Log Book - Week 6 Roof Systems The main uses of a roofing system are shelter, to collect rainwater(gutters) and can also improve the external appearance of the house. The weakness of a roof is the joins between materials such as tiles or corrugated iron. Flat Roofs have a pitch of between 1-3 degrees. They aren’t completely flat because the water will build up on the roof and may cause leakage. Can be constructed out of concrete slabs, flat trusses, beams & decking or joists and decking/ roof sheet. Pitched and Sloping Roofs have a pitch of greater than 3 degrees. These roofs can be constructed out of rafters, beams, purlins and trusses. Concrete Roofs Generally flat, concrete slabs that are supported on concrete beams that transfer the load down the columns to the foundation. The top surface is sloped towards draining points to ensure no water is left surface. IMAGE 1: A waterproofed concrete slab used as the primary roofing material. This roof would be at a slight slant to make sure it doesn't fill up with water.
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Log Book - Week 6!!!!Roof Systems
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The main uses of a roofing system are shelter, to collect rainwater(gutters) and can also improve the external appearance of the house. The weakness of a roof is the joins between materials such as tiles or corrugated iron.
Flat Roofs have a pitch of between 1-3 degrees. They aren’t completely flat because the water will build up on the roof and may cause leakage.Can be constructed out of concrete slabs, flat trusses, beams & decking or joists and decking/roof sheet. Pitched and Sloping Roofs have a pitch of greater than 3 degrees. These roofs can be constructed out of rafters, beams, purlins and trusses.
Concrete Roofs Generally flat, concrete slabs that are supported on concrete beams that transfer the load down the columns to the foundation. The top surface is sloped towards draining points to ensure no water is left surface.
IMAGE 1: A waterproofed concrete slab used as the primary roofing material. This roof would be at a slight slant to make sure it doesn't fill up with water.
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Structural Steel Framed Roofs Flat: Combination of primary and secondary roof beams. They can be lined with metal deck, concrete composite structures or for a lighter choice, sheet metal roofing.Sloping roofs: Usually constructed from roof beams and purlins.Portal frames: A framing system where the columns and beams are connected by a rigid joint.
Trussed Roofs Usually made from timber or steel.Trusses are used because they can span relatively long distances using little material. This meaning they have a high strength to material ratio which every builder and engineer wants.
Light Framed Roofs Gable Roofs: Roofs that have a vertical triangular section of wall at one or both of the ends of the roof. Large openings between rafters can be used to put a chimney through.
A sketch showing the primary components of a gable roof.
IMAGE 12: A traditional flat truss.
IMAGE 13: A gable truss.
!!An Introduction to Metals!
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Pure metals are one element only. Metals are both malleable and ductile meaning that the can be changed into shapes without breaking.!The 3 main types of metals are:Ferrous - iron Non-ferrous - all other metalsAlloys - Combinations of two or more metals.Ferrous alloy if it contains iron,Non-ferrous alloy if to doesn’t)
Properties Hardness depends on the type of the metal. for example, lead can be easily scratched where gold cant.Low fragility.High ductility.Medium-high flexibility/plasticity.!Generally impermeable. Can’t absorb water.High density. Aluminium(the least dense metal) is still 3 times denser than water. Gold is 19 times denser than water.Very good conductors of heat and electricity.!Can be very durable of well finished.Can be reused and recycled.Generally cost effective.
Considerations Metals will react with other metals by donating or accepting another metal’s ions. By looking at the picture, nickel and copper will cause steel to corrode. This is because steel is more prone to corrosion.Galvanised steel has a thin layer of zinc to protect the steel. As zinc is prone to corrosion, it will corrode first leaving the steel untouched.
Considerations Oxidation is the process in which a metal reacts with oxygen forming an oxide which will either protect the metal, or more than likely, make it rust. Aluminium oxidises from contact with the air and instantly forms a protective layer. Steel rusting is an example of corrosion(rust due to oxidation).
IMAGE 2: The metals higher up on the Galvanic Series are more prone to corrosion.
IMAGE 3: An image of a severely rusted chain. You can see parts of the chain flaking off due to the process of oxidation
!Ferrous Metals
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Distinct Properties -Magnetic properties-Very reactive chemically(is able to rust)-Strong under compression
Wrought IronAn old method of shaping iron; around 1000BC. Wrought iron is formed when iron is heated and hammered into a desired shape. These days, wrought irons is used for decorative pieces and can still be used in bars for windows and doors, however it is too labour intensive.
IMAGE 4: A wrought iron gate. These spirals and curves of the iron are common with wrought iron designs.
Cast IronWidely used in the 19th century and the beginning of the 20th century.Formed when molten iron is poured into moulds and allowed to set. Cast iron has a very high compressive strength.Most commonly used in columns because of it’s high compressive strength.
IMAGE 5: Cast iron columns that are most commonly seen in older buildings. These are easily identified to be cast iron because it would be impossible for a human to hit those patterns into a metal with such precision.
!Steel!!
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Properties -Very strong - A good conductor of heat and electricity- Ductile(can be stretched out into a wire)- Long lasting if properly protectedIron Alloys - Steel
Steel is an alloy of iron with the main additional alloy element being carbon.Other alloying elements include manganese, chromium, boron and titanium. These different elements combined with iron result in different types of steel having varying properties.
