Dry rot is a type of fungal decay that breaks down wood from the inside, leaving it brittle, hollow, and unsafe. It’s caused by excess moisture and poor ventilation, and it can spread further than you’d think.

The trouble is, most dry rot symptoms don’t look serious at first. Many homeowners put it down to age or damp until real damage sets in. But identifying it early makes all the difference.

In this post, we’ll explain what dry rot symptoms mean, what causes them, and how to tell if it’s time to get a proper inspection.

What Are the Early Signs of Dry Rot in a House?

Spotting dry rot symptoms early is the best chance you’ve got of avoiding serious damage and expensive dry rot repair work. Here’s what to watch for:

• Paint that bubbles, peels, or flakes without obvious damp nearby

• Timber floors or door frames that suddenly feel springy or soft

• A lingering damp smell — earthy, mouldy, but not always wet

• Hairline cracks appearing in the wood grain, especially near the skirting

• Orange-brown dust gathering in corners or along timber

These dry rot early signs are subtle, and that’s what makes them dangerous. The fungus doesn’t need soaked wood, just timber with a high enough moisture content, often from poor ventilation, plumbing leaks, or trapped humidity.

What do dry rot symptoms actually mean?

Most people spot dry rot symptoms without realising what they’re looking at. But each dry rot symptom tells a clear story, and once you know what they mean, it’s easier to grasp just how serious the problem might be.

• Dry rot symptoms signal that moisture has settled in and ventilation has failed — creating the perfect conditions for the fungus to take hold and spread.

• Crumbly wood, flaking paint or distorted skirting boards mean the fungus is already inside — breaking down the timber’s structure from within.

• A strong, musty smell means fungal growth is active, not just lingering damp. The rot is feeding — and it won’t stop on its own.

• Orange spores around timber joints show the fungus is mature and ready to spread, sending out millions of tiny particles to colonise new areas.

• Visible symptoms often appear late, meaning the rot may have already reached hidden floorboards, joists or wall plates.

• Without proper treatment, dry rot continues to grow behind walls and under floors, weakening the property’s structure with every passing week.

What is the Main Cause of Dry Rot??

Dry rot symptoms aren’t just bad luck; they have clear causes, and most of them are avoidable. The fungus that causes it, Serpula lacrymans, feeds on damp timber.

The moisture doesn’t have to be extreme; even 20% wood moisture content can be enough to kick things off.

Here’s what typically sets it off:

• Leaking pipes or overflows in hidden spaces

• Poor ventilation, especially under suspended timber floors

• Rainwater ingress from faulty gutters or roof leaks

• Blocked air bricks or sealed-up vents

• Rising damp that’s left untreated for years

Once timber gets wet and stays wet, the fungus takes hold. It spreads through walls, plaster, and brickwork in search of more timber to feed on. That’s what makes it so destructive; it doesn’t just stay where it starts.

Helpful article: A Guide to Damp and Timber Reports

What are the four stages of dry rot?

Dry rot symptoms don’t start with a mushroom or crumble your skirting boards overnight. It goes through four stages, each one telling you how far it’s spread and how urgent it’s become.

The stages are as follows:

1. Spore Dust

Dry rot begins invisibly. The fungus lives as microscopic spores, floating around in the air. When they settle on wood, you’ll often see a rusty-orange dust, especially in damp corners or underfloor voids.

At this stage, the spores are harmless unless there’s moisture. But once they find it, they activate.

2. Hyphae

Once the spores wake up, they send out thin, white strands called hyphae. These stretch into the timber, searching for food and breaking down the wood’s structure bit by bit.

This stage happens out of sight inside the timber, so by the time you notice anything on the surface, it’s already progressing.

3. Mycelium

The hyphae join together to form a dense, fluffy mass called mycelium, usually grey or white, with a soft, felt-like texture. This is when dry rot becomes destructive.

Mycelium spreads aggressively across surfaces, including brick and plaster, seeking more wood to colonise. You might spot it behind skirting boards, under floorboards, or in basements.

4. Fruiting Body

The last stage of dry rot symptoms is the most visible, a thick, fleshy, rust-coloured lump. This is the fruiting body (or sporophore), and it’s how the rot reproduces.

It sends out thousands of new spores into the air. If the environment is still damp and poorly ventilated, the cycle starts again somewhere else in your home.

What is the Best Way to Repair Dry Rot?

