School of Engineering
College of Engineering and Computer Science

ASSIGNMENT COVER SHEET

THIS SHEET SHOULD BE ATTACHED TO THE FRONT OF YOUR ASSIGNMENT WHEN IT IS SUBMITTED.

STUDENT ID NUMBER: u4997019

COURSE NAME: Discovering Engineering

COURSE CODE: ENGN 1211

DUE DATE: 1 April 2011
Submission of this assignment constitutes a declaration that:

• No part of this work has been copied from any other person’s work except where due acknowledgement is made in the text; and
• No part of this work has been written by any other person except where such collaboration has been authorised by the course lecturer concerned; and
• No part of this work has been submitted for assessment in another course in this or another part of the University except where authorized by the lecturer(s) concerned.

Student Signature: _____________________________ Date: _________________

Please place a ‘hard copy’ of your assignment in the assignment box provided, located on the first floor of the EngineeringBuilding (#32), ANU Campus.

Roofing methods

Taeho Jung
u4997019

Discovering Engineering, ENGN 1211
Lecturer: Mr Jeremy Smith

Practical Group 5
Team name: The A Team
Team members: James Mitchell, Anna Boyden, Perry Forsyth, Kasper Liu, Taeho Jung
Practical group supervisor: MrAnthony Flynn

Due date: 1 April 2011

The Australian National University


A. Design Topic
The United Nations states that “Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing…” (UN, 1948). However, in many developing and third world countries, a large proportion of people are too poor to have even a decent house. The condition is similar in Devikulam. Devikulam is a small village located in the state of Tamil Nadu, India. There are about 90 households in the village, and almost all of the people are living below the poverty line. Within Devikulam, housesin an area called ‘colony’ arenot adequately prepared for the heavy monsoon rain andpeople have expressed that they would like an improvement on their houses so they have better protection from the rain (EWB, 2011). Our team has identified this issue the prime problem ofthe community.
Houses provide people with security and comfort. Also, if the people in colony have better houses that can safely survive through the monsoon season, they will be able to spend theirresources and time on doing more productive activities, rather than fixing homes every monsoon season. As a consequence, our team has decided providing colony people betterhousing with improved protection from the rain as a design topic.
B. Research tasks
To assist with this topic the following sub-research areas were identified.
1. User needs regarding cultures and people#p#分頁標題#e#
2. The current housing situation in Devikulam
3. Environmental factors
4. Materials available
5. Existing housing solutions
6. Different kinds of roofing methods
This report will focus on identifying and evaluating the existing roofing methods that could be used in the colony.The report examines four different types of roofing methods: thatching, tiling, roofing with slate and wood.A simple set of design criteria will be developed and will be incorporated into a decision matrix to compare each method.Finally, how this information will assist our team in finding the final solution will be discussed and recommendationsregarding the most suitable roofing method will be made.
C. Evaluation of four types of roofs
Approach
There are many existing roofing methods. To be relevant to the purpose of the project, roofing methods that require modern resources and technologies that are not accessibletoDevikulamhave not been considered below. Instead, four roofing methods, thatching, tiles made from clay, roofing using slate and wood, were selected as they are all natural source roofing materials. Pros and cons of each method will be examined and this will be followed by source analysis.
1.Thatching
Thatching is one of the oldest roofing techniques (Letts, Quantrill, 2010). The materials used for thatching depends on the region; in England wheat straw is common(Letts, Quantrill, 2010), tropical countries use palm and Palmyra fronds (Keller, 2010) while countries like Korea where rice farming was extensive, use rice straw. Reeds are also used.
1.1 Advantages
1. It uses the local material and is produced by natural process.
2. As there is no need to import foreign materials, it is cost effective.
3. Attractive appearance (Botes, 2007).
4. It traps heat well; it is cooler in summer and warmer in winter (National Energy Services, 2008)
1.2 Disadvantages
1. Vulnerable to fire risk.
2. Susceptible to decay and decomposition.
3. The pitch of the roof should notbe less than 45 degrees to allow water to shed quickly. The steeper the roof, the greater the durability of the thatch (Botes, 2007).
4. Attracts rodents and birds (National Energy Services, 2008).
The durability of thatching depends on the material used. Thatched roof using long stem grasses lasts long, between 50 to 60 years (Roofing Products, 2011) while that made of rice straw only last one or two years. One way to improve thatched roofsagainst rain water leakage is to use two layers of thatching. Knapp (2003) says that two layers are used for thatching in south India, Coconut or Palmyra fronds as a lower layer topped with a fine layer of paddy straw or grasses to content with monsoon rain.Palmyra trees are abundant in the area, and rice is grown on wetlands (EWB, 2011) so they can be used to form a double layer thatching.
1.3 Source analysis
Botes and National Energy Services are unbiased as they provide evenly weighted discussions of pros and cons. Botes, although he is an architect, is less reliable since the information is explicitly of his own opinion. Roofing Products is more informative than others, presenting facts rather than comparing pros and cons. Knapp back-ups his statements with other various researches which indicates high accuracy. #p#分頁標題#e#
2. Clay tiles
Clay tiles are produced by baking moulded clay. The clay used, the temperature of kiln and the amount of time the tiles spend in the kiln determine the characteristics of the tile. The laying technique also depends on the type of tile used (National Roofing Contractors Association, 2011).Some of common tile types are illustrated in figure 1.

