Dry Rot

How long does it take for dry rot to develop?

No matter how well-built a home or commercial property is, the forces of nature have a way of reminding us who’s really in charge. Something as small and seemingly harmless as fungal spores can do real damage to construction and finishing materials, especially wood. Indeed, rotted wood can become a health and safety hazard if neglected for too long. That’s why it’s important to prevent wood rot and identify it when it occurs so you can take care of the issue.

However, noticing rotted wood is sometimes easier said than done. In many cases, the issue becomes visible only after some of the damage has been done. Even still, the sooner you act, the better. And knowing how long it takes for wood to start rotting can help you address the issue faster. But the time it takes for rot to take hold and cause problems depends on whether you’re dealing with dry rot or wet rot. Let’s discuss these two types of rot, how to spot them, and how to prevent them.

At Hitch Property Constructions, we offer timber repairs work from simple timber repair to almost new structures, renovations, and extensions.

The Stages of Dry Rot

Dry rot is a wood-rotting fungus. There is only one Dry Rot fungus, but a great many Wet Rot Fungi decay timber by digesting the parts of it that give the wood its strength and thick density. According to Wikipedia (https://en.wikipedia.org/wiki/Dry_rot), the term ‘Dry Rot’ was once used solely to identify the fungus that decayed the wood in sailing ships and other structures.

This form of decay turns the wood a distinctive brown colour, and the infected timber became cracked in large cubes called ‘cuboidal cracking’ and crumbled away.

Dry rot has four stages in its life cycle: a spore, hyphae, a larger mass known as mycelium and finally a fruiting body that produces more spores. Let’s take a look at the four stages in more detail.

Dry Rot


Dry rot begins its life as tiny spores, and these spores remain inactive until they come in contact with timber and enough moisture to make them active. Typically 20 per cent moisture content is enough to make the fungus spores start to attack timber.


The second stage of dry rot is a hypha. A hypha is a long branching structure of a fungus – typically what fungus spores will grow into if left untreated. Dry rot hyphae are identifiable by the white fine stringy strands that become visible both inside and outside the timber. These strands allow the fungus to grow rapidly inside the timber.


The mycelium is the name given to a collection or mass of hyphae. Mycelium is the vegetative part of fungi and can spread very far in masonry and behind wall plaster in search of timber to attack, so you should be sure to treat any infected timber quickly. If left untreated for too long mycelium will grow and spread out into a thick mass, before turning into its fourth and final stage.

Sporophores or Fruiting Bodies

The fruiting body is the final stage of the Dry Rot fungus’s life cycle. The fruiting body takes on a mushroom-like appearance, and it produces Dry Rot spores that it emits from the surface to be carried along by air currents out into the air. Fruiting bodies are formed by the fungi when it detects changes in its conditions. The fruiting body is created as an attempt to preserve the lifespan of the fungus by emitting spores to other areas of the property, effectively starting the Dry Rot fungus life cycle all over again.

What is the difference between the two kinds of rot?

The two most common forms of fungal decay found in homes are dry rot and wet rot. Surveyors are often asked about the difference between them, especially as both are associated with fungal decay and tend to affect timber.

Generally speaking, both forms of rot are caused by fungal spores already present in the timber, which grow and spread when enough moisture is introduced into the area. The scientific names for the fungi are Serpula lacrymans – dry rot – and Coniophora puteana – wet rot.

It is important to be able to identify both forms since they can lead to significant structural issues if left untreated. If you believe you have dry rot or wet rot in your home, you should always consult a surveyor.

Wet rot

As the name suggests, growth of wet rot requires a higher moisture content in the timber than dry rot does. Wet rot will begin to grow when the moisture content of the timber or other permeable surface reaches around 50%, while dry rot can grow with as little as 20%. The high amounts of moisture required by wet rot usually result from an external leak or water ingress from plumbing, guttering, stone pointing or downpipes. 

