A Complete Guide To Dry Rot And How To Treat It In The UK

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Dry Rot, Timber Treatments

What is Dry Rot?

Dry rot, scientifically known as Serpula lacrymans, is a type of fungal decay that affects timber. It thrives in damp, poorly ventilated conditions and can cause significant damage to wooden structures. Despite its name, dry rot requires moisture to develop and spread, making it a common problem in properties with high humidity or water ingress issues. Dry rot is not to be confused with wet rot, which also damages timber but does not spread as extensively as dry rot.

Close-up image of dry rot fungus on timber, showing its distinctive orange and white spore structures.

How Does Dry Rot Cause Damage and Why is it Important to Treat It?

Dry rot is a destructive force because it breaks down the cellulose and hemicellulose in wood, compromising its structural integrity. Left untreated, it can lead to severe weakening of wooden beams, joists, and other load-bearing structures, posing safety risks to the property and its occupants.

Treating dry rot promptly is critical to prevent further damage and costly repairs. Failure to deal with it promptly it can lead to safety issues, extensive timber replacement, structural instability, and a decrease in property value.

Dry rot damages floor joists and timber floors which can impact the structural stability of the floors.

What Causes Dry Rot?

Several factors contribute to the development of dry rot:

Moisture: Water leaks, rising damp, or poor drainage can create the damp conditions needed for the fungus to thrive.
Poor Ventilation: Areas with little air circulation, such as basements or crawl spaces, provide the perfect environment for fungal growth.
Lack of Maintenance: Neglected properties with untreated wood or damaged seals are more susceptible to dry rot.
Temperature: Dry rot typically thrives in temperatures between 20°C and 25°C.

Poor ventilation beneath timber floors can cause excess humidity leading to Dry Rot. Ensure you have enough airbricks and they are not blocked.

Fix building defects: Excessive Moisture from water leaks, rising damp, or poor drainage can create the damp conditions needed for the fungus to thrive.

What Are the Signs of Dry Rot?

Detecting dry rot early can save you significant time and money. Look out for these tell-tale signs:

Wood Shrinkage and Cracking: Affected wood often appears dry, brittle, and cracked (It should be noted that wet rot can also display cracking).
Fungus Growth: The presence of orange, white, or grey fungal bodies, white/greyish vine type strands along the timber surface or a cotton wool-like mycelium (Hyphae).
Musty Smell: A smell similar to fresh snapped mushrooms in the affected area.
Discoloured Wood: Timber may appear darker or lighter than usual.
Spore Dust: Fine orange or reddish-brown dust, almost appears like rust, around and below the main dry rot body.

Cracked, brittle wood, fungus growth and musty smells are all tell-tale signs of Dry Rot.

How to Prevent Dry Rot

Prevention is always better than cure. Here are some practical steps to protect your property:

Maintain Proper Ventilation: Ensure good airflow in sub floor areas, lofts, voids. Ensure you have enough airbricks installed.
Control Moisture: Fix penetrating damp issues such as leaks and faulty guttering promptly and address any rising damp issues as soon as they arise. Note. wood rot is often found adjacent to damp walls within a property.
Treatment of Timber: Replace any rotten timbers with pre-treated wood to resists fungal decay. Be sure to also apply treatment to any cut areas or ends of timber. Treatments available include Microtech, Brunosol, and Masonry Biocide.
Wrap joist ends; to prevent timber coming into contact with damp masonry wrap the joist ends with DPC.
Regular Inspections: Check moisture content of timbers with a moisture meter for signs of water ingress or early signs of fungal growth, especially in older properties.
Improve Drainage: Ensure water is directed away from your property’s foundation and is not ponding on the sub floor surface beneath your floorboards.

Preventing dry rot can be done by increasing ventilation, regularly inspecting your property for defects such as leaks, overflowing drains and using a moisture meter to find excessive moisture.

How to Treat Dry Rot

If you’ve identified dry rot in your property, follow these steps to eradicate it:

Identify and Eliminate Moisture Sources: Locate the source of moisture and fix it to prevent further fungal growth.
Remove Affected Wood: Cut away and dispose of all severely damaged timber. Remember to allow for temporary support if replacing any structural timbers.
Treat Remaining Timber: Apply the correct fungicidal treatments to surrounding wood and masonry, even if the wood does not appear to be infected, this will kill any remaining spores and help to stop new attacks flaring up. Timber treatments include Brunosol, Microtech DP and where dry rot spores/mycelium /strands are traveling across brickwork, oversites and concrete use Microtech Masonry Biocide.
Wrap Joist Ends: with DPM to prevent contact with damp masonry.
Replace Damaged Timber: Use new, treated wood to restore structural integrity, again remember to treat any cut ends/areas before fixing into place.
Improve Ventilation: Ensure the area is well-ventilated to prevent build-up of humidity which can cause elevated moisture levels in timbers. Ventilate sub floor voids with additional airbricks.

