Acoustic considerations for roofing
How important is noise control in the design and specification of a roof? In most cases it is arguably not one of the main considerations when it comes to selecting materials for roofing or façade projects, given the need to ensure the building envelope is well insulated thermally, air and water-tight and – particularly since the publication of the Grenfell Inquiry report – safe in the event of a fire.
Noise, however, can be a nuisance in many buildings due to the roof design, to the point where it affects the quality of the internal environment, harming user satisfaction and disrupting activities such as working, studying, or teaching. It can become problematic in many different types of roofs, too, whether it is a profiled metal sheet construction, a standing seam, a flat roof, or even a tiled roof.
Why are roofs noisy?
How effective a roof is at attenuating sound will depend on factors such as its weight, airtightness, and isolation of the layers of construction. There is also an issue where sound bypasses the acoustic insulation materials, known as flanking, through bridging elements or gaps. This is important because noise control measures will often fail to perform adequately as a result of the building details not being constructed as intended.
However, there are three general categories of noise which need to be considered with roof design and build:
Environmental noise (external)
Buildings in densely populated urban areas or next to roads, railways or airports need to be built with sufficient acoustic insulation within the external envelope. That means ensuring the walls, floors, windows, doors and roofs are all constructed in a way that minimises airborne sound transmission so the internal spaces are sufficiently quiet.
In areas where environmental noise is constant or particularly severe, such as close to an airport, the noise abatement strategy could include upgrading the acoustic performance of the insulation in the roof or adding an acoustic treatment to the ceiling, such as the acoustic ceiling systems provided by Hush Acoustics. This is unlikely to resolve an environmental noise issue in isolation, but it could be an important part of the solution.
Impact noise
The sound of rain and hail falling onto a roof can be a nuisance too. When raindrops hit a metal roof or flat roof, a vibration is created, which translates into a sound, meaning that the roof acts like a drum. The problem becomes more severe in heavier rain and with larger roof areas.
This type of noise is often referred to as ‘noise break-in’ and, with metal and flat roofs, it can be treated effectively by incorporating an acoustic membrane or acoustic underlayment. This was the solution deployed by Hush Acoustics at Huntington Primary School in Cheshire, which used Hush 10kg/m2 Barrier Mat to deaden the sound of rain with extremely positive results.
Depending on the type of roof, the target level of improvement and budget, an alternative approach may be preferable to resolving impact noise issues. These include installing acoustic insulation panels, mass-loaded vinyl (MLV), which acts like a sound-absorbing blanket, and spray foam insulation – all of which have their pros and cons.
Reverberation (internal)
Not all noise problems stem from external sources, however. A noisy internal environment can often result from activities within the building, which result in reverberation. This is the issue of sound waves generated by everyday activities, such as speaking, music playing or furniture being moved, reflecting off hard surfaces back into the room rather than being absorbed.
The issue can usually be resolved by mounting sound absorber panels onto walls and ceilings within the room, such as Hush Absorber 50, or suspending absorbers from the ceiling structure on rafts. The latter was the solution provided in a project completed by Hush Acoustics at three city centre office buildings in 2024.
In the case of profiled metal roofs, however, it could be that acoustic infills need to be installed. Hush Acoustics provides a solution here to suit different roof profiles in the form of its Hush Acoustic Infills. These consist of rigid slabs of non-combustible mineral wool available in four different density grades, which are factory cut to suit the upper profile of structural metal roof decks.
Meeting and exceeding acoustic standards
The potential for roof noise or additional insulation within the roof construction must be considered in the context of the various building regulations and standards that apply across the UK.
In residential buildings in England & Wales, including hotel rooms, boarding house rooms, student halls of residence and key worker accommodation, but excluding health and social care buildings, Approved Document E applies.
Whilst this may only set minimum standards for separating walls and floors, and does not cover roofs specifically, that does not mean the risk of excessive noise resulting from the roof design should be ignored. Best practice should still be applied, particularly for many larger new build apartment buildings which feature membrane flat roof systems.
