Performance and Appearance

AUTHORITY

All concrete slates and tiles conform to BS EN 490:2011: Concrete roofing tiles and fittings for roof covering and wall cladding – Product specifications. All clay tiles conform to BS EN 1304:2013: Clay roofing tiles and fittings – Product definitions and specifications. Redland natural slates have been tested in accordance with BS EN 12326-1:2004: Slate and stone products for discontinuous roofing and cladding. Product specification. As there is no British Standard for Cambrian Slate, it has been designed to meet the relevant performance requirements of BS 5534:2014: Code of practice for slating and tiling (including shingles) and has been awarded British Board of Agrément certificate No. 87/1907.

SUSTAINABILITY

As members of the Roof Tile Association, data supplied for our concrete and clay roof tiles enabled the BRE Green Guide to Specification to award the highest A+ rating for generic concrete and A+ rating for generic clay tiles. Redland Cambrian Slates are the most eco-friendly resin slates available; the Green Guide to Specification awards generic resin slates an A rating based upon the data supplied  for Cambrian Slate when part of standard roof constructions, the same as for UK produced natural slates.

Monier Redland Ltd possesses ISO 14001 certification and is working toward achieving BES 6001 Very Good rating at all its manufacturing sites in the UK demonstrating its commitment to achieving the highest standards in responsible sourcing and manufacturing.

COMPOSITION AND MANUFACTURE

Concrete tiles and slates are manufactured by a high-pressure extrusion and compaction process. Rosemary clay plain tiles are extruded; Old Hollow and Cathedral Clay Pantiles are pressed.

PERFORMANCE

All slates and tiles have been rigorously tested in our wind tunnel where combinations of high wind and driving rain are used to determine the products’ performance with respect to wind loading and weathertightness. Slates and tiles will meet the requirements of BS 5534:2014: Code of practice for slating and tiling, providing our fixing recommendations are complied with.

The information contained in this Guide relating to Cambrian Slates, concrete slates and DuoPlains is based on a maximum rafter length of 10 metres at minimum pitch. For rafter lengths greater than this, telephone the Redland Technical Solutions Hotline on 08708 702595 for advice.

The minimum pitch and maximum rafter length may be affected by roof features such as dormers, roof windows and chimneys. For advice on the inclusion of such features in a roof slope contact Redland Technical Solutions.

MOVEMENT

Designed vertical and horizontal laying tolerances will accommodate normal thermal and other movements.

FIRE RESISTANCE

Cambrian Slates are classified as follows: EXT.S.A.A. when tested for fire protection to BS EN 13501-5 2005: Fire tests on building materials and structures – Classification and method of test for external fire exposure to roofs. Class 2 when tested for surface spread of flame to BS 476-7:1997: Fire tests on building materials and structures – Method of test to determine the classification of the surface spread of flame of products. Fire propagation index 12.3 when tested to BS 476-6:2009: Fire tests on building materials and structures – Method of test for fire propagation for products.

Under the Building Regulations there are no restrictions on the use of Cambrian Slates as a roofing material but for mansards above 69° or vertical slating, it is essential to comply with Approved Document B. All other slates and tiles are non-combustible and are classified S.A.A. when tested for fire protection and spread of flame to  BS EN 13501-5 2005: Fire tests on building materials and structures. There are no restrictions on their use under the Building Regulations.

STRENGTH AND DURABILITY

Slates and tiles do not delaminate and despite having high strength properties, are easy to cut. All Redland clay and concrete slates and tiles exceed the minimum strength requirements as laid down in BS EN 1304 or BS EN 490 respectively. Redland natural slates exhibit high flexural strength and are tested in accordance with BS EN 12326-1:2004.

ENVIRONMENTAL EFFECTS

Frost: Unaffected by frost action.
Heat: Unaffected by temperature extremes.
Sunlight: Unaffected by prolonged exposure to ultraviolet light and sunlight.

Atmospheric pollution: suitable for all rural, marine and normal industrial environments. Resistant to all but the most highly polluted atmospheres, where sulphur dioxide levels exceed 70 microgrammes/m3 of air. Redland natural slates are classified S1 under BS 12326 for resistance to pollution.

