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# How To Estimate The Square Footage Of A Roof

## How Many Squares Per Roll Of Underlayment

How to Measure the Square Footage of a Roof

The roll size depends on the type of underlayment product. Synthetic underlayment comes in 10 square rolls, while regular #15 felt comes in 4 square rolls.

So for the 24 square roof example, you would need 2.4 rolls of synthetic underlayment, or 6 rolls of regular #15 felt.

• 24 squares ÷ 10 squares per roll = 2.4 rolls of synthetic underlayment
• 24 squares ÷ 4 squares per roll = 6 rolls of regular #15 felt

Remember: Add 10%-15% for the waste factor on underlayment, as well.

Finally, if you have any questions about your estimate, ask a roofing contractor in your area. Most will be happy to give you a free estimate.

## How Do You Measure A Roof Without Measuring It

Roof surfaces are measured in squares. A roofing square is equal to 100 square feet of the roof. To determine the number of squares on the gable roof example in this post, divide its total of 2400 square feet by 100 . This means you would need 24 squares of shingles to cover that roof.

## How Many Toilets Can Be On A 4 Inch Drain

3 tank-type toilets, one urinal, 4 sinks. a drinking fountain. 2 Floor drains.

What works better than a French drain?

Swales or Valleys

Swales, also called valleys, are an alternative to French drains that capture and divert rainwater. Swales are shallow ditches that do not contain pipes. You can usually find them along a propertys edge, following the natural grade of the land to direct runoff to ditches or wooded areas.

#### How deep should you put a French drain?

French drain depth: About 8 inches to 2 feet deep should be sufficient for many water-diverting projects, though related systems, such as those built around foundations and sub-ground living spaces, as well as the bases of retaining walls, may be deeper.

#### Are rocks good for drainage?

Using rocks, water can be directed towards ditches, for example, that are landscaped as swales and resemble creeks or meadows. Because rocks do not compact or degrade with time, they make excellent components to a yards drainage system and do not require constant upkeep.

How deep should drain pipe be buried?

Maintaining a depth of 12 to 18 inches is best for drain pipes, but the depth of the pipe may vary in order to maintain a downward slope, which is critical for proper drain functioning.

Read Also: How Long Does It Take To Install Roof

## Calculating The Area Of A Complex Roof

Areas of complex roofs with multiple hips and valleys take the most time to calculate. Start by making a rough sketch of the roof. To simplify the calculation, break down the sketch into rectangles and right triangles , then take as many measurements of the roof as you can to match the sides of the rectangles and triangles on the sketch.

Use visual cues from the existing roof shingles or roof sheathing to determine square lines off eaves edges or ridges. These cues will help you measure the lengths of the sides of the rectangles and triangles. For instance, the cutout slots on shingled roofs run perpendicular to the eaves, and nail rows in sheathing are pretty close to square also. It is difficult sometimes to get accurate measurements. Dont get too concerned though just round lengths to the nearest 6 in.

With the sketch filled in with measurements, you can determine the size of the roof area. The area of a rectangle is length multiplied by width, whereas the area of a right triangle is the length of the two sides that meet at the 90-degree corner multiplied together and divided by two .

Tally the square footages of all the rectangles and triangles, which will give you the total square footage for the roof. The example here shows the calculation for a roof with two hips.

Also Check: How To Extend A Metal Roof Overhang

## Estimating Materials Based On Actual Measurements

Measuring each roof plane requires you to actually go onto your roof. If your roof has a number of planes and numerous hips, ridges and valleys, this is the most accurate way to calculate the materials needed. Take a metal tape measure and a pen and paper. Measure each planes length and width. Record your measurements. Once you are safely on the ground, use your measurements to determine the square footage.

For rectangular areas, multiply the length by the width. For example, if a plane measures 30 feet by 100 feet, this would be 3,000 square feet. For triangular areas, you may need to dust off your geometry book. If the area forms a right triangle, you can make use of the Pythagorean theorem. Otherwise, you might want to look up how to calculate the semiperimeter and then use Herons formula to find the area. Be sure to add extra for valleys, hips and ridges.

Read Also: Where Do You Nail Roofing Shingles

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## Draw Each Shape Individually Calculate Each Area And The Total Square Footage Of Your Roof

Now we have eight shapes to find the area of six triangles and two rectangles. Instead of breaking out the old textbooks to calculate triangle areas, we like to use a triangle calculator. It makes figuring out the area of triangles a lot simpler.

In the example above, we have two triangles with sides of 30, 20, and 20 feet. Pop those figures in the three-sides calculator and youll get an area of 198. Since we have two of those triangles, multiply by 2 for a running total of 396 square feet.

We have four remaining triangles, all with dimensions of 15, 20, and 25 feet. That same calculator reveals a result of 150 square feet. Since there are four of those triangles, multiply by 4 to get 600 square feet.

Lastly, we have two rectangles of 15 by 30 feet. This one is easy, just width times height for a total of 450 square feet for each one. Multiply by 2 and their total square footage is 900.

