Residential & office towers

How does Residential & office towers work, step by step?

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   Step 1: Survey the frame and establish the real tolerances

   The concrete or steel frame is surveyed before units are ordered, floor by floor and opening by opening, recording where the structure actually sits against where it was drawn. Frames of this size deviate within their own tolerances, and the deviation accumulates up a building. The survey produces the information the fixing design needs: how much adjustment each bracket has to provide, whether any opening falls outside what the standard arrangement can absorb, and which openings need a specific solution. Doing this early converts a site problem into a manufacturing and detailing one, which is enormously cheaper.

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   Step 2: Plan the logistics before the first unit is made

   Delivery, storage, vertical transport and horizontal distribution are planned as one exercise. That means deciding what goes up by crane and what goes up by hoist, sizing the units against the hoist car if they are going that way, agreeing the delivery sequence floor by floor, identifying laydown areas on each floor that will not be needed by another trade in the same week, and booking crane and hoist time against the programme. On a tower the crane is the scarcest resource on the project, and a window package that has not booked its slots will not get them. Deliveries are usually made in floor sets so that a crew arriving on a floor finds everything it needs for that floor already there.

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   Step 3: Establish the access and edge protection arrangement

   The method for working at each opening is set before work starts: how the perimeter stays protected, at what point edge protection is removed and by whom, what restraint arrangement the crew works to, and how materials are prevented from going over the edge. Exclusion zones below are established for any operation where something could fall. Where external access is needed for sealing or for the facade interface, the cradle, mast climber or platform is programmed and shared with the other trades using it. This arrangement is what governs how many openings can be worked at once, so the programme is built from it rather than imposed on it.

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   Step 4: Install brackets and take up the structural deviation

   Fixing brackets or a support arrangement are installed to the structure first, set to line and level from the building control lines rather than from the local slab edge, which is itself only accurate to the tolerance it was poured to. The brackets provide the adjustment that absorbs the deviation the survey found, so the unit that follows can be set to the finished line the facade requires. Bracket type, fixing and adjustment range come from the designer for that structure and that unit, and are recorded and inspected before the units go on, because everything above depends on them and nothing above can correct them.

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   Step 5: Land, set and fix the units

   Units are brought to the opening, offered into position and set level, plumb and square on the brackets and packing, then fixed. On a tower the setting is against the facade line for the whole elevation, not just against the opening, because a unit that is individually square but out of line with its neighbours will be visible from the ground for the life of the building. Movement provision at the head is respected where the design requires it, since a frame in a tall building has to accommodate movement in the structure without loading the unit. Each unit is checked square again after fixing and before the crew moves on.

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   Step 6: Seal, interface with the facade and reach the weathertight date

   The perimeter is sealed and the unit is tied into the surrounding facade construction so the weathertight line runs continuously across the whole elevation. The interface between the window package and the facade package is where responsibility is easiest to lose, so the detail is agreed in advance and the sequence makes clear which trade completes which layer. Weathertight is declared floor by floor and is what releases the internal trades, so any opening left incomplete on a floor holds up more than itself. On most tower projects the weathertight date per floor is tracked as a specific programme milestone.

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   Step 7: Fit restrictors, ironmongery and safety related requirements

   Opening lights on residential towers commonly carry restricted opening as a design requirement, and the restriction is designed into the unit and set at installation rather than added later. Ironmongery, locks and any access control provision are fitted to the schedule. Balcony and terrace doors are set and adjusted so they operate correctly under the wind conditions at that height, which is a different proposition from the same door at ground level. Every unit is operated, adjusted and recorded, because access to correct it later on a tower is far more expensive than doing it while the access is still there.

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   Step 8: Test, protect and hand over floor by floor

   Where the specification calls for it, sample openings or completed areas are tested at the stage the designer sets, and results are recorded against the requirements. Installed units are protected for the remainder of the fit out, and the protection is maintained rather than fitted once - on a tower the following trades work in the same space for months. Records are compiled per floor: survey information, bracket and fixing installation, sealing, restrictor settings and testing. Handover of an elevation is by record, and the record is what allows anybody later to know what was installed at the fortieth floor without going back up there.