How do you keep the timber from dry rotting?

As the proud owner of an older property, the words “timber decay” are probably the last things you want to hear. Discovering that your woodwork is being eaten away by rot or wood beetles is never good news, and many homeowners, in their panic, resort to drastic measures to restore their home’s health.

The truth is, in many instances, the heavy-duty chemical treatments, insecticides and preservatives aren’t the best solutions. They may be one option, but before you shell out fistfuls of cash for a quick fix, it may be worth paying a small fee to have a specialist timber survey to diagnose the problems in your building accurately, and a prescribe a more reasonable solution. In the long-term, these will often work out cheaper and save your home from a lot of unnecessary work.

‘Timber decay’ are two words you do not want to hear a surveyor say when they are looking over your property. It brings to mind thoughts of extensive repairs and expensive treatments. There must be a better way; a way to prevent the timber from reaching the point of repair or replace and a way to prevent panicked calls regarding treating dry rot or woodworm, right?

Thankfully, there are preventative methods that home and business premises owners can take to ensure their property is protected against invasive insects and structure damaging rot – it’s all about moisture.

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, also known as brown rot, is wood decay caused by fungi, which can ruin any wooden structures inside or outside your home. When dry rot occurs, the fungi break down cellulose and hemicellulose, the components which give the wood strength and resilience. The wood is left weakened and brittle, often with a blocky appearance. Dry rot will only affect timber that is damp, typically with moisture content in excess of 20 per cent. For this reason, removing the source of moisture should form the core of any dry rot eradication strategy. Read below for more tips to prevent dry rot.


How Does Dry Rot Spread?

The dry rot fungus produces spores, which are spread through the air. They will germinate if they land on wood that’s been exposed to a high level of moisture from one of these three sources:

  • The wood was not properly kiln-dried before being used in construction, to lower its moisture content below 20 per cent.
  • The location of the wood is an area of the home with excessive humidity.
  • There has been direct contact with large quantities of water, for example, flooding from a burst pipe.

To grow, the spores need not only moisture, but also a food source (wood), oxygen, and preferably warm temperatures (between 71 and 77 degrees Fahrenheit is ideal).

If not stopped, dry rot will weaken the wood to the point that it could disintegrate.

How to Identify Dry Rot

  • Inspect the wood. Initially, the fungus looks like cotton wool and may have surface water droplets if the surroundings are very humid.
  • Check for hollow or shrunken wood.
  • Notice darkening and cracks in the wood structure
  • Look for affected wood that has flat skin-like growth which may resemble the outside of a mushroom with shades of silver and grey. Often patterned with patches of light purple or yellow, it peels easily. 

Causes of Timber Decay

Timber decay can be caused over time as wood increases in age; however, most causes of timber decay occur due to an increase in moisture or damp conditions. Damp and timber decay are intrinsically linked because moisture helps the spread of fungal infections like dry rot or wet rot and encourages nasty mould growth, both of which contribute to timber damage.

In particular, sub-floor timbers need a dry, well-ventilated environment that is generally provided at ground floor level with adequate sub-floor vents (airbricks). These need to be unobscured and unblocked to reduce the prevalence of damp and timber decay.

Leaks in roofs or penetrating damp through walls can cause timber decay over time, over-saturating wood fibres with water which offers an attractive place for wood-boring insects to lay their eggs. Note that whilst ensuring the safety of structures, keep an eye out for bowing or bending timer; not only is this structurally unsafe, but the physically damaged wood can also be an additional attractor for wood-boring insects, so it’s important to stay aware.

Dry rot or wet rot?Dry Rot Exposure survey

Dry rot is a form of timber decay caused by fungal growth as air-borne spores germinate when they come into contact with a food source such as timber, which has become damp. It is one of the most damaging conditions you can encounter in a property. It severely impacts structural integrity as it aggressively spreads from one area of timber to the next.

