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Sunday, February 5, 2023

AN OVERVIEW OF ROOFING SYSTEMS

Buildings constitute a major part of the Finish national wealth. We simply cannot afford its premature decay. A healthy building can only exist under a well-functioning roof. A correctly designed and well executed roof system means the preservation of our national wealth and natural resources, and implies appreciation of sound professional construction.

The decisions made at three separate stages influence the life span of a roof: during its design, during the actual execution of the work and during its service life. At the design stage we set a goal for the life span of a roof and this has implications for the design of its structural system and details as well as for the choice of materials.

 In the execution of the actual work, the roof is constructed according to design specifications and applying the good building practices and generally approved installation methods of the roofing industry. Correct and sufficiently frequent maintenance during the service life plays a critical role in the durability and functioning of a roofing system. The projected life span of a roof can only be realised when all the stages of the roof’s life cycle are executed correctly and in a predetermined manner.

  1. INTRODUCTION

The primary object of a roof in any climate is protection from the elements. Roof slope and rigidness are for shedding water and bearing any extra additional weight. Roofs must also be strong enough to withstand high winds. In this section, we’ll cover the most common types of roofs and basic framing terms.

  • TYPES OF ROOF STRUCTURES

 The most commonly used types of pitched roof construction are the gable, the hip, the intersecting, and the shed (or lean-to).

  1. GABLE ROOF

A gable roof has a ridge at the centre and slopes in two directions. It is the form most commonly used by the Navy. It is simple in design, economical to construct, and can be used on any type of structure.

Fig 1: Gable Roof

HIP ROOF

The hip roof has four sloping sides. It is the strongest type of roof because it is braced by four hip rafters. These hip rafters run at a 45° angle from each corner of the building to the ridge. A disadvantage of the hip roof is that it is more difficult to construct than a gable roof.

Fig 2: Hip Roof

INTERSECTING ROOF

The intersecting roof consists of a gable and valley, or hip and valley. The valley is formed where the two different sections of the roof meet, generally at a 90° angle. This type of roof is more complicated than the other types and requires more time and labour to construct.

Fig 3: Intersecting Roof

SHED ROOF

The shed roof, or lean-to, is a roof having only one slope, or pitch. It is used where large buildings are framed under one roof, where hasty or temporary construction is needed, and where sheds or additions are erected. The roof is held up by walls or posts where one wall or the posts on one side are at a higher level than those on the opposite side.

Fig 4: Shed Roof

FRAMING TERMS

 Knowing the basic vocabulary is a necessary part of our work. In the following we’ll cover some of the more common roof and rafter terms. Roof framing terms are related to the parts of a triangle.

  1. ROOF

Features associated with basic roof framing terms are shown figure. Refer to the figure as you study the terms discussed in the next.

  1. SPAN

Span is the horizontal distance between the outside top plates, or the base of two abutting right triangles. Unit of run is a fixed unit of measure, always 12 inches for the common rafter. Any measurement in a horizontal direction is expressed as run and is always measured on a level plane.

  1. UNIT OF SPAN

Unit of span is also fixed, twice the unit of run, or 24 inches. Unit of rise is the distance the rafter rises per foot of run (unit of run).

  1. TOTAL RUN

Run is equal to half the span, or the base of one of the right triangles. Total rise is the vertical distance from the top plate to the top of the ridge, or the altitude of the triangle. Pitch is the ratio of unit of rise to the unit of span. It describes the slope of a roof.

  1. PITCH

Pitch is expressed as a fraction, such as 1/4 or 1/2 pitch. The term “pitch” is gradually being replaced by the term “cut.” Cut is the angle that the roof surface makes with a horizontal plane. This angle is usually expressed as a fraction in which the numerator equals the unit of rise and the denominator equals the unit of run (12 inches), such as 6/1 2 or 8/12. This can also be expressed in inches per foot; for example, a 6- or 8-inch cut per foot. Here, the unit of run (12 inches) is understood. Pitch can be converted to cut by using the following formula: unit of span (24 in.) x pitch = unit of rise. For example, 1/8 pitch is given, so 24 x 1/8 equals 3, or unit of rise in inches. If the unit of rise in inches is 3, then the cut is the unit of rise and the unit of run (12 inches), or 3/12. Line length is the hypotenuse of the triangle whose base equals the total run and whose altitude equals the total rise. The distance is measured along the rafter from the outside edge of the top plate to the centreline of the ridge. Bridge measure is the hypotenuse of the triangle with the unit of run for the base and unit of rise for the altitude.

4 PRIMARY CAUSES OF ROOF DAMAGE

When it comes to maintaining a healthy building infrastructure, it is safe to say that the roof is one of the most important elements. Defective roofs can generate significant and often unforeseen expenses to building owners, along with a great deal of other problems if left unchecked.

There are a number of elements that can weaken a roof. It is a good idea to inspect your roof on a regular basis and take care of minor issues before they become major repairs. Below are five major causes of roof damage that all building owners should note.

  • POOR MAINTENANCE.

Inspecting your roof regularly is very important. In fact, for most building owners, this can be lifesaving, as regular inspection of your roof for small leaks and minor damages has been known to prevent major repairs in the long-haul. If your roof has little or no slope, regular inspection helps prevent major leaks from occurring.

  • ICE DAMAGE.

As ice and snow thaw upon your rooftop’s surface, small particles of water can settle under the shingles. As the water refreezes, it can lift the shingles and flashing, making way for even greater water damage to arise. This process is known to create roof corrosion and deterioration. If you live in an area that experiences freezing in the winter, it is a great idea to check your roof every spring.

  • WIND DAMAGE.

