3 minute read
Figure 87 GREEN ROOF EXAMPLE
Green roof is an environmental, social and economical use of the building roof. Green roofs may be installed at any height with an access provided for its maintenance. The planted spaces, may be used to provide human enjoyment and environmental enhancement or energy savings for the users. Broadly, they can be catogorised into two types : 1. Roof gardens : are installed for the access and enjoyment of people. They are also costly to build, require intensive maintenance and are heavy in weight due to the deep soil profiles.
2. Green roofs : are lightweight with thin soil profiles and minimal maintenance requirements. They are cheaper to construct as they are installed for environmental performance and visual improvement only.
Advertisement
Classification Green Roof Systems Traditional roof gardens restricted the planting to containersand planters or used a layer of ordinary soil spread on the roof.The contemporary roof greening systems are however much advanced as they use organic matter instead of soil for the plant growth. The modern green roofs are categorized by the substrate or growing media depth There are three types of systems - intensive (deep), semi-intensive (moderate depth) and extensive (shallow) Finally, small niches are dug into the subtrate and saplings are planted. The remaining functioning and the maintainance of the plants remain similiar to regular gardening.
Working Mechanism After the construction of the roof slab, several layers of water- proofing are applied in order to ensure that there is no leak Of dampness in the future. To further assist an easy drainage system, floor drain trays are often installed which help channel the water in a predetermined location. Another way of doing this is through the use of network of pipes which are more flexible and agile, Once the waterproofing is done, layers of geotextile fabric is applied. This helps the soil and other medium on top of it, retain their place even water runs through them. Furthermore, layers of engineered soil - soil with a variety of mixes for the desired plant species and variety - are laid on top. This becomes the substrate or the growing medium for the plants Finally, small niches are dug into the subtrate and saplings are planted. The remaining functioning and the maintainance of the plants remain similiar to regular gardening.
Figure 87 GREEN ROOF EXAMPLE
3.11.3COMPOSITE BEAM AND COLUMN This technique is extensively used in Auroville since 1993. U-shaped CSEB are reinforced with reinforced cement concrete. Reinforcements vary with the span, but the rod diameter cannot exceed o 12 mm for the Auram blocks 290 & 295 and @ 16 mm for the Auram blocks 240 & 245.
The U blocks are used as lost shuttering, but they also help the compressive strength of the beam. Hence it becomes a composite technique as the reinforced concrete work in tension and the U block works in compression. The concrete cast in the U shape is normally 1 cement: 2 sand: 4 gravel 1/2'. The vertical mortar in between the U blocks is cement sand mortar CSM 1:3 of 1 cm thick-
ness. Three types of beams have been developed: Triple height beams (1 U blocks downwards, 1 plain block in the middle, 1 U block upwards) The bottom part of the beam is cast first in a reversed position. After 1 month it is returned and the incomplete beam is lifted with a lot of care and the rest of the beam (plain block in the middle and U block on top) is done in situ in. - The maximum span for a triple height beam will be limited to 3 m with 2 steel bars . 12 mm on the top and 2 steel bars o 12 mm on the bottom. @ 6 mm stirrups are laid in the thickness of the vertical mortar to link the ten-sile and compressive bars of the beam. Note that this triple height beam is rarely precast fully on site as it is too heavy to lift. - The horizontal mortar joint is with cement sand mortar CSM 1: 3
