Commercial roofing is the design, installation, repair and maintenance of roof systems used on non-residential buildings such as offices, warehouses, retail stores, schools, hospitals, apartment buildings and industrial facilities.
Commercial roofing commonly uses low-slope roof systems instead of traditional residential shingles. The National Roofing Contractors Association generally classifies low-slope roofs as systems installed at slopes of 3:12 or less, meaning the roof rises no more than 3 inches for every 12 inches of horizontal distance.
Commercial Roofing at a Glance
| Topic | Explanation |
|---|---|
| Primary purpose | Protect the building, contents, equipment and occupants from water, weather and heat transfer |
| Typical buildings | Offices, warehouses, retail properties, schools, hospitals, factories and multifamily buildings |
| Common roof shape | Low-slope or "flat" roofs, although some commercial buildings have steep-slope roofs |
| Common materials | TPO, PVC, EPDM, modified bitumen, built-up roofing, metal and roof coatings |
| Main components | Roof deck, insulation, membrane or covering, flashing, drainage and edge details |
| Common services | Installation, inspection, leak repair, maintenance, restoration, re-covering and replacement |
How Is Commercial Roofing Different From Residential Roofing?
Commercial roofing differs from residential roofing mainly because of the building's size, roof design, use and performance requirements.
Residential roofs commonly use asphalt shingles on a relatively steep slope. Commercial buildings often use low-slope assemblies with a continuous waterproof membrane and a planned drainage system. Because low-slope roofs cannot shed water as quickly as steep residential roofs, they rely on drains, scuppers and other outlets to move water away.
Commercial roofs also tend to include:
- Heating, ventilation and air-conditioning equipment
- Roof hatches and skylights
- Pipes, vents and electrical penetrations
- Rooftop walkways and service areas
- Larger roof areas
- More complex flashing and edge conditions
- Insulation and energy-code requirements
- Higher wind, fire, drainage and warranty requirements
The term "commercial roofing" describes the building type and application, not one specific material. A commercial building may have a membrane roof, metal roof, asphalt-based roof or steep-slope shingle system.
What Are the Main Types of Commercial Roofing?
The main types of commercial roofing include TPO, PVC, EPDM, modified bitumen, built-up roofing, metal roofing and roof coatings. Each system has different installation methods, maintenance needs and design requirements.
1. TPO Roofing
TPO, or thermoplastic polyolefin, is a single-ply membrane used on many low-slope commercial roofs. TPO sheets are commonly joined at the seams with heat welding. Reflective versions are also used as cool-roof systems.
TPO may suit a building owner looking for:
- A lightweight membrane system
- Heat-welded seams
- A reflective roof surface
- Compatibility with many low-slope roof designs
The roof's performance depends on the membrane quality, seam welding, attachment method, flashing and other installation details.
2. PVC Roofing
PVC, or polyvinyl chloride, is a thermoplastic single-ply membrane used on commercial and industrial roofs. PVC is one of the common thermoplastic membrane systems used in low-slope roofing.
PVC can be considered for buildings with mechanical equipment, numerous penetrations and a fully welded membrane system. The right product depends on the building's use, roof design and manufacturer requirements.
3. EPDM Roofing
EPDM, or ethylene propylene diene monomer, is a synthetic rubber membrane used on low-slope commercial roofs. EPDM is available in sheet form and is an established single-ply roofing option.
EPDM may suit projects that require:
- A flexible rubber membrane
- A single-ply roof design
- Compatibility with an existing low-slope assembly
- A system that can be mechanically attached, adhered or ballasted, depending on the design
4. Modified Bitumen Roofing
Modified bitumen roofing combines asphalt-based materials with polymer modifiers to create reinforced membrane sheets. It is used in low-slope roof systems and can be installed in multiple layers or plies.
Modified bitumen may work well for buildings that need an asphalt-based roof system with reinforced membrane sheets. Installation methods include self-adhered, cold-applied, hot-applied and mechanically fastened products.
5. Built-Up Roofing
Built-up roofing, often called BUR or "tar and gravel" roofing, uses multiple layers of reinforcement felts, fabrics or mats combined with bitumen. The finished system may include aggregate, a coating or a surfaced cap sheet.
Built-up roofing has traditionally been used on large commercial, industrial and institutional buildings. Its multiple layers can provide redundancy, although installation may require more labor than some single-ply systems.
6. Commercial Metal Roofing
Commercial metal roofing includes exposed-fastener panels, concealed-fastener systems and standing-seam metal roofs. It is often used on warehouses, factories, agricultural buildings, retail properties and buildings with steeper roof slopes.
Metal roofing can also support future solar installations. The U.S. Department of Energy notes that standing-seam metal roofs can allow solar panels to be attached without penetrating the roof surface, provided the structure can support the additional load.
7. Roof Coatings
A roof coating is a liquid-applied layer installed over an existing roof or roof membrane. Coatings can restore weather resistance and extend the service life of some roof assemblies, but they are not suitable for every roof.