Adding all the areas up yields a total of 1896 square feet . Since roofing material comes in 100 square foot squares, youll need at least 19 of them for your roofing project. Itd be wise to get at least 20 to account for mistakes and waste.

## What Is Slope Factor

Taking a 2D measurement of a roof either online via Google Earth or by measuring the exterior walls of the home doesnt account for the elevation of the roof, which adds square footage. Slope factor is a convenient way of using the pitch of your roof to convert a 2D measurement to an accurate measurement of the roofs square footage.

 Roof Slope

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## What Size Drain Is Needed For A 5000 Square Foot Roof

According to the chart, for 1/8 slope per 12 of pipe, for 5,000 square feet of roof area, with a 6 per hour of rainfall, the required pipe size is 8. To size the vertical roof drain for the same parameters 5,000 square feet of room area and 6 per hour of rain consult Table 1106.2.

How do I calculate drain size?

To calculate the volume of water that needs to be stored, multiply the amount of runoff from each drainage zone by 15. The runoff for each zone was in gallons per minute. Multiplying by 15 minutes leaves you with the amount of gallons to be stored.

#### What is the difference between a French drain and a trench drain?

Aside from what weve listed here, the difference between a French drain and a trench drain is that a French drain is used for water that is underground while a trench drain diverts excess water from a surface.

#### How much slope is needed for a drainage ditch?

The field ditches work best on slopes of less than 2 percent. The drain is located across the slope as straight as topography will permit (fig.

How much does it cost to install a roof drain?

Installing drainage runs most homeowners between \$2,099 and \$6,465 with an average cost of \$4,130. Small, simpler solutions could be as low as \$500 and more complicated projects could get as expensive as \$18,000.

## Squares Rectangles And Triangles

How to measure a roof and calculate square feet. | 01/2020

Nearly every roof, no matter how simple or complicated, can be broken down into squares, rectangles or triangles. You can draw lines on your diagram from the ridge to the eaves to make triangles out of the hips. This will leave you with four triangles for the hips, two rectangles for the rest of the hip roof, and another rectangle for the lean-to roof.

Related: 7 Warning Signs You Need a New Roof ASAP

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## Finding The Size Of The Roof In Squares

Roofing contractors estimate projects and materials by the square, so it is crucial to find this measurement to estimate the amount of material needed accurately. A square simply refers to a 10 x 10 square of roofing. This is simply 100 square feet of roof.

To find the squares, divide the overall roof area by 100 and then round up. For instance, if the roof is 1550 square feet, then it is 16 squares.

## Figuring Out The Square Footage Of Your Roof

While it may seem difficult at first, you can divide your roof into 10 x 10 roofing squares, a standard unit of measurement used by roofers.

But first, some terminology youll need to know:

• Ridge Where two sloped roof areas meet
• Valley Where two sloped roof areas meet , often with a metal channel running along the fold
• Hip Roof Type of roof where all sides slope downwards to the walls
• Hip End The triangle shaped end of a hip roof

Related: Roofing 101: What Are the Different Parts of the Roof Called?

Also Check: What Is The Width Of Metal Roofing

## Find The Area Of The Footprint Of The Roof

To calculate a roofs dimensions, you need to measure the roof as if it were flat, then account for roof pitch, , and finally determine how many squares of material are required for the roof.

The calculator above can handle all of this, simply enter the length, width, and pitch, and it will determine the size of the roof in squares.

Start by measuring the roofs length and width in feet as youre standing on the ground. Remember that the length and width need to be found for the roof, not the house, so take into account that the roof overhangs the building.

Then determine the area of the roof as if it were flat. Multiply the length by the width in feet to get the area measurement.

## How Many Bundles Of Shingles Will You Need

The average bundle of shingles covers 33.3 ft2, so three bundles of shingles are needed per square. Asphalt shingles range in price from about \$25 per bundle for a standard 3-tab style to around \$50-\$75 or more for an upgraded architectural style.

Since transportation is a major cost factor, expect prices to vary by location. A typical bundle of shingles weighs about 75 pounds, while some premium products can weigh over 100 pounds per bundle, so consider delivery of materials.

Also Check: Do It Yourself Roofing Shingles

## How Do You Calculate The Square Footage Of Your Roof

Is it time for a roof replacement? Are you trying to figure out how much youll have to invest in your new roof?

If so, youre probably overwhelmed trying to learn everything that goes into the cost of your roof replacement. To help you understand the size of your roof investment, you first need to know the size of your roof. Thats why were going to break down how to measure your roofs square footage.

The team at Bill Ragan Roofing has been repairing and replacing roofs in Nashville and surrounding areas since 1990. We take extreme pride in everything we do, especially our workmanship.

## Calculate The Square Footage Of Your Roof

Now that you thought about the slope and complexity of your roof, youre ready to learn how to calculate the square footage of your roof.