Hospitals and health and social care facilities in England must be built in accordance with NHS England’s Health Technical Memoranda (HTM) 08-01. Unlike residential buildings, this sets criteria for noise intrusion into buildings through the roof.
HTM 08-01 was developed and published in recognition of the fact that ‘acoustic design is fundamental to the quality of healthcare buildings’ and acknowledges the extensive research which demonstrates that unwanted sound affects us both physiologically and psychologically. Its checklist specifically states that noise-sensitive accommodation should be under a roof that “will adequately control rain noise”.
Similar principles apply under Building Bulletin 93 (BB93), which sets performance standards for acoustic design in schools. This was published to help improve the acoustic conditions within learning environments, given that excessive noise in classrooms and other teaching spaces can negatively impact children’s learning outcomes and personal development.
Reducing environmental noise is an important consideration within BB93, but so too is optimising internal spaces to minimise reverberation and echo. Noise levels within classrooms can become extremely high during routine teaching sessions, particularly where the activity being taught cannot be done quietly, such as music lessons. Hence why reverberation is often the most significant acoustic issue schools face.
Cross-sector standards may also need to be consulted in order to ensure the roof is designed to achieve the required acoustic performance, including BREEAM (Building Research Establishment Environmental Assessment Method). An increasing number of buildings are being constructed to its methodology, which applies a globally recognised sustainability assessment method for the built environment, evaluating and improving the environmental performance of buildings and infrastructure projects throughout their lifecycle, from design to operation.
BREEAM’s acoustic performance focus is evident under section HEA 05 (Acoustic Performance). This considers sound insulation between rooms and to the exterior to minimise noise intrusion, Indoor Ambient Noise Levels (IANL), principally to ensure noise from outside does not cause unacceptable distraction, and room acoustics to avoid reverberation and optimise speech intelligibility.
Why bespoke acoustic solutions could be key to resolving issues
With so many different systems and materials available for roof design and construction, in many cases, a bespoke acoustic design will provide the most effective solution. This may involve one or more existing insulation products and can be developed in conjunction with Hush Acoustics’ technical team. They regularly work with customers to integrate effective acoustic insulation products into new build roof designs and recommend solutions for roof refurbishment projects.
One recent Hush Acoustics customer project highlighted the challenges that roof designers and contractors face. Here, the team were approached to assist with an acoustic issue affecting a standing seam metal roof. The customer contacted the team to ask for an acoustic underlayment for the roof, which they wanted to be able to roll out between a ply deck and the metal roofing finish to help dampen sound.
Whilst Hush Acoustics does not offer an acoustic underlayment specifically for standing seam, one of its roofing membranes was proposed as the possible solution. The Hush FR Roofing Membrane is designed primarily for flat roofs, but it may also provide the acoustic performance required in other types of roofs prone to impact noise and vibration.
The 10 mm-thick rubber-based membrane is supplied in 6m rolls with a width of 1.25m. It has been comprehensively tested by UKAS-accredited Sound Research Laboratories (SRL) under BS EN ISO 140-3:1995, to assess its airborne acoustic performance in various roof constructions, and impact acoustic performance generated by rainfall in accordance with BS EN ISO 140-18:2006. In all tests, Hush FR Roofing Membrane demonstrated improvements compared to roof constructions without the membrane.
These flat roof test results may not be sufficient to prove that the product would provide the necessary performance that this particular customer required for a standing seam. However, due to the nature of the issue, the Hush Acoustics team was able to make a firm recommendation which could be confirmed through appropriate testing within the roof build-up.
Find out more
As this article has highlighted, there are a number of challenges facing architects and contractors in relation to the acoustic performance of roofs, and there are relatively few firm performance standards that apply. The best practice to avoid noisy roof issues is to contact an acoustic consultant or product manufacturer at the design and specification stage.
Resources used in this article.
Health Technical Memorandum 08-01: Acoustics
Acoustic design of schools: performance standards