Figure 1: Different types of tiles (Roof Magician, n.d.)
2.1 Advantages
1. Tiles last long because they do not decompose and attract pests such as termites, birds, rodents
2. They are not flammable.
3. Provide good protection from rain.
4. Require little maintenance (RoofGenius, 2011)
2.2 Disadvantages
1. If tiles were to be made in Devikulam, the people need to learn how to make them.
2. Making tiles may require resources that are not reachable from the village. They include;
• Highly skilled personnel who can teach villagers tile making.
• Building a tile making facility may be inappropriate - Set-up cost will be high.
• There may not be adequate fuels to feed the kiln and maintain high enough temperature to produce tiles.
3. Tiles are fragile, they are easily broken.
4. Tiles are heavy; the current mud house is likely to be too weak to support the weight of tiles(RoofGenius, 2011).

Figure 2: Bamboo roof in Osaka, Japan (Telford, n.d.)
Introducing clay tiles seem impossible, due to the cost and the fact that the entire house needs reconstruction with stronger materials. A more appropriate and simpler way is to use bamboo. Split bamboo can be laid similarly to Spanish tiles (see figure 1 for Spanish tile arrangement), using natural overlap to create a smooth surface for water to run from(Roofing Products, 2011). Figure 2 shows the actual bamboo roof made from using this technique in Japan.
2.3 Source analysis
RoofGenius delivers unbiased comparisonbetween different types of roofing. Accuracy is high as the webpage is run by a retired shingler as well as a roofing contractor. Information is clear,simple and easy to understand even for people who do not have any background knowledge of roofing.
3. Slate
A slate is a type of rock that can be split into sheets of the thickness of 4 to 15 mm. These sheets are laid in a way that each layer of slate laps over the piece of slate below so the rain cannot get through the roof (premierslate, n.d.).
3.1 Advantages
1. It lasts long; invulnerable to rot and insects.
2. Well protected from a fire.
3. Little maintenance required.(RoofGenius, 2011)
3.2 Disadvantages
1. It is heavy; therefore houses in Devikulam would require extra strength to support a slate roof.
2. Slates are breakable (RoofGenius, 2011).
Similarly as clay tiles, slate roofs seem unfeasible for Devikulam because of the reconstruction reason. Also, slate or any similar kind of rocks that can be split into sheets may not be found in the area.#p#分頁標題#e#
4. Wood roofs
Wood has been a popular roofing material due to its availability (Roofing Products, 2011). There are two types of wood roofs, using shingles and shakes. Shingles are produced by sawing a wooden block while shakes are split from a wood block (Advanced Housing Research Center, 2000).While shingles are less expensive than shakes, shakes last longer.
4.1 Advantages
1. It requires less specialised knowledge for processing and installation than other roofing methods such as thatching (Roofing Products, 2011).
2. Wood is a widely available resource.
4.2 Disadvantages
1. Regular maintenance is required(Roofing Products, 2011).
2. Susceptible to decay, especially in humid weather. Shakes and shingles that have absorbed moisture can result in swelling, shrinking, cracking and they encourage more moisture to get in. Mildew, moss, algae and lichens can grow on the shake roof which also speed up the decay process.Chemical treatment can be applied to increase the durability but not an option for Devikulam(Advanced Housing Research Center, 2000).
3. Fire risk.
It is clear that wood roofs in Devikulam would not last long because of the humid weather. Furthermore, frequent replacement of wood roofs due to decay may result in deforestation.
4.3 Source analysis
Since Advanced Housing Research Center is under the US federal agency the information is of high accuracy. It is factual and no indication of bias in the information.
D. How this research will be incorporated into team’s design topics
The findings in this report will provide our team background knowledge of different types of natural source roofing. All of the information collected by team members will be collaborated in order to choose a solution that can be successfully implemented in Devikulam. In particular, this report will be considered closely with the available material information so that the local materials are used as much as possible.
E. Recommendations
Even though clay tiles, slates and shingles and shakes come from natural sources, they are not appropriate for Devikulam due to various reasons discovered above. Instead, thatching and bamboo using Spanish tile arrangement have been identified as more suitable roofing techniques. Five possible solutions have been generated using these methods and are shown in the decision matrix in table 1. They are evaluated against five criteria; protection from rain, cost, time taken for building roof, labour and durability.
Table 1: Decision matrix
Criteria

