- Flat roofs are roofs featuring low slope angles. They are defined in California building codes as having a pitch angle of less than 9.5°.
- The roof size and type of material used for your flat roof project are the most critical factors in determining the costs.
- Besides the roof size and materials, a range of extra factors can affect the project’s costs: labor costs, permits, roof removal, and the installation of sealant, drainage systems, or vents.
Flat roofs are roofing systems for houses and commercial buildings that appear flat when viewed from the street. They have a low pitch angle, ensuring rainwater, snow, or debris doesn’t pool on the roof, potentially stressing its foundations.
Flat roofs are a popular choice for buildings of all types in Los Angeles and the Southern California region. If your residence has a flat roof that needs repairs or replacement, you may wonder about the project’s costs. Understanding every factor affecting the cost of your roofing project can help you determine your budget.
What Are Flat Roofs?
A flat roof generally refers to a roof on a residential or commercial building with a pitch angle of less than 10°. In California, the Building Energy Efficiency Standards and the Cool Roof Rating Council refer to this type of roof as low-sloped roofs.
According to these authorities, a low-sloped roof has a rise-to-run ratio of less than 2:12, corresponding to a pitch angle of less than 9.5°.
The main difference between a flat roof and other roof types is the required materials for construction. Flat roof installation, repair, and replacement costs are generally less expensive than traditional steep-angled roofs because they need fewer materials. Consequently, completing a flat roofing project requires less time.
A flat roof features a slight slope angle to ensure water, snow, or debris do not accumulate on its surface. This helps protect the roof and the rest of the building structure from issues like water damage and uneven load distributions.
Flat roofs are also more energy-efficient because their slope angle exposes their surface to more sunlight, making them ideal for solar panel installation. The low slope angle also allows them to reflect more heat, reducing the need to use air conditioning year-round.
How Much Does it Cost to Replace a Flat Roof?
While the average cost to replace a flat roof is about $9,000 for a 1,000 sq. ft. surface, flat roof project costs may vary. Depending on the materials, a flat roof’s cost per square foot can be as low as $4 and as high as $30. These figures do not include additional factors that can further affect the total project costs, such as labor, permits, or the installation of extra roof elements.
The following is a complete breakdown of the elements affecting your flat roof estimates:
Flat Roof Materials
The most important element of your flat roof’s replacement costs is the type of roofing materials selected. Unlike standard roofs, typical materials such as asphalt shingles are not used on low-sloped roofs because they do not offer sufficient water drainage or protection against wind uplift. However, numerous other options are available, each with its own advantages and pricing options.
|Material type||Average cost per square foot|
Standing seam metal roofing
$4 - $30
$4 - $7
$3.50 - $14
$4 - $13
Standing Seam Metal Roofing
Most metal flat roofs in California are standing seam metal roofs. This roofing material is made of interlocking seams designed to fold over themselves, creating an aesthetically pleasing, seamless look.
Standing seam metal panels use interior-facing fasteners so the securing hardware is not visible from the outside. Metal roofs built with standing seam panels are durable and capable of withstanding nearly any weather conditions. Numerous panel types and mounting hardware options are available.
A PVC roof uses a single-ply membrane made of polyvinyl chloride, a type of plastic polymer. These membranes are reinforced with asphalt-like coatings suitable for roofing applications. PVC membranes are flexible, lightweight, waterproof, and highly resistant to fire and chemical exposure.
While slightly less durable than metal, PVC roofing membranes are easy to maintain and repair, potentially decreasing flat roof repair costs. The material is also 100% recyclable, and many manufacturers offer membranes made of recycled PVC for additional cost savings.
Thermoplastic olefin (TPO) is a synthetic material made by blending high-density polyethylene, a type of rubber, and filler elements. The result is a rubber-like membrane with many desirable properties for roofing applications, such as high durability, flexibility, and low weight.
TPO roofing membranes are resistant to the elements, temperature fluctuations, and UV radiation, making them highly durable year-round. They can also feature reflective coatings, increasing their solar reflectance and boosting the roof’s energy efficiency.
Ethylene propylene diene monomer (EPDM) is a synthetic rubber primarily used as a roofing material by commercial buildings. Like PVC and TPO, EPDM is a durable and lightweight material considered more resistant to the element than most other roofing materials.
A professionally installed EPDM roof can withstand rain, wind, heavy snow, and hard impacts. It is also naturally fire-resistant and fire-retardant and can last up to 50 years when well-maintained.
Due to being a rubber material, EPDM acts as an insulator, absorbing and trapping heat. A professional flat roof contractor in Los Angeles may recommend against using this material as it may not meet California Cool Roof requirements. The heat-absorbing property may also increase energy consumption for air conditioning.
Additional Factors Impacting Flat Roof Costs
While knowing the size of your roof and the materials used for your project is crucial to determine the project’s costs, many other elements can affect the total price. Here are some additional expenses you should consider.
- Labor costs: The best way to ensure your new roof is installed correctly is to contact a professional roofing contractor and let them handle the project. Contractors typically charge flat fees or hourly rates. Always ensure you select a highly experienced contractor and ask for a comprehensive quote breaking down all project expenses, including labor costs.
- Permits and licensing: Depending on the extent of your roofing project, you may need to obtain a construction or roof replacement permit before starting. Contact your county or local government office for more information on permits and licensing costs.
- Old roof repairs and removal: If your roof requires repairs or complete removal before installation, a professional contractor may require a tear-off before installing the new roof. The average cost per square foot of roofing materials to remove is $3 to $7, typically included in the labor costs.
- Roof sealant: After installing the new roof, most professional contractors may recommend giving your roof additional protection with sealant. Roof sealant is a material that can protect your roof against moisture and reduce the risk of leaks.
Applying a sealant layer can cost between $50 and over $1,000. The costs vary depending on your roof’s size and the number of elements to seal, such as skylights, vents, or chimneys.
- Drainage system: The water drainage capabilities of a low-sloped roof are naturally lower than traditional, higher-sloped equivalents. Consequently, you may need to factor the installation or replacement of a water drainage system into your flat roofing project.
The average cost of a complete drainage system ranges from $600 to $1,000, labor costs included.
- Roof ventilation: Roof vents allow air to pass from your attic to the outside, allowing heat to dissipate and protecting your roof from moisture build-ups. These vents let your roof breathe during hot summer days, making them essential for California homes. Installing a roof ventilation system costs $300 to $600.
Ensure The Success of Your Flat Roofing Project
Properly installing a flat roof involves multiple elements that homeowners must understand when budgeting for a roofing project in California. The best way to ensure your flat roof lasts for a long time is to choose durable, Cool Roof-compliant materials and entrust your project to a professional contractor.