Flat roofs can be designed as warm roofs or inverted roofs. In the case of an unventilated, single-skin system (warm roof), the insulation is located directly under the waterproofing. In the case of the inverted roof, which is now rarely built, the insulation is on top of the waterproofing. Insulation on flat roofs is often carried out as slope insulation. Most manufacturers offer insulation boards that are made up to measure and cut at the respective gradient. The main materials used are EPS, PUR and mineral wool.
The flat roof is a component that is subject to high stress, especially due to sun, snow, hail and large temperature differences. Flat roof insulation must therefore not only be thermally insulating, but also pressure-resistant and temperature-resistant and must also maintain these properties permanently. A special requirement in the construction of flat roofs is the insulation thickness, which has an influence on the connection heights. This has a particular effect on roof terraces in the area of the door connections. The insulation must also be protected against moisture rising from below (e.g. residual moisture, vapour diffusion, condensation), so that a vapour barrier is usually installed under the insulation.
the system: The compatibility and compatibility of the various component layers with each other must be checked. However, most manufacturers also offer tested systems for entire roof structures for the different requirements, so that there is certainty of layer compatibility for their planning.
Insulation thicknesses according to DIN 4108 Supplement 2: Supplement 2, DIN 4108 can be used as a planning basis for the design of the connections. Design recommendations are presented there, which also determine a reference level for the quality of follow-up training. If the details are designed according to these specifications or if proof of equivalence can be provided, the flat-rate thermal bridge surcharge of 0.05 W/m²K can be applied in the public law certificates according to EnEV.
Minimum insulation parapet according to DIN 4108 Supplement 2:
1 Insulation
2 Ceiling
3 Exterior wall
Slope insulation: The use of prefabricated slope insulation has proven its worth. These are made to measure by the manufacturer in coordination with the planner and the craftsman carrying out the work. With this method, almost any slope situation can be realized. This makes it very easy to produce sloping flat roofs, and slope and thermal insulation are applied in a single operation.
Roof pitch for unused/extensively green roof surfaces: the roof pitch is usually between 2% and 5%. This can result in significant height differences in the substructure, especially in the case of larger roof areas, which can be created, for example, by slope insulation and which must be taken into account, for example, when connecting to rising components or in the area of patio doors. Roof pitches of less than 2% are possible under certain conditions (see also ►Application categories according to DIN 18531). For roof pitches above 5%, additional measures are required to prevent the roof structure from slipping.
Roof pitch for used/intensively greened roof areas: Neither the Flat Roof Directive nor DIN 18195 prescribe a minimum slope for used/intensively greened roof areas. However, appropriate measures must be taken to ensure that surface water that occurs, e.g. through precipitation, is constantly and effectively drained away. If damage to the waterproofing or the overlying layers is to be expected due to prolonged standing water, e.g. in puddles, complete water drainage must be ensured by appropriate measures, such as a slope.
Wind suction protection: If the roof does not receive an additional load, the insulation must also be secured against wind suction. This can be secured by mechanical fixation (dowels) in the substructure. However, bonding to the substrate is also possible, either with the help of an approved industrial adhesive or by hot bitumen on bituminous vapour barriers.
Compact roof: If water penetrates the insulation layer through the waterproofing, there is often the problem that it gets lost under the waterproofing and thus the leakage is difficult to locate. To prevent this underflow, insulation can also be glued to each other and to the substrate over the entire surface. Thus, the damage is limited to the leaking area, making it easy to find and repair. However, the insulation must be specially approved for this purpose, and the corresponding processing instructions of the manufacturers must be observed.
Large-scale roofs: Roof areas of industrial buildings with more than 2,500 m² must be planned in accordance with the Industrial Building Directive. This contains specifications that prevent the fire from spreading over the roof.
Extended warranty period: Some manufacturers offer a significantly extended warranty period for special roof waterproofing systems under certain conditions, e.g. 20 years. In addition to the prescribed use of components from a firmly defined roof system, comprehensive quality assurance is required, e.g. through the use of specially trained installers and TÜV monitoring, both of the production in the factory and the installation on site.
