Case Studies Gallery
Insect Infestation
Timber has been used as a building material for thousands of years and although an extremely versatile material, relatively strong, durable, light and workable, it is susceptible to deterioration when it becomes damp.
Many wood-boring insects only attack timber with moisture content of above fibre saturation (25-30%).
Eggs laid by the adult beetle on timbers hatch to release larvae (grubs) which then bore into the timber, feeding on cellulose and lignin and other components of the timber. These grubs form networks of tunnels and after a period of between approximately (dependent on species) one and seven years of feeding, the grub undergoes a metamorphosis and after the pupal stage, become adult beetles. The adult beetle eats its way through the surface of the timber leaving an exit hole. The whole cycle begins again with the adult beetle laying its eggs on timber.
House longhorn beetle (Hylotrupes bajulus)
Whilst undertaking a loft conversion, this infestation was discovered when the builder started to sand the structural roof timbers inside the loft. We were engaged to investigate the infestation and to report on the condition of the timbers in the loft space. Firstly, the infestation was identified as the House longhorn beetle and several structural windbrace elements of the roof were infested.
A resistograph was used to ascertain the level of damage within the timbers. It was established that galleries of damage ran through 60% of the timber and therefore, the clients structural engineer decided the timbers had to be removed.
Discoveries of this beetle are at present limited mainly to Surrey.
Common furniture beetle (Anobium punctatum)
This photograph shows localised damage to a joist located in a cellar. The timbers had been chemically treated two years previously. The client engaged another timber treatment company to survey the new activity, who recommended that the entire cellar receive more chemical treatments.
The common furniture beetle has a life cycle of approximately seven years, therefore these fresh exit holes could be the result of that cycle being completed. The timbers should not be re-infested due to the chemical treatments, so, the cycle should be broken within the next five years.
However, it is of our opinion that the use of chemicals on all the timbers in the cellar area was an excessive recommendation and that only localised treatments should have been specified.
Fungal Decay
Fungal decay in timber becomes possible when the moisture content of the timber exceeds approximately 22%. However, rapid fungal decay is more likely at above 26% moisture content.
When microscopic, airborne spores settle on suitably damp timber, the mechanisms for fungal decay commence. The spores germinate to form hyphae (thread-like filaments) which release enzymes (chemicals) into the timber.
The decay is caused by these chemicals dissolving the nutrients in the timber. The nutrients are then absorbed by the hyphae promoting further growth.
Dry rot fungus (Serpula lacrymans)
This is a brown rot fungus, infamous for the extensive damage it can cause.
It is able to grow over and through masonry and mortar (but unable to feed on these) in search of timber a food source.
Damp Problems
Throughout history the performance of buildings has been affected by dampness problems often associated with poor building design or maintenance.
Rising Damp
The term ‘rising damp’ applies to the upward flow of moisture through the pore structure of the masonry (capillarity) which can cause damage to timbers, plaster and the decorative finishes in contact with the masonry.
Rising damp is often misdiagnosed and therefore requires systematic investigation. It may be necessary to take masonry and plaster samples for analysis.
Penetrating Damp
Penetrating dampness refers to moisture entering the habitable space from outside the building. This can include rain, snow, and moisture ingress caused by faulty rainwater goods, external drainage and plumbing leaks. External ground level bridging of the damp proof course is a cause of penetrating damp and even more often diagnosed as rising damp.
The defects in this photograph (click to enlarge) are an example of a combination of problems.
The evidence of salts on the wall could suggest that this was a defect caused by rising damp, however, the room in this study was a first floor lounge with a suspended, pre-cast, reinforced concrete floor.
The client had expressed reservations to the builder regarding the apparent brief time that had elapsed between laying the concrete screed and the plastering of the walls. The new plaster was in contact with the floor and as a consequence, excessive moisture from the concrete floor wicked up the plaster resulting in the defects. Furthermore, salt samples were sent for analysis and it was established that the sand used for the concrete floor was contaminated with high levels of salts, probably a batch of unwashed sand. As a result of the aforementioned defect, w.m.c readings of 24.6% were obtained from the skirting board, facilitating an outbreak of Cellar fungus (Coniophora puteana) to the back of the skirting board.
Condensation
Condensation has become a major problem within domestic buildings. These problems are associated with changes in building design and the lifestyles of the occupants.
Environmental concerns and the pressure of a continual increase in fuel prices have led to awareness for the conservation of energy. However, as a result of this awareness, better draught proofing, double glazing and a shift from open solid fuel fires has in many instances contributed to condensation problems.
Condensation occurs when warm moisture laden air comes into contact with cold surfaces (walls and windows etc) and is then cooled. The moisture is then released onto the cold surface.
If ignored, condensation will cause the deterioration of wooden windows, decorative wall coverings, furniture and fabrics. In roof spaces condensation can cause extensive and expensive damage to timbers and insulation materials.
