Choosing a flat roofing system is rarely just a product decision. The existing roof condition, required lifespan, insulation, fire strategy, access, drainage and disruption to occupants all affect the best answer.
A good specification starts with a proper survey. Before choosing between felt, single ply, liquid applied systems or an overlay, the team needs to understand what is already there and whether it is dry, stable and suitable to receive the proposed build-up.
Built-up felt roofing
Built-up felt remains a proven option for many commercial roofs. Modern systems can provide reliable waterproofing, robust detailing and clear warranty routes when installed correctly. They are often well suited to roofs where durability, access and familiar detailing are priorities.
The method of installation matters. Torch-applied systems require careful risk control, while self-adhesive and cold-applied options can be more suitable in sensitive areas.
Single ply and liquid applied systems
Single ply membranes can be efficient on larger, simpler roof areas where sheet layout, laps and fixing strategy are straightforward. They can be particularly useful where weight and speed are important considerations.
Liquid applied systems are often strongest around complex details, gutters, balconies, plant zones and refurbishment areas where a seamless finish is useful. As with any system, preparation and compatible substrates are essential.
Do not ignore insulation and drainage
A roof renewal is often the right moment to review insulation, vapour control, rooflights, outlets and falls. Improving the waterproofing without considering thermal performance or drainage can miss an important opportunity.
The right flat roofing system is the one that fits the building and the client brief. It should be buildable, maintainable and clearly documented, with enough thought given to how the roof will perform after the site team has left.