BIOLOGICAL EFFECTS

Birds and rodents: Tiles and slates are not attacked, or degraded by birds, rodents or insects.
Mosses and lichens: Tile and slate durability is not affected by the growth of lichens and mosses. However, the removal of growths may be necessary when the flow of rainwater off the roof is impeded and valleys, gutters or downpipes become blocked.

 

HEALTH & SAFETY

Data sheets covering properties, storage and safe use of our products are available on request from Redland’s Safety Manager or can be found in the Literature[JB1]  section on the Redland website. Telephone our Customer Service Hotline for details. When cutting tiles or slates using an angle grinder which generates large concentrations of dust, the safety measures defined in the Health and Safety Executive, Guidance Note EH 40 must be followed.

APPEARANCE

Under normal production conditions colour variation may occur in slates, tiles and fittings. Natural weathering may also cause changes in colour and appearance. In both cases this is acceptable under BS EN 490. Scratches and abrasions caused by packing, loading and transportation are also permissible as long as the overall slate or tile quality is not affected.

Cambrian Slates can be pre-weathered during manufacture if required. After installation slight lightening may occur due to natural weathering. Landmark slates and tiles are designed to change over time, just as natural slate and clay mellow and develop character. With the exception of Landmark, efflorescence, which is a surface phenomenon associated with concrete products, may result in a temporary lightening of the surface colour. This will be removed by weathering. Natural slates are devoid of artificial pigments but some natural colour variation, variability in grain and inclusions can occur. Redland natural slate products attain a T1 classification in BS EN 12326 and therefore oxidisation, change of appearance and colour changes which may affect the structure or form runs of discolouration are unlikely to occur.

For the best visual effect on the roof, slates and tiles must be selected randomly from a minimum of three different pallets. When laying tiles in prominent areas it is advisable to ensure that there are sufficient stocks of mixed tiles available to complete the elevation. Slates or tiles of the same colour or profile, which are manufactured at different plants, must not be mixed on the same roof area.

FIXING SPECIFICATION

There is only one recommended fixing specification for Cambrian Slates – they must be twice nailed and clipped using the proprietary nails and clips Redland supply. In addition, verge clips are required for every verge, raking valley cut and rooflight abutment. For information on how to obtain recommended fixing specifications for all other Redland slates and tiles, go to www.redland.co.uk/fixmaster

 

GENERAL GUIDANCE

Special Notes on laying natural slates

·         All slates must be sorted into a minimum of three thicknesses prior to laying.

·         Thick slates should be laid at the eaves with the thinnest used on upper roof sections using slates of consistent thickness in any one course.

·         Fix each slate with two nails through prepared holes.

·         At all eaves, a double course of slates is required.

·         All slates should be laid broken bond and double lapped.

·         Form verges by using standard slates and Slate-and-a-Halves in alternate courses.

·         At ridges and top edge abutments, a shouldered slate should be used in the course below the top course to enable the short top course slates to be nailed directly to the batten.

·         At hips and valleys, care should be taken to preserve an adequate bond by using Slate-and-a-Halves.

·         When used with mechanically fixed ridge or top edge abutment systems, further fixing may be required. Please contact Redland Technical Solutions.

·         Please contact Redland Technical Solutions for use on vertical or on curved roofs.

Special Notes on laying Cambrian and Concrete Slates

·         All slates must be laid broken bonded, normally from right to left. MockBond Mini Stonewold and MockBond Richmond 10 should be laid with a 3/4 tile offset, as opposed to a standard 1/2 tile offset.

·         Use standard slates at the eaves.

·         At right-hand verges for Cambrian Slates, use standard slates and Slate-and-a-Halves in alternate courses. For all other slates except MockBond Mini Stonewold and MockBond Richmond 10 use standard slates and right-hand Half Slates in alternate courses. For MockBond Mini Stonewold and MockBond Richmond 10 use standard slates (with interlocks removed) or right-hand Half Slates and site cut 3/4 width slates in alternate courses.

