Dry rot is one of the most damaging types of fungal decay that can affect buildings in the UK, especially in older or poorly ventilated properties.
When it appears on walls, it can compromise both the appearance and structural integrity of your home.
In this article, we explore what, how to identify it, and treat dry rot on walls if you suspect an infestation.
What Causes Dry Rot on Walls?
It is caused by a fungus known as Serpula lacrymans, which thrives in damp, poorly ventilated conditions.
Walls can become vulnerable to dry rotting if they are consistently exposed to moisture from:
- Leaking pipes or plumbing issues
- Rising damp from ground moisture
- Penetrating damp due to roof leaks, cracked render, or faulty gutters
- Poor indoor ventilation trapping humidity
The fungus feeds on the cellulose in timber and wall laths, breaking down structural components and spreading rapidly if unchecked.
How to Identify Dry Rot on Walls
Common signs include:
- Flaking or bubbling paint
- Cracked or crumbling plaster
- Damp, musty smell
- Discoloured or soft patches on wall surfaces
- Orange, mushroom-like fruiting bodies
- White, fluffy fungal growth (mycelium)
- Cuboidal cracking pattern in the surface material
It often starts behind skirting boards or wallpaper, making it harder to detect until it becomes extensive.
👉 Read our full guide: Identifying Dry Rot Symptoms
Can Dry Rot Spread Through Walls?
Yes, it can spread through walls, particularly if timber elements are embedded in or behind the wall.
The mycelium can travel across non-timber materials such as brick and plaster in search of new food sources.
If left untreated, it can reach adjacent timbers like joists and beams, causing widespread structural problems.
What Does Dry Rot Look Like on Walls?
It manifests in several forms:
- Fruiting Bodies: Rusty orange, pancake-like growths with a spore-dust surface
- Mycelium: White, fluffy strands spreading like cotton wool across the wall
- Wood Damage: Timber embedded in or near walls may shrink, split, and develop a cuboidal cracking pattern
These symptoms can appear in combination, depending on how long the rot has been active.
How Serious Is Dry Rot in Walls?
When it happens on your walls, it can be a very serious issue.
Though the fungus itself doesn’t eat brick or plaster, it uses them as highways to reach structural timber.
In the worst cases, it can lead to timber collapse, affecting floors, ceilings, and structural beams.
It can also create health risks by releasing spores and worsening indoor air quality.
👉 Must read: Who Should Pay for a Damp and Timber Report?
Dry Rot vs Wet Rot on Walls: What’s the Difference?
While both are forms of fungal decay, they differ significantly:
- Dry Rot spreads aggressively and can travel through masonry
- Wet Rot remains confined to damp areas and requires higher moisture levels to survive
- Dry rot is often drier in appearance, while wet rot looks darker and more saturated
Accurate diagnosis is key, as treatments differ.
Dry Rot vs Wet Rot
Side-by-Side Comparison of Wall Fungal Decay
Key Takeaways
⚠️ Urgency Level
Dry Rot: Immediate professional attention required
Wet Rot: Can often wait for scheduled repairs
🔍 Identification
Dry Rot: Often hidden, requires professional inspection
Wet Rot: Usually visible in problem areas
🛠️ Solution
Dry Rot: Extensive professional treatment
Wet Rot: Fix moisture + replace materials
⚠️ Both conditions require professional assessment for proper identification and treatment planning.
How to Treat Dry Rot on Walls
Treating it involves eliminating moisture and eradicating the fungus:
- Identify and fix the moisture source (leak, damp, poor ventilation)
- Remove all affected plaster, render, and timber
- Apply a specialist fungicide treatment to exposed masonry and timber
- Allow walls to dry out completely (may take several weeks)
- Replaster using breathable materials like lime plaster
- Improve ventilation in affected areas
Always wear protective gear and follow safety guidance if attempting minor repairs yourself.
Do I Need to Remove the Entire Wall Plaster to Treat Dry Rot?
In many cases, yes. Plaster and render can hide fungal strands and spores.
Removing wall coverings ensures you can treat the full extent of the infestation and reach embedded timber behind.
A professional surveyor will advise how much material needs to be removed.
Can You Treat Dry Rot on Walls Yourself?
Small, surface-level dry rot patches may be manageable with DIY treatment.
However, due to the hidden and spreading nature of these issues, most cases require a professional help.
Misidentifying or under-treating the issue can result in costly future repairs.
Cost of Treating Dry Rot on Walls in the UK
The treatment costs vary widely based on severity and access.
On average:
- Minor cases: £500–£1,000
- Moderate damage: £1,000–£2,500
- Severe structural cases: £3,000+
Additional costs may apply for timber replacement, replastering, and ventilation upgrades.
How to Prevent Dry Rot on Walls
Prevention is often simpler and cheaper than treatment.
Steps include:
- Maintain guttering and downpipes
- Fix plumbing leaks promptly
- Ensure wall cavities are ventilated
- Use breathable paints and plasters
- Install air bricks or passive vents in damp-prone areas
Who to Contact for Dry Rot on Walls in the UK
Seek a qualified timber and damp specialist through the Property Care Association (PCA).
They provide certification for trustworthy contractors and surveyors trained in diagnosing and treating dry rot.
Frequently Asked Questions
Can dry rot appear behind wallpaper?
Yes, it often begins behind wallpaper or skirting boards where moisture is trapped.
Will dry rot in walls come back after treatment?
If moisture issues are not resolved, they can return. Proper ventilation and monitoring are crucial.
Is dry rot covered by insurance in the UK?
Usually not, unless caused by a sudden, insured event (e.g., burst pipe).
Check your policy.
How long does it take for dry rot to spread?
Under ideal conditions, dry rot can spread several centimetres per week, making a rapid response essential.
What’s the best treatment for dry rot?
To treat the issues properly, you need to start with the cause: moisture.
Without damp conditions, the fungus can’t grow. So before anything else, find and fix the source: a leak, poor ventilation, rising damp… whatever’s making the timber wet.
Next, check how far the rot has spread. If any timber is soft, flaky, or crumbling, remove it completely. Don’t leave any behind — the rot spreads fast if left untreated.
Then treat the remaining wood with a boron-based product, like a gel or spray. This kills off the fungus in the surrounding timber and protects it from future outbreaks.
And finally, keep the area dry and well-ventilated going forward. That’s what keeps dry rot from coming back.
What’s the injection for dry rot?
For larger timbers you can’t easily replace, there’s an option: boron injection. The most common product is Wykabor 40.1 — a thick boron paste.
Here’s how it works:
– Drill into the timber.
– Inject the paste deep inside.
It slowly spreads through the wood, killing the fungus from the inside out.
It’s often used on beams, joists, or other structural pieces that are too expensive or difficult to remove.
Conclusion
Dry rot on walls is more than a cosmetic problem – it’s a serious structural threat.
Recognising the early signs, removing moisture sources, and acting quickly can save thousands in repairs.
For reliable diagnosis and effective treatment, always consult a PCA-accredited professional.
