Construction + Civil Engineering

Properly selected mechanical fasteners ensure the stability of thermal and waterproofing layers, which is particularly important in the context of the loads that can occur on flat roofs. The GLP Warsaw VI Logistic Center has become the first of its kind in Poland to use glulam for a roof’s load-bearing structure, with a set of specialised LINO-13 fasteners with WSR-T screws from Klimas.

Flat roofs are a special type of construction that require detailed calculations due to their structural characteristics, exposure to dynamic loads, as well as the need to comply with building standards. These roofs are often exposed to wind, precipitation and temperature differences, which can lead to the separation of materials. The right fasteners, selected by construction standards and the specifics of the site, help minimise the risk of damage.

Not only the type of fasteners but also their number and placement are important for fastening efficiency. By separating the zones on the roof – corner, edge and centre – the placement of fasteners can be better adapted to the specific loads that occur in each location. The use of more fasteners in the corner and edge zones, where the forces acting on the roofing are strongest, is crucial to ensure safety.

Proper selection and placement of fasteners is also an economic issue. Too few fasteners or their improper use can lead to serious failures, resulting in costly repairs. In the long run, investing in the right fasteners and their correct placement translates into a reduced risk of waterproofing problems, which significantly reduces building operating costs.

In the context of the design and construction of flat roofs, the key issue becomes the correct calculation of acting forces by the current standards, which define both the calculation methodology and the criteria for assessing the safety of the structure. Particularly important is the PN-EN 1991-1-4 standard “Actions on the structure – wind actions”, which is the foundation for determining the value of suction forces and other wind actions affecting the integrity of the roof.

Another important aspect is to determine the strength of the mechanical attachment of the roof system. In this context, it is important to pay attention to three key elements that determine the safety of the entire system. 

First, the fastener’s pull-out strength, according to EAD 030351-00-0402 guidelines, requires testing to determine what loads the fastener can withstand before it is removed from the ground. Second, the strength of the bushing screw connection requires an assessment of whether the connection is strong enough to withstand the anticipated loads. An improper connection can lead to failure of the fastening system. Third, the resistance to pulling the sleeve through the waterproofing material, according to EN:16002, involves conducting wind uplift tests to assess how the sleeve behaves in the face of wind loads. These tests provide information on the effect of forces acting on the roof on the integrity of the waterproofing material.

Taking load-bearing values obtained from wind tests, such as wind uplift tests, into calculations is key to the safety of the entire facility. These values take into account not only theoretical calculations but also the ‘real world’ effects of wind loading and the interactions between the various components of the attachment system. As a result, designers are better able to protect the roof from potential damage, which in turn gives investors confidence that facilities meet normative requirements.

For the GLP Warsaw VI Logistic Center project, Klimas provided a design for the division of a flat roof into wind zones with a set of fasteners for the installation of thermal and waterproofing on the roof slope – a completed LINO-13 sleeve with a WSR-T screw. 

Marcin Duzik, global market development director at Klimas Wkręt-met, highlights: “Thanks to detailed, specialised calculations, we were able to provide the customer not only with a product that meets the stringent requirements for this type of construction but also to ensure its correct application adapted to the shape and geometry of the roof, dynamic loads, as well as sensitivity to local climatic conditions.”

He concludes: “One of the key elements of this project was the precise definition of wind zones. Every section of the roof had to be analysed in terms of the specific loads that may act on it. This made it possible to optimally select the number of fasteners, which in turn translated into the safety of the entire structure.”