The Positive Roof Measuring Method
The positive roof measuring method requires you to break the roof up into measurable sections. For image 1.2 find the area of all sections of the roof, and then add them together to find the total area of the roof.
Area of section A = 20 x 60 = 1200 sqft
Area of section B = 20 x 40 = 800 sqft
Area of section C = 20 x 20 = 400 sqft
Therefore, the total area of the roof plan above is 1200 sqft + 800 sqft + 400 sgft = 2400 sqft
How Do You Calculate The Roof Area
Begin with calculating the area of your house in a plane parallel to the ground. If your house is rectangular, all you need to do is multiply the length and width of the building. If the shape of your house is more complex, simply enter the total area into the appropriate box.
Determine the roof pitch of your house. Roof pitch is the slope created by the rafters. If you donât know how to calculate it, head to our roof pitch calculator. You can input it either in degrees, as a percentage or as a ratio of x:12.
Once you know these values, you will be able to calculate the roof area. Begin by converting the roof pitch to an angle expressed in degrees, using the following formulas:
pitch = x / 12 * 100%
Then, use the following equation to find the total area of the roof:
roof area = base area / cos
Two: Split Tricky Shapes Into Squares And Rectangles
Once you have these figures, return to the safety of your home. Notice in the image above that the hip roof is made of two triangles and two trapezoids. Trapezoids are tricky to get the area measurement of, so were going to split each of them into two triangles and a rectangle:
We know enough about the overall measurements of the roof to fill in the missing values. Lets fill the figures in now:
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What Degree Angle Is A 12 12 Pitch Roof
A 12/12 pitch roof has a pitch angle of 45°. To convert between American roofing ratios and pitch degrees, follow these steps:
How Do You Determine The Slope And Height Of A Roof
The slope of a roof is determined by the rise over the run in other words, the amount of change in elevation divided by the horizontal distance. To find the slope, you will need to measure the height of the roof at two different points, and then divide that number by the horizontal distance between those points. The height of the roof is simply the vertical distance from the eaves to the peak.
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How To Measure Roof Pitch
Knowing the pitch of your roof is useful when designing an addition, installing skylights, or cutting new rake boards. Heres an easy, safe way to determine the pitch from inside your attic.
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Five: Estimate The Amount Of Roofing Materials Needed To Cover The Total Area
Now you have all the measurements, all thats left is to estimate how much roofing material you actually need to cover your entire roof.
Pro roofing tip: To be safe, we recommend buying a little extra roofing material just in case your measurements are a bit off. Dont worry, it wont cost too much!
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Measure The Footprint Of The House
The footprint of a house is a bit different from square footage because it refers to the perimeter of the exterior walls at ground level.
Image credit: Aluminum Lock Roof Inc
Square footage, on the other hand, includes the entire area of the house within the walls, including additional stories. Since you only need one roof regardless of whether its a one-story or three-story house, the footprint is a more accurate starting point than square footage.
To measure the footprint, use a tape measure or wheel and measure the length of each side of the house. Be sure to measure all the way out to the roof overhang, as you can see in the picture above, since thats where the roof ends.
Also, make sure to include any additions to the house like sunrooms, garages, or other bump-outs. As you measure, record your findings on your diagram so that you know which measurement corresponds to which side. This will be important in the next step.
Getting A Rough Estimation Of The Size Of Your Roof
Your home buying documentation should have the exact size of your roof inside, however if you do not have this information, or another document that details the exact size of your roof , then youre going to have to make the roof estimation yourself . While it may seem intimidating, the process isnt that difficult: youll have to know the overall square footage of the ground floor, as well as the pitch of your roof. If the roof has varying pitch sizes then each area with a different pitch will have to be separately measured and added all together in order to find the total roofing area.
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How To Calculate Your Roof Area
Knowing how to calculate your roof area can be a beneficial first step in estimating the cost of a new metal roof. In roofing we call the calculation of roofing materials needed a take-off.
A good roofing contractor will take the time make sure that the take-off is accurate. Proper measurements and attention to roof details ensure that material shortages are avoided and prevent overages .
Calculate Roof Pitch From The Ground In Three Quick Steps
Roof pitch is one of those things that middle school math and geometry instructors can easily point to, and say, See? Learning how to work with rise over run is fun and useful, right? If at any moment you start having PTSD flashbacks to algebra or geometry class, take a deep breath. Well walk you through this slowly in three simple steps. All you need is a tape measure, and possibly a helper to hold it.
Step One: Grab that tape measure, notepad, and pencil and head outside. Find the slope of your roof youd like to measure, and start measuring the distance from the outer edge of the eave to the point at which the plane of the roof slope is barely visible to your eye. Write that number down in both inches. This figure is the horizontal run.
Step Two: Stand directly underneath the gutter or edge of the roof plane you want to calculate the slope for. Measure the distance from your eye to the top of the drip edge of your roof overhang. Write that number down in inches, too. This figure is the roof rise.
