There are woodworm holes in the loft. Do I need the roof treated?

Usually not. Most flight holes in British roofs are historic. Treatment is worth considering where there is evidence of current emergence in timber that is damp enough to sustain it.

Is dry rot as serious as people say?

It is serious because it can travel through masonry to reach dry timber elsewhere, so the affected area is often larger than it first appears. It still starts as a moisture problem, and moisture control is central to resolving it.

My lender wants a timber and damp report. Is this it?

Check the wording of the retention. Lenders sometimes require a report from a treatment company on their panel, which is a different instruction to an independent assessment. Ask KJ before you commission either.

Timber survey (decay and wood-boring insect assessment)

Timber survey

Independent assessment of rot, wood-boring insect activity and treatment claims — what is active, what is historic, and what genuinely needs work.

Ask KJ about timber decay 01706 318200

Last reviewed 31 August 2026

What is a timber survey?

A timber survey examines the accessible structural and joinery timbers of a building for fungal decay and wood-boring insect activity, and assesses whether either is currently active. It covers roof timbers, floor joists and ends, embedded timbers, staircases, skirtings and window joinery where these can be reached. The key distinction it draws is between historic damage that needs nothing and active decay that needs intervention.

At a glance

Two problems: Fungal decay driven by moisture, and wood-boring insect attack.
The decisive question: Is it active now, or is it long-dead damage from a fixed leak?
Root cause: Wet rot and dry rot are moisture problems. Solve the water first.
Independence: The assessment is not attached to a treatment contract.

Decay follows water, always

Fungal decay needs sustained moisture in timber. Wet rot is the common outcome of a leaking gutter, a failed flashing, a bridged damp-proof course or an embedded joist end sitting in a damp wall. Dry rot is less common, more damaging and able to spread through masonry to reach fresh timber some distance from the original wetting.

Both are consequences. Chemically treating decayed timber while the leak continues buys a short reprieve and nothing more, which is why a competent timber report deals with the moisture source before it discusses treatment at all.

Reading insect activity honestly

Flight holes in old timber are extremely common in British housing and, in the great majority of cases, record an infestation that ended decades ago. Frass that is fresh and pale, holes with sharp clean edges and bore dust accumulating below are the signs that matter.

Species matters too. Common furniture beetle in dry, sound softwood is a very different proposition to death watch beetle in damp hardwood in a period building, and the two attract very different responses.

Whether flight holes show any sign of current emergence
Whether the affected timber is structural or joinery
Whether moisture content supports continued activity
Whether loss of section has reduced structural capacity

Reading a treatment quotation

Blanket spray treatment of an entire roof space is frequently proposed and rarely necessary. Where the timber is dry and the activity is historic, there is nothing for a treatment to act upon.

Guarantees also need reading carefully. A long guarantee from a contractor is only worth the contractor's continued existence, and it usually excludes the recurrence of the original moisture problem — which is the thing most likely to bring the decay back.

Active or historic: what the evidence suggests

Indicative signs only. Confirmation requires inspection of the specific timbers.

Observation	Points towards	Usual next step
Dark, weathered flight holes, no dust	Historic insect damage	Record it; monitor; no treatment
Clean pale holes with fresh frass	Active insect attack	Species identification, targeted treatment
Soft, cuboidal cracking, damp timber	Wet rot at a live moisture source	Fix the water, then assess timber loss
White or grey strands spreading over masonry	Possible dry rot	Urgent specialist assessment and moisture control
Sagging or springy floor	Possible loss of section at joist ends	Structural assessment

Who this is for

A good fit if

Buyers whose survey has recommended a further timber and damp investigation
Owners holding a spray-treatment quotation they want checked
Owners of period properties with embedded timbers in solid walls
Anyone who has just resolved a long-standing leak and needs the aftermath assessed

Not the right choice if

Structural calculations or the design of joist and beam replacement
Carrying out chemical treatment, which is a contractor's work
Pest control matters unrelated to timber, such as rodents

Working through a timber report properly

Almost every timber decision improves when the moisture question is settled first.

1.Find and fix the water
Decay stops when the timber dries. Nothing else works while the source is live.
Damp surveys
2.Establish whether the activity is current
Historic damage needs recording, not treating.
3.Assess structural loss where section has been eaten away
Weakened joist ends and rafter feet are a structural question.
Structural inspections
4.Only then consider treatment, targeted to the affected area
Whole-roof spray is rarely proportionate to a localised, active problem.

When to bring in a specialist

Chemical treatment and timber replacement: a specialist contractor, working to the diagnosed cause.
Structural calculations, load paths and remedial design: a structural engineer. A surveyor describes and diagnoses; it does not design.
Suspected asbestos-containing materials: a competent asbestos surveyor, with analysis by an accredited laboratory.

Common questions

Limitations and sources

Only accessible timbers are inspected. Timbers buried in walls, under floors or behind finishes are not exposed.
Species identification of insect activity may require samples examined by a specialist.
The report assesses observed condition; it does not guarantee the absence of decay elsewhere in the building.
Nothing on this page is a professional opinion about a specific property. KJ Surveyors has not inspected your building, and general guidance cannot replace an inspection and report.

Source: RICS · checked August 2026

Source: Historic England · checked August 2026

Source: UK Government · checked August 2026

Last reviewed 31 August 2026.

Where to go next

damp diagnosis — because timber decay is a moisture problem before it is a timber problem.
roof condition surveys — where the wetting has come through the covering.
a Level 3 survey — for older properties where timber is one of several concerns.

Woodworm or rot found?

Tell KJ what was found, where, and whether there has been a leak. KJ will explain whether an independent timber assessment is worth it before you treat anything.

KJonline

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Hi, I'm KJ. Tell me about the property or the surveying advice you need and I'll help you work out the right next step.

KJ gives general guidance only and has not inspected your property. A professional opinion follows an inspection by a surveyor.