Kingswood Estate
Client: Elkins Construction
Location: West Dulwich, London, UK
Approved Installer: P J Mear Ltd
Located in the former grounds of historic Kingswood House, these eight 5-storey blocks form part of the larger Kingswood Estate housing development in Sydenham Hill, West Dulwich.
Providing a total of 165 family homes, the blocks date back to the 1950’s and needed extensive upgrading and refurbishment to improve their appearance, address outdated energy standards and generally increase living standards and comfort for their 1000-plus residents.
With energy performance and sustainability major considerations, Southwark Council’s comprehensive upgrading plans included the addition of high performance external mineral wool insulation to improve the thermal performance of the old external masonry cavity walls and provide a base for the rendered façades that, along with new windows and doors, upgraded balconies and extensive internal work, would transform the appearance of the blocks and give them a new lease of life.
The Challenge
Principal contractors, Elkins Construction and specialist concrete repair and external insulation specialists and Helifix Approved Installer, P J Mear Ltd, had to ensure that the existing external walls were in good condition and capable of supporting the additional weight of the new mineral wool insulation slabs and external finishes.
As part of their detailed survey of the external walls, P J Mear found that, although subject to settlement cracking, the brick outer and lightweight block inner leaves were in generally good condition, although construction was not standard throughout, with cavities varying in width, and solid masonry to gable ends. Poor workmanship also meant that wall ties were not correctly installed, with large areas where ties were either not fully bridging the cavity, and therefore providing inadequate embedment depth, or were missing altogether.
Further reinforcement in the form of remedial wall ties was therefore essential prior to the fixing of the 110mm thick external insulation system in order to meet the quality standard required for the SWIGA (Solid Wall Insulation Guarantee Agency) 25-year warranty.
The solution
Having worked together on similar projects in the past, P J Mear called on the support of Leviat to provide a reinforcement solution using their market leading Helifix range of remedial wall tie solutions.
Following extensive tests on the structures, the recommendation was to use Helifix DryFix, a single piece helical tie, in economical grade 316 stainless steel, that is quick and easy to install using a power driver and special installation tool attachment, without the need for time-consuming grouts, resins of mechanical expansion treatment.
The ties, varying around 195mm in length to accommodate differences in cavity width, were sized to provide constant 70mm penetration into the inner blockwork leaf. PJ Mear installed the ties on a 2.5/m2 diamond grid at 225mm horizontal and 300mm vertical spacings across all external wall areas to meet the specified peak velocity parameter of 0.80kN/m2 and minimum proof load of 1kN. Spacings were reduced around edges and window reveals to provide additional performance.
The ties were installed to all eight blocks by specialist PJ Mear operatives, using a simple 5mm pilot hole, which minimised disruption to the structure and enabled the project to proceed quickly once the grid was established.
Leviat design and installation specialists provided technical support throughout the project, including on-site training to demonstrate correct and safe installation procedures to the DBR operatives, who were able to fix the InSkew fixings quickly and easily using a power driver attachment fitted to a standard (SDS) hammer drill.
The Outcome
Following the strengthening work, PJ Mear went on to successfully complete the external wall upgrade, improving the U-value performance from a very poor 0.69 W/m2K to 0.28 W/m2K, successfully meeting the client’s aspirations and improving living comfort for residents.
In addition to the SWIGA warranty, the project received a comprehensive 25-year performance guarantee from Leviat for the reinforcement solution, covering all design, installation and materials.
The outstanding project, designed by architects, Blakeney Leigh, went on to achieve success in a number of award schemes, including Best Mid-Rise Refurbishment for P J Mear in the prestigious 2024 INCA Awards.
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