Skelton Motorway Services - Kemper System Ltd

The extensive wildflower meadow green roof (designed and installed by ABG and Geogreen Solutions) forms the main feature of the amenity building. The roof structure is made up of a series of interconnected glulam beams, constructed from layers of timber boards glued together. The process allows the beams to be shaped into undulating sections, with curved radii down to 9m possible. The curved beams are spanned using structural deck cassette panels of 20mm thick, in 3 layers. 
 
The Kemperol cold applied liquid membrane (installed by Cawston Specialist Roofing) is applied to the timber panels to give a fully adhered, monolithic waterproofing which is root resistant for the green roof planting and encapsulates the surface to preserve the timber deck and protect it from weathering. Cold liquid applied systems offer a rapid cure time, even in winter when the initial roof structure was installed, and provide a life expectancy of up to 25 years. The green roof system installed protects against UV damage as well, so that an extended warranty can be offered. 
 
A 180mm thick Polyfoam XPS insulation board and water flow reducing control layer is installed directly onto the waterproofing to complete the inverted warm roof build-up. The insulation was ballasted during the install to prevent uplift prior to the green roof installation. 
 
For the base of the living roof structure, a combination of 20mm and 40mm deep ABG Roofdrain multipurpose reservoir and drainage geocomposite is installed directly onto the Polyfoam water flow control layer and XPS insulation. The Roofdrain geocomposite includes an integral geotextile bonded to the top of the board to filter soil particles and prevent the drainage core from becoming blocked, with another geotextile underneath as a secondary filter and protection layer.  
 
The ABG Roofdrain is purposefully designed for green roof applications and facilitated the installation of the design since it is a flexible product that conforms to the undulating contours of the building. The main core structure of the Roofdrain HDPE reservoir board features a grid of storage cups to attenuate storm water and provide irrigation to the wildflower and sedum plants during dry weather. In between the cups are small drainage holes that allow water to drain through during periods of wet weather and to prevent the soil from becoming waterlogged. The geocomposite is supplied in 920mm wide x 50m long rolls, with 110 installed in total for the Skelton Lake green roof. 
 
During the next phase of construction, a biodiverse growing media mix is deposited onto the geocomposite drainage layer and levelled out to 100mm. The material is light-weight to minimise loading and formulated to retain moisture with recycled brick to aid the absorption of rainwater. 
 
To complete the roof structure a total of 4,622m2 of meadow planting was provided by Wildflower Turf Ltd and included 34 different wildflower species. The turf was locally grown to be compatible with the local region and species character profile. The turf was supplemented with 14,200m2 of wildflower seed to encourage development and density of the meadow and pollination of the wider landscape. This meets the conservation objectives of the green roof to integrate the development with its surroundings and enhance the biodiversity and ecological value of the area, whilst providing native grassland for birds and insects.  
 
Challenges included working through prolonged spells of wet weather during the winter of 2019 / 2020. At times this created conflicts and delays due to site access difficulties, requiring daily meetings and re-scheduling with the main contractor and other subcontractors during this period. Further challenges also had to be overcome once the COVID working directives were imposed on site.