Cranbrook Primary School Case Study

Appreciating the challenge 

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 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.

Bauder Building Board

Project: Cranbrook Primary School 
Location: London
Project Type: Refurbishment
Roof Area: 440m² 
Client: London Borough of Redbridge Council  
Approved Contractor: Thameside Roofing Ltd 

Systems installed

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. 

BauderPIR Tapered Insulation  

BauderPIR Tapered Insulation is a lightweight and costeffective 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) 

BTRS is a two-layer bitumen system robust enough to withstand foot traffic and most permanently sited plant. It can be used in warm and cold roof designs and also to overlay 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.  

Challenges and Considerations 

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


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. 

System build-up

Bauder Total Roof System (BTRS)

1 K5K cap sheet in Charcoal Grey A top quality, torch-applied SBS elastomeric bitumen capping sheet featuring a spunbond polyester reinforcement and a mineral finish.
2 BauderTEC KSA DUO 3mm thick technically advanced selfadhesive elastomeric bitumen underlayer with DUO lap technology and glass lattice reinforcement.
BauderPIR FA Tapered Insulation  A cost-effective alternative method of providing falls to a roof. 
4 BauderTEC KSD Mica  A technically advanced, self-adhesive SBS elastomeric bitumen air & vapour control layer. Easy bonding of insulation using the specified Bauder Insulation Adhesive. 
Contact us to discuss your flat roof project