Defects

Common and uncommon defects related to excessive moisture in domestic buildings
Damp Consultants - Timber Surveyor Lancashire

Rising Damp

Rising Damp is simply water from the ground that enters a structure by capillary action. Water that enters or affects a building through any other route can move about in various ways but is not rising damp. Only rising damp can be cured by the installation of a chemical damp proof course.

Rising damp is a commonly encountered problem in some types of building, however it is often misdiagnosed. It is important that the investigations into dampness are undertaken by our trained and competent damp consultants or surveyors who can recognise and understand the problem.

Decayed skirting boards, crumbling or salt stained plaster, discolouration and staining, decayed timber floors, peeling paint and wallpaper are all common when walls are affected by rising damp. These defects are not always evident but when they are, a specialist inspection is always recommended. Most types of masonry used in the walls of buildings will allow some water movement by capillary action; however, this is usually controlled by a physical barrier or damp proof course. If this physical barrier is absent, has broken down or is damaged then it is often possible to install a remedial damp proof course (DPC) to control water rising from the ground.

Water rising from the ground often introduces contaminating salts into the walls and plaster coats. This contamination will often result in a need for the plaster to be removed and replaced using specially formulated salt resistant plasters.
Damp Consultants - Timber Surveyor
Damp Consultants - Timber Surveyor Lancashire

Condensation

The most common form of unwanted dampness in buildings is water from the air that forms as condensation.

The air in buildings can have a high level of relative humidity due to the activity of the occupants (e.g. cooking, drying clothes, breathing etc.). When this water laden air comes into contact with cold surfaces such as windows and cold walls it can condense, causing water to be deposited. The point at which the water held in the air changes from vapour to liquid is known as the dew point.

Condensation is often associated with poor heating and ventilation in buildings. It is more apparent in winter, as the external air temperature is low and external walls and windows are cold.

Fungal Decay in Building Timbers

Dry rot and wet rot can affect buildings of all ages and if decay is discovered it should be identified and remedial action taken without delay.

Fungal decay occurs in timber which becomes wet for some time and is the result of the attack by one of a number of wood-destroying fungi. The most well-known are Serpula lacrymans – the true dry rot fungus -, Coniophora puteana the Cellar fungus and Poria vaillantii the Pore or Mine fungus. Many other fungi also occur and some have recently been particularly linked with decay in door and window frames.

Dry rot is only caused by Serpula lacrymans and is the most serious form of fungal decay in a building. It can spread onto and destroy much of the timber. Wet rot occurs more frequently, but is less serious; decay is typically confined to the area where timber has become and remains wet.

Damp Consultants Blackburn
Damp Consultants Blackburn

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 and eliminating the ingress of moisture and promoting drying is always necessary.

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 be distinguished since they require different treatment.

Damp Consultants - Timber Surveyor Lancashire

Insect Infestation

Common Furniture Beetle/ Woodworm / Anobium Punctatum

The most common wood destroying beetle found in British buildings today is the Common Furniture Beetle Anobium punctatum. This insect 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.

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