Nov 20, 2017 Last Updated 2:18 PM, Nov 16, 2017

Building better lifecycles into the spec

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Stuart Hicks from cold-applied liquid waterproofing specialist, Kemper System, discusses the roofing system at ‘The Mount’, a mixed scheme of private, affordable and social housing at Millbrook Park, North London.

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Millbrook Park is a multi-developer residential scheme in the Mill Hill area of the London Borough of Barnet, designed to create a new community of 2174 homes alongside a range of facilities, including a new primary school and almost six hectares of parks and open space.

Amongst the individual projects being delivered at the development is ‘The Mount’, which comprises a mix of low rise apartments and town houses. The variety of property styles reflects a mix of ownership options, including private sales, affordable units and social housing.

While the affordable and social housing units are slightly smaller than their premium neighbours, the specification of materials varies very little. The roofing scheme delivered by contractor, Cawston Roofing, using Kemper System’s Kemperol V210 cold-applied liquid membrane, is a prime example of this and demonstrates an investment in delivering robust social housing with excellent lifecycle values.

Mixed development

The eight four-storey blocks constructed as part of The Mount have just two apartments per floor, with the addition of a penthouse apartment in blocks A, E and F. The biggest difference between the private and social housing apartment blocks is that only the apartments offered for private sale have a lift. All eight blocks have the same roofing specification however, with a brown roof, incorporating a Kemperol V210 membrane and a solar PV installation.

The development also includes four blocks of three-storey town houses, all of which have balconies at level one, which alternate between the front and the back of the properties to avoid being overlooked. Of the 41 houses within the scheme, properties numbered 30-41 comprise the social housing element, with a smaller footprint but the same waterproofing specification for the balconies.

Inverted roof build-up

The roof build-up for the apartment blocks has been installed as an inverted warm roof, with the waterproofing membrane applied beneath the insulation.

Cawston Roofing first applied Kemper System’s Kempertec EP5 Primer onto the concrete substrate, allowing it to cure before applying the Kemperol V210 resin system in a single wet-on-wet process. The liquid resin was first applied to the substrate using rollers with Kemper System’s 165g flexible reinforcement fleece laid into the wet resin, immediately followed by more resin on top to ensure complete saturation of the fleece. The system was then allowed to cure, forming a monolithic waterproof membrane that is durable, permanently elastic and cannot delaminate.

The use of an inverted system provided a number of advantages in this scheme: firstly Cawston Roofing was able to check the integrity of the waterproofing membrane installation before moving on to the installation of the brown roof build-up. This allowed other trades access to the site to begin work on the interior fit-out whilst other elements of the roofing work continued. The installation of a double thickness of 180mm XPS (extruded polystyrene) insulation on top of the waterproofing membrane also helps to protect it from continuing construction activity on site. The use of the Kemperol membrane also avoided the need for an additional fleece layer as part of the brown roof build-up because Kemperol V210 is certified as root resistant.

The roofs of the apartment blocks were completed with the installation of a slimline deflection membrane on the insulation layer, before paving slabs were laid in the central rectangle of each roof as a base for the solar PV panels. The brown roof was then installed around the perimeter section of each block, with a reservoir board followed by a pre-seeded 120mm thick growing medium with local plant species and an undulated profile to encourage maximum biodiversity.

The Kemperol V210 membrane was also used to waterproof the upstands on the apartment block roofs, some of which are as much as 1.3m tall. These were then concealed using insulated cement board, in line with the aesthetic vision for the scheme.

Terraces

The same inverted system was used for the apartments’ terraces, with a lighter 140mm insulation installed onto the Kemperol V210 membrane, followed by the deflection membrane and paving slabs.

The town houses feature pitched roofs with a zinc finish, but still required waterproofing using Kemperol V210 for the level one terraces, which alternate between south and north-facing along each block.

Here, the substrate was ply so Kemper System’s D primer was used and allowed to cure before application of the Kemperol V210 liquid resin – fleece – membrane system. There was no requirement for insulation on the town house balconies and the completed membrane has been concealed beneath timber decking.

Cohesive community

The first apartments are now complete and occupied with the remainder set to follow shortly. The similarity in specification between the private and social housing units on the same site will contribute to creating a cohesive community as new residents settle into their new homes.

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