How to Treat Dry Rot: Identify and eliminate moisture sources, treat and/or replace affected timbers and increase sub floor ventilation.

Tools & accessories you may need to carry out Dry Rot Treatment and Timber Replacement:

Materials you may need for treatment of Dry Rot

Brunosol Timber Treatment: for remainder of cut out timbers.
Microtech DP Preventative Spray: for surrounding areas (also prevents Woodworm attack).
Microtech Biocide: for masonry, oversite affected areas.
Wykabor 40.1 Paste: for injection of ‘at risk’ timbers.
Wykabor 20.1: brush on gel for treatment of joist ends/cut timbers
Damp Proof Wrap: for protecting joist ends and timbers from contact with damp earth/masonry
Airbricks: to increase ventilation to sub floor voids.
Antinox Heavy Duty Floor Protection: for carpets and floors, useful for foot traffic areas between work area and external doors.

Please note: Dry rot is probably the worst problem that can affect your property, if not dealt with promptly, effectively and with meticulous detail, it is highly likely to return.

We Answer Some of the Most Asked Questions on Google Regarding Dry Rot

What’s the Difference Between Dry Rot and Wet Rot?

Dry Rot requires less moisture to thrive and spreads more extensively than Wet Rot. Wet Rot typically remains localized to areas with consistent high moisture levels, whereas Dry Rot can travel through non-wood materials (including plaster and brickwork) to find new timber.

Is Dry Rot the Same as Woodworm?

No, Dry Rot and Woodworm are different issues. Dry Rot is a fungal decay of wood, while Woodworm refers to damage caused by attack from wood-boring insects. Read Our How To Treat Woodworm Article.

What is the Main Cause of Dry Rot?

The main cause of Dry Rot is moisture, often resulting from water leaks, rising damp, poor ventilation or timber in contact with damp masonry/earth etc.

Is Dry Rot Worse Than Wet Rot?

Yes, Dry Rot can be a lot worse than Wet Rot due to its ability to spread through buildings and cause more significant structural damage.

How Do I Get Rid of Dry Rot?

To get rid of Dry Rot, eliminate the moisture source, remove affected wood, treat surrounding timber with fungicide, and replace damaged wood with treated timber.

Can I Fix Dry Rot Myself (DIY)?

Yes, minor Dry Rot cases can be treated DIY if you’re confident handling the steps. However, for severe cases, professional help is advised. Remember you will be dealing with powerful treatments and will need to be fully conversant with health and safety requirements as well as being competent at joinery work.

What Happens if Dry Rot is Left Untreated?

If left untreated, Dry Rot can spreat throughout the timbers of a property and cause extensive structural damage, making the property unsafe, prone to areas of collapse and requiring costly repairs.

What Does Dry Rot Look Like?

Dry Rot often appears as dry, brittle wood with cracking, discoloured timber, often accompanied by a large pancake like fruiting body sprouting with orange or white or grey fungal growths.

Can You Stop Dry Rot Once It Starts?

Yes, Dry Rot can be stopped by eliminating moisture, treating affected and surrounding areas, and replacing damaged wood.

Can Dry Rot Spread From House to House?

Yes, Dry Rot will often spread between terraced and semi-detached houses and flats. It is always important to check the opposite side of any wall or partition whether it be an internal or party wall. Spores can travel, especially if there is a suitable environment in a neighbouring property.

How Long Does It Take for Dry Rot to Destroy Wood?

The time varies, but under ideal conditions, Dry Rot can cause significant damage within months.

Is Dry Rot Dangerous and Hazardous to Your Health?

Dry Rot itself is not directly hazardous to health, but the conditions that promote it, such as damp and poor ventilation, can encourage black mould growth, which may cause respiratory issues or allergies for some individuals. Addressing Dry Rot promptly can help maintain a healthier living environment.

Does Dry Rot Have a Smell?

Yes, Dry Rot is a fungi and unsurprisingly smells like mushrooms, if you take a mushroom, snap it in half and sniff it, that is very similar to the smell of Dry Rot. Also remember that the main body of Dry Rot (fruiting body or sporophore) gives out millions of tiny spores (like seeds) that have a pronounced ginger to rust colour. These are often visible where the smell is, they can leach out under skirting boards, through gaps in plaster, or gaps in timbers.

Where is Dry Rot Commonly Found?

Dry Rot is commonly found in areas with poor ventilation and high moisture levels, such as sub floor voids, lofts or attics, and behind walls or under floors where leaks or damp conditions exist.