Roof Components – How do they affect the overall cost?

We’re all grateful to have a roof over our heads, as the expression goes. The roof is one of the essential parts of a home, ensuring comfort for its occupants by providing protection from the elements and keeping the interior watertight. However, most people are unfamiliar with the various components that make up a roof, the roles they play, and how they affect the overall cost of a roofing project. Indeed, the cost of repairing or installing a roof largely depends on its components.

From soffits to vents, and including gutters and drip edges, this article will walk you through every part of a roof.

Here are some of the questions we’ll answer:

• What are the components of a roof?

• What are the different types of roofs and their parts?

• Are there specific elements for sloped roofs?

• How much do these different components cost?

What are the names of the main parts that make up a house's roofing system?

Due to our climate, homes must be completely waterproof to provide adequate comfort for residents. Over time, many elements have been added to basic roofs to improve their durability. Let’s take a look at the various parts of a roof and the role each one plays in creating a fully watertight and secure structure.

Roof Frame

Source : Construction Léonard inc.

The frame is the foundational structure that holds up the roof and supports all its components. Often made of wood, it itself is composed of many parts.

The frame is designed to give the roof its shape—whether it’s sloped, flat, or mansard. Waterproofing layers and roofing material are then installed over the frame to complete the roof.

Price: between $10 and $30 per square foot 

Roofing Underlayment

Before installing the exterior roofing material that covers most of the structure, underlayment must be installed. These layers must be waterproof against liquid water while, depending on the type selected, allowing a certain level of vapor permeability to prevent moisture buildup. It helps prevent water infiltration and damage from other types of weather.

Available underlayments in Canada include:

• Asphalt-saturated cellulose fibers

• Woven polypropylene membrane

• Woven polyethylene membrane

• Other synthetic fibers

This membrane is installed directly onto the roof decking (often referred to as sheathing or plywood), which covers the wooden framing. While relatively easy to install, it still requires some expertise to ensure proper placement. That’s why it’s best to hire qualified professionals.

Poor installation can compromise the roof’s lifespan and safety. Underlayment is just as important for flat roofs as for sloped ones—and even more so for green roofs, which we’ll discuss later.

Price: between $2 and $12 per square foot

Roofing Material

Source : Groupe Beaulieu construction

After the underlayment, the chosen roofing material is installed. We’ve written several articles about the different types of roofing materials, but here’s a summary of the options:

• Asphalt shingles

• Fiberglass shingles

• Elastomeric membrane roofing

• Wood shingles

• Clay tiles

• Concrete tiles

• Slate tiles

• Zinc roofing

• TPO and EPDM (synthetic materials)

• Metal roofing (aluminum, copper, steel)

Price: between $6 and $80 per square foot

Soffits

Soffits ensure roof ventilation. They’re installed in the overhanging parts of the roof (those that extend past the house walls). These are perforated panels typically made of aluminum or PVC (vinyl), although adapted wooden structures can sometimes be found on more traditional-style homes.

Price: approx. $10 per linear foot

Fascia Boards

Fascia boards are located near the soffits and their role is to protect the roof edge from the elements. These are usually aluminum or PVC strips installed where the soffits meet the roof. Gutters are often attached directly to the fascia.

Price: between $12 and $25 per linear foot

Gutters

Source : Aluminium sauvé Inc.

Gutters play a critical role by protecting your roof, exterior siding, and foundations from water damage. They collect rainwater and direct it away from your home. Gutters are installed along the roof’s edge and are part of the roof’s drainage system, so they must be installed and maintained properly every season.

Price: between $3 and $50 per linear foot

Flashing

Roof flashing are sealing components in the form of rigid or metallic moldings. These are installed at various strategic locations on the roof where there is a risk of water infiltration (such as at the junctions of walls, chimneys, or skylights). Generally made of aluminum or galvanized steel, they act as a physical barrier to divert water toward the primary roofing material and the gutters.

Price: between $5 and $20 per linear foot

Exhaust Vents (Plumbing and Ventilation)

Ventilation is a key factor in maintaining good indoor air quality. While windows and air exchangers help ventilate the interior, the roof also needs proper ventilation—this is the role of roof vents.