To get a rough estimate for your roofs square footage, youll use this equation:

For example, if you have an easy up and over, walkable gable roof and a house that measures 56 feet lengthwise and 28 feet widthwise, your calculation will look like this:

1,568′ =

x 1.3

2,038 = square feet of roof area

Using this equation wont be 100% accurate, but knowing your roofs square footage is a great jumping-off point to learn how much youll have to invest in your replacement.

Recommended Reading: How Long Does A Roof Last In Illinois

## So What Is A Roofing Square

A roofing square is a measurement, but it has nothing to do with square feet, meters, yards, or miles. A roofing square is commonly used by roofing companies and is roughly equivalent to 100 square feet. This measurement does not change whether it is a square of shingles or a square of tarp. This is because roofing squares are used to make calculating the cost of materials and labor easier than if you had to use square feet or yards.

## Builder Mike Guertin Explains 3 Ways To Calculate The Quantity Of Shingles You’ll Need For Your Next Roofing Job

Roof Area video

One of the biggest challenges for experienced builder and novices alike is accurately estimating materials for a construction projectespecially for roofs, because they can be difficult to access for taking measurements.

But dont fretIn this excerpt from my book Roofing with Asphalt Shingles, I describe three reliable methods for determining the area of a roof, plus Ive included tips for estimating the number of extra shingles youll need for waste, overlaps, and starter shingles.

Note: be sure to take your time and double-check your numbers when calculating the quantity of shingles, underlayment, flashings, and other materials needed for yourroofing project. The more accurate your estimates, the less time youll waste waiting for material deliveries during the project.

Also Check: How To Afford A New Roof

## What Influences A Roofing Projects Cost

Although a roofs size is always a major factor in calculating project costs, other elements may influence a contractors quote, such as:

• Your location and the average roofing project prices in your area.
• Your choice of roofing material
• Roof accessibility and ease of installation
• The contractors certifications and level of work
• Project timeline

## How To Calculate The Square Footage Of Your House

A house that sounds roomy and spacious online may actually have 800 of its square feet contained in a four-foot-tall dirt-floor basement. Whats up with that? In Washington DC, clients are often confused at the square footage discrepancy between whats listed and what they see on tour, and colleagues in other markets hear similar things.

Why the conflicting information? Well, the American National Standards Institute guidelines on how to calculate a homes square footage are considered the standard, but there are no official laws that govern this process. In addition, some Multiple Listing Services report all finished and unfinished square footage of a house as a single number, adding to the confusion. Since the rules arent standard, some listing agents just post their best guess on a homes square footage. As a result, buyers and their agents often have to investigate.

If you love a home, does it matter if the 2,000 square foot charmer turns out to be officially 1,600 sq ft in length? Since square footage is used to determine a homes market value, it can matter a lot. When it comes time for you to sell, 400 fewer feet in measurement can impact the price youll get, particularly in a buyers market. Which is why we created this guide on how to calculate square footage of a house.

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## General Features Of Roof Square Footage Calculations

Mostly a roof has an irregular shape, and many people have know any idea how to perform the calculation. There is nothing scary, you just need to divide the entire surface into individual shapes and to calculate each separately, and then to sum everything.

If you only have a roof view on a paper, it is necessary to know its slope angle, and after receiving the projection area, to determine required materials for the actual space, this number has to be multiplied by cosine of the roof slope.

If you decide to calculate the roof space by yourself, be sure to take into account that any material lies overlap and add 10-15% for waste. If the structure is complex, it is advised to add up to 20% of the waste.

Also Check: Roof Overhang Extension

## What Lasts Longer Pvc Or Cast Iron

Durability: Cast iron often lasts significantly longer than PVC piping when utilized in drainage systems. Cast iron piping can last several decades, if not for a century. One downside of cast iron is that it is susceptible to rusting if not maintained properly.

How many square feet can a 4 roof drain handle?

Example: For a 4 hourly rainfall and 4 leader, each drain can handle 4,600 sq. ft. of roof area.

Read Also: How Much Does It Cost To Replace Camper Roof

Using your computer to get a ballpark estimate of your roof area is easy and fast. However, using satellite imagery may not be an ideal solution if your structure is in a very remote location that hasnt been 3D scanned. Thats because well need to grab an accurate representation of your roofs pitch for measuring purposes. From above with a 2D image, everything looks flat. If you were to just measure your roof area from directly above, you wouldnt be accounting for its pitch, or slope.

Consider two homes with the same base area square footage, but one of them has a much steeper roof pitch than the other. That structure would need to be taller, and there would be a lot more roofing material to account for. If youre just measuring from above in 2D, both of these structures might look identical. If you dont account for roof pitch, youre going to underestimate your materials requirements, which could be a costly mistake.

Satellite technology has progressed a lot in the past few years. With , you can easily find your address and a 3D replica of your structure, including your roofs pitch. Lets get to it. Once you load the site, youll be presented with our beautiful planet:

While you can switch to 2D mode by clicking the button in the lower right, youll want to stay in this 3D view so you can get a good view of your roofs pitch.

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