Roof tiles, also known as concrete roof tiles, are small-format construction elements for covering sloping roofs. They are industrially shaped stones made of sand, cement, water and colour pigments. There are roof tiles with different profiles, usually called pans, as well as flat roof tiles and beaver roof tiles. Depending on the rain resistance of the individual roof tile models and the design of the sub-roof, different roof pitches are possible.
Roof tiles are moulded blocks made of sand, cement, water and colour pigments produced using an extrusion process. The production is very energy-saving and the stones are 100% recyclable, which means that they achieve a good ecological balance overall. Since the paint is added as a pigment during production, it is variable. In recent years, manufacturers have developed coatings and low-pore surfaces, which has reduced the impact of dirt and mosses on the stones.
Roof tiles are extremely break-resistant, frost-resistant and offer good sound insulation due to their mass. Due to the usually large formats, they are often used on large roof surfaces, as they can be installed quickly and thus save time and labor costs. Since concrete roof tiles only have longitudinal seams and no transverse seams, the overlap and thus the cover length is very variable, but also depends on the roof pitch and the type of roof tile.
standard roof pitch, undercut: The standard roof pitch (RD) can be undercut if a so-called additional measure is carried out. Up to a fall below the RD by 8°, undervoltages or under-coverage can be carried out as an additional measure. If the standard roof pitch is undercut by more than 8°, at least a rainproof sub-roof must be built, and if it falls below more than 12°, a waterproof sub-roof must be built. A waterproof sub-roof is also required if, in addition to falling below the standard roof pitch, there are at least two other increased requirements. Increased requirements also include, for example, special roof shapes, exposed or extreme locations or local regulations. The exact definitions and a table on the additional measures to be ordered can be found in the "Technical Rule for Roofing with Roof Tiles and Roof Tiles" from the ZVDH.
Counter battens: The rear ventilation level under the tile covering prevents damage to the underside of the tiles due to condensation and improves the thermal insulation of the attic in summer. As a rule, counter battens measuring 30 x 50 mm are installed for rear ventilation. From a counter batten length of 12 m, counter battens with 40 x 60 mm must be used. From a length of 18 m, the required height is already 50 mm. For the exact dimensioning of the ventilation cross-sections, the minimum ventilation cross-sections for ventilated roofs from the ZVDH's "Leaflet on Thermal Protection for Roofs and Walls" are used.
But the sub-roof can also influence the counter-batten cross-sections. Underlays and on-roof insulation made of wood fibre boards have a lower strength than, for example, wooden formwork. From certain panel thicknesses, special nails or screws must be used to fasten the counter battens, which require a larger counter batten cross-section. In general, however, it should be noted that when using a roof panel, e.g. made of wood fibre, the counter battens should be increased to a thickness of 40 mm (40 x 60 mm). This ensures that the wind-suction-stressed support rails or full formwork are adequately fastened. Otherwise, special nails such as twist or threaded nails must be used.
Battens for flat roof tiles: Since special attention must be paid to a flat substructure for flat roof tiles, a batten cross-section of 40 x 60 mm is specified here from a centre distance of 75 cm. Center distances of more than 90 cm are to be avoided. For larger loads, such as snow loads, larger cross-sections may be required. A statement on this can be derived from the snow load zone, which can be taken from DIN 1055-5 for each location within Germany. A ►Allocation of snow load zones according to administrative boundaries is also available on the homepage of the German Institute for Building Technology (DIBt).
Roof overhangs: The choice of roof tile and roof pitch has an influence on roof overhangs due to different cover lengths and widths.
Cover length: Due to the lack of transverse seams, roof tiles have a very variable cover length. However, depending on the type of roof tile and roof pitch, certain height coverings are specified in the "Technical Rules for Roof Coverings with Roof Tiles and Roof Tiles" of the ZVDH. The minimum height cover is between 7.5 cm and 10.5 cm, depending on the slope and type of roof tile.
Cover width: The cover width of roof tiles is specified by the side rebate.
Sanitary downpipes: The sanitary downpipes must be routed over the roof. The associated passage tiles must be arranged in such a way that unpleasant odours cannot penetrate into nearby dormers or skylights.
Ridge formation: The ridge is always designed as a so-called roll ridge for roof tiles, as there are no roof tiles with a ridge connection seam due to the extrusion process. A cover (ridge roll) made of plastic and aluminium with ventilation openings is placed over the deadline before the ridge stones are covered.
Facilities for chimney sweeping work: The secured possibility of access to the chimney, e.g. via ladder hooks or steps, must be taken into account in the planning. In particular, the specifications of DIN 18160-5 must be observed. Among other things, the standard contains specifications for the safety of horizontal and vertical traffic routes depending on the respective roof pitch, as well as for railings, exit openings and standing areas at the chimney. The responsible chimney sweep can also be involved in this coordination.
covering: Temporary roofing must not be permanently exposed to the weather. If the roof covering is not applied until well after the undercovering, attention must be paid to the specification of the maximum permissible weathering time specified by the manufacturer. If the time limit is exceeded, a temporary cover must be applied.
Wind suction protection: The wind suction protection of roof tiles must be carried out in accordance with DIN 1055-4 and the ZVDH technical information "Wind suction". This describes the fastening of the roof tiles with storm clamps to protect against storm damage depending on the height of the building, the roof shape (gable, hipped or monopitch roof) and the individual roof areas (surface, verge, ridge, ridge, throat, mansard bend, eaves, hip). The type and number of storm clamps are determined by calculations in accordance with the ZVDH regulations. In addition, most manufacturers offer wind suction calculation programs on their websites.
Replacement roof tiles: Some additional roof tiles should be ordered in stock and stored for later replacement in the event of damage.
Soiling: After plastering the façade and before dismantling the scaffolding, the roof covering should be checked for damage and soiling. The ventilation grilles should also be checked, as dirt from the construction phase often restricts the air supply to the rear ventilation level.
Safety: The builder is responsible for safety on his construction site, unless he has appointed an external expert for this purpose. Care must be taken to ensure that the scaffolding is positioned in a sufficiently secure position, including roofer safety protection.
DIN 18160-5, Flue Gas Systems - Part 5: Equipment for Chimney Sweeping Work - Requirements, Planning and Execution
DIN 18338, VOB Procurement and Contract Regulations for Construction Services - Part C: General Technical Contract Conditions for Construction Services (ATV) - Roofing and Waterproofing Work
DIN EN 490: Concrete roof and moulded blocks for roofs and wall coverings – product requirements
German roofing trade: Regulations published by the Central Association of the German Roofing Trade (ZVDH)
Technical information on wind loads on roofs with roof tile and tile coverings, March 2011 edition, published by the Central Association of the German Roofing Trade (ZVDH)
Source: bauwion
