Non-destructive testing (NDT) is a way to gather preliminary information, using technology and equipment, to inform next steps for repairs or further action, including more invasive destructive testing. It’s a toolbox of techniques CANY brings to a much larger scope, saving time and money for the client, allowing for better utilization of resources and more targeted efforts by contractors on complex jobs with multiple moving parts. Our in-house knowledge and capability of NDT allow a better workflow, facilitating face-to-face, on the job questions and answers, avoiding cumbersome delays and protracted processes.
When assessing a building to determine the root cause of an issue, we employ NDT as even our well-trained eyes, ears and extensive experience can only take us so far. So, we set up a hypothesis and, through a series of deductions, will test that using NDT, eliminating possibilities, and revealing others. We deploy technology and equipment to minimize disruption to the use and fabric of the building, before taking further steps to determine the validity of the original hypothesis, establishment of a new one or confirmation of required scope of works.
NDT affords more precision, allowing, for example, investigation into concrete slabs without damaging any of the supporting infrastructure, utility conduits or hidden waterlines. In this instance Ground Penetrating Radar (GPR) could be used, calibrated to detect concrete, air pockets, rebar, or anything other than concrete. We also use GPR for wall tie detection in conjunction with metal detection, which allows us to obtain more information, faster, and cheaper than traditional destructive investigations such as probing.
To determine where and how a leak is damaging a building, NDT would be used in the first instance. That could be spray testing, targeting specific details of a building, often in conjunction with an infra-red camera. An infrared camera minimizes potential damage and identifies leaks invisible to eyes. It detects changing temperatures, cold spots, illuminating points of water ingress or where water could be trapped, such as under a roof membrane. However, temperature changes do not always indicate a leak, so we would also use moisture meters for verification.
When performing NDT, it’s important to gather as much information as possible using various tools to establish the most likely explanation for the observed phenomenon.
Infrared thermography provides thermal analysis to detect energy loss through different parts of building, highlighting failures of insulation and/or fenestration and where to focus to mitigate against such loss.
Acoustics testing evaluates material conditions. It can range from a plastic mallet tapped against masonry or terracotta to locate a spall by listening for sound variations, to high-tech ultrasound equipment to assess the corrosion of steel structurally supporting buildings and facades, rusted, and weakened by weathering. Acoustic testing helps determine the location, the extent of damage, and whether to repair or replace by measuring the thickness of the remaining steel.
Borescopes are small cameras on long thin wires used by CANY to get in the tight spaces and under the skin of buildings. They are especially useful in restoration work as they cause minimal disruption but get eyes in places that would ordinarily incur damage to be properly assessed.
Metal detectors are used to locate the position of anchors and rebars, with GPR used to assess their condition. If the GPR detects an anomaly, minor destructive testing would be necessary to confirm the anomaly and obtain calibration data that can be applied across the whole project. Using all the other collected data with similar response patterns raises the confidence that other anchors behind the stone are in a similar condition and need addressing.
There will always be uncertainties in NDT, nothing is exact or conforms to a cookie cutter pattern. Assessing data provided by non-destructive testing, and applying it correctly within the context of the building and the materials, can offer a wider survey area in a shorter time frame than physically opening sections of a building. However, correctly interpretated and performed NDT will only offer an informed opinion. It is only when the building is destructively tested, opened so that an issue can be physically seen, that the data can be confirmed.
For example, wall tie detection and/or observation, is a FISP requirement for brick masonry buildings with cavity wall systems. Observation means the wall must be opened to reveal the wall-tie at least once per inspection drop, which will be every 60ft for a public facing elevation. If the NDT results indicate insufficient wall tie spacing or missing wall ties, the number of physical observations will be increased until the Qualified Exterior Wall Inspector (QEWI) has enough information to determine the façade condition (Safe, Unsafe, SWARMP).
At CANY, we have the knowledge to know what we don’t know. If there is technology or tool out there that will do the job we need it to do, we will direct our clients’ resources there. We rely on as many resources as possible when making our judgements – that could be using our senses, including sight, hearing, touching, and feeling, plus a range of technology and devices. But the tools are only as good as the people deploying them, and we know through almost three decades of experience, that no amount of technology can replace our inherent understanding of buildings, but NDT can enhance that.
