ROOF AND ROOF COVERING

ROOF AND ROOF COVERING 

  ROOF :-

A roof is part of a building envelope, both the covering on the uppermost part of a building or shelter which provides protection from weather, notably rain, but also heat, wind and sunlight; and the framing or structure which supports the covering

In Simple words “Roof is what, Covers both Material & Human Being”

    QUALITIES OF ROOF:-

-  Must be weather resistant to rain, snow, wind and sun.

-  The durability should be equal to or in excess of those materials used in the remainder of the building.

-  Should have good thermal insulation properties.

-  Should require a minimum of maintenance.

-  Should be constructed in such a way as to retain structural stability when dead and imposed loads are applied to it

Truss & Its Component:-

- Heel - The point on the truss where the top and bottom chords intersect

- Slope - The vertical rise in inches for every 12 inches of horizontal run.

- Panel Length - The horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.

- Peak - The point on the truss where the sloped chords meet.

- Top Chord - Horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.

- Continuous Lateral Brace - Members installed at right angles to a chord or web member of a truss to provide stability to the truss. All lateral braces must be stabilized.

- Overall Height - Vertical distance between bearing and the uppermost point of the peak.

- Wedge - The triangular piece of lumber inserted between the top and bottom chords, usually to allow the truss to cantilever.

- Bottom Chord - The incline or horizontal member that establishes the bottom of a truss, usually carrying combined tension and bending stress.

- Splice - The location at which two chord members are joined together to form a single member. It may occur at a panel point or between panel points.

- Panel Point - Also called a joint, it's the location on a truss where the web members and top or bottom chords intersect and are connected by metal connector plates.

- Web - The members that join the top and bottom chords to form the triangular patterns typical of trusses.

 

Roof Classification Depends on :-

-Area covered

- Materials available

- Type of lighting

- Ventilation needed inside

- Available appliance

Classification of Roof :-

- Gable Roof

-Gambrel Roof

- Hipped Roof

- Mansard Roof

- Flat Roof

- Shed Roof

  Sketches of different types of roof:-

 -  Gabled Roof: - There are many types of gabled roofs (roofs that essentially look like triangles from the front of the home). I enjoy the cross gabled roof which is used in homes with extra wings so that each portion of the home has its own triangular gabled roof as seen in this photo.

-Gambrel: - This type of roof is very similar to the Mansard Roof. The core differences are that the gambrel has vertical gable ends and the roof hangs over the facade of the home whereas the Mandrel Roof does not. Additionally this one is Dutch-inspired instead of French.

-  Hip Roof: - This roof is very similar to the pyramid roof. The difference is that instead of coming to a point at the top the four sides meet at a ridge or a flat spot like we see here. This is architecturally more practical.

The hip roof is slightly more difficult to build than a gable roof. It is a popular choice, but does not provide for ventilation as well as some designs.

-  Mansard Roof: - This type of roof is made up of four slopes, two on each side of the home. The lower slope is a steeper, more vertical slope than the upper slope. The upper slope may or may not be visible from the ground. This French style of roof allows for additional living space or storage space at the top of the house.

-  Flat Roof: - This type of roof is obviously easy to identify! The benefits of a flat roof include that it's easier to construct, safer if you're going to stand on top of it and generally more accessible. The main drawback is that this type of roof requires more maintenance than other roofs in large part because debris will gather on the roof with nowhere to go.

-  Shed Roof: - A shed roof is similar to a flat roof but has more pitch. It is frequently used for additions or with other roof styles.

DESIGN OF ROOF & ITS  FACTORS : -

-      Specific Loads on roof: -

-   The most common loads falling  within the roof load width are:

-  Gravity Dead loads including roof  and ceiling materials  - these are felt by the structure all of the time

-   Gravity live loads including People  working on the roof  and stuff  stacked on it  - these are only felt some of the time by the structure

-   Wind loads including downward pressure or suction that lifts upward – these are only felt some of the time but downward pressure adds to the gravity loads above, while uplift works in the opposite directions.

  

 ROOF COVERING: -

Is a materials which gives a protective surface to the roofing structure The function is only to prevent ingress or egress of heat & moisture into the building

-  Thatch- is the craft of building a roof with dry vegetation such as straw, water reed, sedge, rushes, or heather. Now become choice for rustic look and more ecologically friendly roof.

-  Wood- thin, tapered pieces of wood primarily     used to cover roofs and walls of buildings to protect them from the weather

-  Shingles- roof covering consisting of individual overlapping elements. Can be made of various materials such as wood, composite or ceramic.

-  Tiles-made of a ceramic material and is hard and brittle, poorly suited for places where tree limbs can fall on a house's roof.

-  Slates - is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash

-  Asphalt – known as bitumen, viscous liquid or semi solid form of petroleum.

-  Asbestos cement sheets-known as fiber cement sheet. It is a building material in which asbestos (silicate mineral) fibers are used to reinforce thin rigid cement sheets.

  

-  Corrugated iron sheets-The corrugations increase the bending strength of the sheet. Normally each sheet is manufactured longer in its strong direction.

-  Bituminous felt-bitumen mixed with a filler component such as limestone or sand or polymers to gives rigidity and tear resistance.

-  Sheet metal roof coverings (copper, Zink, etc.)-roofing system made from metal piece, or tiles.

ROOF VENTILATION: - The term “roof vent” can mean many things. As we define it, a roof vent is designed to remove hot air and moisture out of your attic.

- TYPES OF ROOF VENTILATION: -

o   Ridge Vents

o   Turtleback Vents (Box Vents)

o   Power Fans

 RIDGE VENT: - Ridge vent is the best and most consistent system to install. It is installed on the very top of your home at the ridgeline. This is the most natural and cost effective solution to your ventilating needs. Although ridge vent is considered to be the best type of ventilating system it does have one main drawback. If you have a high, hip style roof with little to no ridgeline it may not be suitable for ridge vent.

  TURTLE VENT: - Turtleback vents are typically installed a couple of feet below the ridgeline. This brings us to our first drawback. Because the turtleback vent does not go all the way to the top of the roof it leaves a pocket of air trapped above the vents. Unlike ridge vents, which run continuously across the ridgeline, turtleback vents are seperate units usually placed a few feet away from each other. This allows for gaps in your system and leaves hot and cold areas in your attic space.

  POWER FANS: - power fans draw a great deal of heat out of the attic fast it's still a mechanical based system. This means it is more susceptible to burning up and breaking down. This can lead to costly service calls and expensive electric bills. A power fan runs on electricity and is connected to a thermostat. The thermostat regulates when the fan should turn on and off. However if it's not working properly or installed wrong it may not turn on. In some cases the power fan may also run continuously. Another drawback is there may be a noticeable noise difference when running. Often times after evaluating a customer’s vent system.

MODERN TYPES OF ROOF COVERINGS FOR INDUSTRY: -

3 Layer U PVC Sheets :-

1 Trapezoidal Profile

2.Round Wave Profile/Corrugated

 Properties of UPVC Sheets: -

1.      Chemical Resistance

2.      Fire Resistance

3.      Strength Capacity

4.      Sound Insulation Property

  Size  of UPVC Sheets:-

1.      For 1 mm Thick sheet  lengths are available in 2mtr,2.5mtr  and 3 metre

2.      Width of the Sheet is Internationally Standard that is 1130 mm

3.      Thickness of Sheets is available in 1, 2, 2.5, 3.

4.      For 1mm Thick UPVC Sheet, Purlin Distance should be kept 60 Cm.

5.      For 2/2.5/3mm Thick UPVC Sheet, Purlin Distance should be kept 1 metre.