Projects / 11/26/2025

Lessons from school roofs

A secondary school’s green roof serves as a place for socialisation and wellbeing

In Esztergom, Hungary, the St. Antal Franciscan Secondary School stands out for its innovative green roof, designed as a space for well-being and social interaction. The sustainable roofing system integrates Polyglass solutions for long-lasting waterproofing and insulation. It is a project that combines technology, energy efficiency, and contemporary educational architecture.

The St. Anthony Franciscan High School and Boarding School in Esztergom, a city in northern Hungary, was founded in 1931 by Marian Franciscan Friars. It soon became an important spiritual and intellectual landmark for the city, reflecting the Franciscan Order’s longstanding presence in Esztergom dating back to the 13th century.

A 4,000 m² extension to the school was completed in 2024. The new structure, built partly underground and spread over five floors plus the ground floor, connects the U-shaped wings of the school and dormitories to create an integrated complex. It houses six classrooms, a gym, an underground car park with 16 parking spaces, a lecture hall, changing rooms and technical rooms. On completion of the work, the school also returned to its original name of St. Anthony Franciscan High School and Boarding School in place of its previous designation of Temesvári Pelbárt High School.

High-performance Plana P elastomeric-plastomeric waterproofing membranes from Polyglass were applied to both roofs of the school.

The choice of a green roof

The new wing has a reinforced concrete structure with infill masonry, a façade covered with clinker, metal window frames and modern technological systems. The architects opted for two types of sustainable roofing: an extensive green roof with a gravel finish over the stairwell and an intensive green roof, or roof garden, above the gym. Together they cover a combined area of about 2,200 m².

The stairwell roof is highly resistant to extreme temperatures and drought and has a strong self-propagation and self-regeneration capacity. It requires little water and minimal maintenance and grows on a substrate consisting of inert minerals and a small quantity of organic matter.

The gym roof recreates a traditional garden with shrubs, flowers and trees. Unlike the stairwell roof, it requires regular year-round maintenance, constant irrigation and a deeper substrate, ranging from 15 cm to 1 m, made up of inert minerals and a higher proportion of organic matter.

In addition to the benefits of sustainability and improved thermal and acoustic insulation, the owner also wanted the roof to function as a community space for students and visitors. For this purpose, it features a walkway, planters, grassy areas, seating and a three-tier outdoor stage.

For the roof on the new wing of the building, the waterproofing layer was installed prior to the thermal insulation.

Waterproofing and thermally insulating

The over 2,000 m² of roofing required high-quality waterproofing to ensure effective, long-lasting protection for both the stairwell and the gym. The contractor selected Polyglass solutions, opting for an inverted roof system in which the thermal insulation is positioned above the waterproofing layer. The main advantage of this approach is that the thermal insulation protects the waterproofing layer from thermal shock and mechanical damage.

Work began with the application of Polyprimer, a fast-drying bituminous primer, to the bearing structure. Acting as an adhesion promoter, it stops dusting and saturate pores in concrete surfaces, allowing polymer bitumen membranes to be laid and applied quickly.

For both roofs, the first waterproofing layer consisted of a 4 mm Plana P elastomeric-plastomeric membrane. On the roof garden, this was followed by a second waterproofing layer consisting of Antiradice Flex P 5 mm elastomeric membrane with excellent resistance to root penetration. On the gravel roof, a second layer of 4 mm Plana P waterproofing membrane was applied.

The next step was the application of a layer of thermal insulation consisting of extruded polystyrene foam (XPS) panels resistant to moisture and stress. Finally, the roofs were completed with gravel and vegetation.

A 5 mm Antiradice Flex P elastomeric membrane was applied as a second waterproofing layer on the roof garden to increase protection against root penetration.

Testing

The quality of the waterproofing was tested by flooding the roofs and monitoring them for leaks, a method that reveals even the smallest defects before they are concealed beneath the vegetation. This ensures long-term waterproofing performance and avoids costly repairs in the future.

In recognition of the high quality of the work, the contractor received the “Roof of the Year 2025” award in the Waterproofing section of the Green Roofs/Functional Roofs category. The project demonstrates how innovative, sustainable solutions can be integrated into a modern school building, creating spaces that are both functional for students and in harmony with the environment.