The skylines of many UK cities are ever-changing, with the design and construction of tall and complex buildings altering the cityscape. These towers usually incorporate glass facades, and access can be a challenge.
GAINING ACCESS Facade access describes access to the entire building facade and associated structures.
Access from inside the building envelope can restrict the plan layout and disrupt occupiers.
Openings in the facade also create additional problems such as the need to provide safety eyes and the effect on air-conditioning systems. (For example, an early proposal for one project was to access every floor from a balcony. Due to the nature of the balcony, this required doors every 6m along the facade. This scheme was further developed and the final solution was for a number of building maintenance units to access the outside of the building. ) To avoid these problems, access from the exterior of a building is preferred. This can be provided in a number of ways:
? from below, using ladders or mobile elevating work platforms (MEWPs), in which case the ground conditions need to be able to take the loads;
? from above, using cradles, gantries or abseiling, all of which need some form of anchorage. It is preferable that loads do not impose thrust loads or pull out loads on the building structure.
Note: abseiling can impose greater loads on the building facade and structure; and - through the facade - with opening windows or doors to balconies and parapets.
The Health and Safety Executive (HSE) discusses facade access in various guideline documents such as the Workplace Regulations, Lifting Operations and Lifting Equipment Regulations (LOLER) and Working at Height regulations. The HSE proposes a hierarchy of systems for facade access. The preferred option is to remove the risk; if this cannot be achieved the risk should be minimised. This hierarchy is:
? opening windows and/or balconies with full-height handrails;
? cradles or MEWPs;
? ladders; and - abseiling.
The HSE's basic premise is to produce a safe system, and it requires project teams to design these safe systems.
Most inspectors would consider abseiling to be a last resort.
The Construction (Design and Management) regulations also recognise that the priority is for an access system that is safe and efficient.
ISSUES - Cleaning and maintenance.
With the shape of facades becoming more complex, the need for effective access systems to maintain and clean the facades has increased. If the equipment cannot access all the facades or operate effectively, the building will not be maintained, and in time debris will build up, spoiling the building's appearance. Attention to detail and loads will resolve some issues. For example, winches in a cradle double the suspended load and hence loads into a building when compared to a system that has the winches mounted on the roof trolley.
? Security and safe access.
When access is required through a building there are issues of theft. If the operative is to use a window safety eye to climb through the window, will he actually use the safety eye?
Access in ordinary use and in an emergency.
The design teams need to consider how the operatives will access the cradle from a place of safety, along with how the maintenance engineer will access the unit at any point should it breakdown.
The method of -xing the system to the building.
For example, a bolted--xings trackless system or a freely laid system? The solution will be dependent on the roof -nish and reach required.
Access will obviously affect architectural expression.
If, for example, the building is to have a ush glazing system, the architect will not necessarily want the facade split with external walkways on every oor. It is therefore vital to consider the options available at the earliest possible stage in the design process.