There are many pitfalls in homeownership, especially when it comes to keeping the structure in good condition. Protecting your home from the elements is an ongoing battle that can consume a great deal of your time and money, so it pays to be aware of potential problems to help minimise the risks or at least identify them early in order to find a solution as quickly and efficiently as possible.
Because damp problems have a variety of causes and symptoms, there's a lot of confusion surrounding the subject. This often leads to misdiagnosis, which then means that the wrong treatment is applied. As well as the fact that you will have wasted money on a pointless procedure, the original problem will still remain.
Dry rot is just one problem that can cause serious structural damage to your home and is frequently mistaken for other types of damp-related issue.
The following guide is to help you to identify the problem and apply the right treatment.
To start with, the name is misleading: dry rot isn't exactly dry! Timbers have to have at least 20% moisture (usually much more, between 30-50%) for dry rot fungus to survive and thrive. More recently the name brown rot has been used, though most people don't use this.
The original name comes from a misunderstanding relating to the timber of ships and boats that had been taken out of water for repair. As the wet timber began to dry out it lost the structural integrity provided by constantly being in the water and it began to crumble, leading to the belief that it had rotted after becoming dry, when in fact it had probably been rotten for some considerable time.
Although dry rot needs a source of moisture, it can spread far beyond this, right through the structural timbers of a building, which is where it differs from wet rot (which requires complete saturation of the wood to survive). The process of decay creates small amounts of moisture but the fungi will spread quickly in pre-existing damp conditions.
Though not as common as wet rot, the effects are more severe and damaging.
The problem is caused by a type of wood-destroying fungus called Serpula lacrymans. The microscopic spores appear as a fine, orange dust, and when they find the right amount of moisture they begin to sprout white strands called hyphae which mass together to form mycelium which grows through the wood, finding its way along the grain. The next stage is when the 'fruiting bodies' of the fungi grow out of the rotten wood, which is usually distinguished by its deep rust colour with white fringes and sometimes forms a cluster of mushrooms.
Dry rot fungus feeds on the cellulose within the timber that gives it structure and strength. The fungus breaks down the cellulose as it moves through the wood, leaving it dry and brittle. In severe cases, you will be able to dig your fingers into the spongy timber and it will crumble to dust. This makes it extremely hazardous when structural timbers are affected.
This fungal decay can attack any timber (though some tree species are more resistant) given the right conditions of elevated moisture content, such is in houses suffering from excessive condensation that has soaked through porous materials. Floorboards, joists, panels – any wood that is exposed to damp and humid conditions can be a target for this species of fungi.
A combination of poor ventilation and excess humidity can create exactly the right conditions for the fungal spores to grow. Any place that has a damp problem, whether it's rising damp, penetrating damp, excess condensation, leaking pipes or leaking roofs, they all provide sufficient moisture for dry rot to thrive and cause damage to timbers.
The spores of brown rot fungus are able to pass through porous surfaces of brickwork, masonry, plaster or mortar, which makes it difficult to stop once it finds the right environmental conditions.
You may notice the orange-brown spore dust on timbers and a musty smell. You might also spot grey or white hyphae strands on the infected wood, deep cracks along the grain, or patches of decayed wood that is brittle or spongy to the touch. There could also be mushroom-like fungal growths on the infected timbers.
To make matters worse, woodworm prefers timber with a higher moisture content, which could add to your problems.
Before any dry rot treatment can take place, the cause of the excess moisture needs to be discovered and addressed, as there is little point in treating the symptoms if the cause is still present! Any repairs need to be made before dry rot treatment takes place.
Secondly, you need to know whether this is dry rot or wet rot. As mentioned above, dry rot extends much further into the home as it requires a lower moisture content for the fungal growth to survive.
There are various types of treatment for dry rot, some of which you can possibly tackle by yourself. Cleaning the infected area is essential, removing the mycelium growth, fruiting bodies and spores using a fungicide.
The problem is that it can be hard to locate all the decayed timbers as they are hidden beneath walls in the structure of the building. A professional dry rot expert will be able to advise you as to which bits of timber can be saved and which should be replaced (usually beams, floorboards and joists).
There is a chance that existing plasterwork and even masonry or brickwork may have to be stripped back to reach the affected timbers, but this would only happen in extreme cases.
Pre-treated timber will be used to replace the parts that have decayed beyond repair, and fungicide and wood preservatives will be applied to sound timber and masonry to discourage any more growth.
Though some people do apply treatment themselves, it can be a big task and is probably best left to the experts. It is best caught in the early stages where it can be stopped before it spreads and causes structural damage. If you suspect you have dry rot in your home then you would be advised to seek advice without delay to save you from further expense and inconvenience in the future.