If you’re getting a new roof or replacing your existing roof, one of the most important calculations is determining how many shingles you’ll actually need. This is where the concept of “squares” comes in for roofing projects.
What is a Roofing Square?
In the roofing industry, a “square” is defined as 100 square feet of roof area. Roofing contractors use squares as a way to simplify material estimations for different sized roofs. One square equals enough shingles to cover 100 square feet of roof surface. The number of squares needed depends on the total size and complexity of the roof. Once the total squares are calculated, the roofer knows how many shingles and other supplies are required.
The cost per roofing square varies based on the type of shingles and materials used, as well as labor costs in your region. On average, one square may cost $250-$500 for mid-range architectural shingles installed. Luxury shingles, metal roofing or other premium materials will be higher per square. The total number of squares must be accurate to get a realistic estimate of the full project costs.
Calculating Total Squares for Your Roof
Figuring out the total squares needed for your new roof starts with measuring the total square footage of your roof. This is done by measuring the length and width of each roof section, including the main roof, any dormers or additions, porches, garages, and overhangs. All connected roof planes should be included.
Once you have the total square footage, simply divide by 100 to get the number of squares needed. For example, if you have a 2800 sq ft total roof area, you would need 28 squares (2800 sq ft / 100 sq ft per square = 28 squares).
The shape and pitch of the roof will also impact the squares calculation. Complex roofs with hips, valleys and dormers generally need 20-25% more squares than a simple gable roof due to the increased surface area.
Impact of Roof Pitch and Slope
The pitch and slope of your existing roof will factor into the number of squares needed when replacing it. Pitch refers to how steeply angled the roof rafters are. It’s usually measured in inches of vertical rise per 12 inches of horizontal length. An 8/12 pitch means the roof rises 8″ vertically for every 12″ horizontally.
In general, roofs with a lower pitch/slope will require more squares of shingles compared to steeper roofs. This is because low slope roofs have more horizontal area to cover. Flatter 3/12 to 4/12 pitched roofs may need as much as 20% more squares compared to a steep 10/12 roof.
However, very complex roofs with lots of valleys, dormers and changes in direction can alter this equation. The complexity may require additional squares regardless of the pitch. Your roofer will take all factors into account when estimating total squares.
Considering Roof Complexity and Design
As mentioned above, the complexity of your roof design will impact the number of squares needed. A basic gable roof with two sloped sides is the simplest shape. Once you start adding dormers, skylights, valleys, hips and odd angles, the square footage starts expanding.
Hip roofs need 20-25% more squares compared to a simple gable roof, thanks to the diagonal hip areas which add more surface. Valleys where roof sections intersect are also challenging and use more shingles per square foot.
Complex roofs also often require additional flashings, ice and water shields, and related accessories – adding to the material requirements. Your contractor will factor all this in to make sure you purchase sufficient squares.
Ventilation Needs
Proper ventilation is extremely important for roof health and longevity. Without adequate ventilation, excessive heat and moisture can build up under the roof decking leading to premature failure, rot, and molded attic conditions.
If your existing roof is under-ventilated, your contractor may recommend adding more ventilation as part of the roof replacement. Additional ventilation can include ridge vents, gable vents, roof turbines or attic fans. These improvements require modifying the squares calculations to ensure adequate materials.
Choosing Your New Shingles
The type and style of shingle you select for your new roof will also impact the number of squares required. Standard 3-tab shingles are relatively small in size – generally around 36″ long by 12″ wide. This allows for greater coverage per square compared to larger architectural or luxury shingles.
Larger shingles mean fewer pieces are needed per square to cover the same area. For example, 24″ x 18″ luxury shingles may require 20% more squares than 3-tab. The exposure height also factors in – shingles with reduced exposure need additional courses and squares.
Heavier shingles such as concrete or slate tiles add more weight per square as well, requiring additional decking considerations. Talk through your shingle options with a professional to get an accurate squares estimate.
Waste, Starter, and Other Extras
When calculating the number of squares don’t forget to account for at least 10% waste factor. It’s impossible to perfectly estimate every inch, so roofers pad the materials just in case. You don’t want to run short halfway through and have to wait for more shingles.
Additionally, each new roof requires starter shingles along the eaves and rakes. Hip and ridge shingles are needed for the tops of those areas too. Plus, roof deck protection like felt underlayment, flashing, fasteners, and adhesives are all required materials factored by the square.
The little extras like attic ventilation, pipe boots, chimney crickets and edge metal can really add up. Your roofer totals up everything needed so there won’t be any surprises.
As you can see, accurately estimating the number of squares needed for a roofing project requires professional expertise. There are many variables at play including roof size, shape, materials, ventilation and more. Relying on a qualified roofing contractor is highly recommended.
Professional roofers have extensive experience calculating the squares for all kinds of roofs. They account for all the potential factors discussed above. By hiring a pro you can have confidence that no shortcuts will be taken and you’ll receive the correct amount of materials for the job.
Equally important is that you gain the peace of mind and satisfaction guarantees that come with a professional roofing job. So when it’s time for a new roof for your home or building, partner with an experienced local roofing company to get it done right the first time.
