Timber treatment across Merseyside — wet rot, dry rot & woodworm
Three very different problems, often confused with each other. All three share one thing in common: without fixing the moisture that caused them, the timber will keep decaying no matter what's applied to the surface.
Wet rot, dry rot and woodworm are treated differently
Coniophora puteana & related fungi
- Needs consistently high moisture to grow — remove the water source and it stops spreading
- Timber becomes soft, dark and crumbly, usually localised to the wet area
- Common causes: leaking gutters, roof defects, plumbing leaks, rising or penetrating damp
- Doesn't spread through masonry the way dry rot can
Serpula lacrymans
- The more serious of the two fungal decays — can generate its own moisture by digesting the timber
- Can spread across and through masonry to reach new timber
- Cuboidal cracking, a musty smell and brittle texture are classic signs
- Usually needs isolation of the affected area, removal of infected timber and masonry treatment
Wood-boring beetle larvae
- Larvae tunnel inside timber for several years before emerging as beetles, leaving small round exit holes
- Fine powdery dust (frass) near holes is a telltale sign
- Prefers older, slightly damp timber — genuinely rare in modern, well-heated homes
- Often only becomes obvious once timber is sanded, planed, or fails structurally
Fungicide is a tool, not the fix
Water elimination comes first
Chemical fungicides have a role protecting vulnerable timber, but on their own they're a short-term measure. Until the source of water ingress is found and stopped, any long-term remedy that genuinely preserves the timber and the building can't be assured — the treatment has to include fixing why the timber got wet in the first place, not just what's applied to it afterwards.
The subfloor void is where most of this starts
Wet rot in ground-floor timbers is rarely a timber problem to begin with. Suspended floors were built with airbricks ventilating the void beneath them, and that airflow is what keeps the joists and floorboards dry. Block those airbricks — with a raised path, a new driveway, a flowerbed, an extension, or simply a century of accumulated soil and debris — and the void stops breathing. Moisture builds, and Coniophora puteana does what it does. The mechanism is set out in full in our guide to damp in floors and subfloor voids.
That is why the first thing we check on a suspected timber problem is usually outside the house rather than inside it. A survey that treats the joist and ignores the airbrick has fixed nothing, and the same decay returns in the same place. The other recurring sources are the ones that put water into the fabric from above and beside: roof and chimney defects, failed flashings and leaking gutters, and a dense cement render on a solid wall that traps moisture against embedded timber instead of letting it evaporate.
Where the trade over-treats, and where it under-reacts
Woodworm is the clearest example of over-treatment. Wood-boring beetle larvae prefer older, damp timber and are genuinely uncommon in modern, well-heated homes. Exit holes are evidence that beetles emerged — not proof that an infestation is currently active. Blanket spraying of a whole roof void on the strength of old holes is common, expensive, and frequently unnecessary. What settles it is whether the frass is fresh, whether the holes are sharp-edged and pale inside, and whether the timber's moisture content still supports activity.
Dry rot runs the other way, and gets under-reacted to. Serpula lacrymans can conduct water along its own strands and pass through masonry to reach timber some distance from the original wet area, which means treating only what is visible leaves the problem in place. It needs the full extent establishing before any specification is written, which sometimes means opening up.
Both judgements rest on identifying the species and the moisture source correctly first. We work to the Property Care Association's Code of Practice for the Investigation and Control of Wood Destroying Insects and Fungi and to BRE 453 guidance on recognising rot and insect damage, and the seven-step survey method applies here exactly as it does to damp.
Timber treatment FAQs
Generally, yes. Dry rot can spread through masonry to reach new timber and can generate its own moisture, which is why it's treated more aggressively and quickly than wet rot.
It's much less common than in older or poorly heated properties — the beetle responsible generally needs damper timber than most modern, centrally heated homes provide.
Only alongside fixing the moisture source. Fungicide protects timber but doesn't address why it got wet in the first place — without that, decay is likely to return.
Depends on how far the damage has gone. Sound timber can often be treated; badly decayed sections typically need replacing, particularly with dry rot.
Fresh exit holes look pale and clean, often with fine, powdery frass (bore dust) nearby. Old holes tend to be darker, may be painted over, and produce no fresh dust. If you're not sure, a survey can confirm whether treatment is genuinely needed.
Usually not, since it's generally classed as gradual deterioration or a maintenance issue rather than sudden accidental damage — the same treatment most policies give to rising damp. Check your specific policy, but budget on the basis it likely isn't covered.