Dry Rot

What happens if dry rot is left untreated?

Dry rot is the common name given to the wood-destroying fungus, Serpula lacrymans. However, despite its common name, it will generally only attack damp timber. Initiation of attack is by either a minute dry rot spore or cross-contamination from already infected material, e.g., wood, masonry.

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.

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

What is Dry Rot?

Dry rot is a type of fungal timber decay known as Serpula lacrymans. It occurs when wood becomes too wet with a moisture content of over 20% and the wood-destroying fungus attacks the timber.

Dry rot is the most serious form of fungal decay. Dry rot fungus is very destructive as it spreads across masonry and destroys all timber in its path, including structural timbers, skirting boards, door frames, and flooring. It affects all types of properties, new and old. It can be detrimental to a property if left untreated as the fungus can weaken the structural integrity of a building and cause it to collapse.

The condition develops when excess moisture builds up on wood structures in the home; this moisture builds up to harmful types of fungi on the wood. This fungus attacks the wood, breaking it down and causing it to weaken and rot. The term “dry rot” comes from the fact that this affected wood appears dry and stiff.

If you have any structures in your home that are made of wood, you’re at risk for dry rot.

All that needs to happen is for the timber in your home to start being soaked with moisture content above its acceptable levels (anywhere from 20%-30%, for example). After that, the dry rot spores will start to appear and develop into the fungus; from there, the fungus can spread throughout your house to other wooden structures. This can be wood destroying.

Dry Rot


Dry rot occurs when airborne spores come into contact with damp timber that has a moisture content of over 20%. These spores then germinate and sprout grey root hyphae strands. The hyphae grow into mycelium which covers the timber in a thick cotton-wool like substance. The fungus eats the wood and sucks the moisture from it, leaving it weakened. The fungus then advances into a fruiting body known as sporophore, which sprouts more spores to continue the life cycle.

Dry rot spores develop into the wood-destroying fungus as a result of damp timber, and the fungus thrives in moist, damp, poorly ventilated conditions. There are many reasons why timber could be damp in the home, including penetrating damp, condensation, leaking pipes, faulty drainage, broken roof tiles, or a leaking washing machine, and thus creating the ideal environment for fungi growth.

The Effects Of Dry Rot

For an infection to be initiated there needs to be a spore (or some growth that is viable already present), oxygen, a suitable temperature, a susceptible food source and water, all of which are to be found in buildings. Oxygen and a suitable temperature are almost inevitably present in the internal environment. In a normal ‘dry’ environment water will be present in timber but at a level that is not conducive the germination or growth of dry rot, i.e., less than 20% (Moisture contents of between 8 – 16% may be found in a ‘normal’ dry domestic dwelling). Even when suitably damp, the natural resistance to decay of some timbers (and properly preserved timber) may prevent rot. Thus, dry rot is not inevitable if wood becomes and remains damp, but timbers will certainly be at risk.

Omnipresent in the environment, spores will therefore be present in all properties. However, a spore will only germinate and infect when there is both dampness and a food source (i.e., suitably susceptible wood or some other suitable cellulose-based material). For spore germination to be successful, it appears that free moisture must be present within the wood above the fibre saturation point, i.e., moisture contents over 30%. Thus, for the decay to become initiated, the wood must usually be physically wet. This usually occurs as the result of severe water ingress in the form of rainwater leaks, plumbing defects, floods, long term severe condensation, etc. Further prerequisites for initiation of decay are still and humid conditions. The initiation of dry rot appears less likely as the result of ‘capillary bound’ moisture such as that arising from rising dampness although once initiated such dampness will support growth.

It is recorded in laboratory culture experiments that spores can germinate between 7-10 days following suitable wetting; this may take longer if the spores are older. However, it appears that in practice under field conditions, it often takes some considerable time before rot becomes noticeable.

