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We have found that significant quantities of unanticipated asbestos containing materials (ACMs) are discovered in as many as one in ten building projects involving properties constructed before 2000.
There are various reasons why asbestos removal can be particularly challenging. In some cases, the original asbestos survey may have been incomplete or failed to detect the full extent of the materials present. Asbestos is often concealed behind other ACMs or embedded deep within the fabric of a building — in places even a detailed intrusive survey might not reach. For example, removing asbestos insulating board (AIB) may reveal a second hidden layer, or contaminated debris such as obsolete pipework still insulated with asbestos. Surveyors are not permitted to remove panels during the inspection, which limits their ability to detect what’s hidden behind them.
A recent refurbishment of a 1930s Art Deco office building in Covent Garden illustrates this challenge. Asbestos was only discovered during demolition, concealed beneath screed and behind blockwork added during a 1970s renovation. It had gone undetected despite previous asbestos surveys.
Unexpected asbestos finds can significantly impact project timelines and budgets. For the project manager, cost consultant and quantity surveyor, it’s a major complication. For instance, removing 50 square metres of asbestos ceiling panels discovered during strip-out could cost around £10,000. Decontaminating 100 square metres of asbestos-insulated pipework hidden behind panelling may cost in the region of £25,000.
The Hidden Cost of Delay: The Real Impact of Unexpected Asbestos
While the direct costs of asbestos removal can be significant, they are often far outweighed by the delays imposed on the construction programme. Even a relatively small amount of unexpected asbestos can cause substantial disruption to the project timeline. Here is a typical sequence of events following the discovery of unforeseen asbestos:
As shown, the discovery of unexpected asbestos can result in a programme delay of up to four weeks. This is under ideal conditions, where consultants and contractors are readily available at short notice.
The monetary costs of the delay will depend on the structure of the programme, the degree of flexibility built into the various processes and the experience / capability of the Project Manager. However, even if your PM is able to re-organise and reschedule works during the delay it is likely to involve costs of relocating plant, and may well have to account for subcontractors incurring costs because their operatives are standing idle through no fault of their own. If the asbestos is found at a relatively advanced stage in the project the PM may have several contractors teams onsite expecting some recompense for the downtime.
Then there are the dreaded Liquidated and Ascertained Damages (LADs) which may well be written in to the contract. A reasonably sized building project may well have penalty clauses for late delivery of £10k per week. You can therefore see that the overspend of the additional removal is now overshadowed by the costs of the delays involved. A relatively minor discovery of unforeseen ACMs can lead to £70k or more of additional costs as well as a loss of reputation for the QS/Cost Consultancy involved.
So how can you mitigate this eventuality?
Firstly, make sure you appoint a reliable, competent organisation to carry out the R&D asbestos survey. Although it is not mandatory, UKAS accreditation against International Standard ISO 17020 is a good benchmark to sort out the wheat from the chaff in the asbestos consultancy market. Make evidence of UKAS accreditation a pass/fail item at the pre-qualification stage and obtain evidence that they have the requisite experience of working on the type of buildings involved.
Also give them as much background information as you can about the building and the project to enable them to plan the survey accordingly and match their methodology to the works involved.
If you have a scope or specification for the building works pass this to the consultancy so they can accurately target the intrusive areas to survey. Whenever possible you should be passing them accurate building plans so they can locate service ducts, voids and risers where ACM is often found.
Before commissioning any asbestos removal works, it may be prudent to have an asbestos specification prepared. This document, typically developed by an independent consultant — often the same firm that carried out the original survey — provides a detailed, practical interpretation of the survey findings. While asbestos surveys identify the presence and location of asbestos-containing materials (ACMs), they often do not assess the broader implications for removal.
The specification should be developed in collaboration with key stakeholders, such as the facilities management team, building contractor, and members of the design team. This ensures it takes into account planned activities, access requirements, and the methods and extent of the proposed works.
For example, a survey might identify ACMs in risers at basement and third-floor levels, but not in the floors in between. A competent consultant preparing the specification would consider the likelihood that asbestos debris may also exist in the untested intermediate floors, particularly if the pipework runs continuously through the riser. They may return to site to verify this themselves, or request clarification from the survey team. This step can prevent costly surprises later, or avoid contractors pricing for risks that may not be relevant — potentially inflating removal costs unnecessarily.
Having a well-prepared specification allows for more accurate and consistent tendering, creating a level playing field for licensed contractors and reducing the risk of unanticipated or unquoted work emerging mid-project. While preparing the specification may require a modest upfront investment — typically the equivalent of a few days’ consultancy time — it can result in significant cost savings, potentially reducing removal costs by as much as 30%. This can be a welcome benefit for the quantity surveyor managing the budget.
As a further safeguard, it is advisable to include a contingency of 5–10% in the asbestos management budget to accommodate unexpected findings or variations during the works.
Although asbestos management is never an exact science, careful planning and early-stage diligence can go a long way in avoiding the disruption and cost escalation that unforeseen ACMs can cause later in the project.
