The basic need of any house is to provide shelter to the human residence and the important part of the house is the roof. The roof provides shelter against various atmospheric conditions like heat, rain, snow, etc. The roof shape may be a flat roof or sloping roof.
We have to decide which one will be good for our house between the flat roof and the sloping roof. Each of them has their merit and demerits.
However, in all regions which are all regions, subjected to heavy rain, snow, it is necessary that the rainwater or snow is drained fast to save the house from its adverse effects.
For such regions, a sloping roof was the obvious choice when wood was the most popular and affordable material. The pitched roof system is more popular in a country like the USA considering the availability of wood is abundant.
The pitched roof is a type of sloping roof system and its construction cost is cheaper compared to other construction method. In a pitched roof system, there is a deck or surface which has a gradual slope from the top of the roof or heap of the roof to cover all building structure.
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Sloping Roof Details
The following is the sloping roof construction details,
Sloped roofs are generally provided with a pitch of about 20 degrees to the horizontal for slates and 40 to 60 degrees for tiles.
The minimum pitching or sloping degree for the roof is decided by the minimum slope necessary for excluding the roof covering and drain rainwater to eaves or valley gutter.
The slope of the roof depends upon the span, the climate conditions of the site, and the nature of the covering material. The slope of a pitched roof should be such that people attending repair must be able to walk and work without fear.
The depth of the triangular frames at mid-span is decided on the strength and stability of this pitched roof. The pitched roof is generally light-weighted compared to the flat roof.
The pitched roof system is most favorable in an area subjected to heavy rainfall and snowfall. In recent trends, the sloping roof is constructed by using concrete also.
If Sloped roofs are constructed in a hot region, it is recommended to provide a false ceiling from consideration of thermal comfort.
For false ceiling work material that should be used are plywood, fireboard, and asbestos cement sheet, thermocol, glass wool, etc. unless done in joint fewer roofs like RCC slabs.
This type of roof system consists of rafters and joists. The joist’s function is to control the spread or slipping of rafters/walls, and conveniently give support for the ceiling below.
The cross-section dimension of rafter timber will depend on their length from the wall plate to the ridge, the type of roof covering, and whether purlins are incorporated in the roof.
It is considered more economical to keep a rafter cross-sectional dimension as low as possible, however where open roof space is needed, larger rafters will be necessary.
The normal spacing between rafters about is 400mm (16 inches), the closer spacing will allow small section rafters and batten, that are fixed to the rafters to locate/fix the slates or tiles, to be used. As we increase space between rafters, it requires the thicker the rafter and lath timbers need to be.
Rafters are nailed to a wall plate at the top of each supporting walls, these are normally 100x75mm (4×3 inches) timber embedded on cement mortar on top of the inner skin of a cavity wall, or the inner part of a solid wall.
The wall plate timber section must be joined with a half lap joint where they meet.
Each rafter has a small triangular section (referred to as ‘birds mouth joints’) cut out of them to allow them to fit neatly over the wall plate.
The top of the rafter is cut at an angle and nailed to the ridge board, typically 175mmx32mm (7×21/2 inch) mounted vertically.
Purlins and the associated struts are used to give some additional support for the rafters. The purlins run at right angles to the rafters, the associated struts are positioned under every fourth (or so) rafter to attach to a joist above a supporting wall below.
Hangers, in conjunction with a longitudinal binder running at right angles to the joists, are used to help hold the ceiling up. Each hanger is nailed between the every fourth (or so) rafters and the joist below. The larger the size of the joists, the less likely there will be a need for hangers.
Never make any modification like cutting timber part, remove or the covering of the roof changed (Concrete tiles replace slate tiles) without consulting a structural engineer.
Advantages of Sloping Roof
The roof is one of the most important parts in any building, acting as the first line of defense from all environmental hazards.
Different types of roofing system developed over a years but pitched roof system still give one classic appearance to a building. That said, the truth is that they remain the most common and efficient solution to ensure maximum protection.
Pitched roofs can be built in various shapes and sizes considering simple two side slopes to more complex shapes combining hips and valleys.
2) Thermal insulation
Pitched roof houses are 10 – 15% more compact compare to that of flat roofs. The pitched roof provides higher thermal insulation by simply limiting the size of the surface exposed to the exterior.
3) Energy savings
The building roofing system is responsible for around 25-35% loss of energy within a building. Pitched roofs allow natural ventilation between the outer layer and the building, preserving energy.
4) Protection against environmental hazards
Pitched roofs are most suitable for keeping the house safe from the effect of snow, ice, water, and wind. Shaped like a triangle, they are stable, stronger and ensure perfect water drainage.
The natural slate roofing tiles are extremely tough, waterproof and fire-resistant.
5) Cost-effective additional space
This kind of roof allows for extra rooms or storage spaces below them, without the need to add an additional (and costly) floor to the whole building.
Read More: Types Of Timber Used In House Construction
6) Longer lifespan
Flat roofs require constant maintenance of their drainage systems in order to avoid leaking. While pitched roofs are generally more expensive, cheaper and less frequent repairs compensates for this.
This is especially true is the roof is covered in high-quality natural slate, with a lifespan of over 100 years and no need for any sort of maintenance.
7) Rainwater reuse
This type of roof makes it easier to reuse rainwater than flat roofs. The external drainage system is easier to modify and redirect. Also, certain pitched tiles that are produced without using any chemical products, have no effect on water quality.
There is a wide range of roofing tiles with sustainable credentials, and solar panels are easily and efficiently integrated within the structure of pitched roofs.
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