The Kidwells Estate, a 1960s-built initiative just outside Maidenhead town centre, in Berkshire, is undergoing major regeneration which involves the construction of seven new blocks. These vary from three to six storeys of structural concrete frame and are part timber clad. Long cantilever walkways that service multiple flats on the complex form an unusual feature of the new development and the demands of the walkways presented a technical challenge for the structural thermal breaks used in their construction.
Now known as Parklands, the former Kidwells Estate, is a landmark £27.1 million project, scheduled for completion later this year. It is a scheme for One Housing and in replacing seven 1960s-built apartment blocks, the redevelopment will provide 204 new mixed tenure high quality homes, consisiting of 75 homes for rent to existing and new tenants, nine shared ownership homes and 120 homes for private sale. On completion the development will provide three and four bedroom family homes; as well as one and two bedroom apartments. One Housing manages over 15,000 homes across 27 London boroughs and surrounding counties; and in the last three years has delivered more than 1,500 new affordable homes, with plans to build a further 3,600 by 2019 to help meet the housing shortage.
The unusual construction challenge involving the walkways at Parklands, is brought about because the design consideration, both aestheticaly and for the benefit of residents and visitors, requires as much natural light as possible to be available in the areas around the cantilever walkways.
To meet this requirement, extensive light wells have been introduced at regular intervals along the length of the galleries. These wells are effectively a series of elongated spaces, which separate the walkways from the building for large sections. As a result, there are far fewer structural connection points between the walkways and the building than would normally be anticipated, so the connectivity opportunities are very limited. The walkways themselves being cantilever concrete construction into internal reinforced concrete frame.
Schöck is the supplier of the structural thermal breaks and because of the restricted connectivity point opportunities, the products had to resist a much greater shear load than would be the case with a more conventional design. In addition to this, the support condition of the external columns and edge beams also had to be taken into account and there was a limitation too on slab thickness for the dowel connections.
The solution required a relatively unusual combination of products and the issues were resolved by Schöck designing in its type HPC Isokorb. It is a product utilised only if horizontal, tension and compression forces are present in the design and additionally it is necessary to integrate the type QP90+QP90 Isokorb as well, for linear or point connection to support high shear loads. Schöck type SLD Q50 heavy duty stainless steel dowels were also incorporated to enable the transfer of vertical shear forces and allow two directional lateral movements at the expansion joints. The result was a completely secure thermally insulated load-bearing connection at all of the restricted, but key structural points.
The Isokorb structural thermal break range enables connections to be made between concrete-to-concrete, concrete-to-steel and steel-to-steel – and the many different unit types available, combined with their ability to enable the transmission of shear, bending moment, tension and compression forces, also means that the options available effectively run into hundreds when the different combinations are taken into account.
All units provide BBA Certification and LABC Registration and meet full compliance with the relevant UK building regulations.
The requirement described in BRE IP1/06 – a document cited in Building Regulations Approved Documents Part L1 and L2 and Section 6 in Scotland – that the temperature factor used to indicate condensation risk (fRSI) must be greater than, or equal to, 0.75 for residential buildings, is easily met by incorporating the Schöck Isokorb.
A comprehensive 236 page ‘Technical Guide’ is available, which displays in detail the complete range of thermal break applications for all construction types – concrete-to-concrete, concrete-to-steel, steel-to-steel and concrete-to-timber.
A new free ‘Thermal Bridging Guide’ is also available on request