10. Flat Roofs
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Session 10
Flat Roofs 10.1. Introduction 10.1.1. Elements 10.1.2. Standard representations 10.2. Traditional vs protected 10.3. Details 10.3.1. International standards 10.3.2. Spanish standards 10.4. Case studies 10.5. Bibliography
Based on the original presentations by Prof. Juan Alamillo. Adapted by Prof. Julián García julian.garciam@upm.es Translated by Luis M. Martín
Flat roof building process at Fuenlabrada Hospital. Arch. Andrés Perea
10. Flat Roofs
10.1. Introduction. Spanish CTE DB HS1 states that flat roofs are those that meet the following slope standards:
But there are many other possible classifications. The international standards are: 路 Traditional roofs. Waterproof membrane was usually tarpaper, a 'paper' or fiber material soaked or impregnated in tar. 路 Protected membrane roof. A roof where thermal insulation or another material is placed above the waterproofing membrane. 路 Composite steel deck. A flat roof deck often used for commercial structures.
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10.1.1. Elements. Flat roofs can, according to CTE DB HS-1, include the following elements. · Sloping. Mandatory whenever the support base does not have the required slope. · Vapor barrier. Immediately under the insulation, to avoid humidity by condensation. · Separating layers. Under thermal insulation, under waterproofing membranes, etc. Used to avoid contact of chemically incompatible materials. · Thermal insulation. Appropriate materials. · Protective layers. Over thermal insulation, over waterproofing membranes, etc. Used to avoid cracks or depressions. · Waterproofing layers. To avoid water entrance. · Finishing layer. Various systems. · Drainage system. The drainage system may consist on sinks (vertical) weirs (horizontal) and gutters (linear in edge), or in a combination of them all.
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Slope mortars. Construction of the slope of a flat roof with mortar. Lightweight concretes or mortars are often used in Spain. Mind the details about junctions with walls and parapets: a joint to avoid expansion cracks is always mandatory.
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Vapor barriers, separating and protecting layers. Vapor barriers, separating and protecting layers can have different forms, and be composed of different materials. For vapor barriers, primers are used, most based on bitumen, improved coal tar or asphalt products. Soft protections or separations are often achieved with polyethylene films, that allow contact of chemically incompatible materials.
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Thermal insulation. Its density and thickness is established by the DB-HE-1 CTE. In Madrid climate zone, for a standard 60-90kg/m3 density, the usual thickness is between 8 and 10 cm. The most common material is extruded polystyrene (XPS), due to its low moisture absorption and high durability.
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Waterproof membranes. Waterproof membranes are often composed by one of the following materials: · Modified bitumen. Improved coal tar or asphalt products. · EPDM. Ethylene Propylene Diene Monomer, a synthetic rubber. · PVC. Polyvinyl Chloride, also known as vinyl roofing. · FTPO. Flexible Thermo Polyolefin, a polymer that doesn’t cure, and can be heated again.
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Finishing layer. Various systems, from loose gravel to standard ceramic tile flooring. Most drained systems use plots to create a cavity between the finishing and the runoff surfaces. In these cases, the roof finishing can be really flat, as the joints between the tiles act as a huge rack that hides water as is flows to the drainage system.
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Drainage system. The drainage system usually consists on vertical sinks, most made in EPDM or PVC. Weirs, usually covered with metal racks, are used in pedestrian areas. Gutters in edge are appropriate for pitched roofs.
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10.1.2. International graphic standards – Zentralverband des Dachdeckerhandwerks
Waterproofing membrane – Bitumen Waterproofing membrane – PVCs and EPDMs Waterproofing membrane – Reinforced membranes Thermal insulation Vapour barriers Separative layers Mortar layers Slopes Protective layers Drainage layers
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10.2. Traditional flat roof vs. protected membrane roof. Tile finishing. Elastic joints every 3-4m. Cement mortar. Waterproofing layer Slope Thermal insulation Vapour barrier
Structure or substructure
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Protected membrane roof. Tile finishing. Elastic joints every 3-4m. Cement mortar. Separating layer Thermal insulation Waterproofing layer Slope
Structure or substructure
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10.3. Details 10.3.1. International standards
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10.3.2. Spanish standards
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10.3.3. Special junctions. Wall – flat roof.
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Special junctions. Drains and overflows.
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10.4. Case studies Protected membrane roof. DANOSA Catalog.
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Details. Protected membrane roof. DANOSA Catalog.
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Case studies Protected membrane roof. Plot system. DANOSA Catalog.
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Details. Protected membrane roof. Plot system. DANOSA Catalog.
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Case studies Protected membrane roof. Drained system. DANOSA Catalog.
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Details. Protected membrane roof. Drained system. DANOSA Catalog.
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Case studies Vehicle flat roof. DANOSA Catalog.
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Details. Vehicle flat roof. DANOSA Catalog.
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Case studies Protected membrane roof. Loose gravel. DANOSA Catalog.
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Protected membrane roof. Loose gravel. DANOSA Catalog.
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Case studies Protected membrane roof. Self-finished roofing felt. DANOSA Catalog.
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Details. Protected membrane roof. Self-finished roofing felt. DANOSA Catalog.
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Case studies Lightweight deck. Self-finished roofing felt. DANOSA Catalog.
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Lightweight deck. Self-finished roofing felt. DANOSA Catalog.
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Case studies Intensive green roof with drainage layer. DANOSA Catalog.
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Details. Intensive green roof with drainage layer. DANOSA Catalog.
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10.5. Bibliography Deplazes, A (Ed.) (2009) Constructing Architecture. Materials, processes, structures. Birkhäuser, Basel Knaack, U.; Klein, T. (2009) The Future Envelope 1: A multidisciplinary approach. 2009. Research in Architectural Engineering Series Knaack, U.; Klein, T. (2009) The Future Envelope 2: Architecture - Climate – Skin. Research in Architectural Engineering Series Sedlbauer, K. et al. (2010) Roof Construction Manual. Flat Roofs. Birkhäuser, Basel Spanish regulations: · Código Técnico de la Edificación: · Normas UNE-EN 10077-1, UNE-EN 12210, UNE-EN 12207, UNE-EN 12208, UNE-EN 12400, UNE-EN 12567-1, UNE-EN 14351-1 y UNE-EN -ISO 140-3