A coating project generally requires a roof that is mechanically sound, dry enough for application and suitable as a substrate. The U.S. Department of Energy identifies coatings as one option for low-slope roof retrofits, along with single-ply membranes and metal roofing.
What Does a Commercial Roof System Include?
A commercial roof system includes the deck, control layers, insulation, membrane, flashing, drainage and edge details that work together to protect the building.
A typical low-slope commercial roof may include:
- Structural roof deck: The base that supports the roof assembly.
- Vapor or air control layers: Materials used where required by the building design and climate.
- Insulation: Helps control heat flow and may improve energy performance.
- Cover board: Adds protection, durability or a suitable surface for the membrane.
- Roof membrane: The primary waterproofing layer.
- Flashing: Seals roof edges, walls, curbs, drains, penetrations and other transitions.
- Drainage components: Drains, scuppers, gutters and tapered insulation direct water away from the roof.
- Edge systems: Perimeter metal and attachment details help secure the roof and manage wind forces.
NRCA guidance identifies roof decks, air and vapor retarders, insulation, membranes, fasteners, surfacing, accessories and re-covering as parts of a complete membrane roof system.
What Are the Benefits of Commercial Roofing?
The benefits of a properly designed commercial roof include weather protection, temperature control, usable rooftop space and a longer service life when the roof is maintained.
A commercial roof can provide:
- Protection from rain, snow, wind and ultraviolet exposure
- Better indoor temperature control through insulation
- Space for HVAC equipment, solar panels and building services
- Less disruption when repairs are planned and maintained
- Longer service life through inspections and preventive maintenance
- The option to use reflective or "cool roof" materials
Cool roofs use surfaces that reflect more solar energy and can reduce roof temperatures. The U.S. Department of Energy states that cool-roof options are available for many traditional roofing materials and are often most economical on low-slope commercial and industrial buildings in warm climates.
A cool roof is not the right choice for every property. Climate, insulation levels, heating needs, roof orientation, existing membrane and local requirements should be reviewed before selecting a reflective system.
What Are the Main Commercial Roofing Risks?
The main commercial roofing risks involve water management, flashing, roof traffic, hidden moisture, maintenance and workmanship.
Ponding Water
Low-slope roofs need properly designed drainage. Standing water can add loads, speed up deterioration and expose weaknesses in seams, flashings and membrane surfaces. Tapered insulation can create or improve drainage when the roof structure and design allow it.
Flashing and Penetration Failures
Flashing seals interruptions in the roof, including walls, curbs, pipes, drains and expansion joints. Poorly installed or deteriorated flashing can let water into the roof assembly even when the main membrane remains intact.
Hidden Moisture
Water can become trapped below the visible roof surface. A roof assessment may use moisture scanning, test cuts or core samples to evaluate the condition of the insulation and lower roof layers. NRCA identifies core cuts as a method for obtaining information about the construction of a low-slope roof system.
Roof Traffic and Equipment Damage
Maintenance workers, HVAC contractors and other trades can damage membranes, flashings and insulation. Designated walkways, service paths and protective materials can reduce this type of damage.
Worker Safety
Commercial roofs may contain skylights, roof openings, fragile surfaces and unprotected edges. OSHA guidance emphasizes guarding or covering openings and skylights and using suitable fall-protection systems.
How Should a Building Owner Choose a Commercial Roof?
A building owner should choose a commercial roof system based on the building, existing roof assembly, climate, drainage and planned use of the roof.
Important factors include:
- Roof slope and drainage capacity
- Local climate and severe-weather exposure
- Existing membrane and roof-deck condition
- Required insulation and energy performance
- Rooftop equipment and maintenance traffic
- Chemical, grease or industrial exposure
- Fire and wind requirements
- Compatibility with solar panels
- Repair, restoration or full replacement options
- Manufacturer and contractor warranty requirements
- Expected maintenance and future access needs
A roof replacement should not begin with a material choice alone. The first step should be a professional roof assessment covering the existing assembly, moisture condition, drainage, deck condition and available repair or replacement options.
What Does Commercial Roofing Cost?
Commercial roofing costs vary by project because the work may involve a localized repair, coating, membrane re-cover, full tear-off or structural deck replacement.
The main cost factors include:
- Total roof area
- Existing roof layers
- Membrane or metal system selected
- Insulation and cover board requirements
- Tear-off and disposal
- Deck repairs
- Number of penetrations, curbs and drains
- Roof access and building occupancy
- Code upgrades
- Warranty level
- Safety and equipment requirements
Commercial roofs can cost more than residential roofs because low-slope systems need watertight assemblies and integrated drainage instead of relying mainly on steep slope to shed water.
Bottom Line
Start with the roof assembly and its condition, not with a material name. An inspection and written assembly recommendation should come before replacement prices so the building owner can compare repair, restoration and replacement options on the same basis.