Cranbrook Primary School in Ilford, London, was experiencing some major water ingress due to the advanced deterioration of the existing roof system. A roof survey was conducted by Stuart Parratt, Bauder area technical manager, where core test samples were taken to identify the existing roof construction to deck level and to provide an indication of the roof condition. The survey revealed that the existing waterproofing was in extremely poor condition, with extensive evidence of water ingress.  

The specification

The original waterproofing had been poorly overlaid with EPDM which had subsequently debonded. Before the installers could begin laying the new system, they had to strip the substrate back to the original asphalt. The client required a robust system that would deliver durability, value and longevity. 390m² of bitumen waterproofing, Bauder Total Roof System (BTRS), was specified for the main roof areas and 50m² of our cold applied liquid waterproofing, LiquiTEC, for an area that had limited upstands due to clerestory windows that could not be repositioned. 

Products applied

BauderPIR tapered insulation:
A lightweight and cost-effective alternative method of providing falls to a roof, whilst also providing thermal insulation. The client opted for this scheme at Cranbrook to minimise standing water on the roof. 

Bauder Total Roof System (BTRS):
A two-layer bituminous waterproofing system robust enough to withstand foot traffic and most permanently sited plant. For use within warm and cold roof scenarios, as well as overlaying existing roofing materials. BTRS meets current UK Building Regulations Part B for external fire protection and features torch-free and safe to torch installation on combustible details. 

LiquiTEC Cold Applied liquid waterproofing:
Utilising Bauder’s PMMA cold applied liquid waterproofing on one of the roof areas ensured a fully watertight solution around rooflights and below upstands that could not be raised.  

Project challenges

Although the deck appeared to be in a reasonable condition for reuse as part of the refurbishment, there were large deflections in some areas and the existing waterproofing that overlaid the original system had been poorly installed and had pulled away from the asphalt below so needed stripping before works commencing. 

The existing insulation was inadequate and left the building falling short of the current requirements. A thermal upgrade was incorporated into the works using a tapered insulation scheme which helped to solve the deflection issues by creating falls on the roof. To meet the minimum upstand requirements, the existing extractor vents needed to be removed to allow for an increase in the kerb height. Large continuous structural rooflights providing natural light to the building below were deemed thermally inefficient. The rooflights were upgraded during the refurbishment to meet current standards. 

The result

Bauder systems are only installed by Bauder approved contractors to ensure quality. The installation on this project was expertly carried out by Thameside Roofing Ltd, overseen by Dave Gregory and John White. After sign-off from Bauder site technician, Paul Osbourne, this system was awarded a comprehensive guarantee. 

Bauder Total Roof System (BTRS) with Tapered Insulation