Subsoil: In order to carry out the roof pitch, which is often planned at a minimum gradient, in accordance with the rules, the subsoil of the warm roof, usually the vapour barrier, must be designed as evenly as possible and without major unevenness. Otherwise, the waterproofing above will fall below the required minimum gradient.
Wind suction protection: If a flat roof is designed with an additional load and without mechanical fixation or gluing, care must be taken to ensure that the construction progress is carried out quickly and taking into account the weather conditions and that the additional load is applied immediately after completion. Bonding or fixing the panels is safer.
Slope insulation: Slope insulation boards are usually ordered after exact measurements have been taken by the fabricator. In the meantime, the roof has not been completely sealed. Only the vapour barrier is an emergency seal. This must therefore be processed very carefully and the time span should be kept as short as possible and divided according to the weather conditions.
Care: Flat roofs are usually designed with minimal slope (e.g. 2%) so that water can flow to the drains. When laying the insulation, care must be taken to ensure that this low gradient is maintained and is not reduced by residues or dirt under the insulation. The surfaces should be tightly jointed and installed without offsets, so that an overlying seal (in the case of a warm roof) can be applied cleanly on the slope.
Solvents: Insulation materials are often not resistant to all solvents. Therefore, any impact must be avoided.
Storage: Roof insulation boards should also be stored in a dry place on the construction site and protected from direct sunlight.
Note: DIN 4108-1 (Thermal insulation in building construction; Sizes and Units) has been withdrawn and replaced by DIN EN ISO 7345.
DIN 4108 Supplement 2, Thermal insulation and energy saving in buildings - Thermal bridges - Examples of planning and execution DIN
4108-2, Thermal insulation and energy saving in buildings - Part 2: Minimum requirements for thermal insulation
DIN 4108-10, Thermal insulation and energy saving in buildings - Part 10: Application-related requirements for thermal insulation materials - Factory produced Thermal insulation materials
DIN 4109, sound insulation in building construction; Requirements and verifications
DIN 4109 Supplement 2, Sound insulation in building construction; Instructions for planning and execution; proposals for increased sound insulation; Recommendations for sound insulation in one's own living or working area
DIN 4109/A1, Sound insulation in building construction - requirements and verifications; Amendment A1
DIN 4172, Measurement Regulations in Building Construction
DIN 18195, Parts 3, 5, 8-10, Building Waterproofing
DIN 18338, VOB Procurement and Contract Regulations for Construction Services - Part C: General Technical Contract Conditions for Construction Services (ATV) - Roofing and Roof Waterproofing Work
DIN 18531, Part 1-4, Roof Waterproofing
DIN 18234, Structural fire protection of large roofs, fire stress from below
DIN EN 826, Thermal insulation products for the building industry - Determination of behaviour under compressive stress
DIN EN 13162, Thermal insulation products for buildings — Factory made products made of mineral wool (MW) — Specification
DIN EN 13163, Thermal insulation products for buildings — Factory-made products made of expanded polystyrene (EPS) — Specification
DIN EN 13164, Thermal insulation products for buildings — Factory-made products as extruded polystyrene foam (XPS) — Specification
DIN EN 13165, Thermal insulation products for buildings — Factory-made products made of rigid polyurethane foam (PU) — Specification
DIN EN 13167, Thermal insulation materials for buildings — Factory-made products made of foam glass (CG) — Specification –
DIN EN ISO 7345, Thermal insulation - Physical quantities and definitions
Flat Roofs Directive (technical rule for waterproofing), Rule for waterproofing of unused roofs, Rule for waterproofing of used roofs and surfaces
EnEV Energy Saving Ordinance for Buildings, Ordinance on Energy-Saving Thermal Insulation and Energy-Saving Plant Technology for Buildings
►Handling of mineral wool insulation materials (glass wool, rock wool), instructions for action of the German Employers' Liability Insurance Association for the Construction Industry – BG BAU
Source: bauwion.de
