’t asked about as directly, but both count as material information a seller generally shouldn’t withhold if directly asked, or if it’s likely to affect a buyer’s decision — an independent survey before marketing is how most sellers avoid an awkward conversation partway through a sale.
If a survey has just handed you one of these three findings and you’re not sure whether it’s a footnote or a five-figure problem, that’s exactly what an independent building survey is built to establish before you commission any treatment. Call 07946 618203 or get in touch and I’ll give you a straight read on what you’re actually looking at.
Small print. This guide is general information, not advice on a specific property, and it doesn’t replace a proper survey and specialist quote for your own home. Prices were researched and correct to the best of my knowledge on 4 August 2026; costs move and vary by region and property. Always get at least three written quotes, and check accreditation (PCA for knotweed, HSE licensing status for asbestos) before commissioning any specialist work.