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In the United Kingdom, extreme conditions of prolonged winter snow combined with sub-zero temperatures are fortunately quite rare. However, the potential exists with climate change to experience such conditions more frequently. It is, therefore, important that property owners and occupiers are prepared for such conditions and do not lose sight of the fact that significant weight loads introduced by snow on buildings have the potential to damage the structure resulting in significant property damage, damage to the contents and business interruption.
The most hazardous conditions are likely to arise in the UK when repeated snow falls, that can take place over several days, do not have sufficient time to melt from roofs consequently accumulate and exceed the design capability of the roof. Furthermore, conditions can be exacerbated when rain follows heavy snow falls as rain water will initially be absorbed by the snow layers which will further increase the weight of snow.
Snow and ice on a roof exerts vertical loads that can cause a roof to deflect or bow downwards. Also these extremes in weight load can transfer horizontal forces through the structure that can cause walls to deflect outward at either the top of or base of the wall. Where snow loads imposed on a roof are within the design limits for the roof then generally any minor sagging or deflection that may occur will usually be temporary and simply disappear after the load is removed.
In addition, melting snow combined with rainfall can overwhelm building drainage systems as well as local drainage systems in the area which can result in flooding and damage.
Any work on roofs and gutters will involve work at height and safe methods of working must be used at all times. Any work at height during adverse weather will have the added risk of snow, ice and cold weather. It is important that a full risk assessment is carried out and a safe method of work established. It may be that the work could be more safely carried out by qualified and competent contractors.
Whilst severe winter weather cannot be avoided, following these simple practical guidelines will help avoid or mitigate damage to property and prevent business interruption.
To protect against the likelihood of snow related damage to your property, it is important to develop a timely prevention and maintenance program before the winter weather commences, during and after the winter period. These simple practical measures should form part of your building maintenance program.
BUILDINGS AT GREATER RISK
If in doubt, specialist advice from chartered structural engineers or other appropriately qualified persons should be sought about the loads acting on a building or how these loads can be safely accommodated by the structure to ensure your buildings are best prepared for the anticipated snow loadings they will experience.
HOW DO ROOF FAILURES DUE TO WEIGHT OF SNOW OCCUR
Roof collapses due to excessive weight of snow can happen for a number of reasons including:
MAINTENANCE BEFORE THE WINTER WEATHER BEGINS
Regular and systematic building inspections are a key part of any maintenance programme in order to help identify problems promptly.
Early remedial action by a competent person is essential to reduce further, more costly, damage. It may be necessary to engage a competent person with the appropriate skills and equipment to carry out inspections in certain areas e.g. roofs.
Intervals between inspections may vary depending on such things as the location, age, construction, usage etc. of a building.
Log books are indispensable for keeping track of maintenance regimes, identified problems and actions taken.
Rainwater Removal - Gutters, Gulleys, Downspouts and Drains
Blocked or damaged rainwater removal systems will allow damage to the building fabric, water ingress and most importantly may prevent water being drained away from the property and in freezing temperatures this can result in ice dams forming during snow and prolonged cold conditions. Ice dams can form when heavy snow melts during the day, flows and cannot sufficiently drain away and then refreezes at night. After several melting-freezing cycles combined with further falls of snow the weight load on the roof will obviously increase.
There are a number of practical measures that should routinely be undertaken throughout the year as part of your overall building maintenance plan that can help prevent damage caused by heavy snow and ice dam formation which include:
Again log books are indispensable for keeping track of maintenance regimes, identified problems and actions taken.
Roofs generally need to be inspected at least twice a year or following particularly stormy weather during the the non-winter months - debris on the ground from broken slates and tiles indicates that there is a problem. In some cases roofs can be inspected using binoculars or vantage points from nearby higher buildings.
Ice can form when heavy snow melts during the day, flows under the roof tiles, and then refreezes at night. After several melting-freezing cycles tiles may be displaced, and water may often enter the roof space and damage insulation, ceilings, walls, contents and even the building itself.
Repair or replace:
In addition moss, which retains moisture, needs to be removed since it can cause slate to delaminate and can gradually erode all metals particularly lead work - a seasonal brushing down is often all that is required to prevent excessive build up.
Internal inspection of the roof and framework must also take place
STEPS THAT CAN BE TAKEN DURING WINTER WEATHER
By taking some simple practical steps during severe snow conditions it may be possible to reduce the likelihood of roof collapse. The following steps should be taken during such weather events:
BE ALERT FOR THE TELL TALE SIGNS
Often before a roof collapses due to the excessive weight of snow and ice the building will generally exhibit some signs that the roof is under excessive load including:
Safety of life is of utmost importance so if there is any doubt about the integrity of a roof in such extreme snow conditions then the building or area should be evacuated until professional advice can be sought.
HEALTH AND SAFETY
It is important that you are aware of the following risks:
SNOW AND ICE ROOF MELTING SYSTEMS
There are a range of snow and ice prevention systems available from specialist installers that can reduce the build up of ice, snow and the dangers posed by heavy snow building up on roofs which can lead to structural damage.
Typically these are electrically powered trace heating systems comprising of heated mats and cables which are routed and positioned in critical areas of the roof, eaves, valleys, gutters and downspouts etc. Such systems are designed to activate automatically by strategically located thermostatic and moisture detection that switches on the heat source whenever the ambient temperatures fall below a set point.
Being prepared for such events will increase your businesses resilience and enable your organisation to resume operations in the most effective and shortest possible time should disaster strike.
Although headline disasters capture the attention, businesses need to be aware that other more specific events are just as likely to threaten their organisation. Disasters can and do happen and will cause healthy businesses to fail. Disasters create missed opportunities, cash flow problems and can often result in bad publicity. All this can lead to a loss of client confidence and your competitors will take advantage.
Planning makes a substantial difference to the possibility of surviving an incident. While it may seem an extra burden to prepare a plan, challenging situations place severe pressure on individuals to make decisions and take action under stressful conditions. Experience proves that it is easier to consider all the issues surrounding a potential crisis objectively beforehand.
Insurance has a vital role to play in supporting your recovery, but it makes sense to have a plan as well. This should give you the opportunity to reduce the risk of some incidents occurring and to know what immediate measures to take to minimise the initial impact.
Business Continuity Plan doesn't need to be complicated and does not need to deal with every scenario. If your plan enables you to cope with the worst case scenario, it will also help you to deal more easily with less serious incidents.
The Business Continuity Planning process is designed to help you reduce the likelihood and impact of risk occurring and becoming a disastrous event, as well as putting in place suitable contingency plans that will enable your business to maintain its revenue and client base, assist with the continuity and recovery of your business and ensure its survival should the worst happen and disaster strike.
The Business Continuity Planning process is an on going business process that would normally consist of the following key elements:
Key Action Steps
Effective precautions are required for all work on roofing surfaces, no matter how short the duration, whether the work concerns construction, maintenance, repair, cleaning or demolition.
Building Regulations 2000, Approved Document A - Structure
BS6399: Part 3: 1988 Imposed Roof Loads
The Building Standards (Scotland) Regulations - Technical Standards
Structural Euro Codes BS EN 1991-1-3:2006
This document contains general information and guidance and is not and should not be relied on as specific advice. The document may not cover every risk, exposure or hazard that may arise and Aviva recommend that you obtain specific advice relevant to the circumstances. AVIVA accepts no responsibility or liability towards any person who may rely upon this document.
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