Remedial timber treatment

The remedial measures used to eradicate infestation in building timbers can be divided into two distinct activities. On the one hand, general building work deals with all repairs which are required to ensure that the fabric of the building becomes weathertight and waterproof. On the other hand, specialist timber treatment can remove all severely decayed wood, preserve timber which is to remain in situ, ensure that all replacement timber is preserved and prevent the recurrence of fungal decay and insect attack.

As with so many building operations today, timber treatment has become the province of specialist companies such as Apollo Damp & Timber. Specialist timber treatment almost always involves applying wood preservatives in situ. Brushing or spraying on a wood preservative will not normally achieve total penetration through the timber – better penetration will invariably be achieved on rough-sawn softwood timber with a large amount of sapwood and a low moisture content, but there are many associated factors which can reduce the penetration of wood preservatives. If the timber is damp, which it almost certainly will be when decay is present, wood preservatives which are applied with a spray will be less penetrative.

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This page features all common causes of structural dampness and timber decay... Defects found in the Home Structural Dampness Timber Decay Insects Lifecycle of an Insect Fungi Lifecycle of a Fungus

Key to House: Defects in Pitched Roof Covering Defects in Flat Roof - Covering, Fall, Design & Construction Defects in Chimney Flashing Defects in Chimney Flaunching Faulty Down Pipes & Gutters Defects in Valley Gutters Penetrating Dampness through Walls - Bridged Cavities Penetrating Dampness through Walls - Around Windows Penetrating Dampness through Walls - Cracked Rendering Plumbing Leaks in Bathroom Plumbing Leaks in Kitchen Condensation in Roofs Rising Damp - Failed or Bridged D.P.C Blocked Air Vents

If you have timber which requires remedial treatment, please e-mail us.

Structural Dampness Structural dampness can cause a variety of problems in buildings, as the following pictures reveal.

Pictures of Structural Dampness Flow of Rising Damp in Walls Position of Damp Proof Course Condensation Rising Damp Hygroscopic Salts Mould Growth Mode of action of a chemical D.P.C Application of a chemical D.P.C

Flow of Rising Dampness in walls.

Position of Damp Proof Course (D.P.C) in a typical wall.

Mode of action of a Chemical Damp Proof Course

Application of a Chemical Damp Proof Course

Timber decay Timber can fall foul of insects such as the common furniture beetle and the deathwatch beetle, as well as from fungi such as dry rot and wet rot.

Common furniture beetle "Woodworm" is the most common cause of insect attack of softwoods in buildings, and is often to be found in structural timbers, roofs, floors and joists. The female adult beetle lays her eggs onto the susceptible timbers, and they hatch into larva which in turn burrow into the timber, gradually weakening it. This process can take at least three years, with the larvae growing to a length of 2.5mm. After the pupal stage, the adult beetles emerge from the timber through a 2mm flight (exit) hole.

Deathwatch beetle The deathwatch beetle causes deterioration in structural hardwoods such as oak, elm and chestnut, which have already been partly decayed by wet rot. This pest is more of a threat to large timbers in older buildings and occurs mainly in the Southern and Central areas of England and Wales. It has yet to be recorded in Scotland.

Powder post beetle This beetle attacks the sapwood of larger-pored hardwoods, and is more commonly found in flooring, plywood and furniture.

Wood-boring weevils After the Furniture Beetle, wood-boring weevils are probably the most common timber pest. They are commonly found attacking partly decayed wood, with both adults larvae causing the wood to break down by burrowing, principally along the grain, and leaving thin paper walls of wood separating the borings. of more commonly found in flooring, plywood and furniture. Flight holes are ragged in outline and less than 2.5mm in diameter.

House longhorn beetle This beetle – a notifiable pest – causes severe damage to the sapwood of softwood roofing timber in parts of Surrey, Hampshire and Berkshire. The larvae burrow into the timber and, when fully grown after anything from 3 to 11 years, can measure over 25mm in length. The adult emerges through a flight hole 6 - 8mm in diameter.

Lifecycle of an Insect

Dry rot This fungus mostly causes decay in areas with restricted ventilation, high humidity and a moisture content of between 30-40%. However, dry rot can remain active in timber with as little as 20% moisture and can also attack dry timber. It can grow through the fabric of a building if conditions are suitable, by penetrating brickwork and masonry and behind plaster, decaying any timber in its path. Decaying timber develops "cuboidal" cracking and is usually overgrown by masses of grey-white mycelium. Plate-like fruiting bodies produce millions of rusty-red spores (seeds) as a reddish dust, and these spores spread the fungal infection to other areas.

Wet rot Wet rot develops as a result of rain water penetration, such as in the opened mitres of door and window frames, where paint films have broken, where plumbing is faulty or a major leak is occurring. High moisture levels (of 40 - 50%) are necessary for wet rot to develop, and the wood characteristically splits along the grain where decay occurs. There is usually a small amount of surface mycelium, but fruit bodies are not common.

Lifecycle of a Fungus