Poor roof ventilation can trap hot air inside, leading to problems like mold and premature material degradation.

Plumbing vents are connected to the plumbing system to balance pressure in the pipes and release harmful gases safely outside the house.

Price: between $60 and $100/ unit

Roof Vents (Exhaust Caps)

Roof vents also help ventilate air from range hoods, bathroom fans, and air exchangers. These elements are key to maintaining airflow and preventing moisture buildup in the attic or roof structure.

Price: between $60 and $100/ unit

What’s unique about a pitched roof?

Source : TRX Mécanique

While most components listed so far can be found on all roof types (flat, sloped, or mansard), there are some components specific to pitched/sloped roofs.

Roof Valleys

Some sloped roofs have multiple sides that meet and form concave angles. Roof valleys are installed in these sections to protect them and guide water toward the slopes and eventually to the gutters.

Without valleys, water could accumulate and damage the roof.

Gable Ends

Gable ends are triangular sections of an exterior wall that rises beneath the slopes of a pitched roof. Although it is part of the building's facade rather than the roof covering itself, it is inseparable from the roofing structure. The presence of a gable cleanly encloses the space beneath the rafters to create an attic. Additionally, it offers a strategic location for installing vents to ensure proper attic ventilation. Visually, the gable provides a strong aesthetic appeal, adapting equally well to modern constructions and classic architectural styles.

Drip Edges

Drip edges are a type of flashing installed at the roof’s edge under the roofing material. Shaped like an L or T, they direct water into the gutters. They are available in galvanized steel, PVC, or aluminum.

Ridge Caps

Ridge caps are crucial for roof waterproofing, along with flashing, drip edges, soffits, and fascia. On sloped roofs, ridge caps are installed where two sides of the roof meet.

The ridge is the highest point on a roof structure. If your roof has multiple slopes, there will be several ridges.

Dormers

What could be more charming than a dormer on a sloped roof? These are windows that project out from the roof slope and are common in homes where the attic has been converted into living space (bedrooms, offices, lounges).

Building a Roof: What You Need to Know

The roof is one of the most important elements of a house—alongside the structure, foundation, windows, doors, and exterior siding. A faulty roof means the home will not be comfortable to live in.

Whether you’re installing or renovating a roof, never improvise. These jobs should always be carried out or at least supervised by professional roofers.

Roofing FAQ

What are the advantages of gable roofs?

Gable roofs offer excellent ventilation under the roof, promoting better airflow through the home. Their shape also makes it easier to gain living space by converting the attic. Plus, the sloped surface helps rainwater drain off easily, reducing the need for advanced drainage systems like those used for flat roofs.

How do you reinforce the roof frame?

If your roof structure needs reinforcement, it often involves the roof trusses (also known as “trusts” in English). These wooden structures support the rest of the roof (eaves, underlayment, accessories, and exterior covering).

Start by inspecting the current elements and replacing any damaged wood. If everything is intact but you plan to install a roof deck or garden, you may need to add beams or rafters.

Who should you call for roof repairs?

Always contact a certified roofer. Make sure they have experience with your type of roofing material and structure. Some companies specialize in certain roofing types, like shingles, flat roofs, or metal roofs. For major work, hire a specialist rather than a general contractor.

What is the most critical component of roof design?

The most critical component of roof design is the roof structure (or framing). This includes the beams, trusses, and rafters that provide the foundation and support for the entire roof system. Without a solid structure, the roof would not be able to support the weight of roofing materials or withstand external forces like wind, snow, and rain.

Which roof component is a fascia board fixed to?

A fascia board is typically fixed to the rafter ends or roof trusses. It runs along the edge of the roof, providing a smooth surface to attach gutters and protecting the roof from moisture damage. It also gives the roof a finished look.

What are roof finishing components?

Roof finishing components include the parts of the roof that provide both functionality and aesthetic appeal, such as:

• Ridge caps: Installed at the peak of a sloped roof to ensure waterproofing.

• Soffits: Installed under the roof's eaves for ventilation.

• Fascia boards: Cover the ends of the rafters and provide a neat edge to the roof.

• Gutters: Channel rainwater off the roof and away from the foundation.

• Drip edges: Guide water into gutters and prevent water damage at the roof's edge.