Constructing Environments
Week 8 Journal – In Detail (Part one) By Wenjie Cai (634077)
Case Study: Extension of Queens College Interrogation of detailing decisions 1. The canopy -‐ The canopy outrigger is used for supporting the overhanging roof. PFC is used to support the outrigger. Colorbond flashing that connected with the flat sheet is used to prevent water seeping into the house. A half round gutter is used at the end of the roof for better drains of the roof. Flexible sealants are used at the bottom of the roof to seal the gap between the compressed sheet and other structural members. Bolts are used as the joist of outrigger and the flashing. The battens are used to locate the roof covering sheet.
Figure 1: The canopy
Figure 2: The glass block window
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2. The window -‐ It is a glass block window between two precast concrete panels. Two steel frames are used between the concrete panel and the glass block. For the joist of the glass blocks, mortar joint is used. The steel frame above the window is connected with an expansion material and the one below the window has two reinforcing rods. The use of the reinforcing rods is to strengthen its force for the compression. There are two studs at the top and bottom of the window beside the precast concrete panel. The plasterboard that covers the steel stud is connected with the stud by nails. Timber sill is located on the bottom one and connected with the steel frame. The gap between the plaster board and the sill is painted to match plasterboard
Composition 1. For the overhanging roof, the main composition includes plywood (plywood under flat sheet and battens), steel such as flat sheet, half round gutter and PFC. Plywood
Steel
2. For the windows, the main composition includes precast concrete panel, steel for studs and frame and glass.
Glass Block
Precast concrete panel
Steel stud
Building process 1. The canopy outrigger is the first step of the construction. It is connected with the precast concrete panel by bolts. Then the battens will be built on both the top and the bottom side of the outrigger following by construction of the plywood, the flashing and the flat sheet. The last step of building process is the half round gutter connected with the PFC. 3
2. The steel glass block frame is built right after the construction of the precast concrete panels (the expansion material is constructed at he same time). Then the glass blocks will be constructed between the steel frames and the mortar joint connects them. The plasterboards and the timber sill are then built and connected with the steel frame. After that is the construction of the steel stud nailed with the plasterboards.
Pros and Cons 1. In this detailing design, there is a gap between the flashing and the flat sheet. Water may flows into the canopy by this gap so there should be silicone to seal this gap and also the gap between the plywood and flashing so that the construction does not damaged by water. 2. Timber sill is used to provide protection from water. However, in this case, there is no slope of the sill which means it does not drains well. This may cause damage to both the windows and the sill in long term. The gap between the plasterboard and the sill should insert an silicone so that the stud is not damaged by water. However, the uses of the sealants provide well protection to the canopy and the half round gutter provides better drains when the water flows from the flashing.
Sustainability and Environmental Analysis 1. The use of colorbond roofing helps with reducing cooling and heating costs, which is also the advantages of using steel roof. The material using for the canopy is steel that is recyclable. This provides conservation of the natural resources. Plywood using in this construction reduce the energy cost by transportation because it is lighter than other materials such as concrete. It used relatively lower energy to complete its construction. 2. Construction glass often ends up with landfill which is not very sustainable. However, there is a lot of recyclable materials used in this construction such as timber and steel.
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Economic Implications of Decisions The materials that used in these constructions are mostly precast concrete panel, steel and glass. For the canopy, colorbond is used for the flat sheet, flashing and the gutter. Colorbond roofing is relatively more expensive than some roofs such as tile roof. This causes more money during construction but it makes the color of the roof last longer so it reduce the cost of maintaining. Glass block is also an expensive material compared to some other material. However, the cost of the precast concrete panels and timber are lower.
Where and why things goes wrong in this type of detail Cracks may occur on the plasterboard after years because of the ages and the lack of supporting. The gap between the flashing and the flat sheet may cause leaks that damage the construction. The timber sill without slope may also cause leaks when the water does not flow away and stay on the timber for long.
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