Liquid and felt systems can both be appropriate. The right choice depends on the deck and existing build-up, moisture condition, detailing, traffic, falls, planned lifespan and site fire controls—not a universal claim that one material is best.
Where liquid can help
A compatible liquid system can form a continuous coating around complex penetrations, upstands and outlets. It is normally applied without a flame, but that does not remove the need for safe systems of work, ventilation controls or product-specific installation conditions.
Where an overlay is unsuitable
Do not assume an existing roof can be covered. Saturated materials, unstable or poorly bonded layers, significant deck defects, trapped moisture, failed drainage or an incompatible substrate may require investigation, removal or a different design. A survey should establish these points before a system is selected.
Compare evidence, not slogans
Ask each tenderer for a roof-specific specification, the product data and certification relevant to the proposed build-up, preparation and moisture findings, details at interfaces, maintenance requirements, programme/weather assumptions and the guarantee terms. Hot-work proposals should be assessed under appropriate fire controls. Read more on our liquid waterproofing service.