What are the benefits of tapered roof insulation?

24 April 2020 Building Innovation

Roofs bear the brunt of adverse weather conditions, whether it be gales, rain, snow, hail or freezing temperatures. For flat roofs in particularly this means a great deal of care and attention is needed to create falls which channel any moisture that ends up on the roof into drains. Whilst these falls were traditionally achieved through structural approaches, tapered insulation systems can now provide a simpler, lighter solution which can also ensure roofs meet the U-values required for a project.

What problems can occur when a flat roof doesn’t drain properly?

Before we look at the different approaches used to create a fall, it’s important to understand why achieving a correct fall is so important.
The most obvious concern for any flat roof is water ponding, where rainwater is allowed to sit on the roof for an extended period of time. This can occur for a number of reasons, including an insufficient or poorly designed fall, blocked drainage channels or roof debris.
As the water sits on the roof, it can cause damage to the waterproofing system, magnifying UV-radiation, weakening bonding adhesives and stripping oils from asphalt. Over time, these can lead materials to become brittle, reducing their lifespan and potentially causing leaks – particularly around junctions in the waterproofing system. This can be exacerbated in the winter months where any standing water can enter tears or gaps in the surface and freeze, opening them up further.
Water which drains slowly, or doesn’t drain at all, can also allow dirt and other sediments to gather on the roof, providing an ideal substrate for vegetation and moss to form. It also adds structural loading to the roof deck. If it is not addressed, this can cause the surface to deflect, allowing even more water to become trapped and potentially lead the surface to fail.

How much of a fall should a flat roof have?

Traditionally, flat roof falls were created in a couple of ways. The first is to lay screed to a fall. Whilst this creates a robust roof surface, it adds considerable weight to the construction and can require weeks to properly dry.
Alternatively, contractors could lay firrings below OSB or plywood sheets. These are wooden battens which have been cut to a 1:40 angle length ways. . Whilst this construction is lighter than the screed option, it will still require a separate thickness of insulation to be fitted in order to achieve a compliant U-value. This can significantly increase the thickness of the overall construction.
Our tapered roof insulation solutions address these issues. By combining a fall and insulation in a single solution, they can allow both drainage and thermal performance requirements to be met with a slim construction. As we discussed in our ‘Why Choose PIR Insulation’ blog , in most cases Building Innovation recommend polyisocyanurate (PIR) insulation for tapered applications as the thermal conductivity (λ-value) these boards achieve help to limit the required thickness of the insulation layer.
The light weight of our tapered roof insulation solutions makes them suitable not only for new-build applications, but also for flat roof refurbishments and, in many cases, they can be installed directly above the existing waterproofing layer. The installation is also faster as the tapered insulation solutions perform twin roles and no time is lost waiting for solutions to dry. Building Innovation can help to further reduce project timescales, carrying out surveys and detailed modelling and calculations to ensure the solution performs as expected. We supply clear plans with the materials, allowing site teams to easily understand how the solution should be laid out and can also offer factory cut pre-mitred hips and valley boards reducing onsite labour and waste.

Safe installations during the Coronavirus pandemic

To ensure  the safety of workers and reduce the spread of the Coronavirus, the Department for Business, Energy and Industrial Strategy (BEIS) has now published a guidance document for construction sites. This is supported with local guidance in England, Wales, Scotland and Northern Ireland  and specific Site Operating Procedures from the Construction Leadership Council.
The BEIS document requires a risk assessment to be carried out covering all aspects of sitework including travel, shift scheduling, lunch arrangements, deliveries and waste. It sets out which workers should remain at home along with best practice with regards to cleaning site touchpoints, and the pre-planning that is required to ensure workers can carry out all tasks whilst maintaining 2 metre social distancing (or 1 metre with correct risk mitigation where this is not possible).
To meet its requirements, we would recommend that when Building Innovation tapered insulation schemes are ready for installation, they are mechanically lifted onto the roof space to limit site traffic to and from the delivery vehicle. Smaller boards should be light enough to be handled by individual workers whilst any over 2 m in length can be handled by two workers standing at either long end of the board. When handling and installing the tapered insulation, workers should maintain correct distancing and ideally face either away from one another or in a parallel direction rather than face to face. Staff should also retain any tools used to cut the boards, ensuring both the tools and their hands are cleaned regularly. 

Tapered insulation products

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