How to estimate a roofing job for an informed decision

It can be quite stressful when you have to discuss a large-scale roof project with a roofing contractor. The reason is that most homeowners are unaware of the exact cost such a home improvement project entails. A well-installed roof generally lasts for decades without requiring any major repairs. When it’s actually time for some repair work, homeowners are clueless about the roofing terminology, roofing materials, and how to estimate a roofing job. 

In this guide, we have some tips on how to estimate a roofing job, including how to calculate the roofing materials and roof shingles. This knowledge will help you budget the project better. Most importantly, it will make it simpler to evaluate the estimates given by the roofing contractor.

Keep in mind that when estimating the cost of the roofing job, you will have to take into account the rate per square foot, the material cost, labor cost, the contractor’s overhead costs, and other miscellaneous costs.

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How to evaluate your roof’s square footage?

• Take a tape and measure the width and length of the house from point to point to estimate the overhang of the roof.
• For an odd-shaped house, you can measure the width and length of each section.
• Multiply the width and length of each section to get the square footage.
• Add the total square footage to derive the roof’s square footage.

Try our newest estimator tool to get a proper estimate on your roof in minutes.

What is a roofing square?

One roofing square is equal to 100 square feet. Since roof shingles come in bundles, and generally three bundles of shingles are required to cover each square, it’s important to know the exact square footage. That way, you can estimate the bundles you’ll require. 

Once you’ve calculated how many shingles your roof needs, you can add 10% more to that total to account for any wastage. Remember that there’s no way you can avoid shingle wastage in your roofing project.

How does a contractor price a roofing job?

Once you have a good idea of the kind of work you need on your roof, it will be easier to prepare yourself for the roof repair or replacement cost quoted by your contractor. Here are some of the steps that they use to decide how to estimate a roofing job.  

Understand the scope of work

The contractor will visit the site and understand what the job entails. They would speak directly with the clients to understand the roof problem in totality.

The questions could be about the house’s age, style, the type of roof the client wants, and the budget.

Look up the building codes of the area

You may be limited in what materials you can utilize by specific building codes. For instance, to guarantee that every house is uniform, certain enclosed housing complexes require you to use specific materials and colors.

Survey the roof

The roofer will carefully conduct a roof inspection to identify the damaged areas, the condition of the valleys and flashing, and any unusual roof features.

Measure the roof

Correct roof measurement helps the contractor calculate the number of squares to install. Keep in mind that according to the standard roofing terminology, one roof square is equivalent to 100 square feet.

The roofer will take the external dimensions of the house and divide them by 100 to arrive at ground-level squares.

Determine the roof pitch

A roof’s pitch is expressed as a ratio. For example, a ratio of 4:13 will mean that your roof rises 4 feet for every 13 feet of horizontal length. A roof pitch can be low (lower than 5:12), medium (6:12 to 9:12), or high (10:12 to 12:12) – depending on how steep it is.

The contractor will then multiply the number of ground-level squares by a standard pitch multiplier.

• 3:12 (roof pitch): 1.15 (multiplier)
• 4:12: 1.20
• 5:12: 1.24
• 6:12: 1.24
• 7:12: 1.30
• 8:12: 1.35

Estimate the roof material cost

The total roofing cost will depend largely on the type of roof it is. You can choose between asphalt shingles (the most common roofing material), metal roofing, solar tiles, stone-coated steel, slate roofing, or rubber slates. The contractor will include multiple price estimates for different roofing materials.

You can expect to pay between $3.60 and $5.50 per square foot for asphalt shingles. Also, you need to factor in the cost of materials such as nails, flashing, underlayment, and vents. 

Estimate the total labor costs

The contractor will determine the labor hours and multiply this figure by the number of employees on the job. For example, if it takes two roofers 40 hours to complete the roof job, the labor hours will be 80. As the average hourly rate is approximately $17.95, and the taxes and insurance add up to 20%, the total hourly wage will be $21.54.

The contractor will multiply the labor hours by the hourly wage for the total labor cost. 

Add in the overhead costs

The contractor will include accounting, uniforms, office rent, insurance, and roofing tools as part of the overhead cost. They will also add their markup. This will help them avoid undercutting their profit margins and help them sustain their roofing business.

How to calculate other roofing expenses?

Apart from the cost of the roof shingles and the cost of the underlayment, you need to consider the following at the time of the total cost estimation.

Labor cost: Don’t forget to ask the roofer how they are estimating the roof bid – whether they are adding materials and labor expenses separately or as a total lump sum. 

Shingle disposal:  The old, broken shingles will have to be removed. Usually, the roofer will handle this with the help of a roofing dumpster. However, if you want to save some money on your roof project, you can discard the shingles yourself.

Flashing: The roofer will have to set up flashing in the roof valleys, vents, and chimneys to safeguard against water damage.

Read more: How long do roofs last

Last thoughts

Going over the estimate with your contractor is the most crucial step in getting a roof estimate. Remember, it’s essential that the estimate be as detailed as possible so that you understand why replacing your roof will cost what it costs. And, why the contractor bids a roofing job the way they do. The bottom line is that after spending money on a new roof, no homeowner wants to put themselves in a difficult situation or spend more money than necessary.

Written by Ramona Sinha. August 1, 2022

Ramona is a content writer for Kukun. This experienced blogger uses simple and succinct words to decipher the complex phenomenon called life. An avid traveler, she’s a digital nomad at heart and an animal lover from the depths of her soul.