Roof tiles are coarse ceramic, small-format building elements made of clay, clay and pores filled with water for covering sloping roofs. The tiled roof can be made of unlocked, traditional tiles, such as the beavertail tile, or of modern interlocking tiles, such as flat roof, reform, smooth, double troughed seam and hollow seam tiles.
Depending on the rain resistance of the individual tile models and the design of the sub-roof, different roof pitches are possible. In addition to their function as the outermost covering layer of the roof, the roof tiles also have an important design task. Depending on the architectural concept or the function of a building, different covers can be considered. Clay and loam are natural raw materials. Roof tiles have a long service life, are recyclable and do not emit any pollutants, which makes them one of the sustainable natural building materials. They are colour, frost, UV and acid resistant as well as open to diffusion. Bricks are available in many different shapes, sizes and colours, which opens up a wide variety of design options.
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: The support rail (battens for short) is mounted on the counter battens with wire pins and supports the roof covering. The distance between the slats is determined by the chosen roof covering. As a rule, support rails have a cross-section of 30 x 50 mm (grading class S 10 according to DIN 4074-1). However, from a centre distance of the counter battens of more than 80 cm, slats with 40 x 60 m are to be used (grading class S 10 according to DIN 4074-1). For center distances of more than 1 m, a mathematical proof is required. The exact dimensions according to static specifications are specified in the ZVDH's "Notes on Wood and Wood-Based Materials".
Roof overhangs: The choice of roof tile has a considerable influence on the roof overhangs due to different cover lengths and widths. These should be calculated and agreed on at an early stage.
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.
Refurbishment / Renovation: During refurbishments or renovations, attention should be paid to the deck length. Not all roof tiles are also available as sliding tiles, which can be used to compensate for different roof lengths.
Ridge formation: The ridge can be designed either with ridge connection tiles or as a so-called roll ridge. Ridge connection tiles are surface tiles with a special head rebate, which are covered in the top row of tiles of a roof surface and to which the ridge tile can connect.
However, since there are no ridge connection tiles for some tile coverings, the roll ridge is carried out here. A cover (ridge roll) made of plastic and aluminium with ventilation openings is placed over the deadline before the ridge tiles are covered. Although the version with a ridge roller is somewhat more cost-effective than the ridge connection tiles, the ridge roller is a plastic element that is more susceptible to weather influences in the long run.
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 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 - 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 1304, Roof Tiles and Shaped Tiles - Terms and Conditions 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, published by the Central Association of the German Roofing Trade (ZVDH)
Source: bauwion
