How Much Does a Flat Roof Cost?

Flat Roof Cost – Flat roofs are felted horizontal roofs that are often seen on garages and other home extensions. These are not completely flat and are slightly slanted to aid drainage of water. Flat roofs are less expensive as compared to pitched roofs and also offer greater accessibility.

Flat roofs are great for anyone considering renovating their garage, shed, or conservatory. They offer greater safety and durability and provide long-term protection against bad weather. Because of their insulation ability, flat roofs are commonly seen safeguarding the home extensions.

When deciding to install a flat roof, it is important to the different types of flat roofs and compare their costs to select the most optimal solution.

Types of Flat Roof

There are several types of flat roofs available today. We are listing five of them here that are most commonly installed by homeowners.

Built-up Roof

The traditional hot-tar-and-gravel roof is comprised of three layers of a roofing material, water-resistant materials, and tar. Fiberglass is the most commonly used waterproof material in the construction of a built-up roof. Built-up roofs last for up to thirty years.

Built-up roofs are the cheapest of all the flat roof varieties, and are fire retardant because of presence of gravel. However, these are very heavy and often require strengthening of joists to provide optimal support to the roof. Also, it cannot be done as a DIY job and require hiring of a professional roofing contractor.

Singly Ply Roof

Unlike built-up roofs, singly ply roofs consist of only single layer of any roofing material. The most commonly used materials for constructing singly ply roofs are polyvinyl chloride (PVC), a rubber polymer EPDM, and a plastic polymer TPO. Singly ply roofs have an average life of 30 years.

EPDM is a durable material that is engineered to resist sun-damage. However, it’s more vulnerable to punctures as compared to other types of flat roofs.

Sprayed Polyurethane Foam

SPF is a liquid material that is sprayed over the existing roof to enhance its performance. When the foam is dried, another layer of a protecting coat is applied for added protection. SPF roofing acts as an insulator and lasts for thirty years or more. However, protective coating may have to be re-sprayed after 10 to 15 years to maintain the roof performance.

Asphalt Roll

One of the oldest and cheapest types of flat roofs are a asphalt roll roof. It is comprised of a smooth layer of shingles constructed using fiberglass felts or asphalt. One of the disadvantages of asphalt roofing is its life. On average, the roof lasts for about 10 years only.

Flat Metal

Flat metal roofs, which are also known as standing seam roofs, are made from panels of different metals. Steel, aluminum, copper, and iron are the commonly used metals used in the construction of flat metal roofs. Flat metal roofs are the most expensive among all types of Flat Roof cost.

Flat metal roofs are light weight but extremely durable, lasting for 25 to 50 years or even longer.

Installing Flat Roof Cost

There are several factors to consider when estimating the cost of installing a flat roof to your home. The price of a flat roof is dependent on:

  • Specifications of the roofing material – Every job demand different roofing material. The quality, trims, and finish of the material determine its cost. Also, there are other job-related requirements as well such as insulation, ventilation, internal drainage, etc.
  • Accessibility of the roof – Installing a flat roof three storys up require scaffolding to be used, which will increase the project budget.
  • Size of the roof – Small roofs cost more per square foot than a large roof due to increased labor costs and cost of equipment used in building the roof.
  • Location – Large-city contractors tend to charge more than contractors working in rural areas.

Estimated a Flat Roof Cost

Type of Flat Roof roofAverage per square foot cost Average cost for a 1,500 square feet
Asphalt roll$1.5 to $2.5
$2,250 to $3,750
Built-up roof$2.5 to $5
$3,750 to $7,500
Single ply rubber or plastic roof$3 to $4
$4,500 to $6,000
Spray-on roof

$1.5 to $6
$2,250 to $9,000
Flat metal roof$5 to $10
$7,500 to $10,000

This is a general guide about the cost of installing a flat roof. The exact cost depends on various factors, which should be carefully considered by a buyer.