Defect Detectives

Roger Watts, London City’s executive director, on foundation failures:

The issue of cracking in buildings is complex. Firstly, you need to assess what the ground conditions, then the foundations. Given the age and material of the property, I suspect it’s a shallow trench and a hardcore type/stone footing.
The issue clearly happened long ago so the cause is not now visible. My view is the cracking could be caused by drain failure or nearby excavation – possibly works to adjacent buildings affecting underground water courses/ground water levels.
Other causes could be gutter failure or plant growth e.g. root damage. Once this has been decided, you could then discuss construction and repair options.

Lauren Nelson, Glasgow’s assistant building surveyor, on wet rot:

For wet rot to flourish in the first instance there must be a constant source of moisture to the timber. In this case, there had been a historic leak in the toilets directly above. Whilst the pipework had been replaced to fix the leak, the leaked water had been trapped within the building fabric at ground floor level and never fully dried out. (in older buildings with thick masonry walls this can take many months).
When tested with a moisture meter, the wood moisture content was around 35% – ideal conditions for the timber to be susceptible to wet rot as well as an attack from woodboring beetles. Typically, these beetles like the moisture-softened timbers and often wet rot and beetle infestations are found together.

Phillipa Burgin, London City’s building surveyor, on dry rot:

The photos show “fruiting bodies” – soft, fleshy fungus, with an orange-ochre surface and an unmistakable indication of dry-rot. There was red spore dust around the fruiting bodies, and when the timber skirting boards were removed we uncovered a network of white mycelium strands which is effectively the “roots” of the fungus.
The mycelium strands allow the rot to spread far from its initial point of growth and sometimes across other materials to reach other timber elements within the building.

Pritesh Patel, Birmingham’s building surveyor, on congested gutters:

Vegetation growth in this building’s box gutter has caused rainwater to overflow, resulting in stains to the cladding. The static water created by congestion can cause rainwater to penetrate the roof and let water in, damaging internal finishes and fixtures.
Other defects that occur as a result of congested gutters include cut edge corrosion. The metal edges are open to corrosion when exposed to oxygen, and often made worse by water and pollutants. If left untreated, the coating deteriorates, allowing water to corrode through the roof sheets causing leaks.
A maintenance plan should be assigned to ensure gutters are regularly cleaned of vegetation and debris. This protects buildings from water ingress, reduces repair costs and improves appearance.

Billy Thorpe, Manchester’s assistant building surveyor, on nickel sulphide inclusions:

Nickel sulphide inclusions occur when undetected nickel particles react with sulphur, which over time grow and eventually impart enough stress to cause spontaneous failure. The glass fractures can occur due to a number of reason such as design flaw, vandalism and poor manufacturing techniques.
It is important to analyse the true cause of failure, as spontaneous failure isn’t always due to a nickel sulphide inclusion. Analysing samples using optical microscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy, can identify the presence and nature of inclusions.

Pete Ewbank, Manchester’s senior associate director, on steel corrosion:

Most metals are susceptible to rust and corrosion by water penetration. When a boat is submerged, or has been capsized at sea, the saltwater breaks down the protective oxide layer on the steelwork, allowing corrosion to occur.
The seawater – a mixture of moisture, oxygen and salt – eats away at the metal, corroding it much faster and resulting in failure.
Over longer periods of time, the corrosion eats away at the boat or ship wrecks causing the ship to fall apart and often results in an unsafe and dangerous structure left as remains on the sea bed, which can be hazardous to divers and marine life.