How to Identify Signs of Dry Rot

Dry rot is a serious issue in the UK. Untreated, it causes expensive damage and weakens the structural integrity of your home.

It’s important to recognise dry rot when you see it, to avoid costly repairs. Read on to learn how to identify the signs of dry rot, including what it looks like during different stages, and how it differs from wet rot. Plus, what to do next if you think you’ve found some.

What is dry rot?

Dry rot is an aggressive, wood-eating fungus that thrives in damp conditions. It can damage wood, plaster, and other building materials. Unlike other fungi, dry rot can transport water from the source to its outer extremities, allowing it to feed and spread through homes.

Buildings of any age can develop dry rot issues, and it’s often caused by poor ventilation, leaks, or rising or penetrating damp.

What does dry rot look like?

Despite its distinctive appearance, dry rot can be difficult to identify, especially in its early stages. Here are some common signs:

Spore dust

Dry rot is a fungus, and one of the ways it spreads is through spore dust. Look out for piles of distinctive brick orange or rust-coloured particles. These spores are pumped out into the air by mushroom-like fruiting bodies, helping spread the dry rot to a new area.

New dry rot starts as spores, but they won’t germinate unless they find a damp environment or suitable timber to consume.

Fungal strands

Once spores take hold in a suitable environment, you’ll see grey and white strands grow on the damp timber’s surface.

These hyphal threads can penetrate mortar and plaster, allowing dry rot to affect large sections of walls and easily move from room to room. As an early sign of dry rot, it’s important to act if you recognise hyphae growing on damp wood or floorboards in your home.

Like mouldy bread, not all fungus is visible – if strands are visible on the timber’s surface, the inside may already be rotten!

Wool-like fungus

In more advanced stages, hyphal threads merge into a cotton-like growth with a silky texture. It tends to be white or grey coloured.

This mass is called mycelium and is typically found in dark, damp spaces like cellars or underneath floorboards. These wool-like fungal masses help break down wood for food. They spread aggressively, so it’s vital to address the problem if your dry rot is at this stage.

Fruiting bodies

The final stage of dry rot is the distinctive fruiting bodies, which look like pancake-shaped mushrooms. The fruiting bodies are a rusty orange colour, with a pale rim around the edge. When mature, the fruiting bodies release spore dust into the air, starting the cycle again.

If you identify any of the above in your home, it may be dry rot. Call a dry rot specialist to be sure, to prevent further damage.

Other signs of dry rot

The early signs of dry rot can be tricky to spot, as it can be difficult to differentiate it from other rot or types of damp problems. As well as visual cues, you may be able to identify dry rot from other factors e.g. how it smells, how it affects wood, and how quickly it spreads.

• Damp, musty smell – A lingering, mushroom-like odour is often an early sign of dry rot. This smell comes from the fungus breaking down wood fibres. It’s the smell of the digestion process and can be very noticeable in enclosed spaces.
• Cracks in wood – Cracks and cuboidal fractures in the timber can be a sign of dry rot, often accompanied by a deepening of the splits over time. This is sometimes accompanied by a shrinking and cracking of the surrounding plaster or masonry.
• Colour and sound – Dry rot can cause discoloured and darkened timber, including skirting boards, architraves, or rotten floorboards. There may be a hollow sound when tapping the timber, indicating that it has lost its structural integrity.
• Aggressive growth – With the right conditions, dry rot can spread rapidly, consuming timber and penetrating other materials. It typically moves silently through walls, ceilings, and floors before visible damage to your home becomes apparent.

Again, these signs don’t necessarily mean you have dry rot. The only way to know for sure is to ask an expert to check and confirm.

How is it different from wet rot?

Unlike wet rot, dry rot can transport water from a source to its outer extremities, allowing it to feed and expand quickly. Wet rot cannot penetrate and grow through masonry, meaning that it generally remains confined to the damp area in your home where it started.

Here are some key differences between the signs of dry rot and wet rot, including what it looks, smells and feels like to touch.

	Dry rot	Wet rot
What it looks like	Orange spore dust, white cobweb-like fungus, brittle and cuboidal cracked timber, pancake-like fruiting bodies	No orange spore dust or pancake-like fruiting bodies, dark fungal strands, water stains and damp, discoloured timber
What it smells like	Musty, and reminiscent of mushrooms	Musty and damp, like rotting wood
What it feels like	Timber can feel dry and crumbly, and makes a hollow noise when you strike it	Timber can feel soft, spongy, and damp, and crumbles easily due to moisture

Where can I find signs of dry rot?

Many homeowners find dry rot in forgotten areas of their home, and by then it’s already at an advanced stage of damage.

Look for the telltale orange spore dust underneath old shelves or on floors, as this is a distinctive sign of dry rot. Dry rot can often develop in hidden areas like behind furniture or in cellars, so it’s important to uncover and inspect hard-to-reach areas regularly.

Tapping on wood may reveal unseen damage. Check for internal decay or brittleness if you have a creaky or loose floorboard.

Tips for early detection include investigating musty smells in unused rooms, examining areas near external walls or plumbing for changes in texture, or using a screwdriver to test wood for brittleness. Unsure? Take away the guesswork and call a professional.

Get help from an expert

Dry rot is a serious issue, but identifying its early signs and tackling the causes can save your home from extensive damage.

Consult a professional damp proofing specialist to assess the situation and recommend the best course of action. Treatments typically include removing affected timber, applying fungicidal treatments, and improving ventilation or addressing sources of damp.

Don’t wait – take steps today to protect your property. We also offer free damp and timber surveys for properties in Yorkshire.