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Standards Extra Slates – no more grey areas For many years slate roofs have been acknowledged as the premier roof covering for pitched roofs but in recent times there have been concerns about the durability and appearance of certain slates. The change from the British Standard, BS 680 to European Standard BS EN 12326-1 and -2 has resulted in a need for the user or specifier to specify what level of performance and durability they want. Whereas BS 680 gave a simple pass or fail for several tests and two quality ‘grades’ BS EN 12326 does not. Because of the wide range of qualities of slate which are acceptable throughout Europe, each with different durability, it provides a set of levels of performance against a series of tests. The user can and should choose what level of performance they want for each test. To address this issue NHBC has been working with the industry to establish what should be the minimum specification to meet with NHBC Standards to ensure the product has acceptable durability. Under BS EN 12326 consignments of slates should now have an “accompanying commercial document (ACD)” from the producer/supplier indicating the slate’s performance. An example of the full ACD, containing an explanation on the information it should provide, can be view at www.stoneroof.org.uk/tests2.html Below is an example of the first page of the ACD together with the level of test results that NHBC now looks for to meet our Standards. Accomanying commercial document - Information requirements Producer – Sufficient details are required to identify the producer/supplier. Number of this commercial document – This can be a number issued by the test house or the producer/supplier. Date of issue – The ACD should be relevant for the batch of slates being supplied. Retesting and updating of ACD’s should be carried out at least once a year and more frequently where large volumes of slates are being extracted and for every new source or vein of rock extracted. Commercial document issued by – this can be the test house or the producer/supplier. Location of mine or quarry – required for traceability of slate. Date of sampling & date of testing – If more than one date is applicable to sampling and testing they should be indicated against the individual test results. The sampling and testing dates should be as close as possible to the ‘Date of issue’ of the ACD. The ‘Date of issue’ should be used to establish when further sampling and retesting is required at the frequencies set out in NHBC Standards. Product description & commercial name – Name or description given to slate by the producer/supplier. Dimensional tolerances – These are to be within those set down by the Standard. Note: Slates, which fall within the tolerances, still require proper selection and fixing on site to achieve an acceptable finished roof covering. Nominal thickness – Thickness of the roofing slates, as declared by manufacturer and the amount by which individual thickness varies as a percentage of the nominal thickness. Characteristic modulus of rupture (MoR) – a measure of the slate’s mechanical strength both along and across the slate. Slates from weaker rocks may need to be supplied thicker than those from stronger rocks to achieve a satisfactory performance in use. The Standard provides equations, which are used to establish the minimum slate thickness. The minimum thickness is calculated using the CMoR and a National (i.e. UK) factor, which takes into account the weather conditions of the country of use. It is the producer’s/ supplier’s responsibility to ensure all the slates in a consignment are at least as thick as the minimum value obtained using the UK factor. Water absorption – For compliance with NHBC Standards the water absorption should be no greater than 0.6% i.e. A1 code. Freeze thaw – This test is not required when slates have a ‘Water absorption’ no greater than 0.6% Thermal cycle – This is a test for reactive metallic minerals within the slate, which may cause staining, pitting and/or delamination and potential failure of the slate. For compliance with NHBC Standards a slate should achieve a T1 code. Carbonate content – High carbonate content can cause colour changes in the slate and potential for accelerated erosion and break down. For compliance with NHBC Standards a slate should achieve a S1 code. Note: It is acknowledged that some slates, that do not achieve a S1 code, have a history of satisfactory performance for at least 60 years in the UK. If such a slate is being considered please discuss its acceptance with NHBC Technical in the first instance. Non-carbonate carbon content – to meet the standard this should be less than 2%. Exposure to fire, reaction to fire & release of dangerous substances – Roofing slates meet these requirements. An abbreviated version of the ACD, as shown in BS EN 12326 should also be attached to each crate of slates. Accompanying commercial document ACTION Ensure that your slate supplier provides an accompanying commercial document with each consignment of slates, and check the slates have properties at least as good as those listed under information requirements above. 6
