A unitised curtain wall arrives as large, factory-assembled panels that are already glazed, sealed and finished. That is its main advantage: less work on site, in a controlled quality environment. It is also its main logistics problem. Every panel is a big, heavy and fragile object that has to be packed, driven through city traffic, lifted past other work and set accurately against a neighbour. This article sets out what that involves, so that the questions can be asked before an order is placed.
Panel size is set by the route as well as the factory
A designer may draw a panel the full height of a floor and as wide as the module. Whether that panel can actually reach the building depends on the vehicles, the roads, the gate and the lift or crane that will carry it. The largest panel the factory can make is not always the largest one that can be delivered.
Ask the manufacturer for the maximum panel size and weight that their transport and handling allow, and compare it with the panel schedule. If an access road, a tunnel or a low bridge on the route limits size, it is cheaper to split the panels in design than to discover the limit when the first truck is stopped.
Packing and protection
Panels are normally packed upright in racks or frames made for the purpose, with soft protection between units and at corners, and with the glass and finished surfaces covered. They are secured so that they cannot rub against each other on the road. Damage most often happens at the edges and at the glass corners, which is where protection should be checked.
Ask how the packing is labelled so the right panel can be found without unpacking the wrong ones, and whether the labelling matches the installation sequence. A panel that has to be dug out from the back of a rack is a panel that has been handled twice. Spare units should be packed and recorded separately, so replacements are not mistaken for sequence panels.
Inspection on arrival is the point at which responsibility is clearest. Check each delivery against the packing list, look for damage to glass, finishes and seals, and photograph anything doubtful before the panel is unpacked or moved. A defect reported at the gate can be resolved between supplier and carrier. The same defect found after the panel is on the fifteenth floor is much harder to deal with.
Delivery sequence and storage
Panels should reach the site in the order they will be installed, with a small buffer so that a delayed truck does not stop the crew. That means the factory's production order, the loading order and the installation sequence should be the same list. If they are not, panels are reshuffled on site, which takes time and increases the chance of damage.
Most sites have little space. A panel may be unloaded and lifted straight to its floor, stored upright in a protected area inside the building, or held on the vehicle until needed. Each has costs. Storage on a slab means the slab must be strong enough, and other trades must be kept away. Direct lifting from the truck needs close timing and a road that can be blocked while it happens. Choose with the site team and write it into the programme.
Lifting: crane, hoist and the lifting points
A crane can lift panels directly from the delivery vehicle to the face of the building. A mast-climbing platform or a hoist is also used, particularly on tall buildings or where crane time is short. A small crane or an internal hoist may move panels along a floor. The choice depends on panel weight, height, wind exposure and what else is happening on site.
Panels are lifted with a spreader or frame that attaches to dedicated lifting points on the panel or its frame. These points are designed for the panel, and they should not be improvised. Ask the manufacturer for the lifting method and check that it is compatible with the equipment on site. Wind is a real constraint on a large flat panel hanging from a crane, and a lift plan should say what wind condition stops work.
Safety is part of the same plan. A hoisted panel needs an exclusion zone below, trained riggers and signallers, and a clear way of communicating between the crane operator and the people at the face of the building. Work at height, edge protection and the way panels are held while they are being fixed should all be written down in the method statement and understood by the crew, not just filed.
Setting the panel against the anchor
A panel is hung from or fixed to an anchor cast into or fixed to the slab. The installers guide it into place, adjust it in three directions and lock it. Adjustment is designed in, to absorb building tolerance, but it is not unlimited. If the anchor is out of position by more than the system can accept, the panel cannot be set correctly.
That is why anchor positions are surveyed before the panels arrive, and why the survey is shared with the facade contractor in time to correct a problem. A late discovery that anchors are out of position can hold up a whole floor. The sequence of site work is covered in the facade installation sequence on site.
Interface with the neighbouring panels
A unitised wall relies on joints between panels that are sealed and drained, and on the panel above and below being in the right place. A panel that is set slightly out of line carries the error into its neighbour. Installers therefore set, check and adjust each panel before it is released from the hoist.
Check that the joints are clean before panels meet, that the seals have not been damaged in transit and that the drainage path is clear. The differences between unitised and stick systems, including how joints are formed, are explained in stick versus unitised curtain wall.
Tolerance is worth a separate conversation. The slab edge, the anchor and the panel each have a permitted variation, and those variations add up. A panel that is perfect in the factory can still be difficult to set if the structure behind it is out of line. Agree who measures what, when the readings are shared and who decides whether a panel is shaved, shimmed or re-ordered. That decision is far easier to make before the panel is hanging from a crane.
Weather, wind and working windows
Large flat panels catch the wind. Lifting stops when the wind on the face of the building makes a panel hard to control, and the limit depends on the panel, the equipment and the rigging. Rain adds its own problems: wet surfaces are slippery, open joints take on water before they are closed, and glass edges and seals should not be left exposed to weather longer than necessary.
Plan the programme with some allowance for lost days, particularly in monsoon or high-wind seasons. If installation is being sequenced around weather, the delivery plan must be flexible too, so that a day of lost lifting does not become a pile of panels with nowhere to go. The contractor should say what weather stops work and who makes the call.
Night working or early starts are sometimes used where roads or crane time are restricted. These bring their own needs for lighting, noise control and permits, and should be discussed with the neighbours and authorities early, not announced on the morning of the first delivery.
Use the mock-up to rehearse the handling
A mock-up is usually seen as a check of appearance and performance. It is also a chance to rehearse handling. Ask the manufacturer to pack, move and lift a panel using the proposed equipment, then to set it against the mock-up frame. Problems with lifting points, packing and edge protection appear at this stage and are cheap to fix. More on the review process is in facade mock-up review.
Questions to settle before ordering
- What is the largest panel the transport route and the site can accept?
- How are panels packed, labelled and protected for transit?
- Is the delivery order the same as the installation order?
- Where will panels be stored, and is that area strong and protected enough?
- What lifting equipment and lifting points will be used, and what wind limit applies?
- Who surveys the anchors, and when is the result shared?
General guidance for orientation, not a specification. Applicable standards, values and details are confirmed per project with the facade consultant.
