The roof is one of the building elements that function as a top cover for a building. Generally, the roof has three components, roof truss, roof frame, and roof cover. A roof truss is the main foundation to support all the roof structures. While roof frames consist of; purlins as rafter holders in the mid-span; the ridge is a horizontal beam as a rafter holder at the top; valley or hip roof is a frame to join between two roofs meet and as a gutter holder. Wallplate is a horizontal beam as load-bearing for rafters.
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What Are Common Roof Types People Used
Based on the shape, the roof can be classified into five types, gable roof, shield roof, conical roof, modified roof, and flat roof.
Gable Roof Type
The gable is a triangular roof model. The gable roof will make rainwater flow from two sides. Gable roofs are widely used in housing that has the same building size as the land area or in factory buildings, warehouses, aircraft hangars, workshops, and so on. The gable roof has a minimum risk of leaking because there is no hip or valley roof so it does not require gutters.
The advantages of gable roof are
- quick installation,
- less material used,
- minimum risk of leakage.
While the disadvantages of gable roof are
- less aesthetic,
- gable wall area will receive stronger wind pressure.
Pyramid or Hipped Roof Type
As the name implies, this roof type has a shape like a pyramid and uses a hip or valley roof. A pyramid roof is very suitable for houses with larger building sites and land areas.
The advantages of a pyramid roof are
- has a more beautiful model,
- suitable for L or T building sites,
- low risk of wind pressure
While the disadvantages of pyramid roof are
- use more material,
- use more roof covering materials, ridge and roof tiles,
- leakage often occurs when using gutters
- drainage flows to four sides so that it’s not suitable for narrow housing,
- the installation is more complicated.
Conical Roof Type
A conical roof is a type of roof that has a slope angle of more than 30°. Usually, a small tower is made at the top. Cone roofs are more identical to castle roofs in Hollywood movies. Its distinctive shape often makes this roof as a focal point in a building.
The advantages of conical roofs are
- looks unique and classic,
- suitable for homes with L, T, or U building sites,
- reduce heat effectively because it has a high roof space.
While the disadvantages of conical roofs are
- using more building materials,
- installation and maintenance are more complicated,
- high risk of wind pressure because it has vertical surfaces,
- high risk of collapse due to earthquake if the truss structure calculations are not accurate.
Combination Roof
A combination roof is a roof that uses two or three types of roofs in one building. Combination roofs are more widely used in modern homes today.
The advantages of a combination roof are
- the model is much more beautiful,
- flexible on all types of building sites,
- make the room cooler because you can install a jalousie on the roof area.
The disadvantages of a combination roof are
- higher costs because it uses more building materials,
- use more roof covering materials, ridges, gutters, roof tiles,
- leaks often occur when using a lot of gutters,
- installation and maintenance is more complicated.
Flat Roof
Flat roofs are very different from other types of sloping roofs. The flat roof surface is almost level with just have one roof plane only. The slope angle of this roof is less than 10o. Usually, this roof is used for warehouses, factories, or supermarkets. These roofing materials are PVC roofing, metal roofing, modified bitumen roofing, and TPO roofing (Thermoplastic Polyolefin).
The advantages of a flat roof are
- suitable for a home upgrade or story-building,
- flexible on all types of house footprint,
- easy to modify according to the house shape.
The disadvantages of a flat roof are
- not a good conductor of heat,
- expensive installation costs,
- leaks often occur if the installation is not properly,
- need skilled labor for installation and maintenance.
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Timber or Steel Roof Truss, Types of Trusses And Their Uses
The roof truss is a structural framework functioned to support a roof, including load-bearing and roof formers. Generally, the construction is a triangular shape. However, the shape can be modified according to the roof type, material, and weight.
Classified from materials, there are three types of roof truss, wooden truss, light steel truss, pipe truss, and reinforced concrete truss. The reinforced concrete truss is used for wide and high span buildings such as auditoriums, sports centers, malls, churches.
Timber Roof Truss
The wood that is usually used for roof truss is red fir or grand fir from California; red cedar and yellow pine; spruce wood from Colorado; and others.
If you plan not to install a ceiling, then roof trusses can be exposed to make beautiful looks. The exposed roof truss is widely used for garages, pergolas, open areas, and jettying. Douglas fir is the best wood for exposed truss because it has beautiful wood grain.
In timber, it is necessary to check the strength factor of the wood used. There are six types of wood strength, as follows.
1) Tensile strength, is a calculation of the tensile force to know how strong the tensile stress. For example, a wooden beam tied at both ends to pull objects using animals or vehicles.
2) Compressive strength, is the strength of wood to withstand compressive loads, both perpendicular and parallel.
3) Flexural strength, is the strength of wood to withstand loads until the wood is bent. In contrast to the compressive strength where the wood is laid down on a plane, but the flexural strength at the end only has support like a beam.
4) Shear strength, is the strength of wood fibers to withstand shear loads that can crack the fibers. For example, the beam under the end of the truss gets sloping pressure from the beam above it because there is a slope of 30 °.
5) Fracture strength, is the strength of wood fibers to withstand the fracture load that can break the fibers. For example, for pegs or nails.
6) Torsional strength, is the strength of wood to withstand torsional forces. For example, for cantilever.
The need for roof truss is calculated in m³ unit. The raw material for the truss is wooden beams with a size of 6/12 cm, 8/12 cm, 8/15 cm according to the construction plan. Calculations for truss construction are known as Cremona diagrams.
The advantages of timber roof truss are
- easy to install,
- low costs for areas with a large supply of wood,
- almost all labors can install it,
- lighter than steel,
- looks beautiful when exposed.
The disadvantages of timber roof truss are
- not resistant to termites,
- easily rotten when exposed to water,
- high-quality wood is difficult to obtain.
Steel Truss
Steel trusses are widely used for wide span buildings because the installation is difficult when using timber truss. The strength factor, steel is relatively strong compared to wood. However, the major reason people using steel is if the wood price is very expensive; high-quality wood is difficult to obtain; and high termite growth.
The steel truss unit usually uses kg (kilogram) and each iron profile (IWF / H / L) has a weight table. The number from the table is multiplied by the length requirement. If it is difficult to use the weight table, it is advisable to use the length measurement. It’s mean, the length is measured to obtain the steel requirement in meters. If the material is C / H / U / IWF iron, then on the market the length is 6 m, while the L iron is 4 m long.
Besides the steel above, other types of steel are used as roof truss is light steel or coated steel which uses 55% aluminum and 45% zinc as additives. This steel is called zincalume which has a silver color. However, there is also silver-colored steel which is galvanized. It’s just that, the durability is much lower than zincalume light steel. The light steel truss developed very fast. Almost every house uses this steel frame. Besides lightweight, this steel is also resistant to rust for up to 25 years. This light steel truss is purchased in a set or unit according to the roof truss design.
The process of making steel trusses can be applied on-site or in a factory or workshop. The steel trusses made in factories are called fabricated trusses. This steel trusses can be set directly on-site, often called a steel erection.
The advantages of steel truss are
- adjustable material size,
- easy to find in urban areas,
- can be manufactured in fabrication,
- high durability.
The disadvantages of steel truss are
- not everyone can install it,
- the price is more expensive when the site location is remote,
- need welding equipment or drill machine if you want to trim or join it.
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