The European Standard, BS EN 12811-1, specifies performance requirements and methods of structural and general design for access and working scaffolds. Requirements given are for scaffold structures that rely on the adjacent structures for stability. In general these requirements also apply to other types of working scaffolds.
The purpose of a working scaffold is to provide a safe working platform and access suitable for work crews to carry out their work. The European Standard sets out performance requirements for working scaffolds. These are substantially independent of the materials of which the scaffold is made. The standard is intended to be used as the basis for enquiry and design.
Scaffolds are only rarely independent structures. To provide stability for a scaffolding (at left) framework ties are generally fixed to the adjacent building/fabric/steelwork.
General practice is to attach a tie every 4m on alternate lifts (traditional scaffolding). Prefabricated System scaffolds require structural connections at all frames - ie.2-3m centres (tie patterns must be provided by the System manufacturer/supplier). The ties are coupled to the scaffold as close to the junction of standard and ledger (node point) as possible. Due to recent regulation changes, scaffolding ties must support +/- loads (tie/butt loads) and lateral (shear) loads.
Due to the different nature of structures there is a variety of different ties to take advantage of the opportunities.
Through ties are put through structure openings such as windows. A vertical inside tube crossing the opening is attached to the scaffold by a transom and a crossing horizontal tube on the outside called a bridle tube. The gaps between the tubes and the structure surfaces are packed or wedged with timber sections to ensure a solid fit.
Box ties are used to attach the scaffold to suitable pillars or comparable features. Two additional transoms are put across from the lift on each side of the feature and are joined on both sides with shorter tubes called tie tubes. When a complete box tie is impossible a l-shaped lip tie can be used to hook the scaffold to the structure, to limit inward movement an additional transom, a butt transom, is place hard against the outside face of the structure.
Sometimes it is possible to use anchor ties (also called bolt ties), these are ties fitted into holes drilled in the structure. A common type is a ring bolt with an expanding wedge which is then tied to a node point.
The least 'invasive' tie is a reveal tie. These use an opening in the structure but use a tube wedged horizontally in the opening. The reveal tube is usually held in place by a reveal screw pin (an adjustable threaded bar) and protective packing at either end. A transom tie tube links the reveal tube to the scaffold. Reveal ties are not well regarded, they rely solely on friction and need regular checking so it is not recommended that more than half of all ties be reveal ties.
If it is not possible to use a safe number of ties rakers can be used. These are single tubes attached to a ledger extending out from the scaffold at an angle of less than 75° and securely founded. A transom at the base then completes a triangle back to the base of the main scaffold.
In 2013, there were 1,751 registered bamboo scaffolders and roughly 200 scaffolding companies in Hong Kong. The use of bamboo scaffolding is diminishing due to shortages in labor and material. Despite the lack of labor force and material, recently problem of safety has become another serious concern.
The labor shortage may be due to the reluctance of younger generations to become scaffolders. “They even think that it’s a dirty and dangerous job. They are not going to do that kind of work,” said Yu Hang Flord, who has been a scaffolder for 30 years and later became the director of Wui Fai Holdings, a member of the Hong Kong and Kowloon Scaffolders General Merchants Association. “They refuse to step in, although we give them high pay. They are scared of it. Young generations do not like jobs that involve hard work.” Another reason fewer people are becoming scaffolders is that new recruits need to undergo training with the Hong Kong Construction Industry Council in order to acquire a license. Older scaffolders generally learned in apprenticeships, and may have been able to gather more hands-on experience.
Material shortages are also a contributing factor to the decline. The bamboo scaffolding material was imported from mainland China. Bamboo—which matures after three years to the wide diameter and thick skin perfect for scaffolding—came from the Shaoxing area in Guangdong. Over the past two decades, firms have had to look to Guangxi instead. The industry's fear is that one day supplies will be blocked due to export embargoes and environmental .