Metal roofing examples (C) Daniel Friedman How to Diagnose, & Repair Roof & Structure Noise Problems in Buildings

  • NOISE TRANSMISSION in ROOFS - CONTENTS: Building roof or other structural noise transmission: causes, cures, and detection methods for indoor noise pollution coming from outside through the building roof. Roof noise transmission: comparing metal roof noise levels to other roofing materials. Roof noise insulation and roof noise isolation techniques. How to build a quiet building under an airplane flight path, near airports or near highways. Roof booming noises, roof creaking or groaning noises
  • POST a QUESTION or READ FAQs about building roofs & noise or sound transmission or noises coming from roofs themselves

Roof & building structural noise transmission &control, causes & cures:

How does exterior noise (rain, hail, highways, aircraft noise) transmit through a roof to the building interior and how can we soundproof building roofs for a quiet building interior?

These articles discuss building noise control: how to inspect, diagnose & cure noise or sound problems in homes or commercial buildings.

Information is provided about auditory (hearing), visual, historic, medical, or other clues of building condition that explain various sounds heard in buildings. We also discuss methods of sound or noise control in buildings during construction or as a building retrofit.

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Roof & Structure Noise Transmission & Structural Noises in buildings: Sources, Causes, Remedies

Metal roof installation (C) D FriedmanAre metal roofs more noisy than other roof covering types?

Metal-covered roofs in modern building installations are not necessarily noticeably noisier than other roof covering types - depending on the choice of type of metal roofing, underlayment, roof decking, fastener method, and roof insulation method.

The metal roof home shown in our photo (left, courtesy Galow Homes), was installed on a New York home and used solid metal plywood roof decking.

The roof framing support is comprised of I-joists, and the roof cavity is insulated with blown-in foam. During heavy rain, from inside the space below the roof, we could hear only a very muted sound of rainfall on the roof surface and in our opinion the sound level was not different than under an asphalt-shingle roof of similar design and use.

Nevertheless, reader questions & comments (see our roof noise FAQs below) as well as our own field experience make clear that some metal roofs and some roofs covered with other materials can be very noisy and at some buildings there are serious occupant complaints about roof noise levels observed at roofs of various designs and materials.

How is Roof Noise Transmitted into a Building?

Regardless of their source, roof noises are transmitted into buildings by two methods.

  1. Airborne Sound: Sound waves traveling through air move between building areas - such as through open windows, doors, or stairwells.
  2. Mechanically transmitted sound: When sounds move through solid building components such as floors, ceilings, walls, framing, carrying sound from one area to another the sound transmission is referred to more technically as impact insulation class transmission or IIC sound transmission.

Metal roof, Key West FL (C) Daniel FriedmanCertain building configurations, such as occupied attics or under-roof areas with cathedral ceilings, low slope or flat roofs, and metal roofed buildings may transmit noises to the building interior through the roof sheathing and building framing.

Where roof-transmitted sound reduction is most sought is in buildings located close to high noise areas such as under the flight path to airports.

Our photo of metal roofed homes (left) shows two older houses in Key West, Florida.

A Catalog of Types of Roof Noises & Sounds

Roof noises may be described as those attributed to an obvious source: the patter or even the roar of falling rain or hail, popping and cracking noises (perhaps due to thermal expansion and contraction of roof coverings, metal roofing, or roof structure), and transmitted noises from other external sources such as low-flying aircraft or nearby trains or auto & truck traffic from a nearby highway.

Very loud roof "booming" noises may be heard in cold climates when water freezing on a flat or low slope roof becomes cold enough to fracture.

Other noises sometimes attributed to building roofs are actually traced to other building components on or near the roof, such as antennas, wires, cables, signs, and roof-mounted equipment.

Role of Roof Covering Material in Noise Transmission

Choice of roof covering affects roof noise: Choices of roofing materials can reduce roof transmission of sound to the interior, including use of bituminous or asphalt shingles, or more effective, higher-mass roofing materials such as roofing tiles of clay or concrete. Metal roofing can be sound-transmission reduced by installing the metal roof over plywood and solid foam insulation. Keep in mind that roof skylights are likely to increase sound transmission through roofs.

Green roofs reduce roof noise transmission: One of the benefits claimed for "green roofs" is that by virtue of their stiffness and high mass, green roofs provide very good resistance to sound transmission from outside the building. Quoting:

Green roofs can provide a higher [noise] transmission loss than the additional ceiling element and improve [sound] transmission loss throughout the full architectural frequency range, specifically desirable in residential occupancies below aircraft flight paths. the field testing conducted on two 33 m2 low profile extensive green roofs indicated an increase of 5 to 13 db in [sound] transmission loss over the low and mid frequency range (50 Hz to 2000Hz) and 2 dB to 8dB increase in [noise] transmission loss in the higher frequency range relative to the transmission loss [sound transmission resistance] of a reference roof. - Connelly & Hodgson, [1]

Connelly & Hodgson reference Dr. Ben H. Sharp, an expert in sound transmission through structures who developed sound transmission theory and who proposed (Sharp 1973) improvements to roof sound transmission resistance thorough roof/ceiling assemblies that combined increased mass with low stiffness.

