How to calculate roof replacement costs

Written by carolyn williams
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When considering replacing your roof, a number of factors will impact the cost. Besides the area of the roof to be replaced, you also need to assess the difficulty of accessing the roof, the slant of the roof and the market rates in your neighbourhood. Once you have this information, you can calculate an approximate cost. Generally, you multiply the square footage of the roof by the cost per square foot for your roof type. The trick is determining your roof type and making sure you and your contractor negotiate the complexity of the job prior to determining a final price.

Skill level:


  1. 1

    Identify the area to be roofed. Typically, the roof is half again the size of your home. So, if you have a 1,500-square-foot home, you can assume the roof is about 2,250 square feet.

  2. 2

    Determine the pitch of your roof. Most ranch-style homes have a standard, gable roof, which is considered the simplest, and thus, the cheapest, to replace. The steeper the roof, the more expensive the replacement, since the contractor will need to include specialised equipment such as harnesses to access the roof.

  3. 3

    Evaluate how difficult your roof will be to replace. If it's a simple gable, again, it's easier to replace. But multiple dormers will increase the difficulty and the cost. If you have multiple skylights or solar energy panels on your roof, this will also increase the complexity and the cost.

  4. 4

    Determine if your roofing contractor will remove the existing roof. While this is more labour intensive, it may be required depending on the condition of the roof or if you are switching materials from wood shingles to asphalt shingles.

  5. 5

    Find out the going rate in your neighbourhood. Regional costs vary widely, so make sure you're comparing roofing information that's specific to your area (see Resources below).

  6. 6

    Consider material. Asphalt shingles vary widely in and of themselves but are more expensive than metal roofing material. Similarly, some homes require terra cotta tiling, which is not only expensive in terms of material, but also in terms of specialised knowledge required to lay this tiling correctly.

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