If you discover wet rot, you should investigate and repair any leak before treating the rot itself to prevent a recurrence. Once the moisture is removed, wet rot will stop growing. Typically, you will also need to replace the timber in the affected area.

Common signs of wet rot:

  • damp or musty smell
  • cracking timber
  • softened or spongy timber
  • discoloured or distorted timber
  • weakened timber
  • black–brown fungal growths.

Dry rot

As mentioned, dry rot requires roughly 20% moisture content in the timber to begin growing. Although its name suggests otherwise, dry rot will not grow in dry conditions.

Homes with high humidity and poor ventilation are often susceptible to dry rot. One early warning sign is on the windows. If you live in a particularly wet or humid area, you should take care to ventilate your home properly to prevent moisture build-ups.

Moisture can come from a leak, as it can do when there is wet rot. In either case, it is important to identify and remove the source of the moisture before treating the fungus itself.

Dry rot is often found in areas hidden from view, such as under floorboards or behind a wall. If it is not identified early on, it can cause severe damage to timber and spread through the home.

While dry rot can be treated with a fungicide, it is always best to have a surveyor assess the full extent of the damage. It may be necessary to remove plastering to investigate. As is the case with wet rot, you will most likely need to replace any affected timber.

Signs of dry rot include:

  • damaged or decaying timber
  • damp or musty smell
  • deep cracks in the timber grain
  • brittle timber or timber that crumbles in your hand
  • concentrated patches of orange-brown spore dust
  • grey strands on timber
  • fruiting bodies that look like large mushrooms.

How Long Does it Take for the Rot to Do damage?

The speed and spread of rot can vary widely. However, all cases of rot require the proper conditions to “activate,” so to speak. These conditions include oxygen, proper temperature (often between 65 and 90 degrees Fahrenheit), moisture, and “food” (wood, in this case).

Lab experiments have recorded that dry rot spores can germinate approximately seven to ten days after the wood has become damp enough. Older spores can take longer to germinate. As mentioned earlier, though, it can take a long while for signs of dry rot to appear after germination. 

As for wet rot, it isn’t easy to establish a regular timeframe for its rate of growth. That said, wet rot can only spread to those areas damp enough to accommodate it. So, if you notice wet rot, you can mitigate it by removing any moisture.

Check out our range of timber repairs Melbourne at Hitch Property Constructions. 

Ways to Prevent Rotted Wood

If you want to keep your wood rot-free, there are a number of measures you can take. Some methods include:

  • Using pressure-treated wood, to begin with
  • Repairing any cracks or holes in wood with caulk
  • Maintaining/repairing pipes and gutters to prevent water leaks
  • Hiring painting services to properly paint, stain, or seal your wooden features to protect them from the elements
  • Keeping your wooden features clean (via scrubbing and/or power washing)

Diagnosing Wood Rot

A Fine Mess

Virtually every homeowner has to deal with wood damage at some time or another. It’s so common that the materials for replacing and repairing damaged wood make up an estimated 10 per cent of all wood products annually produced in the United States.

Tool Chest

Fungi are plantlike organisms. They can’t synthesise food on their own, however, so they have to absorb nutrients from other sources, such as wood. Mushrooms are well-known fungi.

Wood rots for one simple reason: It gets wet. It can happen to wood anywhere in your house—in structural timber, door trim, eaves, exterior trim—you name it. Wood rot is also common on boats and plants and can even be found in musical instruments.

All wood has the potential for rotting, as it contains a certain amount of moisture. If the moisture content is below 20 per cent, rot typically isn’t a concern. Anything over this provides a potential breeding ground for fungi, which is what causes wood rot.

Moisture is just one thing that fungi need to survive. They also need the following:

  • Favourable temperatures. Anything in the 40°F to 100°F range will do.
  • Oxygen.
  • A food source. The fungi that attack wood prefer carbohydrates in the form of cellulose and lignin.

Wood is made up of cellulose and lignin, and the other factors are pretty hard to control, so fungi abatement efforts generally focus on the one variable—moisture—that we can do something about.