Contrary to its name, dry rot needs moisture to flourish and grow, and it can be hard to spot because it often grows where people do not look, such as under floorboards, behind panelling, in lofts or behind plaster away from light. Affected timber will be covered in a white growth of fungal strands (mycelium) on its reverse side and have large cracks across the wood grain called ‘cuboidal cracking’. Orange/red spore dust may be present too when the fungus produces a fruiting body (mushroom) on the affected timbers too. Dry rot can spread many metres away from the source of moisture.

Wet rot is not as harmful as dry rot, but it can still cause substantial damage to properties. It attacks timber in much wetter conditions, making it a common cause of structural defects, particularly when allowed to go untreated. When excess moisture is absorbed by timber, it can allow fungal spores to germinate and produce enzymes which break down the cellulose in timber leading to the timber losing its strength. Wet rot can be identified by a damp, musty smell, small cracking across the grain and softening of timber and noticeable discolouration of the wood. Wet rot will only occur where the moisture source is located.

Tackling both dry rot and wet rot

The primary action is to locate and cure the cause of the moisture ingress. Dry rot and wet rot survey

Dry Rot 

Exposure work’ is required to trace the full extent of the outbreak because Dry rot can spread behind wall plaster and travel along with other construction materials such as steel. To treat the fungus growing on the walls and timbers (known as mycelium), affected wall plaster is removed. Holes are drilled into the wall around the perimeter of the affected masonry, and a masonry biocide is pumped into them. A surface application is then applied to all the exposed masonry. The treatment has the effect of ‘sterilising’ the masonry to prevent further dry rot mycelium growth.

Wet rot

The decayed timber needs to be cut back to what is called ‘sound’ timber (wood that remains in a safe condition and structurally intact), and any decayed sections repaired. Finally, the timbers should be treated with a fungicidal spray that is quick to dry, low odour, non-flammable, and HSE approved.

Treatment for Dry Rot

Epoxy treatments. Fill in channels within the damaged wooden structure with an epoxy treatment. This will not only kill the rot, but also strengthen the wood’s structure.

Commercial antifreeze. Treat dry rot with antifreeze to kill the fungus and prevent further growth of dry rot.

Copper compounds. If you plan to splice in new wood to repair dry rot damage, first remove the rotten section. Then saturate the surface of the existing wood with a copper compound, before adding the new wood.

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

Dry Rot Prevention

Preventing dry rot is pretty simple. Do your best to limit exposure of wood in your home to moisture with these steps:

  • Siding: Have wood siding sealed properly and installed by a skilled siding installer.
  • Painting: Make sure any wood for outdoor use is primed on all six sides before painting.
  • Roofing: Have your roof checked once a year to identify and prevent and potential water damage, mould, or dry rot. Install gutters to direct rainwater away from your home’s walls and foundation.
  • Plumbing: Plumbing leaks commonly cause dry rot. Check underneath vanities and cabinets and around toilets for leaks. If you find any, have them repaired ASAP.
  • Ventilation: Make sure your bathrooms, attic, and kitchen have proper ventilation installed to remove excess moisture from the air.
  • Deck: Have your deck properly sealed. If you hire a carpenter to install a new deck, have it built at a slight slope so water will shed easily.
  • Landscaping: Position lawn sprinklers so that they do not spray onto your home’s exterior trim.

Dry Rot Control and Treatment

Dry rot will only affect timber that is damp, typically affecting timber with moisture content in excess of 20%. For this reason, removing the source of moisture should form the core of any dry rot eradication strategy.

Timber can become damp for a number of reasons. Among the most common causes are leaking washing machines, shower trays, baths, condensation etc.… The dampness can also come from outside the building, for example, leaking roofs, rising dampness, or dampness penetrating through walls. Whatever, the source of the dampness, if it is rectified and the timber allowed to dry out properly, the dry rot will eventually be controlled.

However, it is not always possible or practical to be sure that the timbers will remain dry in the long term. Therefore, secondary measures must be taken to defend against re-infection. Any affected timbers should be removed and replaced 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 isolated using physical containment and masonry sterilisation.

Any external-facing timber should be appropriately treated with a waterproof paint or damp-proof membranes to prevent the ingress of water. Pay attention to seams or areas where two materials meet and water could collect. To prevent water on external walls, ensure gutters are cleared of any leaf litter or debris and check that connections are tight and rubber seals are in good repair where lengths of materials are joined.

