Heat-applied bituminous systems offer cost-effective protection for flat roofs, with relatively low material costs and life up to 25 years.
However, installation and replacement issues are increasingly driving specifiers to seek alternatives.
One main issue is disruption. The presence of hot tar means the top floor cannot be occupied during installation, while the smell can permeate, disrupting occupants.
Furthermore, these systems use flammable materials, necessitating a dedicated fire marshal, adding to cost. The presence of heat-producing equipment also necessitates training while raising insurance costs.
Meanwhile, the climate can halt the job – if rain occurs during installation, the felt is left effectively unsealed and prone to leaks.
Single-ply membrane systems pose no fire, heat and odour problems. However, protection is governed by the quality and application of the bonding adhesive used. Meanwhile, strong winds can force apart the roof surface and membrane before the adhesive sets.
A further issue is uneven roof surfaces or obstacles like chimneys, vents and aerials. These require the membrane to be cut and stuck down, with inaccuracies creating water ingress opportunities.
Single-ply membranes are designed to be laid with their edges butting up to each other. However, if timber supports in the roof expand, the membrane sheets can be pulled apart.
Single-ply membranes can also be damaged by ladders or scaffolding placed onto the roof – and there is no guaranteed way to repair a damaged membrane.
Finally, a problem of both bituminous systems and single-ply membranes is disposal, with landfill often the only solution.
A third alternative is cold-applied liquid membranes. These are generally water-based, meaning no disruption to building occupants. Their ease of application requires no special training, while they form an intrinsic chemical bond with the substrate, offering optimum protection. As they are brush or roller applied, they can cope with obstacles, while many products can be applied in all weathers – offering great reassurance if a failure occurs during heavy rain.
At the end of their life or whenever a ‘top-up’ is required, more coating can be applied; there is no requirement to remove the coating or substrate, meaning no waste.
For further inf visit www.3Mconstruction.co.uk.