Selling a House with Wet Rot: What Sellers Need to Know

Wet rot is one of the most common issues surveyors flag in UK properties, and discovering it during a sale can be unsettling for both buyers and sellers. The good news is that wet rot is generally more straightforward to deal with than its more destructive cousin, dry rot. It affects only timber that is directly and persistently damp, it does not spread through masonry, and repairs are usually localised and affordable.

That said, wet rot still needs to be handled properly if you are selling your home. Left untreated, it can cause structural damage to floor joists, window frames, and other timbers. It must be disclosed on your property information forms, and it will almost certainly come up if the buyer commissions a survey. This guide explains everything sellers in England and Wales need to know about selling a property affected by wet rot.

What is wet rot?

Wet rot is a form of fungal timber decay caused by several species of wood-destroying fungi. The most common is Coniophora puteana (also known as cellar fungus), which accounts for the majority of wet rot cases in UK buildings. Other species include Fibroporia vaillantii (previously known as Poria vaillantii) and Phellinus contiguus, which tends to affect external timbers such as window frames and fence posts.

Unlike dry rot (Serpula lacrymans), which can grow through masonry and other non-timber materials to infect new wood, wet rot fungi can only survive in timber that has a consistently high moisture content — typically above 50 per cent. Once the timber dries out, the fungus becomes dormant and eventually dies. This fundamental difference means wet rot is almost always a localised problem. It affects the timber that is wet and does not spread beyond it.

The fungus breaks down the cellulose and lignin in the wood, weakening its structural integrity over time. In advanced cases, affected timber can lose so much strength that it can no longer support the loads it was designed to carry. This is why wet rot in structural timbers such as floor joists, lintels, or roof members requires prompt attention.

How to recognise wet rot

Wet rot has several distinctive signs that distinguish it from dry rot and other timber defects. Knowing what to look for helps you assess the situation before listing your property.

• Soft, spongy timber. Affected wood feels soft when pressed. A screwdriver or bradawl will penetrate easily, often sinking in without significant resistance. In severe cases, you can crumble the timber between your fingers.
• Darkened or discoloured wood. Wet rot typically darkens the timber, giving it a brown or black appearance. This is in contrast to the lighter, more bleached look that can accompany some forms of dry rot.
• Cracking along the grain. Wet rot tends to cause timber to crack and split along the grain rather than across it. This distinguishes it from the characteristic cuboidal (cube-shaped) cracking pattern of dry rot, which fractures both along and across the grain.
• Musty, damp smell. An active wet rot outbreak produces a damp, earthy odour. This is generally less distinctive than the mushroom-like smell associated with dry rot, but it can be noticeable in confined spaces such as sub-floor voids and cupboards.
• Paint damage. Where wet rot affects painted timber, the paint may bubble, crack, or peel. This is often one of the first visible signs on external window frames and door frames.
• Fungal growth. In some cases, thin, dark fungal strands may be visible on the surface of the timber. Unlike the white, cotton-wool-like mycelium of dry rot, wet rot fungal growth is typically less prominent and does not extend beyond the damp timber.

Common causes and affected areas

Wet rot develops wherever timber is exposed to persistent moisture. The key word is persistent — a one-off leak that is quickly repaired is unlikely to cause wet rot, but ongoing dampness over weeks or months creates the ideal conditions for the fungi to establish themselves.

Common moisture sources

• Leaking or blocked gutters and downpipes that allow rainwater to saturate fascia boards, soffit boards, and adjacent wall timbers
• Failed or deteriorating window seals and putty, allowing rainwater to penetrate window frames and sills
• Plumbing leaks beneath bathrooms, kitchens, and utility rooms, particularly slow leaks that go undetected for long periods
• Poor sub-floor ventilation that allows moisture to build up around ground-floor joists, especially in older properties with suspended timber floors
• Defective flat roof coverings that allow water to pond on or penetrate the roof decking
• Rising damp or penetrating damp where the damp-proof course has failed or been bridged

Most commonly affected timbers

Wet rot versus dry rot: why the distinction matters for your sale

The difference between wet rot and dry rot has a significant impact on how buyers, surveyors, and mortgage lenders respond to the finding.

Getting a correct diagnosis is essential. If a general surveyor flags potential timber decay, a specialist timber survey will confirm whether the problem is wet rot or dry rot. This distinction alone can make the difference between a buyer proceeding with a modest price adjustment and walking away from the sale entirely.

Treatment: what is involved and what it costs

Wet rot treatment follows a straightforward process, but the most important step is addressing the moisture source. Without this, any repair to the timber will eventually fail because the conditions that caused the rot in the first place will still be present.

1. Identify and eliminate the moisture source. This could mean repairing a leaking gutter, replacing failed window seals, fixing a plumbing leak, improving sub-floor ventilation, or addressing damp problems. Until the moisture source is resolved, new or remaining timber will continue to be at risk.
2. Assess the extent of the damage. A specialist will probe affected timbers to determine how far the decay has progressed. Timber that retains its structural integrity may be treatable in situ, while severely decayed timber will need to be cut out and replaced.
3. Remove and replace affected timber. Decayed sections are cut away and replaced with pre-treated timber. For structural timbers such as joists, the replacement must match the original specification or be designed to carry the same loads.
4. Apply preservative treatment. Remaining sound timber adjacent to the affected area is treated with a fungicidal wood preservative to prevent any residual fungal spores from developing if moisture levels rise again in the future.
5. Reinstate finishes. Once repairs are complete and the area has dried out, any plastering, painting, or other finishes can be reinstated.

Typical costs

These figures are indicative and will vary by region, contractor, and the complexity of the moisture source repair. Always obtain at least two quotes from PCA-accredited specialists.