Once initiated a minimum timber moisture content of around 20% is required for the infection to survive although the optimum moisture content for active growth is reported around 35 – 50%; however, the rate of decay at 20% and just above is likely to be very minimal. Timbers within a building are usually kept well below 20% moisture content and are therefore not vulnerable to fungal decay. However, should timbers become damp, then, given the requirements described above, dry rot has the potential to establish and develop.

What are the Dangers of Dry Rot?

Dry rot treatment and prevention Dry rot can grow through damp masonry, brickwork and behind plaster, causing widespread structural damage. Dry rot’s ability to spread so rapidly can make treatment more complicated than with other types of rot – but if left untreated, the fungus can spread through an entire property causing the collapse due to the structural timber and masonry damages.

Anyway, the dry rot itself is not a treat to human health. However, its presence in a home may indicate high levels of dampness and condensation, which can cause respiratory problems and lead to other problems which can affect the health of you and your property, such as woodworm, wet rot, and mould growth. Just in case you might notice a dry rot outbreak at your home, it is important to ask for professional help, employing an experienced maintenance company like Peter Cox, for example.

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

Prevention and Treatment

Detect the Source of Damp

As dry rot is caused by damp and moisture entering the home, it is important to thoroughly inspect the interior and exterior of your home to find any source of damp. With professional assistance from Peter Cox’s dry rot specialists, you will be easily able to identify such sources like leaking gutters, rising damp, water leaks and poor ventilation that can also contribute to the problem.

Damp Proofing Treatment

You can also make your home more resistant to damp penetration with the help of Peter Cox’s damp proofing specialists. Peter Cox’s DryWall Thermotek masonry protection cream is applied to walls affected by damp as part of the damp proofing process. It will help to prevent damp entering the home, thus not only helping prevent dry rot problems but also helping to retain heat and thus conserving energy levels. Because of its eco-friendly, energy-saving properties (a single-coat application can yield an energy saving of 29%), the DryWallThermotek solution qualifies for a 5% VAT rate.

Dry Rot Elimination

Remove all infected timber and replace with pre-treated timber. Any remaining timbers at risk of being affected by the dry rot should be treated with an effective fungicide. Where the dry rot has passed through the masonry, it should be treated with a water-based biocide.

Selling Your House With Dry Rot

If you’re getting ready to sell a house that’s affected with dry rot, know that this problem can severely affect the eventual price. Potential buyers won’t be too enthused to dish out a great deal of money for a home that has this type of affliction, and the presence of dry rot can also prove to have a negative effect on the potential buyer’s ability to secure a mortgage on the property – which pushes prices down further.

It’s probably the best bet to sort those dry rot repairs on your home before you put it out on the market.

Is there a fast way to sell your house with dry rot? 

If you don’t want to go to the time, effort and expense of making the repairs – and if you don’t want to wait for a buyer to come along who’s happy to purchase despite the dry rot, then our service may be a great option for you.

We aren’t put off by property issues like these. We buy any house – meaning we can buy your home even if it has dry rot. In a nutshell, we can make you an offer quickly and then buy your home from you in as little as 2-3 weeks (dry-rot and all).

Identifying The Dry Rot Outbreak

The first sign of the existence of dry rot is often the sudden appearance of a fruiting body (sporophore), or the shrinking/distortion of timbers. This latter feature can be quite dramatic and sudden, the change from dimensional stability to the instability of the wood visually taking place relatively suddenly; this explains the sudden appearance of dry rot frequently reported. It should be noted, however, that fruiting bodies are not always formed.

Unlike many other wood-destroying fungi dry rot can readily grow over and through porous masonry provided that there is a nutritional source (wood) from which it can spread; this ability allows the spread of the fungus from one area to another. This generally only occurs to any significant level where the masonry is damp either via severe sources of water ingress or rising damp, etc. Dry rot will not spread over or through masonry that is ‘dry’, i.e., that does not contain free (capillary) moisture.

