Stick curtain walling

How does Stick curtain walling work, step by step?

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   Step 1: Develop the system and the interface details

   The facade engineer and the specialist contractor take the architect's intent and develop the mullion and transom arrangement, the infill make-up, the fixing back to the structure and the movement provision. Interfaces do most of the work in a stick system - head, base, corners, junctions with solid construction, openings and any brise soleil or louvre all need drawn, approved details. Loads and building movement are established by the designers, and the anchor arrangement is engineered from that. Sample panels or a small mock-up are common even where full performance testing is not, because they settle appearance and workmanship expectations before the facade starts.

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   Step 2: Survey the structure and set out

   Setting out for a stick facade starts from a survey of the structure as built, not from the design grid, and on refurbishment work that survey often finds substantial deviation. Datum lines and levels are established, the grid is set out floor by floor, and the anchor positions are marked so that adjustment is used deliberately and consistently rather than being absorbed in one bay. Because the facade is built up from components, small deviations can be taken up as work proceeds - but only if they are known and planned for, otherwise they accumulate and show in the finished line.

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   Step 3: Establish access and protection

   Unlike a unitised facade, most stick work happens on the outside of the building, so external access is a package in its own right - scaffold, mast climbers or cradles - and it has to be designed, erected, inspected and coordinated with every other trade that needs the same face of the building. Edge protection, exclusion zones below, and the plan for lifting glass to the working level are all agreed before installation starts. Access constraints frequently shape the installation sequence more than the facade design does.

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   Step 4: Fix brackets and install the mullions

   Brackets and anchors are fixed to the engineered detail at the positions the setting-out gives, then mullions are lifted into place and fixed back, plumbed and aligned. Mullion splices and expansion joints are made exactly as detailed, because they are what allows the facade to move with the building instead of fighting it. Each mullion is checked for line and plumb as it is fixed rather than at the end of the elevation, since a lean corrected late means dismantling. Fixings are checked for type, embedment and tightness as work proceeds.

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   Step 5: Fit transoms and form the drained frame

   Transoms are fitted between the mullions to form the glazing grid, with the drainage and ventilation slots, baffles and gasket arrangements installed as detailed at each junction. The mullion to transom junction is where most stick facades leak, so it is made up in full - end seals, drainage routes and continuity of the air line - and inspected before it is glazed over and becomes invisible. Frame alignment across the grid is checked so that glass units go in square and the pressure plates seat evenly.

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   Step 6: Glaze the openings and fit pressure plates and caps

   Glass and infill panels are lifted to the working position, usually with a glass manipulator or vacuum lifter, set onto setting blocks in the correct positions and located in the pocket. Gaskets are fitted continuously with the corners made up as detailed rather than butted and left, and pressure plates are fixed at the specified spacing and torque so the seal is even, then covered with the capping. Handling large panes at height is wind-sensitive work with a lifting plan, a wind limit and an exclusion zone. Panels are inspected for edge damage before they go in, because a chipped edge is a future failure.

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   Step 7: Seal interfaces, test and protect

   Perimeter interfaces, movement joints, fire stopping at the floor edge and junctions with adjoining construction are completed to the approved details and inspected before they are covered. Site hose testing on a sample of joints is carried out during installation so that a workmanship problem is found while the crews and the access are still there. Any leak is traced to its cause and corrected in the construction, not sealed over. The facade is then protected from following trades and cleaned down before handover, with the cleaning and maintenance access strategy confirmed.