Issue 43 December 2008 Secure escape In Standards Extra Issue 31 December 2004 we published an article about locks to individual flat entrance doors. The article explained the need to provide good security whilst still providing escape in the event of a fire without the need for a key i.e. keyless egress. Since that time NHBC has been working with representatives of the lock industry, police, insurers and the fire service in developing a suite of British Standards that cover security and means of escape for all types of dwellings. The first British Standard for locks, which addressed enhanced security for dwellings, was BS 3621 ‘Thief resistant lock assembly - Key egress’. The Standard covers single point locking operated by a key from both sides of a door. For locks which operate without the use of a key on the inside either via a thumb turn or handle, BS 8621 ‘Thief resistant lock assembly - Keyless egress’ was developed and published in 2004. BS 8621 locks provide keyless egress at all times but there may be times when it would be desirable to lock the internal thumb turn or handle when leaving a dwelling unoccupied. This feature is useful in preventing someone breaking in through a window and removing large items via the entrance door. To address this a further British Standard, BS 10621 ‘ Thief resistant dual-mode lock assembly’ was developed and published in 2007. This lock has the facility to lock the internal thumb turn or handle by an extra operation of the key from the outside when leaving the property unoccupied. The latest editions of these three British Standards cover single point locks for all types of dwelling. In some cases it may be desirable to fit two locks to achieve sufficient resistance to forced entry and the recommended lock functions. An alternative would be to fit a multi-point lock, which has the same recommended lock functions. With different dwelling types it is important that the right lock(s) is fitted to ensure no one can accidentally become locked in or out of their own property. Below is a description of the lock functions that should be used in each dwelling type. Main entrance door Dwellings – All All entrance doors of individual dwellings should be fitted with one (or more) securely fixed lock and keep or multi-point locking system, which has: ■ at least 1000 differs ■ a fixing which, if burst open, would not pull out without breaking the door or its frame ■ a hardened steel bolt or inserts to prevent sawing ■ latch and deadlocking facility. Locking devices fitted to entrance doors should permit emergency egress without the use of a key when the dwelling is occupied. Any glazing which, if open or broken, would permit release of the thumb turn by hand or arm entry should be laminated. Dwellings - With an alternative means of escape. (These are typically houses with a front and rear door) Lock(s) should provide initial security by use of a latch operable with a key externally and a handle/thumb turn release internally. The full deadlocking facility should be engaged and be operable with a key externally and a handle/thumb turn release internally. Locks, which comply with BS 8621, meet these requirements. External handles on multi-point locking systems should be split spindle to avoid operating the latch. Enhanced security can also be achieved by providing the facility to deadlock the internal handle/thumb turn when leaving the dwelling un-occupied. Locks, which comply with BS 10621, meet these requirements. Dwellings - Without an alternative means of escape opening direct to outside. (These are typically ground floor flats or maisonettes) The door should be held close by use of a latch operable with a key externally and a handle/thumb turn release internally. The full deadlocking facility should be engaged and be operable with a key externally and a handle/thumb turn release internally. Locks, which comply with BS 8621, meet these requirements. External handles on multi-point locking systems should be split spindle to avoid operating the latch. Dwellings - Without an alternative means of escape opening onto a communal access. (These are typically flats accessed off a communal stairs) The door should be held close either on a latch operable with a handle both internally and externally or a roller bolt, so that the door cannot slam shut locking the homeowner out without a key. The full deadlocking facility should be engaged and be operable with a key externally and a handle/thumb turn release internally. Locks, which comply with BS 8621, meet these requirements. Secondary external access doors The door should be held closed on a latch and operable by use of a handle both internally and externally. A deadlocking facility should be operable by use of a key both internally and externally. Locks complying with BS 3621 meet these requirements. Alternatively a thumb turn may be used internally in place of a key operation. Locks complying with BS 8621 meet these re quirements. In addition bolts should be fixed securely at both top and bottom of the door on the internal opening edge. Where multi-point locking systems are used bolts may be omitted. ACTION When specifying door locks select the appropriate lock(s) that provides the recommended lock functions for the different dwelling types as stated above. 7
Page 1 and 2: NHBC’s technical newsletter Stand
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Page 11 and 12: NHBC Foundation The NHBC Foundation

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