Hear from Our Experts: Specifying Balcony Connectors for Safety & Compliance

How early in the design process should structural fixings for balconies be considered to avoid later redesigns or compliance issues?

We would prefer to be engaged as early as possible once the initial design stage is complete, especially for potential bespoke designs, which may require a longer turnaround time and more input. Another key reason for early involvement is to enable us to provide our client with a detailed calculation report and customer drawing, helping to streamline their gateway application process.

What are the common pitfalls you see when it comes to specifying balcony connectors in high-rise / complex residential buildings?

Designing balcony connectors presents several challenges that, if not addressed early, can lead to costly delays or structural issues. Common pitfalls include:

• Limited Anchorage Space: Often, the available slab area for anchoring connectors is restricted, especially in retrofit or high-density designs, which can compromise load transfer and structural integrity.
• Firestop Positioning: Incorrect or late consideration of firestop placement can interfere with connector installation or reduce fire safety compliance.
• Offset Between Balcony and Slab Finish Levels: Variations in elevation between the balcony and the main slab can complicate connector alignment and waterproofing detailing.
• High Applied Loads: Balconies subject to large live or dead loads require robust connector systems, which may not be feasible in constrained slab zones without early coordination.
• Corner Clashes: At building corners, multiple structural and architectural elements converge, increasing the risk of clashes and limiting connector options.
• Congested Slab Zones: The presence of reinforcement, post-tensioning cables, services, and other embedded items can severely restrict the space available for connector installation.

To mitigate these issues, early coordination between structural engineers, architects, and suppliers is essential. This proactive approach allows for optimised connector selection, better integration with fire and thermal detailing, and smoother construction sequencing.

What are the key structural forces acting on cantilevered balconies, and how should balcony connectors be specified to safely manage these loads?

The primary structural demands on balcony connectors typically include moment and shear forces due to dead loads, as well as tension forces resulting from tie action or accidental loading scenarios. In the case of high-rise buildings (HRBs), additional considerations may include uplift forces and minor axis loading, which can arise from wind effects or dynamic building movements.

Design calculations must be carried out in strict accordance with relevant standards and references, ensuring all load cases and structural behaviours are appropriately addressed.

Material selection is also critical. To prevent bi-metallic corrosion, avoid combining dissimilar metals, especially in components that may be exposed to moisture. The fire resistance of the entire assembly must be considered, including insulation, connector materials, and surrounding structural elements.

Finally, it is essential to procure certified materials and implement a robust manufacturing and quality control process to ensure long-term performance and compliance with safety regulations.

How do balcony connectors contribute to achieving high levels of fire resistance in multi-storey buildings, and what classifications should specifiers be looking for?

Materials used in the manufacture of balcony connectors must possess adequate fire resistance to comply with building safety standards. Leviat thermal breaks are fully compliant with the material combustibility requirements of the Building Regulation 2018 with options available that offer REI 120 fire resistance classification.

During the design stage, specifiers must also ensure that appropriate fire barriers are incorporated around the balcony connectors. This is essential not only to maintain the fire resistance of the entire assembly but also to:

• Prevent excessive heat transfer to the balcony’s structural elements, which could compromise their integrity.
• Inhibit the spread of fire between building compartments, supporting overall fire containment strategies.

Why is thermal bridging a concern at the balcony-to-slab interface, and what are the most effective ways to mitigate heat loss in this area?

Thermal bridging at the balcony-to-slab interface can lead to several significant issues:

• Heat Loss – This results in increased energy consumption and higher heating or cooling costs.
• Condensation – Cold spots can cause moisture to accumulate, leading to dampness and mould growth, which may pose health risks to occupants.
• Increased Maintenance Costs – Long-term exposure to moisture and temperature fluctuations can degrade building materials, leading to higher maintenance and repair costs.

To mitigate these risks, it is essential to:

• Incorporate adequate insulation within the cavity, particularly around penetration points.
• Minimise the use of highly thermally conductive materials at the interface.
• Introduce low thermal conductivity materials to create an effective thermal break and reduce heat transfer.

What insulation thickness or thermal performance values are typically required for balcony connections?

In accordance with UK Building Regulations (Approved Document Part L), the building fabric must be designed to minimise thermal bridging and prevent gaps in the insulation layer. 

