Waterproofing Systems for Rooftops

An exposed membrane is left directly exposed to UV, rain, and temperature - it must be UV-stable and self-protecting. A buried (inverted or concealed) membrane is protected by insulation, paving, or growing medium above it. Exposed membranes require polymer-modified systems with UV stabilisers; buried membranes may use a wider range of cementitious products. The application determines the product selection - our technical team confirms the correct system for your rooftop assembly during specification.

Refurbishment applications over existing membranes require careful assessment: adhesion of the existing system, presence of water trapped beneath it, structural capacity for the additional layer weight, and compatibility between the existing and new membrane chemistries. In some cases, the existing membrane must be removed; in others, overcoating is possible with appropriate primers. Gemite's technical team provides on-site assessment and refurbishment recommendations - contact us with details of your existing system.

Building regulations and roofing standards typically require a minimum fall of 1:80 (approximately 1.25%) on flat roofs to ensure drainage and prevent prolonged ponding water. However, Gemite's waterproofing systems are designed to remain watertight even under standing water conditions - the minimum slope requirement exists to protect the roofing assembly as a whole (thermal performance, load distribution) rather than because the membrane itself fails under ponding. For rooftops with inadequate drainage falls, our technical team recommends additional drainage layer solutions in combination with the waterproofing system.