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When the time comes to install or replace your roofing, you’ll have a huge variety and number of products to choose from. Although asphalt shingles may be the most common, roofing sheets and plastic tiles are on the rise. Your decision should be informed by your geographical location, roof slope, budget, and aesthetic considerations.
The purpose of this guide is to provide an overview of the various features, benefits and drawbacks of each roof covering, and thus help you make an informed and durable choice.
What are the weather conditions in my area? Cold, snow, rain, wind?
What is the pitch, or pitch angle, of the roof slope?
Who will be installing the roof covering? A specialized company, or will I?
What is my budget?
Are there any restrictions in my city or community?
Roofing is composed of several elements. The roof covering is one of these elements. Here is a list of elements and a brief description of each one.
The roof structure is composed of rafters and other solid materials that support the roof covering. Before you install a new roof covering, you must make sure the structure is sound, without any structural weaknesses and completely rot-free. If you want to install a heavy roof covering (ex.: slate or concrete tiles), your roof structure must be able to support the extra weight. If you have any questions or doubts, consult a structural engineer, who may advise you to reinforce your roof structure.
The sheathing is the layer of a roof that is used as the base for roof coverings to be nailed to. It’s underneath the underlayment, the eaves protector and covering. It generally consists of 5/16 to ½’’ plywood. Panels are nailed to the rafters and supported with metal H-clips. It also acts as another layer of protection for the roof.
The drip edge or edge treatment is a metal edge that must be installed on the roof’s perimeter, on the sheathing (for efficient water shedding at the roof’s edge).
Flashings are metal treatments designed to protect those areas vulnerable to leaks and installed around skylights, vents and chimneys. They are set, or embedded, with plastic glue or asphalt plastic cement.
Waterproof membranes, eaves protection sheet and underlayment are intended to waterproof the roofing. The eaves protector and underlayment are installed before the roof covering is installed over the entire roof surface. The eaves protection sheet protects the eaves against water infiltration. It should be installed first. Next is the underlayment, which is placed over the eaves protection sheet.
The membranes used on a flat roof constitute the roof covering. For asphalt flat roofs, several membrane layers are necessary (built up flat roof felt). Only one membrane layer of TPO membrane is required, however, since TPO is a single-layer roof covering.
Ridge vents are installed along the roof peaks for the purpose of ventilating the roof timbers and attic space.
Asphalt plastic cement is the glue used to set the flashings and to waterproof effectively around those areas vulnerable to leaks.
During the preparation stage before installing the roof covering, several elements are already present on the roof. Following is a brief description of each:
The valley is the internal angle formed when two roof slopes meet. Valleys that are called "open valleys" are typically lined with sheet metal, with the flashing exposed. “Closed valleys” are valleys covered with shingles.
The hip is a peak of the roof where two sloped roof planes meet at the top at a projecting angle more than 180o.
The rake is the cut end of a roof above a gable end.
The ridge is the top of the roof, where the rafters meet.
The covering is the product that covers the roof and protects it against weather conditions. Roofing options include asphalt shingles, sheet metal, plastic tiles, concrete tiles, copper and aluminum.
There is a range of roof coverings for sloping roofs. The choice of covering changes the appearance of your home. Most people are used to seeing roofs covered with asphalt shingles; there are, however, other possibilities. The table below provides an overview of these roofing options.
|Model||Features and Composition||Benefits, Drawbacks, Guarantee/Warranty||Types and colours|
Two compositions: organic covered in crushed stone, or fiberglass.
There are two kinds of wood shingle available: cedar and pressure-treated wood, cedar being the more wide-spread.
Available in many shapes:
Constructed with a combination of clay, resin and fiberglass. Imitates cedar roofing shingles without the risks associated with fire.
Made chiefly of steel sheeting, (galvanized or stainless), copper sheeting and tiles. The cost of a steel roof varies according to the sheet profile, paint used, and shape of the roof.
Associated with luxury roofs and expensive homes;
Available as copper sheeting or tiles,
Galvanization protects the metal against corrosion. There are various processes: galvalume (registered trademark) is covered with zinc to improve its weathering capabilities, and galvanized steel is made by passing it through a bath of molten zinc.
Available in large sheets or tiles
Square, rectangular or diamond-shaped
Imitates the appearance of slate, but it’s a lot less expensive and less fragile during installation. Installation is fairly simple, and an underlayment is not required.
Imitates slate, cedar shingles, clay tiles
Natural stone (shale clay) extracted directly from the earth.
Limited range of colours, variations on blue-grey
Clay Roof Tiles
Product more widely used in Mediterranean climates;
Resembles a cylinder cut length-wise
Concrete tiles have many interesting features;
Manufactured using a mould, which makes it possible to create various sizes and shapes of tiles
There are three different types of roof coverings for flat roofs: the traditional asphalt covering, the Elastomeric Membrane EPDM, and the Thermoplastic Olefin Membrane (TPO). Over the past number of years, elastomeric membranes and TPO membranes have become very popular, since installation costs have gone down and compared to asphalt, they have a superior life span. Their popularity is due in part to the fact that some municipalities now call for light-coloured roof coverings to reduce urban heat islands.
|Model||Features and Composition||Benefits, Drawbacks and Warranty||Colours and Types|
Multilayer roofing including three layers of organic felt combined with molten asphalt; a final coat of gravel is poured on top
Black, grey or white gravel covering (white gravel is mandatory in some municipalities to reduce urban heat islands)
Made of synthetic rubber, this is a smooth membrane not covered with gravel.
Two types: EPDM and modified bitumen membrane (SBS)
Thermoplastic Olefin Membrane
Constructed from ethylene propylene rubber and filler materials (ethylene and propylene are bonded together with the rubber); available in panels up to 10’ wide, thereby reducing the number of joints during installation; installation options include hot air welding (without a blowtorch), which makes it feasible to install under variable weather conditions.
Many colours available
Other more specialized roof coverings are also available: the green roof and solar roof. You may need to reinforce the structure of an existing house before installing a green roof. You may also need to call on green roof specialists for help and advice when you install the waterproof membrane and when you develop the landscape design of the roof. Solar roofs come in many variations (photovoltaic shingles or solar panels) and also require specialists’ help to install. More than simply a roof covering, it is an energy generating system.
Roofing quantities vary according to the product. Generally-speaking, you need to measure the total surface area of the roof and note how much surface each package of roofing product will cover. This information is given on the packaging. By dividing the total surface by the surface covered by one product package, you will know how many packages you will need to cover the entire roof surface area.
The installation of roof coverings varies according to the product. Tile-based products (shingles, concrete tiles, plastic tiles, etc.) are laid in straight rows, starting at the bottom of the roof and often nailed to the sheathing. Other products such as copper or steel sheet are laid in large panels on the roof and secured with nails or the appropriate fasteners. Certain sloping-roof coverings can be installed by the home owner (such as wood shingles, asphalt shingles, plastic tiles), whereas others should be entrusted to professionals (such as slate, clay tiles, copper, concrete tiles).
All types of flat-roof coverings must be installed by roofing specialists.
Ladder, secured to the roof top and on the ground
Some roof coverings are more environmentally-friendly than others. For example, steel often contains a good percentage of recycled material and is 100% recyclable. The same holds for EPDM elastomeric membranes and TPO reinforced roofing membranes. The opposite is true for asphalt shingles and flat-roof asphalt covering, which are non-recyclable petroleum-based products.
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