Dry vs Wet Rot

People used to distinguish between different kinds of wood rot as being dry or wet. This was misleading, as it made it seem like dry wood could develop rot. This isn’t possible. All rotten wood is wet wood or has been wet at one time.

Tool Chest

Brown rot causes infected wood to turn dark brown, hence the name.

Still, you’ll hear people call certain types of rot “dry rot.” What they’re referring to is brown rot, which is one of three types of wood rots. This rot cracks wood against the grain, causing it to split and crumble. In advanced stages of brown rot, after the rot has taken all the nutrients out of the wood, it can also become dry and powdery.

The other types of wood rot are

  • White rots. As the name suggests, these rots cause affected wood to take on a white appearance, which can range from greyish-white to yellowish. In their advanced stages, white rots make wood look stringy and feel spongy or springy.
  • Soft rots. These are rare inside of homes, but they have been known to attack wood shingles in wet climates.

Some rots can grow inside wood for a long time and cause extensive damage before they are detected. Others develop crusts called “fruiting bodies” on the surface of the wood.

Rot vs Mold

Mould (and mildew) are also fungi that spring up around moisture. While they indicate moisture problems and can cause discolouration, they don’t cause wood decay. They can, however, increase wood’s absorption ability, which can make it more prone to fungal growth.

Another type of fungi called “sap stain fungi” looks like surface mould. However, it, too, doesn’t weaken wood structures; it only discolours them. Sap stain fungi stop growing when the wood dries out. Its presence typically indicates wood that was wet at one time but no longer is.

What Are The Long-Term Effects of Dry Rot?

Dry rot is one of the most serious forms of damp that can manifest itself in property and, if left untreated, it can cause potentially irreversible damage to the building. As specialists in treating dry rot, we strongly advise regularly inspecting your property for signs of an infestation.

Often, the presence of dry rot does not come to light until the damage has already been done due to the areas in which the issue is likely to be. Dry rot is commonly found in humid, secluded areas with little in the way of ventilation.

Structural Damage

The main cause for concern when it comes to dry rot is damage to the building’s structure, which in serious cases can result in the need for major renovation works. In London, owing to highly populated streets, houses are at high risk of dry rot forming in secluded areas of the home such as the loft.

Unlike wet rot, the fruiting bodies of dry rot can spread throughout the building on surfaces with a high density of moisture. This means that while the cause of the problem could be in one area of the home if left untreated, dry rot can penetrate any room leaving your entire home at risk.

Worst Case Scenario

What’s the worst that can happen? Your entire home could cave in on itself as a result of structural beams becoming too weak to support the building.

Below are some brief explanations of each of these approaches.

Primary Measures for Control and Treatment

The most vulnerable feature of fungi is that it usually requires water. It is for this reason that treatment requires the complete elimination of damp. This forms the primary measure of removing both dry and wet rot.

It is important to find and rectify the fungi’s source of water which is causing and maintaining the rot. Another important thing to do is to promote and maintain immediate drying conditions.

Removing the source of water for fungi is the first point of attack. Therefore, it is important that you stop further ingress of water. This action alone will help to treat and eliminate the activity. This action is required to promote and maintain a good drying condition, eradicating the organism.

Secondary and Supporting Measures

After doing the primary measures for treatment and control, you need to remove the infected wood. Removing the food source is a big step towards stopping the growth and further spread. This may mean removing a large amount of timber, depending on the specific case. However, it is important to note that in cases where rot occurs in a historical setting, a much less destructive approach should be taken. Drying techniques are used, which are monitored carefully at all times.

Once isolated, you may be able to reinstate the timbers using joinery wrap and joist hangers. These will deny the fungi a possible source of food and prevent timbers from becoming wet.

Furthermore, you may reinstate a pre-treated timber, pressure impregnated, or double vacuum as needed. Inert materials like steel, concrete, and more can also be used. You should consider the use of preservatives for steeping joist ends before reinstating.

