When trying to determine the cost of a roof replacement, there are various factors to consider that cannot be easily summed by an online roofing calculator.
Investing in a new roof will help to protect your home from the elements, and can save you money on energy bills or repairs, not to mention a boost in curb appeal and overall value.
We’ve put together 14 key factors that we recommend considering when trying to decide to repair or replace your roof.
Key Factors That Impact the Cost of a New Roof
Every roof is unique and requires a professional roofing contractor to thoroughly inspect and provide an estimate that is specific to your roof.
While you might want to multiply the size of your roof by an estimated number for the cost of roofing materials and labor, this is an oversimplified calculation that leaves out many critical factors that can drastically skew the total cost of your roofing project.
The size of your roof directly impacts its replacement cost. The more surface area you have, the more materials you’re going to need, including OSB/plywood, underlayment, and shingles.
Roof Square Footage
The square footage of your home is not the same as the square footage of your roof, though you can use that number as a starting point.
Your home’s square footage is a sum of all gross living areas. It includes each level of a house with multiple stories, but it usually doesn’t account for garage space, basements, and interior walls.
The roof square footage, on the other hand, includes all covered living spaces along with:
- Front entryways
You can get a rough idea of how large your roof is in square feet by multiplying the length by width of all flat planes and adding them together. All measurements should run to the edge of each surface, so that they include any eaves or overhangs.
Residential roofs may have steep slopes, low slopes, or a combination of both. Roof slope is expressed either as a ratio or fraction indicating how many inches the roof rises vertically for every 12 inches it runs horizontally (rise/run).
For example, a roof with a 9/120 (or 10:12) slope is much steeper than a roof with a 4/120 (or 4:10) slope.
In general, the steeper the roof, the more expensive the project cost, and this is typically due to safety reasons. A very steep roof might require special equipment for the roofers to use while they work on it, for instance and makes the overall job tougher in general.
Roof Slope Factor
The slope factor of the roof also contributes to the total square footage. If you know your roof’s slope, you can find the slope factor using a table or online calculator. If you’re measuring the roof square footage from the ground, then a pitch factor needs to be added.
Roofing contractors typically add somewhere between 10-15% to the total roof square footage to account for waste factor, but this calculation can vary based on roof style or roofing materials. In roofing, waste factor accounts for material that is overlapped in valleys & hips, as well as cut off material around flashings, penetrations, and gable ends.
When you work with roofing contractors, you may hear the term “squares” being discussed as part of roofing material estimates.
Roof surfaces are measured in squares. A roofing square is an area of your roof that equals 100 square feet and covers a 10’ x 10’ area. The number of roofing squares needed for a project is calculated by dividing the total roof area by 100 (which is 1 square).
For example, if your roof covers a 2200 square-foot area, divide 2200 / 100 = 22, so your project would require 22 squares of shingles to cover your roof.
The type of roofing shingles and materials you choose, or may even be required to have installed based on your geographical location and local building codes or HOA rules, will also impact the cost of getting a new roof. For example, traditional three-tab shingles may not cost the same as architectural shingles that also meet COOL roof code requirements.
In addition to shingles, you may also need to replace or install new:
- Flashing, around chimney, skylights, or roof to wall transitions, for example
Products within these categories vary in cost due to their own differences in materials, performance, warranties, design or look, and other factors.
Roofing Design and Shape
The architectural design of a roof will also impact the cost of reroofing. For instance, your roof might have a steep A-frame, multiple dormers, or have a combination of gables and valleys.
A roofing contractor will likely consider the architectural design when providing a roof replacement cost estimate.
Condition of the Existing Roof
If you need a total roof replacement because your existing roof is heavily damaged, then this may affect the cost as well.
For example, if your roof has a hole in it that requires work on the underlying wood structure, this involves extra labor and materials. Water may have seeped into your attic and upper floors, causing damage that needs to be repaired.
In general, minor roof damage may not be that expensive, but major roof structural damage is likely to be much costlier.
Other Factors to Consider in Roof Replacement Costs
Local Building Permits and Inspections
Many communities require building permits for roofing installation, which must be obtained from the proper municipal authorities. These fees should be factored into an estimate.
In some areas, many inspections take place as the installation progresses, which may add both time and cost to the roofing project.
Material Disposal Fees
If your roofing project involves removal and disposal of existing roofing materials, then your contractor may add disposal fees onto the total cost of the job. This might involve a dumpster rental if the job is big enough, or might be a general materials disposal fee.
If it’s determined that your roof doesn’t have adequate ventilation, then installing new vents may impact your roofing project’s costs and timeline. Use our ventilation calculator to estimate your minimum ventilation requirements. Please consult our Ventilation Training Manual for more information on determining proper ventilation.
Roof Repair vs Roof Replacement
When your roofing contractor evaluates your project and provides you with an estimate, they likely will let you know whether or not you need a roof repair or roof replacement.
Some things that might affect their decision include:
- Age of roof
- Existing roof leaks
- The extent of roof damage, such as if the damage is aesthetic or structural
- Geographical area
Minor or Moderate Damage: Roof Repair
Partial reroofing or repairs may be an option if the physical damage to your roof is mild or moderate. For example, wind damage may have removed several shingles from a certain area of your roof or perhaps the damage is more moderate, but confined to one side of a roof instead of widespread.
In both cases, a roof repair or partial reroof project is likely going to cost less than a total roof replacement.
More Significant Damage: Roof Replacement
If your roofing contractor finds in their evaluation that the damage to your home’s roof is more extensive and/or involves critical structural components, then it might make more sense to get an entirely new roof.
Investing in a complete roof replacement may help you avoid further damage and costly repairs. Getting a new roof helps to protect your home and your own peace of mind – and you’ll be able to choose a shingle style and color of your choice rather than simply trying to match existing materials.
The Bottom Line
The only way to truly know how much your roofing project is going to cost is to talk to a reputable roofing contractor.
- Costs can vary greatly when it comes to roofing projects, whether it involves a repair or complete roof replacement.
- Online roofing calculators can help you estimate costs based on the size of your roof, roofing material types and other factors, but are an incomplete estimation.
- Be wary of roofing contractors with significantly lower rates. Significantly lower rates could be a red flag that they’re uninsured, trying to cut corners, or using substandard materials.
Ask About Finance Options
Fortunately, roof financing options make it easy to get the roof you need without emptying your wallet. Look for loans with low monthly payments, no prepayment penalty, and deferred payments. Ask your roofing contractor about finance solutions when requesting your estimate.