by Anthony Lymath
As another period of dangerously-high winds hits the country, it provides a timely opportunity to review the risks to both property and construction activities, how to reduce those risks, and what to do in the event of wind damage.
The British Isles typically experience high wind events on an annual basis, normally in the autumn but, as is the case currently, can also occur later in the winter season. They are caused by abnormally low-pressure depressions, and tend to be linked to the geographical position, strength and movement of the jet stream in the upper atmosphere, which itself varies through the seasons.
There is some evidence to suggest that the frequency of high winds could be linked to climate change, and this is discussed in detail in the Climate change adaptation in buildings series.
Risks to property and person
Risks to property primarily arise due to damage, particularly of lightweight materials (although not exclusively), but can also be attributed to (or exacerbated by) poor detailing or workmanship. Pay particular attention to the following areas:
- Fences are particularly vulnerable due to their inherent lightweight construction, and the fact that they act as a physical resistance to the wind
- Roofs are also a high-risk part of constructions, particularly lightweight and low-pitch roofing. Wind uplift is caused by a reduction in air pressure above the roof surface, as the wind accelerates over it. The resultant pressure differential pushes the roof upwards from the higher-pressure air underneath, towards the lower-pressure air above (Bernoulli’s principle and the Venturi effect)
- Wind-driven rain can exacerbate problems due to tile uplift, and either poor detailing or defects (e.g. flashings, abutments, felt laps, inadequately secured materials)
- Unsecured or unbraced masonry walls in a temporary condition on construction sites can be blown over before permanent bracing has been fixed. Temporary propping can fail if not in itself secured. This can be a particular concern close to high-level building edges
- Falling debris from either roofs (e.g. tiling or cladding panels) or masonry (from chimneys or unsecured gable walls) is of the utmost concern, due to consequential damage to property below, as well as injury and damage to third parties e.g. parked cars. Cladding panels can also be a risk, especially lightweight with light fixings (see http://www.bbc.co.uk/news/uk-england-suffolk-24733301).
In addition, legal and financial arrangements should be reviewed for adequacy:
- Check insurance cover, whether a ‘buildings’ policy for existing structures, or a contractor’s ‘all risks’ policy for construction work in progress. Check the policy wording, excesses and, most importantly, any exclusions. s
- Inadequate contractual robustness – Any storm-related damage sustained on a construction project is likely to lead to a delay claim by the contractor for an extension of time. Check that the list of ‘relevant events’ in the contract covers this eventuality, and make sure that any delay claim is assessed and processed accurately, to avoid potential disputes later on.
There are also a number of pieces of pertinent legislation, including the following:
- Occupiers Liability Act – perhaps not often used, but places a duty on premises owners (whether property or land) to protect visitors’ safety. Trespass is no exception to this obligation
- Health & Safety at Work etc. Act 1974 – the principal and overarching piece of legislation that places a duty of care on employers for their employees’ health and safety
- CDM Regulations – for construction work, all risks should be assessed, and designed-out where practical, with the remainder being identified as ‘residual risks’ (note that these are due to be revised in 2015 – draft guidance has already been published). Risks to be considered include those arising from construction, operation, use, maintenance/repair and demolition.
Preparing for storms
There are a number of steps that can be taken, in preparation for storms, which, if followed, should help to minimize the risks:
- Monitor weather forecasts – establish likely prevailing wind direction and pay particular attention to securing property in its path
- Secure loose or unstable structures and materials, whether fixed or stored loose on site
- Prop temporary works and unsecured areas of e.g. single skin masonry walling and parapets, or gables not yet roofed-over
- Don’t leave doors open on the windward side, as wind uplift danger to the roof is substantially increased
- Review insurance cover, and construction contract provisions for both insurance and delay claims (including relevant events) as highlighted above
- Pay particular attention to construction detailing – roof tile clipping; ridge tile mortar bedding and bolting; roof structure strapping; flashings. Consider specifying easily-repairable fencing (spikes for posts, clips for panels) or concrete/metal posts to withstand rot at the post base, which prematurely weakens large sections of fence (i.e. 2 panels for every post); avoid climbing/trailing plants on e.g. larch lap panels, which can cause premature failure by delamination. Design masonry garden walls to include adequate bracing/stability (and suitable foundations, to prevent early failure due to settlement cracks); consider specifying hit-and-miss fencing to reduce wind pressure, in lieu of close-boarded or other ‘solid’ panels
- Establish and maintain rigorous maintenance schedules, to inspect and repair damage in vulnerable areas regularly, before it becomes severe (such as mortar deterioration to ridge tiles, flashings, roof coverings of limited life e.g. felt, or exterior timber including fencing).
Dealing with the aftermath
In the event that a storm has caused damage to the property for which you are responsible (or to surrounding property), then there will be a number of important steps to take in order to deal with the resultant consequences:
- Notify your insurer(s) claims department as soon as possible, even if other parties may be liable (either in whole or in part). The respective insurance companies will liaise with one another to establish liabilities.
- Cleaning up – should be carried out as soon as practicable; however, before commencing, ensure that any affected areas are safe to enter. If any damage or debris is liable to cause a danger to the public, then notify the emergency services before proceeding any further. In addition, the Health & Safety Executive must be notified in accordance with the RIDDOR (Reporting of Injuries, Diseases and Dangerous Occurrences) Regulations 2013. Reports must be submitted ‘without delay’ and must be received by the HSE not later than 10 days after the incident being reported.
- Particular care should be taken if dealing with asbestos-containing materials such as asbestos cement sheeting, which is still commonly found on old roofs (or wall panels on domestic garages). Disposal of asbestos requires a commercial licence; removal is covered by the Control of asbestos regulations 2012.
Classification of hazardous waste is changing on 1st June 2015, with the relevant legislation being the List of waste decision (2000/532/EC) (or European waste catalogues) and Annex III of the Waste directive (2008/98/EC). These in turn are driven by the Dangerous substances directive (67/548/EC) and the Dangerous preparations directive (1999/45/EC), although this is being replaced by the Classification, labelling and packaging regulation (CLP) (2008/1272/EC). This introduces a new system of chemical classification based on hazard classes, categories and statement codes (rather than risk phrases and categories of danger). As a consequence, Annex III of the Waste directive has been revised in accordance with the CLP, and provide hazardous waste criteria based on hazard statement codes. The List of waste has also been revised to align with the CLP and Annex III, include criteria for persistent organic pollutants (POPs), and to make other amendments arising from a review of the List itself.
As a result of these changes to legislation, the Environment Agency is in the process of updating its existing Technical guidance WM2, and the updated draft document called Waste classification and assessment – Technical Guidance WM3 is currently out for public consultation until 3 February 2015
- Damage to third parties – whether property, vehicles or other items – should be covered by either property insurance or contractor’s all-risks insurance. Alternatively, company ‘public liability’ insurance may be used, and, in complex circumstances, underwriters from respective insurers may need to establish the extents of their respective liabilities.