WOODWORM

Woodworm is a collective term for any beetle which infests timber. The most common attack in the UK is Common Furniture beetle (Anobium punctatum). This usually infests the more nutrient sap wood edges of softwood timbers and sometimes the softer edges of some hardwood timbers. The second most common attack is Death watch Beetle (Xestobium rufovillosum). This generally infests hardwood timbers and can cause structural damage since it can affect the core of the timber.

The life cycle of woodworm varies between 3 – 10years depending on the species, e.g.  Common Furniture Beetle, 3yrs, Death watch 8-10 yrs. It is the Larvae which causes the damage, burrowing and tunnelling below the surface of the timber for almost the length of the life cycle. Towards the end of the life cycle the larvae forms a pupil chamber, just below the surface of the timber, where it pupates to become the beetle. Adult beetles only live for a few days. They mate lay eggs on the surface of timbers and die. The eggs hatch, producing the larvae and the life cycle continues.

Two additional wood boring beetles capable of extensive damage are Wood Boring Weevil and House Longhorn Beetle. The former are often found in wet timbers, usually softwood joist ends suffering from wet rot. House Longhorn is found in softwood timber in a very specific part of the country, usually Surrey or just over the boundaries. (It is often referred to as the Surrey Beetle) It can cause massive structural damage to timber, taking out the core and leaving a thin laminate surface. It is reportable to the BRE if discovered.

Identification

It is critical that the type of wood borer infestation is diagnosed correctly in order that the most suitable treatments are prescribed. In fact some species do require treatments and /or timber replacement and some do not.

What to look for ;- 

1. The timber itself will provide a clue – softwoods- likely to be common furniture beetle attack, hardwoods – death watch beetle attack
2. If the flight holes appear clean and there is evidence of timber dust (Frass) around the hole perimeter, this usually indicates there is activity, as the beetle emerge from the timber.
3. The flight holes vary in shape and size depending on the species. This will give an indication of the beetle species.
4. Beetle – You may find a beetle, usually on window boards during the flight season (March – October). We can look under a x10 looking glass to determine species.

Treatment

Most infestations are light to moderate and only require the application of low risk environmentally friendly preservatives. This must be applied by spraying every available surface of the timber to provide maximum effect. The beetle ingests the preservative as they emerge from within the timber and die. Likewise any eggs laid on the surface of treated timber will not hatch. A heavy infestation which may badly affect softwood timber floor boards will usually require replacement of those boards. However timber joists are usually not structurally affected so will be salvageable but will require preservative treatment.

FUNGAL DECAY

We will discuss Dry Rot and Wet Rot. There are two main differences between dry and wet rot;

• There is only one dry rot fungus – Serpula lacrymans, whereas there are numerous wet rot fungi  ( well over 50 )
• Dry rot can grow well beyond the original outbreak, often undetected, whereas wet rot is localised to where the wet problem is on the timber.

Dry Rot

For dry rot to start and grow there are 3 basic requirements

• Air
• Water
• Food source – Timber

The risk of a dry rot outbreak occurring increases if water comes into contact with timber. This is usually a result of poor maintenance of buildings  eg missing rainwater goods, leaking pipes, blocked gutters, faulty roof coverings, rising damp, penetrating damp etc.

There is a specific moisture gradient within which dry rot operates – between 23 – 30% moisture content. Timber with this level of moisture is at high risk of a dry rot infection, particularly since dry rot spores are omni- present, everywhere. If spores land on timber with this level of moisture, within a building, the spores are likely to germinate and the dry rot life cycle begins. The first stage of the life cycle is the Hyphael growth stage where germ tubes form and colonisation of the timber occurs. As the hyphae grow and expand they form a mass, referred to as Mycelium growth. (It is a white, cotton wool type of appearance). This is the second stage of the life cycle. It is the mycelium which causes the main damage to the timber taking the Lignum from the timber and causing the timber to crack, shrinks, twist and warp. When the growth exhausts the food supply of a section of timber it goes in to stress and at this stage Fruiting Bodies often occur. This also tends to happen as the fungus reaches light or daylight. This is the final stage of the life cycle. The fruiting body is called a Sporophore and is the reproductive part of the growth. The outer section (white) of the fruiting body is the immature section with the inner red ochre section being the mature spore bearing area. The sporophore blows off spore dust into the atmosphere and the life cycle continues when spores land on timber with the ideal conditions for germination.

What to look for;

1. Smell – A damp, mushroom smell in the building will indicate the likely presence of rot
2. Visual signs of dry rot fruiting bodies on door / window frames, skirtings, door linings, ceiling cornices etc
3. Spore dust (a fine brick red colour) on horizontal surfaces.
4. A very distinctive cuboidal cracking pattern on the timber.
5. Paintwork on timber which shows signs of blistering and cracking
6. Hyphael  and Mycelium growth on timber / masonry/ plaster

Treatment

1. Resolve the source of moisture – e.g. repair leaking pipes, replace faulty rainwater goods, repair faulty roof coverings, prevent rising damp etc
2. Strip out all dry rot affected timber and remove from site – we usually cut back 600mm beyond extent of the growth.
3. Reinstate with new pre-treated timber or introduce other methods of repair ie steelwork or resin repair system.
4. Hack off plaster to masonry in the affected area to trace extent of growth ( 600mm beyond extent of growth).
5. Treat masonry with biocide to sterilise the wall to kill off any growth<

Wet Rot

There are numerous wet rot species – the most common is Conniophora Puteana  (cellar fungus).

When the moisture content of timber exceeds 30 -32% it becomes too wet for dry rot to exist so the risk is that one of the wet rot species occurs.

You will usually find this happening on floor joist ends, rafter feet, wall plates, window frames, door frames etc.

What to look for;

1. Springy suspended timber floors – an indication that the joist ends are wet, soft and decayed. Very wet timber Longitudinal cracking pattern of the timber

Treatment

Since the problem is localised it is a lot less onerous to deal with than dry rot;

1. Resolve the moisture problem Cut out the rot affected section of timber and replace with new pre treated timber section.
2. Cut out the rot affected section of timber and replace with new pre treated timber section.

Ross Allan
Development Director

Timberwise (UK) Ltd
Kirkfields Business Centre, Kirk Lane, Yeadon, Leeds, LS19 7ET

Tel:  0113 250 4402
Mob: 07970 602007
eMail: rossallan@timberwise.co.uk
Visit: www.timberwise.co.uk

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