Overview

Prince Henry’s High School in Evesham is an Ofsted ‘Outstanding’ Academy for students aged 13-18 that has worked collaboratively with chartered building consultants, PR Associates, and CARLISLE Construction Materials (CCM), to secure a Condition Improvement Fund (CIF) grant for a roof upgrade.

The project involves a thermal upgrade to three roof areas, totalling 1100m², along with an overlay with RESITRIX hybrid membranes; a single layer system that combines the robustness of bitumen and flexibility of EPDM. The roof refurbishment also involves improvements to drainage to address issues with ponding water.

Despite the challenges of the pandemic, the project is now well underway, with phases 1 and 2 complete, and phase 3 is due to take place during the summer break.

CIF Funding Bid

The school campus is typical of many high schools, with multiple additions to the original main building. Consequently, there are a number of different roof levels and roof areas in varying conditions, with a mix of existing coverings that had reached the end of their service life. In some areas, the roof was leaking and a small roof area over the main entrance was in need of particularly urgent attention because the rain was draining onto it, resulting in ponding water.

The chartered building consultant worked with CCM to develop a technical specification, which contributed to Prince Henry’s High School’s CIF application.

“We often find that a collaborative approach between the school, the building surveyor and our technical team at funding bid stage is instrumental in outlining the business case for a CIF grant,” explains Allen Coldrake, technical director at CCM. “Carrying out a full condition survey and providing a technical specification at this stage ensures that the bid considers the full scope of works and that the school makes decisions that will reduce future maintenance costs and disruption.”

The Project

The project involves a thermal upgrade to all three roof areas, along with an overlay of the RESITRIX system and improvements to drainage to address the issues with ponding water. As part of the refurbishment, tissue-faced insulation was specified for installation directly onto the existing roof surface. For the phase 1 and 2 roofs, a 130mm flat insulation board has been specified, but a tapered insulation scheme will be used for the phase 3 roof due to issues with drainage, which have been causing ponding water.

Following the installation of the insulation, CCM’s FG 35 primer is applied directly into the insulation board and the 1 x 10m rolls of RESITRIX membrane are rolled out onto the roof. Once the membrane is in place, the AJR team peel back the release film and the membrane bonds to the primed insulation on contact, with no requirement for heat activation or mechanical fixings.

For each roof area, the roofing contractor AJR cleaned and prepared the existing roof surfaces, cutting out blisters and carrying out patch repairs where required. CCM’s technical team then carried out penetration tests to ensure there was no water tracking under the existing coverings and, once checked the existing roof covering was used as the air and vapour control layer (AVCL).

Allen Coldrake adds further: “Compatibility and ease of installation as an overlay are key advantages of the RESITRIX system. This is particularly important for school roof refurbishment projects because it helps to reduce the length of the programme and potential disruption by avoiding strip-out, provided the existing covering is properly prepared. Using the existing covering as the AVCL also saves time and cost and RESITRIX only needs a primer and a single layer to complete the new roof covering.”

The specification requires a 50mm lap for the join between each 1 x 10m roll of RESITRIX laid out onto the roof. Each lap must be sealed using a hot air welding tool and, for this project, an automatic welding tool is being utilised, following a test weld. The roofs involve a range of details, including roof lights (which are being replaced), drainage outlets, a parapet wall and a tank room. A number of rainwater/ overflow outlets will also be installed to CCM installation guidelines. For most details, the AJR team can use offcuts of the membrane to form these details because the RESITRIX material bonds to itself.