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Curtain Walling Fixing Methods

A very large number of buildings constructed in the Middle East region in the past 25 years have used curtain walls as their external facades, indeed some of these have become iconic buildings of the region and known throughout the world. Many of these buildings have been constructed using in situ cast concrete frames and floor slabs, which has allowed the curtain walling to be fixed using traditional expanding anchors or cast in fixing channels in the face of the concrete.

The various methods of building construction are changing and increasingly steel frame construction is being used. This form of construction increases the speed of erection and very often incorporates trapezoidal steel permanent formwork to support the concrete floor slabs while curing.

In such floors the edges are supported on steel beams and the thickness of the slab is often only 160 mm at the thickest part and 80 mm in the thinner parts. Such floor slabs do not allow fixing into the edge to be used and as many Middle Eastern buildings do not have raised access floors or even screed on top of the slab, this creates the problem of where exactly the curtain walling fixing can be located.

One option is to locate the fixing on the steel beam, (see diagram below) however in many instances the steel beam is set back from the edge of the slab and this creates a number of problems:

A popular method to overcome these problems that has been used elsewhere in the world is to incorporate a continuous fixing channel in the angle pour stop at the edge of the concrete. Whilst this may at first appear to be a more expensive method, the greatly increased speed of installation of the curtain wall system more than offsets the increased initial cost. If we also consider the major cost benefits to other construction trades on the building the savings in time, manpower, equipment and subsequent costs make this a much more economical solution to the building costs overall. Alternative methods of curtain wall fixing are likely to be significantly more expensive to the total cost of the building.

The pour stop system incorporates a continuous fixing channel, which is anchored back into the body of the concrete slab and because it is continuous there is no risk that the fixing will be incorrectly positioned.

Some of the advantages that such fixings offer are:

The benefits of such construction methods are significant with the commonly used stick curtain walling systems. However in recent years unitized curtain walling systems have become more widely used and in order to fully benefit from the advantages of the rapid erection that these systems offer, the fixing brackets need to be installed quickly and with sufficient allowance for adjustment to allow the panel to be positioned to the millimetre. The installation of unitized curtain wall systems requires such fixing methods to ensure the full benefits of these systems are enjoyed.

Planning

The key to making such innovations work is planning. Very often the curtain walling contractor is not involved in a project until the frame of the building is well advanced and it is too late to incorporate fixing channels within the pour stop. Therefore it is essential to establish if such fixings will be required for fixing the curtain walling (or similar types of facade construction) early in the construction of the main building frame. This requires the main contractor and the curtain wall contractor to be communicating and co-operating at an early stage in the building construction.

Check

If the answer to the following questions is yes then it is likely that pour stops with integral fixing channels will be an advantage and will ultimately result in cost savings on the project:

If the conclusion is that a pour stop with an integral fixing channel is required then the next stage must be to discuss the requirement early, either with the curtain walling subcontractor or the structural engineer, who can advise specifically on a project by project basis and thus ensure that pourstop channels are incorporated into the concrete casting programme.


Typical Fixing Diagram top
Marina Diamond Project