Nine Year Old School Roof Needs Replacing

A SCHOOL built just nine years ago in 2016 needs its entire roof replacing as it is suffering widespread interstitial condensation.

The single storey building has both flat and pitched roofs, constructed using Structural Insulated Panels (SIPs) and with metal and single ply membrane coverings.

Leaks were reported within five years of first construction and although these were repaired, ongoing damp and mould was observed. In 2024 the rooftop solar PV panels were removed to reduce the structural load on the roofs following engineer advice.

The roofs have had to be supported by 510 acro props to protect the school’s 300 pupils and the playgroup/early years wing has had to be closed entirely to ensure safety.

Pembrokeshire County Council are now devising a plan to relocate the Tenby VC School 3–11-years-old children while the roofs are fully replaced.

Design Flaws

The school’s roofs are a mixture of mono pitched SIP panelled roofs with metal profiled sheets and areas of SIP panelled flat roofs with a single ply membrane covering.

The roof’s problems are thought to be caused in part by their design, created by the Council and its engineer Andrew Scott.

In a report by Lawray Architects, the SIPs’ construction is thought to be causing interstitial condensation. Moisture is thought to have been first introduced during a delay between the SIPs construction and their single ply covering installation to make them watertight.

While the SIPs were said to be dry by the installer before the single ply installation, it is thought moisture was trapped.

The SIP panels are made up of:

• An outer layer of 12mm OSB grade 3 board
• Core of 226mm polyurethane insulation
• Inner layer of 12mm OSB grade 3 board
• Vapour Control Layer (VCL) below inner layer with fire lining plasterboard below in some locations.

The VCL is thought to be ‘sweating’, trapping condensation against the structural board above. This has resulted in the insulation being regularly saturated while OSB layers have become brittle from numerous saturation and drying out cycles with fixings now also corroding.

Members of Pembrokeshire County Council’s Cabinet have now voted for a complete new roof built to traditional construction at Tenby VC school, following examination of the options explored in the architect’s report. A further vote to put the new roof out to tender was taken on 4 November 2025.

A plan to relocate the school’s 300+ children for 18 months while the new roofs are installed will be considered by the Council in January 2026.

>> Read more of the latest roofing news