Steel balconies

A common design feature in the UK is to connect a steel balcony to an interior concrete slab. Schöck Isokorb® type KS is the solution which thermally separates the exterior balcony from the interior slab. The main body of Schöck Isokorb® type KS consists of 80 mm thick EPS insulation. It offers high thermal resistance by using stainless bars to act as tension, shear and compression reinforcement.


Figure 16: Schöck Isokorb® type KS for steel balconies.


Figure 17: Typical residential building, supporting structure made of concrete. Steel balconies are thermally broken by Schöck Isokorb® type KS.

A modelling study was undertaken by Oxford Brookes University to determine the effectiveness of Schöck Isokorb®. The aims of this investigation were to determine the heat loss, minimum surface temperature and hence temperature factor (fRsi) resulting from use of Schöck Isokorb® type KS14 units connecting a steel balcony support to a concrete floor slab. To simulate the real life situation for a balcony, the study included the glazing element as part of the building envelope.


Figure 18a: Wall construction with a direct steel balcony connection.


Figure 18b: Schöck Isokorb® type KS14 installed in construction.

Further information about the boundary conditions and the thermal conductivity of the used components can be found in reference 3.


Figure 19a: Direct connection (Case 1): temperature distribution (section)This detail does NOT conform to UK Building Regulations Part L requirements for minimum temperature factor in dwellings (fRsi = 0.75)


Figure 19b: KS14 H200 connection (Case 4): temperature distribution (section). This detail conforms with UK Building Regulations Part L requirements for minimum temperature factor in dwellings (fRsi = 0.75)

From table 2 it can be seen that the KS14 unit, with fRsi = 0.90, exceeds the minimum temperature factor value cited in IP1/06 (fRsi = 0.75) and will therefore meet the requirements of Building Regulations Approved Documents L1 and L2. The construction without a thermal break does not meet the temperature factor value required for dwellings. The heat loss by incorporating Schöck Isokorb® KS is reduced by almost 70%.


Figure 20: Schöck Isokorb® type KS incorporated into the interior slab. Steel balcony to be installed afterwards.


Table 2: Thermal modelling results