Overview

Newton Close is situated in North London on the banks of The New River.  The New River was an artificial waterway opened in 1613 to supply London with fresh drinking water and runs from its source in Hertfordshire to its original end in Islington, London.

The design concept of this project focuses on the demolition of an existing building and replacing it with a new build mixed use development of 6 storeys (plus basement) comprising of 9 self-contained units (8 x 2 bed and 1 x 3 bed) on floors 1-5 and 377sq m of commercial space on the basement and ground floors.

During the Phase 1 Primary Risk Assessment, borehole and trial pits revealed Dibenzo (a,h)anthracene, CO², TPH and Asbestos contamination.

Delta and MemTech Registered Installers, Renlon were called upon to offer a solution to this property, taking into consideration the proximity of The New River and the risk from ground gases.  The proposed remedial strategy to be adopted at the site was one of managing the pathway between the source of contamination and the critical receptors on-site.

Renlon’s specification combined both waterproofing and ground gas remediation which satisfies BS 8102:2009 and BS 8485:2015+A1:2019 and would be able to meet verification requirements in accordance with CIRIA C735.

Ground gas protection systems can be installed standalone or combined with a waterproofing system when a twin system is required, this rapid cost-effective installation is compatible with all types of construction.

Methodology

Phase 1

A Koster Polysil TG 500 priming coat was applied to the new concrete slab to reduce the risk of excess free lime leaching out during the curing process followed by 2 applications of MemTech Pro Liquid Gas Barrier “LGB” to the floors and walls of the basement to seal the entire underside of the building.

In advance of the Delta waterproofing system being installed, the drainage channel area (perimeter channels) was reinforced with MemTech Flexi Tape.

MemTech LGB is a ready for use specialist styrene butadiene latex based liquid applied gas membrane. It offers a simple, continuous passive gas prevention barrier against the ingress of Methane, Carbon Dioxide, Radon, Ground Gas, VOC, air & moisture into buildings.

MemTech LGB complies with the latest codes of practice as published by BR211, CIRIA and BSI (BS 8485:2015+A1:2019). Suitable for use as gas protection for NHBC GREEN, AMBER 1, and AMBER 2 site characterisations.

Prior to the installation of the Type C Cavity Drainage System, the installation of the ground gas membrane was tested and verified.  The technician attending site to verify the gas membranes was incredibly impressed with Renlon’s specification and installation.

Phase 2

The Type C system comprised BBA certified Delta MS 20 cavity drain membrane to the floor and BBA certified MS 500 cavity drain membrane to the walls. Perimeter channels which had previously been treated with MemTech LGB and MemTech Flexi Tape to house Delta’s Channel drainage conduit.  Channel drainage conduit diverts any water entering behind or beneath the membranes. To allow for maintenance of the system, access ports were installed to the Delta Channel every 10 linear metres.

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Case Study Results

Renlon in adopting a simplistic approach and designing a robust solution to both the ground gas contamination and high water table were able to undertake site works which were performed in accordance with methods given in BS 8102:2009 and BS 8485:2015+A1:2019 and that met verification requirements in accordance with CIRIA C735.

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