Roofing installation is a meticulous process that requires careful attention to detail. It involves a number of different elements that work together to protect your home and improve its energy efficiency.
Before the roofers begin installing shingles, they’ll remove any existing ones and make structural repairs as needed. This will add a few days to the timeline.
Insulation
Insulation is a material that actively traps heat inside your home, and stops it from passing through walls or floors. There are many types of insulation; cellulose, mineral wool, cotton fibre and sheep’s wool are common choices, but rigid foam such as PIR or XPS foam is also a viable option. Insulation is designed to reduce energy costs by reducing heating and cooling bills and making your home more comfortable year-round.
During roofing installation, your roofer will install the appropriate level of insulation for your climate zone. The insulating material’s resistance to the flow of conductive heat is measured or rated in terms of R-value. The higher the R-value, the greater the insulating properties.
Your roofer will also waterproof any attic areas, known as valleys, which are the spaces where the slopes of your roof meet and form a V-shaped angle. Waterproofing is essential to protect the integrity of your insulation, as well as your roof.
Structural insulated panels, or SIPs, are prefabricated insulated structural elements that provide superior and uniform insulation in comparison to traditional stud or “stick frame” construction. They are made of a sheet of structural sheathing (typically precoloured metal) on both sides, and a dense closed-cell foam core such as PIR, PUR or XPS. The sheathing and foam are bonded together either using glue or by press or vacuum.
Shingles
Shingles come in a wide variety of colors, styles and materials. Wood shingles add a warm, stately feel to many homes and can be hand-rived or milled for a more traditional look. Asphalt shingles are the most common choice, but metal panels are increasingly popular for their longevity and energy efficiency.
Once the underlayment is in place, it’s time to lay the shingle course. Begin at the bottom and work upslope, overlapping each row by about a half inch.
When you reach the end of a row, nail a full shingle up against it and use the chalk line to mark the position for the next one. Hammer nails straight down and up from each cut shingle so they aren’t exposed to the wind (4-6 nails per shingle is generally recommended, although 6 nails may be required in regions with heavy rain).
After the shingle courses are installed it’s important to install an ice and water membrane. The membrane’s rubberized asphalt helps seal around the shanks of each shingle, adding an extra level of water-shedding protection.
If you’re installing a slate roof, it’s important to have a skilled tradesperson on the job to help with the complicated process of laying the slate. Slate is heavier than asphalt shingles, and can be quite expensive to install. Once it’s in place, however, the slate will last for decades.
Underlayment
When it comes to roofing installation, you’ll want to make sure that the underlayment is secure during shingle attachment to prevent water infiltration and potential roof damage. The underlayment slots in between the roof deck and the primary roofing material, a critical part of a sturdy roof that’s resistant to moisture and other weather elements.
There are several underlayment options for your roof, including asphalt-saturated felt, rubberized asphalt, and non-bitumen synthetic underlayment. Each type has its own pros and cons, but all serve the same critical function of preventing moisture infiltration.
Felt roof underlayment is the traditional option that most homeowners are familiar with. It is typically made by saturating sheets of a felt material, usually cellulose (called organic felt) or fiberglass, with asphalt for waterproofing. Felt roof underlayment is less expensive than other underlayment options, offers excellent resistance to wind uplift, and can be easily installed using common tools.
However, a significant disadvantage to this underlayment is its weight, which can add up quickly when it is used for large areas of the roof or in harsh climates. Another issue is its tendency to wrinkle or crack when exposed to cold and heat, which can impact its ability to resist water penetration. It also tends to require more material per square foot than other underlayment options and can be heavier to transport and install on the roof, which can add to labor costs for a new or reroofing project.
Flashing
Flashing is thin, corrosion-resistant sheet metal bent to line a joint. It helps prevent water from getting beneath roof shingles and other roofing materials, where it can cause rot, mold, mildew, or pest infestation. It is generally installed in areas where leaks are prone to occur, such as roof valleys or the area around a chimney or other penetration on your roof.
Some areas of your roof require two pieces of flashing to properly seal the gap. This is the case with chimney walls and dormer openings, where a circular penetration requires both a metal component and a rubber gasket. These two components must be paired to direct rainwater away from the crevice and toward the shingle surface.
Other areas of your roof may only require one piece of flashing, such as where the roof plane meets a vertical surface like a wall or dormer. For this type of flashing, a roofer will use step flashing, which consists of rectangles of flashing that overlap each other like fish scales.
Finally, for corners of your roof where the roof plane meets a wall, your roofer will use corner flashing. This is usually made from corrugated aluminum, which is easy to bend into a clean, tight corner. It is nailed into place along the roof edge, and then a shingle is placed on top of it.