Construction ENVS 2024 Technology

Question: Suggest some methods of constructing the flat roof structure, and its connections to the structural frame. Discuss the issues in the production of a specification to include materials, performance and workmanship for the flat roof covering? Answer: 3. Mainly three types of flat roof structures: Warm Roof: it has insulation layer above the deck, to keep it warm (Nfrc, 2015). Because of maintaining higher temperature inside the room, there are chances of penetration of vapor Figure 1 (Typical Warm Flat Roof) Source: https://www.pinterest.com/explore/flat-roof-materials/ moisture into the insulation and to prevent it Vapor Control Barrier (refer 4-figure 1) is always installed below insulation layer and to prevent water penetration from above the insulation, Waterproof Membrane (refer 1-figure 1) is installed to completely cover it (Bauder, 2017). Cold Roof: just opposite to the warm roof, in this case insulation layer (refer 4-figure 2) is installed above the ceiling and waterproofing membrane (refer 1-figure 2) is installed above the deck. It helps in maintain colder temperature inside the room. But at the same time in cold Figure 2 (Typical Cold Flat Roof) Source: https://www.pinterest.com/explore/flat-roof-materials/ weather like in Stoke-on-Trent, where average temperature varies between 20 C to 150 C (Holiday-weather, 2017) this type of roof can be vulnerable to condensate the vapor moisture trapped in between insulation and waterproofing membrane and can decay the insulation layer. To prevent the condensation, perfect through-ventilation need to be maintained and it is very difficult to maintain. Inverted Warm Roof: in this type insulation layer is placed above the waterproofing membrane to maintain membrane, roof deck and ceiling at constant lower temperature. It also Figure 3 (Typical Inverted Warm Roof) Source: https://www.greenspec.co.uk/building-design/timber-flat-roof-insulation/ protect membrane from heat and mechanical damage (GreenSpec, 2017). The uplifting of insulation layer is protected by placing ballast as weight above it. As discussed above, among all types of flat roof structures due to having low average temperature in Stoke-on-Trent, Warm Roof construction is the most feasible option available. It is even cheapest among all and will provide extra cushion in budget of the project. Connection of Flat Roof with building structures: must be done using best technique to obtain the desired result. Different designs can be adopted for steel and concrete frame buildings Figure 4 (Typical connection of Flat Roof with a Steel studs b with Timber) Source: https://buildingscience.com/documents/insights/bsi-050-parapets-where-roofs-meet-walls (refer figure 4) and protect against wind, heavy rain and high temperate issues. Entirely adhered air control is obtained by using Gypsum casing on the top of deck tied by screw and above insulation must be tied with deck for support and cover board above is again screwed with deck and finally the roof membrane is entirely stick to the cover board. Different types of materials used as roof top coverings: Rubber roof or EPDM: is a membrane applied over the roof, cheapest among all available material but absorbs sun heat and are not as durable as PVC membrane, it has a life of around 10 to 15 years only (RoofingCalc, 2017). PVC membrane: are single layered membrane joined by applying hot air and are the most famous application material, these are white in color so it reflects sun light and does not absorb heat, but are expensive, it has a life of around 15 to 30 years. Built Up Roofing (BUR): is a layer wise application of tars with gravels as last layer. It is the oldest form of covering, can take maximum foot load above it but due to its self over load it adds dead load on structure and requires stronger structures. It has a life of around 15 to 20 years. TPO: is a combination of EPDM and PVC like material, it is most durable but because of its new introduction very few contactors are available in market. It has a life of around 7 to 20 years. Modified Bitumen: is multi-layered but like EPDM absorbs heat and need skilled manpower for installation with a life of around 10 to 20 years. Silicon Spray: can be applied just after proper cleaning but is expensive with a life of up to 20 years only. So, based on the durability, life, performance and availability of skilled manpower for its application we can use any of the above material as roof top covering. References: Nfrc (2015). The Householders Guide to Flat Roofing. [Online]. Available at: https://www.nfrc.co.uk/docs/default-source/form-protected-documents/homeowners/householders-guide-to-flat-roofing-2015.pdf?sfvrsn=2 (Accessed 13 March 2017). Printrest (2017). Flat Roof Materials. [Online]. Available at: https://www.pinterest.com/explore/flat-roof-materials/ (Accessed 13 March 2017). Bauder (2017). Flat Roof Construction Thermal Design and Condensation. [Online]. Available at: https://www.bauder.co.uk/technical-centre/design-guides/flat-roof-design-considerations/thermal-design-insulation-and-condensation (Accessed 13 March 2017). Holiday-weather (2017). Stoke-on-Trent: Annual Weather Averages. [Online]. Available at: https://www.holiday-weather.com/stoke_on_trent/averages/ (Accessed 13 March 2017). GreenSpec (2017). Housing Retrofit: Timber Flat Roof Insulation. [Online]. Available at: https://www.greenspec.co.uk/building-design/timber-flat-roof-insulation/ (Accessed 13 March 2017). Buldingscience (2017). BSI-050: Parapets where Roofs met Walls. [Oline]. Available at: https://buildingscience.com/documents/insights/bsi-050-parapets-where-roofs-meet-walls (Accessed 13 March 2017). RoofingCalc (2017). Flat Roof Materials: PVC vs. TPO, vs. EPDM Rubber, vs. Modified Bitumen vs. BUR vs. Spray On, Plus Costs and Pros and Cons of each System. [Online]. Available at: https://www.roofingcalc.com/flat-roof-materials/ (Accessed 13 March 2017