Guardian Preservation Services LLP

Fungal decay always arises because the wood has become wet; usually timbers will be in excess of 20 per cent moisture content. Finding the source of dampness, eliminating the ingress of moisture and promoting drying is always necessary. Condensation can occur under suspended floors which greatly increases the chances of fungal decay in floor timbers.

Fungal Decay to floor within Stroud Railway Station

Outbreaks of dry rot and wet rot start in similar ways. The mature fruiting bodies of wood-destroying fungi that develop during an attack produce millions of microscopic spores and these are widely dispersed by air currents. If they fall on untreated damp wood they will germinate by pushing out a hollow tube called a hypha which grows and branches to form a mass of hyphal threads called mycelium. Mycelium develops inside the timber and breaks down the wood for food. The timber may darken in colour and develop a characteristic cracked appearance. Some wet rots may result in bleaching of the wood; these are more common in doors and window frames. Eventually, the wood loses its strength and in some situations may become dangerously unsafe.

The main differences between dry rot and wet rot are the degree of development of mycelium on the wood surface and the ability of the fungus to spread into other timbers via adjacent masonry. It is important that the two types of decay are distinguished since they require different treatment.

Dry Rot attack to timber sash window

Dry Rot Serpula lacrymans develops extensively on the surface of infected timber and in still, humid conditions produces a mass of cotton wool-like growth. Water droplets are often produced on the surface of the mycelium.  Mycelium spreads over the timber surface by the continued growth and branching of the delicate hyphal threads growing with time. Specialised strands develop within the mycelium and these supply water and nutrients to the growing Fruiting Bodies. The strands assume their real significance when the fungus spreads from infected timber onto the surface of adjacent stone or brick walls. The tiny hyphal threads penetrate the mortar joints and plaster layers and large areas of damp wall can then become infected.

Wet rot (mycelium) within a domestic property

Wet Rot is caused principally by Coniophora puteana. Poria vaillantii is another important wet rot fungus and a number of less common fungi also occur. While each fungus has its own unique features, the general appearance of wet rot is similar – as is the treatment. Wet rot is typically confined to the area of dampness because the mycelium does not spread into walls.

Identification and Treatment as we have shown it is very important that the type and cause of the fungal decay are correctly identified before any corrective action can be considered. It is for these reasons that it is important that one of our qualified surveyors carries out a detailed diagnostic inspection followed by the submission of a report that details both the cause of the decay and the proposed remedial action.

Insect Infestation/Woodworm

Common Furniture Beetle Anobium Punctatum is the most common wood destroying beetle found in British buildings today and commonly occurs outdoors infesting dead tree trunks, branches and other forms of exposed timber but, the main cause for concern is its ability to infest indoor timbers in a variety of situations.

Adult beetles emerge from timber in the spring and summer. Very soon after mating the female beetle lays approximately 30 eggs, often into cracks and crevices in the timber she has just vacated. Usually within a month the eggs hatch and the young grubs begin burrowing into the timber. Here they remain for between two and four years slowly eating and burrowing beneath the surface of the wood. Eventually the mature lava excavates a pupation chamber just beneath the surface of the wood. Following the pupation process the adult beetle cuts a hole in the surface of the timber and emerges to start the process once more. It is the appearance of new emergence holes and the dust (frass) that falls from them that often indicates the presence of an active infestation of woodworm.

The woodworm beetle is significant because given the right conditions it can infest a wide variety of timber products including structural building timbers, furniture and wooden ornaments. If left unchecked infestations can lead to severe structural weakening and eventually total collapse.

Treatment - before making a decision on the type of treatment needed one of our surveyors will consider the condition of the infested timber, the type of woodworm attack and the risks and hazards associated with any work that is to be recommended.

In preparation for the application of preservatives the timbers should be cleaned down to remove any excessive dust and debris. Treatments using water based insecticides are very common and are generally successful and cost effective. Chemicals are often applied by low pressure spraying but some insecticides can be applied by “fogging” or are brushed on.

Other wood destroying insects

Death Watch Beetle Xestobium rufovillosum – this insect is often associated with historic buildings and usually affects the sapwood of hardwoods that are damp or have been affected by fungal decay.

House Longhorn Beetle Hylotrupes baljulus – this relatively large insect affects sapwood and is predominantly associated with roofing timbers. They are limited in range to a small part of south east England. Infestations if left unchecked can lead to severe structural weakening in a relatively short period of time.

When infestations by the Death Watch Beetle and House Longhorn Beetle are discovered, treatments will always be dictated by site conditions and formulated by one of our experienced specialists.

Click here for pictures of different types of timber attacks to help you identify potential problems, or contact us today for honest, independent advice.