·         At left-hand verges for Cambrian Slates, use left-hand verge slates and left-hand verge Slate-and-a-Halves in alternate courses. For all other slates except MockBond Mini Stonewold and MockBond Richmond 10 use standard slates with interlocks removed, and left-hand Half Slates in alternate courses. For MockBond Mini Stonewold and MockBond Richmond 10 use standard slates with interlocks removed or Left-hand Half Slates and site cut 3/4 width slates in alternate courses.

·         At side abutments, allow for cover flashing and secret gutter.

·         In the top course use standard slates.

Additional Notes when laying Cambrian Slates

·         For rafter pitches below 45º with mitred hip, Double Slates will be required on all courses either side of the hip. At pitches greater than this Slate-and-a-Halves can be used.

·         For rafter pitches below 25º for valleys, dry and mechanically fixed bedded hip, Double Slates will be required on all courses either side of the valley or hip. At pitches greater than this Slate-and-a-Halves can be used.

·         For advice on the replacement of individual slates, contact the Redland Technical Solutions Hotline.

·         All mortar bedded hips/ridge must be mechanically fixed.

Special Notes on laying plain tiles

·         At eaves, use double courses with purpose made eaves/top tiles for the undercourse.

·         At verges and abutments to maintain broken bond, use standard plain tiles and Tile-and-a-Halves in alternate courses.

·         Adjacent to hips, valleys and angles use Tile-and-a-Halves.

·         At side abutments, allow for stepped flashing and soakers.

·         At top courses use double courses with purpose made Eaves/Top Tiles for the top course.

·         For Winchester Cuts use two Tile-and-a-Halves per course. Winchester Cut detail must not be used to abut roof pitches below 40º or in exposed locations. In these cases soldier or double soldier courses must be used.

·         For Heathland and concrete Plain Tiles, secure top course with a Top Tile Clip, with mortar bedded ridges and top edge abutments.

Special Notes on laying DuoPlains

·         All tiles must be laid broken bond with a three-quarter tile offset, normally from right to left. On gable-to-gable roofs try and lay out the tiles so that the eaves course starts with a standard tile and finishes with a left-hand verge (three quarter) tile.

·         At right-hand verges use standard tiles and right-hand verge (three quarter) tiles in alternate courses.

·         At left-hand verges use standard tiles with interlocks removed and left-hand verge (three quarter) tiles in alternate courses. If it is not possible to end the eaves course in this way, cut verge tiles of the required length from standard tiles.

·         Do not use any cut pieces of tile smaller than a left-hand verge (three quarter) tile.

·         At hips and valleys use Half Tiles as the penultimate tile in each course as required either side.

·         At side abutments, allow for cover flashing and secret gutter.

Special Notes on laying Profile Tiles

·         Tiles must be laid straight bonded, normally from right to left.

·         Eaves Comb must be used at all eaves situations with Landmark Double Pantile, Grovebury, Regent, Fenland Pantile, Cathedral and Old Hollow Clay Pantiles.

·         At left-hand verges, use standard tiles with interlocks removed. At right-hand verges, use standard tiles. Half Tiles must not be used at verges. Use left-hand verge tiles with Cathedral and Old Hollow Clay Pantiles.

·         Dentil slips must be used for mortar bedded ridges and hips with Cathedral and Old Hollow Clay Pantiles, Landmark Double Pantile, Landmark Double Roman, Grovebury, Regent, 50 Double Roman and Fenland Pantile.

·         Half Tiles should be used with Landmark Double Pantile, Landmark Double Roman, Grovebury, 50 Double Roman, Regent and Renown to avoid the use of small pieces of tiles. Use Two-Thirds Tile with Cathedral Clay Pantile.

·         As Old Hollow Clay Pantiles have no interlocks, it is very important that perpendicular lines are struck prior to laying to ensure the correct side overlap of 40mm is achieved.

·         Spirtech 400 2S must be used as the underlay when using Old Hollow Clay Pantiles.

TIMBER SARKING

Roofing practice in Scotland includes the use of timber sarking and counterbattens. Insulation board is also widely used as rigid sarking throughout the UK. The presence of sarking board in either of these forms will affect many of our standard details. It must be noted that the combined thickness of the sarking and counterbatten chosen may alter details slightly. For insulation board, advice on the size and fixing of the counterbattens should be obtained from the specific insulation manufacturer.