Part 1: Architect’s Guide 1 - 37 WIND SNOW, Maintenance WIND Watertightness Pressure and depression External and internal hygrometry Durability Accessibility and maintenance Figure 5.9 Requirements for building envelope Roof typology depends on several criteria, including shape, roof slope, external appearance, material colour, type of support and the materials used. Roofs are usually divided into three types: Flat roofs with no slope Pitched roofs (slope between 3 and 7%) Steep or arched roofs ‘T’ Intersection roof with gable side Overlaid Hip roof with gable side Hipped roof Flat roof Figure 5.10 Roofs For low slope roofs, the most important elements for the steel frame are the quality of fixings and arrangements for rainwater evacuation (Figure 5.11). 5.2.2 Flat roofs The principle of flat roofing systems on surface support elements can be applied using lightweight partitions, a metal sheet (see Figure 5.12) or the concrete topping technique with a concrete compression decking. A vapour screen, thermal insulation and waterproofing, with or without protection, are installed on the upper side. In order to provide the parapet which will be used to increase water tightness, it is possible to use a secondary steelwork façade which can be en extended to the required height. 5.2.3 Pitched roofs In the case of a low pitch roof (slope between 3 and 7%), water tightness is also obtained by applying bituminous products or PVC watertight membranes. Insulation is applied directly to the galvanized steel sheet tray. The process is light and economical for non-accessible roofs. Phonic insulation is adjusted through thickness of the materials and the order in which these are superimposed.
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