Possible
solutions Protection from rain (x5) Durability
(x4) Time taken for building roof (x3) Labour (x2) Cost (x1) Total
Thatching –
single layer 2 2 4 4 4 42
Thatching –
double layer 3 3 3 3 3 45
Bamboo only 1 1 5 5 5 39
Bamboo+Thatching (single layer) 4 4 2 2 2 48
Bamboo + Thatching (double layer) 5 5 1 1 1 51

The matrix clearly shows that using bamboo and double layer thatching is the best option. I agree with this result as this methodis expected to provide the best protection from the rain.This will increase the durability of thatch underneath the bamboos as the bamboo layer will prevent rain water from contacting the thatch directly, thus keeping it dry. As a result, my recommendation is to utilise a double layer thatched roof with bamboo laid in a Spanish tile arrangement on top.#p#分頁標題#e#

F. References
Advanced Housing Research Center, 2000, Wood Shakes and Shingles: http://www.ttc-switch.com/dissertation_writing/Engineering/2012/0227/1067.html Tips for Longer Life, viewed at 27 March,
Botes, J, 2007, Thatch Roofing – The Pros and the Cons, viewed 25 March 2011,
Engineers Without Borders Australia, 2011, 2011 EWB Challenge Design Brief, viewed 20 March 2011,
Keller, M, 2010, How to Build a Palmetto Thatched Roof, viewed 26 March 2011,
Knapp, R,G (ed), 2003, Asia’s Old Dwellings Tradition, Resilience and Change, Oxford University Press, Oxford, p 56.
Letts, J, Quantrill, K, 2010, Thatching with ‘Long Straw’, viewed 26 March 2011,
National Energy Services, 2008, Thatched Roof Coverings, Factsheet, viewed 26 March 2011,
National Roofing Contractors Association, 2011, Clay tile and concrete tile, viewed 26 March 2011,
premierslate, n.d., What is slate?, viewed 27 March 2011,
Roof Magician, n.d., Clay Roof Tile Installation, viewed 27 March 2011,
RoofGenious, 2011, Popular roofing materials, viewed 26 March 2011,
Roofing Products, 2011, Biomass Roofing For All Needs, viewed 26 March 2011,
Telford,R, n.d., Bamboo roof, Osaka, Japan, viewed 27 March 2011,
United Nations, 1948, The Universal Declaration of Human Rights, Article 25, viewed 27 March 2011,