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CONTENTS
A roof is the uppermost parts of any building which give protection against animals, and most especially weather, be it rain, snow, sunlight, heat, wind and so on. A roof also beautify a house but the primary purpose of a roof is to protect against any form of weather.
Roof Trusses can be said to be the skeleton of the roof. As you known the skeleton produce the shape of animals even humans. The Roof also depend on its trusses for it shape. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins. The space between each truss is known as a bay.
Roofing is one of the most important project to undergo while constructing a house. The types of roof you build for a particular structure depends on many conditions such as:
TYPES OF ROOF
Throughout the past couple hundred years the styles of roofs vary from area to area. The varying designs, styles, and shapes of roofs exist and have been created to accommodate the needs of the structure they are covering. Some of the most primary needs that a structure demands from a roof are protection from the weather, overall design compatibility with the existing structure, and housing of internal elements such as piping, electrical wiring, ventilation, insulation.
Below are the common types of roof:
[1] FLAT ROOF
As the name implies, this roof appears flat in structure, although it is always pitched at a wider angle to allow water runoff. Typically, flat roofs are ideal for drier areas, not those that receive large amounts of rainfall. They are easier to construct, easier to access (especially for those that love watching the night sky) and accord the house a modern look. Their main downside is the accumulation of materials on the roof, which requires regular maintenance. They also require waterproofing to prevent infiltration of water.
Flat roofs are common especially with commercial buildings. Flat roofs are definitely the most simple roof to build because they have little to no pitch. The most common types of roofing systems used with flat roofs are rubber roofing systems.
[2] GABLE ROOF
The gable is roof is typically triangular, forming an inverted/upside ‘V’ shape. It is basically made of two sides with a middle gap called a gable. While they are some of the simplest when it comes to roof construction and provide room for a spacious attic, they are not ideal for places with high, strong winds. When not well fastened, the roof can easily be blown off by the wind. Gable roofs are not ideal for areas with high wind because they easily can catch the wind much like a sail would.
[3] HIP ROOF
hip roof is made of four or more sloping sides/planes and can be square or rectangular. The planes are designed to slope downwards from the ridge at the top, at an angle determined by the size of the house. Function wise, they are good for areas of high wind and strong storms. They are noted for their strength, stability and shade-giving eaves but are also more complex and expensive to construct, courtesy of their complicated truss and gable structure. Variations include the cross and open hip roofs.
Hip roofs are a common residential style roof. This type of roof is more difficult to construct when compared to flat roofs and gable roofs because they have a more complicated truss and rafter structure.
[4] GAMBREL ROOF
Similar to both the gable and mansard roofs in design, the gambrel roof is made of two planes sloping downward from a top ridge. Much like the mansard, one plane of the roof has a distinct lower pitch than the other. More living space and lower cost of construction are the main benefits, while their limited strength is their main downside. They are not recommended in areas of high winds and heavy snowfall.
The best way to describe a gambrel roof is by saying barn roof. The gambrel style roof is most commonly used on barns. However, it is also used in residential construction. This type of roof has the benefit of providing a good amount of space in the attic. In fact, it provides so much extra space that it is often turned into bedrooms or other living areas.
[5] BUTTERFLY ROOF
In contrast with the gabled roof, this roof shape is made of two planes slanting downwards toward each other to form a butterfly wing shape. Their middle point of contact is fitted with a trough for rain water, eliminating the need for gutters like on normal roofs. A modern exterior and feel is one of the advantages of this roof shape, while its disadvantages include expensive construction and inefficient water collection.
The butterfly roof is not a roof style that is widely used. The style provides plenty of light and ventilation but is not the effective when it comes to water drainage.
[6] MANSARD ROOF
The mansard roof is a four-sided roof with a double slope on each side. Originally used in France, the lower slope on each side is steeper than the upper, with the sides being flat or curved. Its advantages include added living space in the attic and beauty. On the downside, they are not ideal for areas that receive heavy snowfall, especially when lowly pitched, and can be expensive to construct. The mansard roof is a french design and is more difficult to construct than the hip or gable roof.