Replace inefficient or broken extractor fans in bathrooms and kitchens to ensure warm, moist air is sufficiently removed and isn’t allowed to pool on wooden surfaces (like window frames). Upgrading to more modern humidistat fans is common practice and may prevent the need to use dehumidifiers in problem properties.

If your property is prone to condensation issues, consider having further ventilation installed via more modern, more efficient sub-floor vents (air bricks). Make sure that doors stay closed during a bath or shower to prevent moist air from moving throughout the property.

Moisture levels of only 20% and above create the perfect environment that leads to timber decay, so it’s important to consider how moisture can get around within your property.

Don’t get stuck with expensive home repairs or renovations; by taking preventative measures, you should be able to protect your home from the most common types of timber decay.

How serious is dry rot?

If it’s spotted and treated quickly, localised dry rot can be tackled without too much trouble. However, its ability to spread through buildings can quickly escalate the severity of a breakout, and an accurate cost for remedial work will often require the full extent of the damage to be inspected beforehand. This may mean that significant parts of the property need to be stripped out before treatment.

Rectifying the source of the damp should prevent the fungus from germinating, ultimately drying it out and killing it off. Improve the ventilation in rooms affected by dry rot (a dehumidifier can help in extreme cases), and make sure to fix the root of the moisture properly. If the rot has already extensively spread, badly damaged timbers may have to be removed, and remaining woodwork may require protective treatment.

Replacing timbers

Decayed or structurally weakened timbers must be removed and replaced. The most vulnerable sections of timber are usually those that bear into the wall structure because it is at those points where the timbers typically tend to absorb moisture.

This means it’s often only the ends of the timber which need to be replaced. The traditional method to achieve this is to splice in new sections using steel plates or bolts, and timber connectors fixed through the timber. While this is effective, the steel plates can be quite unsightly if the timbers remain exposed. Also, remember to check ventilation, especially under timber floors. Blocked airbricks contribute to moisture condensing on timbers causing them to rot, not just at their ends but mid-span too.

For large section beams, an alternative is to use epoxy resins for carrying out structural repairs to these large sectioned damaged timbers. This is an aesthetic and economical method since repairs can often be carried out relatively quickly, without having to cut out large areas of the existing timber and with minimal disturbance to the surrounding structure and the presence of unsightly steel plates.

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

What is the Best Dry Rot Treatment and Repair Method?

There are a number of ways you can treat and repair dry rot-affected timber.

Remember that if there’s any indication that there is a damp problem in your house, you will need to find the cause of this and treat it before treating and repairing dry rot damage.

This is because any new damp will dilute the treatment chemicals that you have applied – the dilution will happen. After all, all of these chemicals are water-soluble so that they can enter damp masonry and timber.

If you do have Dry Rot present in your house, you should use the Fugenex sensor sticks mentioned above to understand how far the rot has spread in your house.

If you’re sure that the rot is only present in exposed timber, i.e. exposed joists, then you will need to treat the timber itself, along with any masonry that the joists are in contact with.

If the rot has severely damaged your timber’s structure, you will need to replace it (or get it replaced by a building professional). More information on which timber to use for different applications is available on the Timber Trade Federation website.

Once this is done it is still a good idea to treat the surrounding masonry and timber as fungal strands may have already entered that area too – they can be invisible to the naked eye if they are small.

If you have visible signs of dry rot on your wall as in the pictures above, or your sensor sticks indicate the presence of dry rot within the wall, you will need to strip the plaster off the wall and treat the bare wall underneath before replastering.

Timber plays an important structural and aesthetic role in most buildings, so some care and attention are important to prevent damage and maintain a property’s value. A professional survey is the first step towards identifying the extent of any damage caused by wood rot or woodworm.

With the proper attention, timber decay doesn’t have to be a life sentence for your home or your bank balance. The golden rule is to keep your home well-ventilated throughout the winter months and lookout for signs of trouble.

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