A further feature of the fungus is the formation of ‘strands’, thick-walled structures which develop in the fungal growth. These are resistant to desiccation and carry nutrients from the food source to the growing tips of the fungus when the organism is growing through or over nutritionally inert materials, e.g., masonry, soil. They support the spread of growth. However, without a source of food growth is terminated.

When the decay is advanced the shrinkage causes the wood to split in a cuboidal manner (this is typical of a number of wood-destroying fungi), and it is therefore not always easy to distinguish between dry rot and other fungi (wet rot — brown rots) in the absence of fungal growth. Click the following link for more information on what is wet rot.

Dry rot on a cellar wall should infected timbers dry out, or the food source is removed the growth will cease but, depending on conditions, it can take considerably longer for the fungus to die. For example, in timbers that have dried down to below 20% moisture content, the fungus can remain dormant for up to about a year at ambient temperatures before dying. However, this period may be prolonged at lower temperatures.

If infected wood is removed, then the growth is very limited and quickly terminated. Still, the growth can remain viable in damp masonry at low temperature (e.g., 7oC) for up to 9 years, and up to 1 year at ambient temperatures. Should new, untreated or inadequately treated wood be put back into direct contact with damp infected masonry, even though the original decayed wood had been removed, then fungal growth may start and spread into the new wood so initiating further decay.

It is not practical to precisely define the rate of growth of dry rot due to variation in the nutritional quality of the food source, dampness, the environment, etc., but in buildings that have been studied growth rates of between 0.04m and 0.8m per year have been recorded (Building Research Establishment Digest 299); C.R.Coggins (1980) gives a slightly higher general figure of about 1 metre per year. Savory (1971) reports figures in an experimental house of between around 1m – 1.45m. The author has reliable figures giving a growth rate of around 1.5 metres per year. In the laboratory, however, growth rates of about 2.9m to 4m per year have been recorded. A further difficulty arises in establishing growth rates in that it is not always possible to tell if the decay is the result of a single outbreak or the merging of several individual outbreaks. However, the use of published rates of growth may be useful to help identify if an outbreak could have possibly grown a specific distance in a given time period.

In most cases, the optimum conditions for growth and decay of timber have been derived under carefully controlled laboratory conditions. In practice, however, it is highly unlikely that such optimum conditions would be present, or at least for any length of time. Thus, for growth and decay, the use of ‘optimum data’ within a field situation to evaluate the growth or decay activity by dry rot is unlikely to prove valid. Furthermore, dry rot can remain ‘dormant’ under unsuitable conditions for a while, only to become ‘active’ when such conditions become more favourable.

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

How the Dry Rot Treatment is carried out

The procedures for the control and eradication of a dry rot infection are given in Building Research Establishment Digest 299 and British Wood Preserving Association Code of Practice for Remedial Treatment; where remedial works are envisaged then the work should be undertaken in strict accordance with the principals and instructions given within the above publications. The control of all rots is a matter of good building practice, but it also requires a thorough understanding of the nature of this particular organism.

At Timberwise, we first undertake the fundamental procedure to control and eliminate the rot, and that is to eliminate the source of water, to remove infected timber if the rot is active, and propagate and maintain drying conditions. Without either food or water, the fungus cannot grow and will eventually die. However, where decay is limited, and wood/masonry is now dry, or will rapidly dry once the source of water has been eliminated, then we may leave such timbers in situ if deemed appropriate and structurally sound thereby minimising the number of repairs necessary and maintaining the structure of the original building; this is particularly important in the case of historic and listed properties.

We regard ancillary chemical measures as secondary to the above in the control of dry rot. It should also be considered that chemical treatment of timber and masonry must be capable of resisting the rot for at least the period of drying down; this could take several years in some cases.

Dry rot is one of the most damaging conditions a property can suffer. If not controlled immediately, the condition can cause enormous damage in a short period of time. Precaution and prevention, but also the remedial procedure in case of dry rot it is very important. Asking for experts will help you to have a clean and safe home.

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