Known to weaken the shingles, nails, and other roofing materials currently holding your roof together, moderate gusts of daily wind often have the power to threaten your roof’s stability. 90 percent of high wind and hail damages claims result in some form of expense for building owners. Regular inspections on this type of roof damage are highly critical to prevent further damage from occurring.

  • OTHER WEATHER CONDITIONS.

Known to be both nurturing and often destructive, Nature can cause a plethora of issues when it comes to roofing. UV radiation from sunlight can gradually contribute to roof deterioration, especially when it comes to asphalt shingles. Once this occurs little can be done to protect the interior sheathing and thus the roof is further exposed to the raw elements.

  • IMPROPER INSTALLATION.

Roof replacements, installations, and repairs should be completed by an experienced roofing contractor. Not only can proper installation bring leverage and security, but it can also aid in property value.

Like many aspects of structure improvement, roof stability is of high significance. To ensure your roof has the upmost vitality year around, contact a professional roofing contractor as soon as possible.

5 ADVANTAGES AND DISADVANTAGES

Of all the different roof types for homes and buildings, one of the most controversial is the flat roof. Used commonly on large buildings and outbuildings, the flat roof has its own special set of needs and challenges. If you’re considering this type of roof for your building or residence, make sure you understand the advantages and disadvantages it can bring.

  • FLAT ROOF ADVANTAGES

By far the biggest advantage of using a flat roof is the expense. The initial building and installation to the materials most often used to cover the roof, flat roofs are fairly cheap. Many types of material used for installation run about .80 a foot, which makes a flat roof extremely affordable both for the initial installation and the maintenance and upkeep.

Another advantage to using a flat roof is the fact that you can now make use of the space once the roof is done. Get your air conditioning units up off the ground and put them on the roof. Install solar panels on the roof that are less obvious from the curb. Plant a roof top garden or design a living roof. The possibilities of how you can use a flat roof are nearly endless, and this is by far one of the greatest benefits to using one.

Going hand in hand with the last advantage is the fact that with a flat roof, you have the ability to have a more versatile interior space as well. Finished attics and the use of a top floor apartment become more readily available without the sloped walls that a traditional pitched roof would produce. This makes a nice option for homes where the maximum amount of interior space is needed.

Finally, flat roofs are generally more accessible than sloped roofs. So cleaning your gutters, making repairs, and installing things like satellite dishes or solar panels become easier and less expensive to do as well.

  • FLAT ROOF DISADVANTAGES

The biggest disadvantage to installing a flat roof is the drainage, or lack thereof. Flat roofs do drain, but not nearly as efficiently as a roof with any kind of pitch. Therefore water has a tendency to puddle and remain on the roof, which could lead to the roofing material breaking down or to eventual leaks, particularly along the seams.

The second disadvantage is the lack of roofing material options. The vast majority of flat roofs use a type of rolled roofing; rubber, EPDM, TPO, or bitumen. These are all relatively inexpensive materials and easy to install, but most of them have a limited lifespan of 10 to 15 years. Rubber shingles are available that can be installed in conjunction with rolled rubber roofing, and some new materials such as polycarbonate roofing and PVC roofing are becoming available that may last longer and give some style options, but these come at a higher price, and lack the kind of history that can help predict how long they will last.

PITCHED ROOFING – ADVANTAGES

  1. LOFT SPACE

Pitched roofs, which have at least two slopes that rise to meet at a peak, are constructed in such a way as to afford plenty of usable space in the loft area, either as much-needed storage or even as additional living space, such as a study or playroom. In the process of designing the roof, any planned usage of this area can be incorporated into the plans so this type of roof offers an unmatched flexibility that a flat roof cannot.

  1. LIFESPAN

The pitched roof, if constructed properly, is almost certain to offer a much longer lifespan than a flat roof, with materials that are more durable and weather resistant. The internal accommodation will be more efficiently insulated and will not suffer from the extremes of temperature that tend to afflict rooms under flat roofs.

  1. NATURAL

Installing a pitched roof also means the building can be more effectively blended in to either the rest of the property (in the case of an extension) or to neighbouring buildings, while also helping to retain a sense of individuality and character.

PITCHED ROOFING – DISADVANTAGES

  1. EXPENSE

Unfortunately one consequence of this is the increased expense, as the more complex design, additional building materials and extra man-hours cost significantly more than a flat roof.

  1. FOUNDATIONS

Pitched roofs also place a greater burden on the foundations of the building and this may have implications for the depth of the footings. Replacing a flat roof with a pitched roof on an existing structure is therefore not always feasible.

CONCLUSIONS

Composition shingles are an inexpensive option for your home in the short term. However the need to re-roof over time can make this an expensive option over time.

Clay tile and slate looks beautiful and can provide your home with a traditional and classic appearance, but the initial expense and fragility of this product can make this choice more expensive than just the initial investment. The heavy weight of this material adds some concern of structural safety in the event of an earthquake or fire.

Wood shingle and shake will give your home a natural appearance. In some areas wood is no longer allowed due to the danger of wildfires spreading among neighbourhoods. With the product being produced today out of second growth wood, it is more susceptible to becoming brittle and shrinking then the wood shingles and shakes of years ago.

Metal roofing can provide your home with the look of any other common roofing material. The initial expense of installing this product on your home is quickly realized as a solid investment, as this product eliminates the need for future re-roofing and maintenance. And, modern metal roofing systems retain their appearance and colour for decades.

Aluminium Metal roofing is an environmentally sound choice, since it reduces the homeowner’s environmental footprint. This is due to the fact that aluminium roofing is made from recycled products, and can be totally recycled again and again, causing no further environmental waste. Landfills are therefore spared the huge waste that comes with the disposal of temporary roofing materials.

Author

Shamanth
Shamanth Kumar M, Project Engineer and Manager of Design Services, Salarpuria Sattva Group

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