Some other treatments include:

  • Fungicidal Paints and Rendering – Function by forming effective chemical barriers in accordance with the use of zinc oxychloride.
  • Physical Containment – Joinery lining around the adjacent timbers.

Masonry Sterilisation

This is the application of a special water-based fungicide to the masonry. Usually conducted through a surface spray that has a masonry biocide, sterilisation is often all you need. However, with a more severe case, a toxic box or cordon sanitaire may be used. This involves a drilling perimeter in the rotted area, and the masonry is injected under pressure. The work will be done with a spray for liberal surfaces or a brushing treatment with the sterilant.

Traditional irrigation is on the complete wall and is done using standard water-based fungicides. These are then injected under pressure. The process may introduce too many problems, and it is not necessary.

It will also introduce excess water to the masonry and cause more damage than dry or wet rot. Full saturation may not be attained, and it is also not necessary to use biocide chemical treatment for timber.

Fluid Injection

This involves injecting fungicides carried in organic solvents through special plastic valves driven into the wood. The fluid needs to be injected under pressure. This may give a good distribution of the fungicide but ensures that the wood is not too wet.

Unlike the conventional paste preservatives, fluid is being injected within the wood. It does not depend on surface penetration. However, it is very likely that timbers are wet or damp. When this treatment is applied, it may only result in a poor distribution of preservative. This is because there is a presence of resident moisture.

Conventional Fungicidal Pastes

Typically conventional pastes consist of a water and oil emulsion, with a high oil content carrying the fungicide. You tend to get deep penetration as long as you apply a sufficient amount, with the wood not being wet. However, there are many cases where the wood has been damp, leaving them at risk of decay. In these cases, the conventional paste preservatives will not be likely to penetrate to any great extent. This is due to the resident moisture in the wood.

Additionally, any applied paste to the surface will rely on diffusion to reach deep within the wood. Through these pastes, the necessary fungicide level for rot prevention is not likely to be attained. This is because the paste will stay nearer the surface.

Borate Rods

This preservative is supplied as rods that look like glass. Consisting of a special fusion of boron compounds, it is inserted into holes and drilled into the wood. The rods are soluble in water and need to become damp. This is so that the rod will slowly dissolve and distribute the preservative by diffusion toward the areas that are wet.

Once the rod has been embedded in the wood, the preservative is distributing accurately into those areas. This acts as a risk to the decay. They have ideal use in those areas which are risky to decay but still not affected. This includes window joinery, embedded joist ends, and more.

Other Treatments

It is important to control and treat the spread of both forms of rot. These treatments should be considered when preventing the survival and growth of dry and wet rot. Prevention is used alongside the practices and methods for its treatment and control. The emphasis is to attack the important requirements for survival and growth.

On places where chemical treatment is being used for supporting the primary treatment, the wood should be assessed. To lessen the decay risk to damp timbers, it is important entire parts of wood at risk are treated.

Boron can be effective when compared to conventional pastes. The boron-based materials are particularly designed to work in high-risk cases, including when the timbers are at risk to decay and are damp. The glycol and boron formulations have the additional benefit of distributing quicker than that of the solid borate rods. Therefore, they create greater possible protection and lessen the risk of rotting.

It is often used where the contents of moisture for dry and wet rot serve as the process for survival. The solid borate rods do not distribute as effectively under these marginal conditions.

We have a wide range of Melbourne timber repairs for your home renovations. Check out Hitch Property Constructions.

Undertaking Repairs to Timber

The treatment for dry and wet rot needs to be the responsibility of specialist treatment providers and companies. This includes all the attendant building works and any chemical treatment whenever important. A specialist company will fundamentally understand all of the involved elements. They can thoroughly assess the outbreak of wet and dry rot. These act together with the importance of the treatment measures and risks associated.

Aside from that, the use of a damp specialist will help you to remove the problem of spread responsibility. When different persons apply several treatments, there is no consistency in the work completed. A specialist can manage the full situation; third-party treatments may not work together cohesively.

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