Structural steelHot rolled steel: The steel is shaped while it is still hot. Generally used as primary structural elements such as girders and tend to be heavy.Cold formed steel: The steel is made into a sheet that has been previously cooled. This sheet is then folded to make cold formed steel.Reinforced bars have a deliberate uneven edge to help grip onto the concrete more
IMAGE 6: Cold formed steel. This image shows that this type of steel is thin which makes it a lot lighter than hot rolled steel and therefore cheaper.
IMAGE 7: Hot rolled steel being used as the primary structural element.
!!!!!!!!!!!!!!Non-Ferrous Metals!
Stainless steel alloys Chromium is the primary alloying element (minimum of 12%).It is a very high quality steel.Commonly used in sheets, plates and wire and used for kitchen sinks.
Aluminium !Properties -Very light in comparison to other metals-Non-magnetic and non-sparking -Easily constructed !Uses -Window frames-Cast door handles and catches for windows-Rolled aluminium is for cladding panels IMAGE 8: A window frame made out of aluminium.
IMAGE 9: Electrical copper wire with an outer plastic coating. This coating is used because plastic is a poor conductor of electricity ensuring the current doesn't escape from the copper.
Copper Properties -Reddish in colour with a bright metallic glow -Turns green when exposed to weather(oxidation)-Very malleable and ductile -Good conductor of both heat and electricityUses Copper is traditionally used as a roofing material where it is green because of it’s exposure to weather. It’s also widely used in electricity cabling and for domestic water and heating.
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IMAGE 10: A zinc coated steel coin. In 1943 copper wasn’t able to be used due to WWII. Steel was used instead with a zinc coating.
IMAGE 11: Lead gutters used on a roofing system. They were thought to be efficient materials as they could last hundreds of years. However the health risks were not taken into account.
Lead Lead used to be commonly used in roofs, tank linings and flashing strips for waterproofing. However due to the health risks involved, it is less commonly used today. As it is a heavy metal, it stays in the body for extended periods of time causing lead poisoning.Properties -A soft metal -Highly malleable -Ductile -Poor conductor of electricity-Resistant to corrosion but deteriorates upon exposure to air
ZincThe most common use of zinc in modern construction is a coating on the outside of steel. This helps prevent corrosion of the steel and is known as galvanising. It’s primarily used in roofing where the roof is always exposed to weather. It’s brittle at ambient temperatures, but is malleable at 100 to 150 degrees celsius.It’s a reasonable conductor of electricity.
Plates A plate structure is a rigid, square structure that disperses applied loads in a multidirectional pattern with loads distributed evenly. ‘A common example of a plate structure is a reinforced concrete slab’(Ching, 2008).
IMAGE 14: An example of a Z shell folded plate structure.
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Knowledge Map of the demolition of 12 Paterson St, Princess Hill
Knowledge Map of the construction of 173 Cecil St, Williamstown
!!Glossary Rafter: Long beams which forms part of the internal framework of a roofing system. Attached to the ridge beam(very top beam).Cantilever: A beam or structure that is only fixed at one end.Portal Frame: ‘A rigid structural frame consisting essentially of two uprights connected at the top by a third member.’!! ! ! https://www.google.com.au/#q=portal+frame+definition Eave: A part of the structure that overhangs past the wall of the building.Alloy: A metal made by combining to or more natural metals(elements).Soffit: The underside of any element of a building. Eg. Beam, arch etc.Top Chord: An inclined or horizontal member that establishes the upper edge of a structure(truss).!!!!!References:E-learning:http://www.youtube.com/watch?v=q5ms8vmhs50&feature=youtu.behttp://www.youtube.com/watch?v=RttS_wgXGbI&feature=youtu.be http://www.youtube.com/watch?v=SQy3IyJy-is&feature=youtu.be !http://www.youtube.com/watch?v=EDtxb7Pgcrw&feature=youtu.be !!IMAGE 1: http://www.connoisseurroofs.co.za/concrete-roofs.htm IMAGE 2: http://www.amacgroup.com.au/index.php?ID=12 IMAGE 3: http://merlin252.deviantart.com/art/Rusted-Chain-26559026 IMAGE 4: http://www.sunkingfencing.com/decorative-wrought-iron-gates.html IMAGE 5: http://ancientpoint.com/inf/97196-antique_fluted_cast_iron_columns___fluted_and_structural.html IMAGE 6: http://www.structuremag.org/article.aspx?articleID=355 IMAGE 7: http://blog.lamidesign.com/2006/03/6030-house-floor-beam-day.html IMAGE 8: http://www.gurujiwindowsolution.com/alwindows-next.html IMAGE 9: https://www.servicecentral.com.au/article/how-much-does-it-cost-to-rewire-a-house/662/ IMAGE 10: http://www.retrothing.com/2008/01/1943-steel-penn.html IMAGE 11: http://www.k-roofing.co.uk/images/slates_and_lead_gutter.jpg !IMAGE 12: http://www.trusstek.com/?page_id=19 IMAGE 13: http://home.howstuffworks.com/home-improvement/repair/house9.htm IMAGE 14: http://ketchum.org/ShellTandF/ http://www.wisegeek.org/what-is-a-soffit.htm Ching, F. (2008) Building Construction Illustrated (4th ed.). Hoboken, New Jersey: John Wiley & Sons, Inc. (p. 2.18)KEY TERMS(TRUSS)> http://www.alpeng.com/index.php?option=com_content&view=article&id=73&Itemid=9