Accurate diagnosis of the source of roof noise transmission is important in deciding what remedy may work best. For example, check during rainfall to accurately determine the loudest sound source - you might find that more noise is transmitted to the building interior through skylights than through the roof surface itself.

Below at our roof noise FAQs we suggest investigative steps useful in diagnosing and thus curing annoying roof noises & sounds.

Metal roof noises & Roof Underlayments

Metal roofing examples (C) Daniel FriedmanDepending on installation details, metal roofing can transmit rain noise into buildings at levels exceeding 70 dB (equivalent to street traffic noise).[2]

Noise generated by the roof covering material itself may be a factor where metal roofing is installed, particularly if the metal roofing is not properly insulated and if its connections to the roof deck fail to secure the material properly, including providing an allowance for movement. Quoting:

Enkamat underlayment and composites made with Enkamat reduce sound levels from 9.5 to 13.5 decibels compared to a metal roof directly over a weather barrier fabric.

When the entangled filament underlayments were combined with a gypsum ceiling and thermal insulation the sound reduction further increased to 21.5 decibels. When considering that a sound reduction of 10 decibels is perceived by the human ear as cutting noise levels in half, a reduction of over 20 decibels is significant. - Colbond [2]


One frequently cited disadvantage of metal roofing is that it generates a noticeable noise when struck by rain, hail, or even dropping acorns. If installed directly to purlins with no roof sheathing, the noise might be heard in the building interior. However, when installed over a solid substrate, with normal levels of insulation, the noise should not be noticeably different than with other roofing types.

The Role of Metal Roof Profile Type in Roof Noise Levels

The metal roof profile type may also affect the level of noise transmitted by the roof to the building interior. Raised profile metal roofs may be noisier than a flatter profile roof on the same building. Metal roofing that is supported directly by the roof deck below will deflect less and should be more noise and sound resistant than metal roofing that has a raised profile. For example, some metal roof shingles employ a raised profile that includes an empty air space below the metal shingle surface.

Suggestions for Reducing Noise Transmission Through Metal-Covered Roofs

These metal roof installation options can reduce roof noise transmission from metal roofs, such as the sound from falling rain or hail:

  • Re-roofing with metal roofing over existing asphalt shingles, if permitted by local building codes, will afford some sound insulation.
  • Install metal roofing over sound-absorbing foam insulating panels to reduce noise transmission through the roof to the building interior.
  • Installing metal roofing over an insulated attic space will transmit less noise to the building interior than installing a metal roof over a flat or low slope roof that does not include an insulated attic space between the roof and the occupied space.
  • Install metal roofing over underlayment products designed to permit ventilation and whose properties also are sound-isolating. Colbond underlayments; Enkamat 7008/1010 reduce the sound transmission of the impact noise of rainfall or hail on metal roofing.
  • Selecting a heavily-formed, heavily profiled, or textured metal style roof product may reduce its noise transmission property.
  • Use the proper metal roof fasteners, in the right location, and at the right interval as specified by the roofing manufacturer. Too few fasteners, or loosely-fastened or improperly secured metal roofing is likely to be more noisy as temperatures vary.
  • Use multiple layers of building insulation, tight construction, and sealants in gaps or sound transmission pathways - NAIMA [4] quoted just below:

Adding faced metal building insulation alone to the metal building construction can reduce noise levels in a metal building by 5-6 dB. However, construction techniques do impact the way sound travels. To maximize a metal building’s acoustical performance, the wall and/or roof panels should include at least one layer of faced metal building insulation, and one layer of unfaced metal building insulation. Additionally, the construction should be tight, with attention to detail such as filling gaps with flexible sealants to assure that sound does not transit via air leaks from one space to another. - NAIMA [4]


Metal roofing references and other detailed articles about metal roof selection, installation, diagnosis & repair begin at METAL ROOFING

Sound Transmission Class - STC & OITC: Sound Transmission Loss Properties for Building Walls & Roofs

STC or sound transmission class is defined as the level of reduction of sound transmission from outside noise sources to the building interior. Higher STC numbers mean higher resistance to sound transmission to the building interior, or as acousticians would describe it, higher STC means greater sound transmission loss between outdoors and the building interior. Typical STC values for metal buildings are STC=20 to STC=55.

OITC or Outdoor-Indoor Transmission Class describes the sound transmission loss properties of building exterior components like windows and walls against noise from traffic, trains, or low flying aircraft. - General Steel Corporation [3]

Details about sound transmission are at SOUND TRANSMISSION CLASS RATINGS

TPO Roof Noise

Reader Question:

5/9/2014 said:

Interested in rain impact sound transmission on TPO Roofs



Thermoplastic polyolefin (TPO) single-ply roofing membranes are rather recent roof products for which I have not seen much research on noise transmission. Here are a few citations of interest but you'll see the focus has been for the most part elsewhere. Nebesnak (patent disclosure) discusses the need for sound-isolating underlayment. Baskaran et al have done a bit of research and may have some data for you as may Beer who've researched a decade of TPO roof performance. Thanks for the query. I'll continue to look at this question.

