The ongoing pandemic has seen temporary structures pressed into many alternate uses - from ‘mail-order’ warehouses, to classrooms and COVID-19 testing stations.
Lockdown has also had an impact on regular entertainment events. This means various novel structures have been introduced such as giant screen supports for drive-in cinemas and inflatable marquees.
Temporary structures may also be planned for other outdoor locations such as beaches and on carpark rooftops where weather conditions can be more mixed. Temporary structures need to be safely erected, safe in use and safe to dismantle.
Below are some considerations for those involved with temporary structures. More detailed advice is provided by Temporary demountable structures: Guidance on procurement, design and use (TDS4):
- As well as event licensing, planning and building regulation approval may be required
- There should always be a competent person or firm appointed to carry out design and checking services as well as the provision and construction of the structure
- Ad hoc employment of materials and components designed for alternate use should be resisted
- Temporary structures should be signed off once erected and after any alterations
- Clients and event organisers will be responsible for staff and public safety, and the CDM regulations will apply alongside legislation such as the Health and Safety at Work Act or similar legislation in other jurisdictions
- Some structures may be used for longer periods and in more difficult weather conditions than they are usually expected to experience. This is especially true where snow, high wind speeds and winter icing of components are concerned
- Often planning time is at a minimum and some designs, eg for support scaffolding, may be in the hands of inexperienced firms
- Structures should not be pressed into use without bespoke calculations for the site in question and without suitable management plans being in place, ie to deal with adverse weather, etc. Temporary structures will not normally be able to withstand the full wind speeds that a permanent structure on the same site could handle
- The allowable bearing capacity of the ground or structure involved should be fully understood and suitable load spreaders and holding down provisions adopted
- Fire precautions and escape provisions may be more difficult in unusual locations. For example, the fire load from parked cars may be considered a high risk and provision of suitable car spacing, escape routes, fire extinguishers and trained stewards is essential
- Where kentledge or ground anchors are used, suitable factors of safety are required, and the calculated resistance weights may be much more than imagined or indeed derived by simplistic calculation
- Wind uplift can reduce bearing pressures at certain support points and hence reduce the frictional resistance to sliding of the structure at that point
- Structures with large openings or open sides will be subject to significantly higher wind loads than closed structures. Where loose boarding or cladding is applied to a structure, this will need to be tied down/ restrained against wind forces
- Regular inspections should be carried out and remedial measures put in place as necessary
- Inspections should be documented and undertaken by a competent person
- The hire company should arrange a schedule with the client to advise when inspections will be undertaken