[7] SKILLION / SHED ROOF
This roof shape is similar to the flat roof; it only has a steeper slope to allow for better drainage. Also called the shed roof, it is usually not attached to another roof. Their advantage lies in the various design options that can be incorporated in them while their disadvantage is their cost of construction and low ceilings in some designs.
[8] BONNET ROOF
This is a mansard roof in reverse with the lower portion at a lower pitch than the upper portion.
You May Also Read Components of a Roof
TYPES OF ROOF TRUSSES
Since there are different types and variation of roof trusses, let’s find out which ones are the most popular and what distinct features they have.
[1]
KING POST TRUSSCentral vertical post used in architectural, working in tension to support a beam below from a truss apex. This truss usually spans up to 8 meters, which makes it perfect for multiple types of houses, especially the smaller ones.
[2]
QUEEN POST TRUSSA very reliable, simple and versatile type of roof truss where you can use at any given time. This kind of truss offers a span of around 10 meters, and has a simple design which makes it perfect for a wide range of establishments.
[3]
HOWE TRUSSkind of truss having upper and lower members, a combination of steel and wood or both. One thing that makes this truss extraordinary is that it has a very wide span, as it can cover anything from 6-30 meters. This is very useful for a wide range of project types.
[4]
PRATT TRUSSPratt truss is the most popular steel truss since it is very economical. It includes vertical and diagonal members that slope down towards the center (opposite of Howe Truss). Pratt truss can cover lengths ranging between 6-10 meters.
[5]
FAN TRUSSFan truss is a simple design made out of steel. Most projects with larger span of around 10-15 meters uses this kind of truss.
[6]
NORTH LIGHT ROOF TRUSShave a wide set of lattice girders that include support trusses. North light truss is the oldest, and most economical kind of truss. These are found in industrial buildings, drawing rooms and large spaces, with a span of 20-30 meters.
[7]
QUADRANGULAR ROOF TRUSSThis is a type of truss having parallel chords and an arrangement of web members of tension diagonals and compression verticals. It is mostly encountered in auditoriums or railway sheds.
[8]
PARALLEL CHORD ROOF TRUSSconstructed with two chords running parallel to each other and supported by reinforcing trusses in between the top and bottom chords. This roof truss reduces the condensation problems and mold conditions since they create a vapor barrier.
[9]
RAISED HEEL ROOF TRUSSprovide a cost-effective way to meet more stringent energy efficiency codes and improve the energy efficiency of your building envelope. Raising the truss higher greatly simplifies attic ventilation and it leaves ample room for insulation above exterior wall top plates
[10]
SCISSOR ROOF TRUSSThe bottom chord members cross each other, connecting to the angled top chords at a point intermediate on the top chords’ length, creating an appearance similar to an opened pair of scissor. A scissor truss provides for a vaulted ceiling in the same time frame as standard trusses. Cathedral is one of the best example of this kind of truss.
THE COMPONENTS OF A ROOF TRUSS
[1]
WALL PLATE / BEARINGThe first timber to be placed, it’s always horizontal and it’s placed at top of the external walls. Structural support of trusses (usually walls) normally with a timber wall plate.
[2]
TYE BEAM / BOTTOM CHORDAlmost same as wall plate, but it’s not place on the wall it’s most time 1.2m apart, purposely use for the placement of ceiling. Horizontal along the spacing of the building. The tye beam is place after the wall plate.
[3]
RAFTER / TOP CHORDThe rafter is in slant form always from one edge of the wall plate to another all meeting at the top of the key post. It’s also most time 1.2m apart.
[4]
WEBSMembers that join the top and bottom chords to form a triangular pattern.
[5]
PURLINS / BATTENSIt’s always been the last. It is put horizontally across the rafter. Which is most time 0.9m apart.
[6]
APEXHighest point where the sloping top chords meet.
[7]
CANTILEVERPart of structural member that extends beyond its support.
[8]
CLEAR SPANHorizontal distance between interior edges of supports.
[9]
HEELPoint on a truss which top and bottom chord intersect.
[10]
JOINTSPoint of intersection of one or more web(s) with a chord.
[11]
NAIL PLATEGalvanized steel plate punched to form a nail pattern integral with the plate and used to connect timber members.
[12]
OVERHANGExtension of the top chord of a truss beyond the bearing support.
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