  • Baskaran, B. A., R. M. Paroli, and P. Kalinger. "Advancements and changes in the North American commercial roofing industry." In International Conference on Building Envelope Systems and Technology, vol. 2007, p. 275e86. 2007.
  • Baskaran, A., Y. Chen, and U. Vilaipornsawai. "A new dynamic wind load cycle to evaluate flexible membrane roofs." Journal of testing and evaluation 27, no. 4 (1999): 249-265.
  • Beer, Hans-Rudolf, and Stefan Keiser. "Flexible polyolefin roofing membranes: ten years of field experience." In Proceedings of Waterproofing technology and the environment, IXth International Waterproofing Association Congress, Amsterdam, pp. 154-172. 2000.
  • Nebesnak, Edward, and Li-Ying Yang. "Flexible polypropylene roofing membrane." U.S. Patent Application 10/925,097.
  • Yang, Li-Ying. "Single ply thermoplastic polyolefin (TPO) roofing membranes having superior heat seam peel strengths and low temperature flexibility."

Reader Question: What causes roof noise in our flat roof during cold nighttime weather? How can we fix it?

Roof noise - during the winter our torched-on membrane (180g. polyester base sheet & 280g. polyester SBS Cap Sheet) covered flat roof (installed 2002 on the apartment building) makes noises typically at night which disturbs the tenants and has caused some to move out. There are no leaks and the roof looks properly installed. What causes the noise and what can be done about it? Regards, Steve Rickard

Reply: suggestions for diagnosing cold weather flat roof noise - the diagnosis will define the steps to cure roof noise

Steve: re: how to diagnose & cure annoying night time noise from a flat roof.

Tar and gravel roof with ponding (C) D FriedmanWith no information and no building inspection, we can't say with confidence exactly what is causing the annoying roof noise you report. An onsite expert should be able to help however. Here are some of the roof noise diagnosis observations that we would expect a roof noise consultant to consider:

  • What are all of the materials in the roof structure: support, roof deck, layers and coatings - thermal expansion rate differences during night time cooling might explain movement between materials and thus the noise.
  • How are the various roof layers fastened to the roof deck itself? What is the roof decking material? For example movement of materials over a metal roof deck may indeed telegraph noises to the interior
  • What is the leak history of the roof; even a roof that is not leaking now may contain moisture from prior leaks or from condensation due to moisture penetration from the building interior (again material and installation dependent) that could in cold weather be forming ice or contributing to thermal movement and noises
  • What is the roof insulation scheme - where has insulation been placed and using what materials. It may be possible to correct the noise problem by a review and improvement of the roof insulation. For example, adding insulation at the building interior may reduce the differences in temperatures experienced by the two sides of the roof structure - the interior side vs the exterior side. If thermal changes are a key in movement that is the source of the roof noise problem.
  • What else is on or near the roof and the rest of the building structure that might be moving or otherwise serving as a noise
    source: loose building components, antennae etc. ?
  • What HVAC or mechanical systems are mounted on the roof or penetrate the roof?
  • Where is the building located? To what extremes of temperature is the roof exposed?
  • Is there standing water on the roof - are the roof drains working? See our photo [above left] of a tar and gravel flat roof located in northern Minnesota.[5]
  • Is there ice formation on the roof surface? In some climates such as northern Minnesota, as standing water on a flat roof freezes during temperature drops, very large booming sounds can be produced by the roof. These roof booming noises are familiar to Minnesotans who live along the shores of Lake Superior, as ice freezing and fracturing on the lake itself produce the same sounds. [5]
  • Are there other nearby external sources of noises that may be transmitted through the roof (falling acorns, airports, road traffic)?

Other more general observations that can help track down roof noise sources

  • Weather & roof noises: At what times, weather conditions, temperatures, wind directions, operation of mechanical systems etc. map to when the noises are observed; where, spatially, are the noises loudest?
  • Building components & roof noises: Do those locations track possible noise sources to specific building components.

Comments, suggestions, or questions from readers are welcome in helping to diagnose this roof noise issue.

Also see NOISE / SOUND DIAGNOSIS & CURE where we describe how to locate the source of, identify and correct various building sounds and noises indoors or on occasion, noises from outside that penetrate indoors at annoying levels.

Separately at SOUND CONTROL in buildings we provide a series of detailed articles on reducing unwanted building noise levels through building design, insulation, sound isolation, and noise barriers.


Continue reading at SOUND ABSORPTION vs. SOUND ISOLATION or select a topic from the More Reading links or topic ARTICLE INDEX shown below.

Or see NOISE / SOUND DIAGNOSIS & CURE - home, for details about how to track down building-related noises & sounds.

Suggested citation for this web page

ROOF NOISE TRANSMISSION at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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