There’s no shortcut here. Proper dry rot symptoms treatment involves three steps, and skipping any one of them usually means it comes back.

• Find and stop the moisture source: You can’t treat dry rot without drying out the timber. That means fixing leaks, unblocking air bricks, or tackling rising damp first.

• Strip back the affected area: All infected timber, plaster, and even brickwork needs to be removed. Sometimes that includes hidden joists or flooring that still looks intact.

• Apply a fungicidal treatment: This is where a dry rot treatment spray or paste comes in. Professional-grade solutions soak into the masonry and remaining timber, stopping spores from regrowing.

• Replace Timber and Other Materials: Once the area is dry and treated, replace all removed sections with treated timber or rot-resistant wood. In key areas like subfloors or support beams, this is vital for structural safety.

• Improve Ventilation and Airflow: Dry rot thrives in damp, stagnant air. Improve ventilation by installing air bricks, adding vents, or opening up sealed areas. This helps keep moisture levels down and prevents future fungal growth.

• Monitor for Recurrence: After treatment, keep an eye on the area. Use moisture meters to check damp levels and look out for early dry rot signs, like a musty smell, cracking wood, or paint bubbling.

Helpful resource: What Percentage Damp Is Acceptable In Walls?

How to Treat Dry Rot at Home? (And When Not to)

You can treat small patches of dry rot yourself, like a bit of damaged skirting where you’ve already dried the area out.

But here’s the truth: once it’s spread behind plaster or into subfloors, this isn’t a DIY job.

Still, want to give it a go? Here’s how to treat dry rot at home:

1. Dry the area fully — use dehumidifiers and ventilation.
2. Cut out all affected wood, plus 500mm beyond any visible damage.
3. Clean the masonry, brushing off spores.
4. Apply fungicidal spray generously across wood and brick.
5. Replace with treated timber, not regular wood.

But if you’re seeing white strands, large spore dust patches, or fruiting bodies, call someone in. It’s not just about fixing the visible dry rot symptoms; it’s about cutting it off at the source.

👉 Our full guide: Dry Rot Treatment: How to Identify and Eliminate the Problem (UK Guide)

What’s the Best Dry Rot Treatment Spray?

Most professional surveyors won’t just grab a spray off the shelf; they’ll use an industrial-strength fungicide designed to kill dry rot deep in walls and wood fibres.

That said, if you’re tackling very early-stage dry rot symptoms (and you’ve stopped the moisture source), some of the most commonly used dry rot treatment sprays in the UK include:

• Soluguard Dry Rot Fungicidal Treatment

• Ronseal Wet Rot Wood Hardener (for very minor, localised use)

• Permagard Masonry Biocide

How Much Does Dry Rot Repair Cost in the UK?

👉 Related article: Who Should Pay for a Damp and Timber Report?

Can Dry Rot Come Back After Treatment?

Yes, and it often does if the underlying issue isn’t sorted. Dry rot spores are incredibly hardy. All it takes is a bit of moisture and the right temperature, and it’s back.

That’s why dry rot treatment isn’t just about spraying a fungicide. Proper ventilation, permanent damp proofing, and treated timber are what stop it returning.

Also, always check hidden areas after any treatment; under stairs, behind skirtings, or under floors. If it’s made it there once, it’ll try again.

Wet Rot vs Dry Rot: How Can You Tell the Difference?

Wet rot and dry rot can look similar, especially early on, but the treatment and urgency are very different. Here’s how to tell them apart:

Which is Worse, Wet or Dry Rot?

If you’re dealing with rot, neither is great news. But dry rot is usually the bigger problem.

That’s because dry rot spreads. It can move through timber and even travel across brickwork to reach other areas of your home. And unlike wet rot, it doesn’t need much moisture to keep going. Once it’s in, it can quietly grow in places that seem dry on the surface.

Wet rot tends to stay where it starts. It only affects timber that stays damp, like a leaky windowsill or a floor joist above wet ground. It’s still damaging, but it doesn’t travel.

Final Thoughts

Dry rot is sneaky. It starts small, spreads fast, and thrives in homes that don’t seem that damp on the surface.

The real trick is knowing what to look for; those early dry rot symptoms like flaky paint, springy floors, or that sweetish mouldy smell. If you spot it early, it’s manageable. Leave it too long, and you’re into costly repairs and timber replacement.

So don’t ignore those strange changes in your home. A quick check could save you thousands — and your floorboards.

Questions People Ask About Dry Rot Symptoms