PCA surveyors and specialist inspections

The Property Care Association (PCA) is the UK trade body for timber treatment and damp-proofing. Using a PCA-accredited surveyor and contractor is important for several reasons:

• Their reports are widely recognised by mortgage lenders and conveyancing solicitors, which helps the sale proceed smoothly.
• Treatment work carried out by PCA members comes with a transferable guarantee, typically covering 10 to 20 years. This guarantee passes to the buyer on completion, providing ongoing protection.
• PCA members follow the association\u2019s code of practice, which sets standards for survey methodology, treatment specifications, and consumer protection.

A specialist timber survey from a PCA-accredited surveyor typically costs between \u00a3150 and \u00a3400, depending on the size of the property and the extent of the investigation. This is a worthwhile investment if you know or suspect wet rot, as it gives you an accurate diagnosis, a clear scope of repairs, and cost estimates that you can use in negotiations with buyers.

Disclosure on the TA6 Property Information Form

When selling a property in England or Wales, you are required to complete the TA6 Property Information Form. This form asks about the condition of the property, including any known defects, and your answers are legally binding.

In relation to wet rot, you must disclose:

• Current wet rot. If you know your property has active wet rot, you must declare it, even if it has not yet been investigated by a specialist.
• Previous wet rot treatment. If wet rot has been treated in the past, you should disclose when the work was done, who carried it out, and what guarantee was provided.
• Supporting documentation. Provide all treatment certificates, guarantees, specialist reports, and invoices to your solicitor so they can be shared with the buyer\u2019s legal team as part of the conveyancing process.

Honest disclosure protects you legally. Under the Misrepresentation Act 1967, a buyer who discovers undisclosed wet rot after completion could pursue a claim against you. The Consumer Protection from Unfair Trading Regulations 2008 also requires that material information about a property is not withheld. Disclosing wet rot along with treatment documentation actually strengthens your position, as it demonstrates that the problem was identified, addressed, and properly managed.

How wet rot affects the buyer's survey and your sale

If the buyer commissions a HomeBuyer Report or Building Survey, the surveyor will inspect accessible timbers and may identify signs of wet rot. Here is what typically happens next.

1. The surveyor flags timber decay. The report will note visual evidence of decay, elevated moisture readings, and a recommendation for a specialist timber survey.
2. The buyer arranges a specialist inspection. A PCA-accredited surveyor carries out a more detailed investigation, confirms the diagnosis, identifies the moisture source, and provides a treatment specification with costs.
3. Renegotiation may follow. Based on the specialist report, the buyer may ask for a price reduction reflecting the treatment costs, request that you carry out repairs before completion, or seek a retention from their mortgage lender.
4. Mortgage lender conditions. If the lender\u2019s valuer has flagged wet rot in structural timbers, the lender may require treatment before releasing the full mortgage advance or impose a retention until the work is completed.

Having your own specialist report and treatment quotes ready before the buyer\u2019s survey can significantly reduce delays. It demonstrates transparency and prevents the buyer\u2019s surveyor from setting the narrative with a potentially alarming report that lacks specialist detail.

Practical steps for sellers dealing with wet rot

1. Get a specialist diagnosis. Do not rely on your own assessment or a general surveyor\u2019s opinion. Commission a timber survey from a PCA-accredited specialist. This gives you a definitive diagnosis, confirms whether the problem is wet rot or dry rot, and provides a clear scope and cost for any treatment needed.
2. Fix the moisture source first. Whether the cause is a leaking gutter, failed window seals, poor ventilation, or a plumbing leak, eliminating the moisture source is essential. Without this step, any timber repair will eventually fail.
3. Carry out repairs where practical. For most wet rot cases, the cost of repair is modest relative to the potential impact on your sale price. Treating the rot before listing removes a negotiation point and opens the property to the widest pool of buyers.
4. Use PCA-accredited contractors. Treatment carried out by PCA members comes with a transferable guarantee that is recognised by mortgage lenders and solicitors. This is one of the most valuable documents you can provide to a buyer.
5. Gather and organise documentation. Collect all treatment certificates, guarantees, specialist reports, and invoices. If previous treatment was carried out but you have lost the paperwork, contact the original contractor for replacement documents.
6. Disclose honestly on the TA6. Answer all questions about timber defects and damp truthfully. Provide copies of all documentation to your solicitor so it can be shared proactively with the buyer\u2019s legal team.
7. Be prepared for the survey. Even with treated wet rot, the buyer\u2019s surveyor may note historical timber repairs. Having your specialist report and guarantee ready allows the buyer\u2019s solicitor to resolve any queries quickly, keeping the sale on track.

Sources and further reading

• PCA (Property Care Association) — UK trade body for timber treatment and damp-proofing; guidance on wet rot identification and treatment, and a directory of accredited contractors: property-care.org
• RICS (Royal Institution of Chartered Surveyors) — Surveying standards and guidance on assessing timber defects in residential property surveys: rics.org
• BRE (Building Research Establishment) — Research and technical guidance on timber decay in buildings, including BRE Good Building Guide 11 on wood rot: bregroup.com
• Timber Research and Development Association (TRADA) — Technical guidance on timber decay, preservation, and repair in buildings: trada.co.uk
• GOV.UK — Building regulations guidance for England, including Approved Document C on moisture resistance and timber preservation requirements: gov.uk
• The Law Society — Guidance on seller disclosure obligations and the TA6 Property Information Form: lawsociety.org.uk
• Which? — Independent consumer guidance on damp, rot, and timber problems, including advice on choosing specialists: which.co.uk
• Historic England — Guidance on treating timber decay in historic and listed buildings, where conservation-sensitive approaches may be required: historicengland.org.uk

Frequently asked questions