At the balcony-to-slab interface, this is particularly critical due to the high risk of heat loss and condensation.

Typically, an insulation thickness of around 80 mm is used at these junctions. However, this can vary significantly depending on the project’s energy performance targets. For example, Passivhaus standards often require insulation thicknesses of 120 mm or more to meet their stringent thermal performance criteria.

According to industry guidance, the thermal conductivity (λ-value) of the entire balcony connector assembly should be low enough to ensure that the surface temperature factor (fRsi) remains above 0.75. This threshold helps prevent internal surface condensation and the associated risk of mould growth

To achieve compliance:

• Use high-performance thermal break elements.
• Ensure continuous insulation, especially around penetration points. 

What flexibility exists in balcony connector design to accommodate unusual balcony geometries or architectural detailing?

The flexibility of balcony connector design depends on various parameters, including applied loads, geometry of the structural elements, and finishing levels.

Depending on the specific product and project requirements, several aspects of the connector system can typically be adjusted, such as:

• Vertical and horizontal spacing of anchorages
• Diameter of fixings
• Thickness of the back plate
• Bending shape of the anchor rods
• Bracket section profile
• Addition of stiffeners or reinforcement elements

For projects involving complex or non-standard balcony geometries, Finite Element Analysis (FEA) software is used to simulate performance and optimise the design. This approach helps deliver cost-effective and structurally sound solutions tailored to the client’s needs.

How do connector systems typically meet structural and regulatory requirements such as those outlined in Parts B and L of the Building Regulations?

Balcony connectors must safely transfer loads (moment, shear, tension, and sometimes uplift) from the balcony to the main structure. To meet structural requirements:

• Designs follow Eurocodes, such as BS EN 1990 for structural reliability and BS EN 1992/1993 for concrete/steel components
• Products are often manufactured to BS EN 1090 and other relevant regulatory requirements, which mandates CE or UKCA marking (or other relevant certificates, such as BBA) for structural steel and aluminium components
• Finite Element Analysis (FEA) is used to model complex geometries and ensure performance under various load conditions.

Part B (Fire Safety) requires that materials used in balconies, especially in buildings over 18m, must be non-combustible:

• Balcony connectors and associated components must be made from materials rated A1 or A2-s1, d0 under BS EN 13501-1
• Fire barriers must be integrated around the connector to prevent fire spread and protect structural elements from elevated temperatures
• Manufacturers such as Leviat conduct fire resistance testing to ensure products meet classifications such as REI 120, which covers load-bearing capacity (R), integrity (E), and insulation (I) for 120 minutes.

Part L (Thermal Performance) focuses on reducing heat loss through the building envelope:

• Balcony connectors are a known thermal bridge. To mitigate this, systems incorporate thermal break elements made from low-conductivity materials
• Insulation thickness typically ranges from 80 mm to 120 mm, depending on the building’s energy performance targets (e.g., Passivhaus standards require higher insulation levels)
• The temperature factor (fRsi) must be above 0.75 to prevent condensation and mould growth on internal surfaces.

What practical considerations during construction, such as tolerances or sequencing, should influence how balcony connectors are selected and detailed?

Project-specific tolerance requirements will be assessed on a case-by-case basis, and the detailing of balcony connectors will be tailored to reflect the contractor’s specifications.

The installation sequence of slab-edge structural elements must be carefully planned to ensure, for example, that there is adequate access to fixings and sufficient spacing for tools and personnel. Early coordination between design and site teams is essential to avoid clashes and ensure smooth installation.

What are the benefits of involving a product manufacturer during early design stages? 

As we discussed in question one, early engagement enables a smoother gateway application process for clients by allowing sufficient time for detailed design development and the accommodation of any structural requirements that may arise during the design stages. This is particularly important for complex scenarios where bespoke solutions are needed.

It also allows the manufacturer to plan and execute production under controlled conditions, ensuring on-time delivery and alignment with the overall construction programme.

Moreover, early involvement fosters clearer and more efficient communication among all relevant stakeholders, helping to avoid miscommunication and ensuring alignment across various design and construction aspects.

To find out more about specifying high-performance balcony connectors, including Leviat’s Halfen HIT and Ancon STC (Steel-to-Concrete) and Ancon STS (Steel-to-Steel) insulated connectors, email info.uk@leviat.com or call 0114 275 5224.