Specifying a ceiling is not always done by an architect, it might be done as part of a contractor’s design portion, as part of a design and build project, or even as part of offering alternatives. Whichever way, it’s crucial to get it right says FIS Technical Director, Joe Cilia, as the person producing the specification carries the responsibility that the products can be safely installed while meeting the requirements of the building regulations.
On the face of it specifying ceilings seems simple enough”, said Neil Miller, Chair of the FIS Ceilings and Absorbers Group, “consider the look, the performance and cost and there it is; if only it were that simple there would not be cases where fire compartmentation fails, partial and full collapses occur, or ceilings fail to perform because the potential wasn’t apparent during the specification process”.
In BS EN 13964 Suspended ceilings — Requirements and test methods, a ceiling is defined as: a construction covering the underside of a floor or roof, providing the overhead surface. The Standard defines the tests and
tolerance of ceilings, in fact, it is now a UK designated standard requiring systems to be UKCA marked when put on the market in the UK (UKNI mark for Northern Ireland and CE marked when put on the market in the EU) and is a good starting point when understanding the types of ceilings and the performance tests required before they can be put on the market.
Function of a ceiling
A ceiling’s function could be to conceal services, lower a slab height, help to control acoustics in a space or in adjacent spaces, reduce rain noise, protect a building element in case of a fire, provide compartmentation, reflect light and contribute to a space where air movement is managed. At the same time, it has to function in a space which may have high humidity such as a leisure facility, be able to resist impact from balls as in a sports hall, be cleanable in a food production space, be completely visually flush in a house, allow access but not provide ligature points, or it may even have to allow an exposed soffit and the services to be seen but still absorb sound energy.
The permutations are frankly endless and each project should be specified on its performance, its function, its aesthetics, its location and finally, its cost. Remember also that the way it will be supported and fixed to the structure is equally important, yet often described as simply ‘using suitable fixings’!
FIS guide for specifying ceilings
To help this process, a new guide for specifying ceilings and absorbers has been written by an FIS working group made up of expert specification writers with help from NBS, and is available now to FIS members and specifiers at www.thefis.org/membership-hub/publications/specifiers-guides/ceilingsandacousticabsorbers/
Neil Miller said: “This guide pulls together decades of experience, from specification managers who almost instinctively know the FAQs on all aspects of ceiling specification such as performance, material characteristics, sustainability and environmental, conformity marking, installation, maintenance and end of life. There are some 36 parameters to consider to ensure a safe, compliant and complete specification can be written.”
The guide firstly addresses what a good specification looks like and how it should be structured, it even includes 10 top tips to producing a specification. It then breaks down the key performance issues around fire and acoustics and the other issues of volatile organic compounds, light reflectance, impact resistance, air permeability, wind loading, sustainability and conformity marking.
The types of ceilings are described as continuous (wall to wall) or discontinuous types (often referred to as rafts or islands) and has a section devoted to installation, and why ceilings fail or experience partial or total collapses.
It’s worth remembering that a well written specification ensures the installation meets the client’s requirements, and it also means the specifier’s requirements are less open to interpretation, prices at tender stage are more accurate and performance needs are clear.
Ceiling performance testing
The actual performance of a ceiling or absorbers may only come to light during an onsite acoustic test to provide evidence that the reverberation time (in a school for example) meets the requirement laid down in the Building Bulletin (BB) for schools or the Health Technical Memorandum (HTM) in hospitals.
Sometimes the installation can impact site performance, especially with absorbers fixed directly to a wall. This is because the gap, or lack of a gap, behind an absorber will affect the absorption of sound energy, so it’s important to understand what and how the product was tested and under what conditions, as the Class A absorber may be reliant on a large gap behind the absorber to perform.
Fire performance is a different subject entirely. Reaction to fire is the measurement of a material’s contribution to the development and spread of fire, generation of smoke and the production of flaming droplets. Reaction to fire is classified under BS EN 13501-1. Products are tested using a number of standards dependent on their predicted performance.
Fire resistance is shown in the test report in minutes, 30 (30 minutes), 60 (60 minutes) etc. This refers to the ability of the whole construction to satisfy the European resistance to fire rating (REI) – loadbearing capacity, integrity and insulation. It’s crucial that performance claims are checked ensuring that the ceiling has been tested under the type of structure the specification is being written for, and if the structure/floor has been tested under load. For example, an exposed grid ceiling is unlikely to have evidence of conformity to provide compartmentation, and as the tiles are removable, it leaves the possibility of a breach in the compartment, so a metal furring (MF) ceiling system with appropriate test evidence would be more appropriate. This is explained in more detail in the guide.
There are 13 materials used to create the tiles, panels and fabrics in ceilings and absorbers and a range of systems using the materials to offer designers a palette of visual options as well as performance. Some systems are installed externally, or in huge spaces like airport concourses, or to help with acoustics in spaces like the Royal Albert Hall. No matter what materials are used, the installation quality tolerance method and, importantly, anchors should be thought through and described in the specification.
Starting with the anchor, conceivably a key element in the detail, it should not be left to a general ‘suitable’ description, as the correct top fixing method is critical and should be noted on the relevant drawings (BS EN 13964 A.5.7).
Top fixings should be specified using this approach:
1. identify the application parameters;
2. check that the structure can take the load of the ceiling and any other plant;
3. check the need for redundancy, i.e what happens if a fixing or hanger fails?
4. check the environmental conditions; is it humid or subject to wind loading?
5. specify an anchor with a European Technical Approval (ETA); and
6. if in doubt, carry out a preliminary test.
The FIS best practice guide to selection and installation of top fixings for suspended ceilings provides more information and help at www.thefis.org/membership-hub/publications/best-practice-guides/topfixings-and-suspended-ceilings/
It should be specified that the installation is carried out by competent professionals trained by the manufacturer in the installation of their products, especially where performance is key to compliance, and that the installation should be carried out in accordance with the manufacturer’s installation details and the FIS best practice guide to installing ceilings at www.thefis.org/membership-hub/publications/best-practice-guides/installation-of-suspended-ceilings/
It is important to remember that the person specifying the ceiling is responsible for its safe installation, that meets the requirements of the Building regulations (AD B, AD E) and that any maintenance can be carried out safely.
Neil Miller concluded: “There has never been a time in construction where the specification has been more important, so this first specification guide from FIS sets out our desire to help everyone involved in the specification of products and systems, and our commitment to raise the safety of residents, occupiers and those who use the built environment”.
The specifiers guide for ceilings and absorbers can be downloaded at www.thefis.org/membership-hub/publications/specifiers-guides/ceilingsandacousticabsorbers If you have any queries, email email@example.com