Step Three: Take the roof rise figure in Step Two and divide it by the horizontal run from Step One. In the example above, the rise is 60 inches and the run is 120 inches. This reduces down to a roof pitch of 6/12. Well use this figure in just a bit, so keep it handy.
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Calculate The Slope Of The Roof
The next piece of information you need is the slope of the roof. Finding the slope is important because so far, weve only figured out how big the roof would be if it were flat across the footprint of the house. Since residential roofs are usually sloped, creating more space on the roof surface than if it were flat, you need to account for the extra square footage.
Image credit: Roofing Calculator
As you can see in the image above, finding the slope is based on the geometry of a right triangle. The slope is the longest side of the triangle , and the rise and run make up the other sides, forming a right angle. When finding the slope, the run is always going to be based on 12 inches. So you just need to determine the rise and youll be all set.
There are a few ways to do this without getting all the way up on the roof. The first is to measure from inside the attic if you have access. Heres how:
- Gather up a level, a tape measure, and a pencil.
- Measure 12 inches from one end of the level and make a mark.
- Place the end of the level against the bottom of a roof rafter and hold it perfectly level, using the bubbles as a guide.
- Measure vertically from the 12-inch mark on the level straight up to the underside of the rafter. This is the number of inches the roof rises in 12 inches and is called the slope.
How To Measure A Roof
This article was co-authored by David Bitan. David Bitan is a roofing professional, licensed contractor, and the owner and founder of Bumble Roofing based in Southern California. With over 12 years of construction industry experience, David specializes in restoring, repairing, and maintaining residential, commercial, and industrial roofs. With over 60 years of combined experience, Bumble Roofing provides easy, friendly services to structures including residential, commercial, industrial, multi-family, and government buildings along with hospitals, hotels, and churches.There are 13 references cited in this article, which can be found at the bottom of the page. This article has been viewed 360,743 times.
Measuring your roof is the first step in a successful re-roofing project. You can actually get an estimate of your roof’s measurements from the ground if you’d rather not climb a ladder and get up on the roof yourself. Otherwise, you can climb up onto your roof to take more accurate measurements. Either way, we’ve got you covered! This article will walk you through each process step-by-step.
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Calculating The Area Of Complex Roofs
If your roof is not the classic Gable shape, or if it has multiple sections such as hips and valleys, wed recommend splitting the roof into each section and working out the areas individually. If youre unsure of how to do this, get in touch with a roofing professional. Learn how to find a good roofer.
Or, alternatively get in touch with us! Our customer service team will be able to help you calculate your roof area, and anything else you might need for your project. Call them on 01295 565 565, email , or use the handy live chat below.
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Kalk.pro is online shed roof calculator – program determines basic material consumption for roof building, roofing underlayment volume, all quantitative and dimensional values of the shed pent roof truss system: Dimensions and area of a shed roof, materials quantity for it, the roof angle .
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How To Measure Roof Rise
Typical vinyl siding has 4 exposure, so 3 spans would be equal to 12 or 1 foot. Calculate the number of spans from the base line to the peak. Since most homes have a Rake wood, which is usually 6-8 wide, you can add that width to the rise.
Example: If you have 19 spans of siding at 4 exposure of each span, and a 6 rake board, the rise would be:
/ 3 = 6 10 roof rise.
Converting pitch to degrees can be useful in figuring out the roof geometry, or for European contractors who are not accustomed to th eUS system. See Table below:
Calculate The Simple Roof Areas
On a simple hip or gable roof, multiplying the eave to ridge length by eave length will give the area to be multiplied by pitch factor. Ridge vent openings are best finished with coil rather than partial shingle. Using flat coil stock allows the ridge caps to lay flat and can also be formed with an extra water stop at the ridge opening.
Area for the roof in Figure 3 is 1784 ft2 The blue dash line divides the roof into 2 rectangles. There is a small area calculated as 8/12 that is actually 4/12. On a small area such as this, it is better to err on the side of the higher pitch since it should not significantly affect the total.
Pro Tip: Pythagorean Theorem can be used to calculate the length of the valleys. A general rule of thumb is to add at least 12 lineal inches of valley material to be safe.
Figure 3. Calculating Simple Roof Areas
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How To Measure Roof Slope From Inside The Attic Or Inside Of A Cathedral Ceiling Structure
You need: a tape measure and a carpenter’s level. The procedure is like the on-roof example above, but flipped upside down.
As with measuring roof slope on the roof, inside the attic all we need is a simple carpenter’s level and a tape measure. We use the level to measure out from the roof surface horizontally for a distance of 12″.
Then from that point on our level we measure the distance straight up to point of contact with the roof surface.
That distance in inches will be the inches of rise per foot of horizontal run for this roof.
Watch out: if you do not keep the level at right angles to the roof your vertical measurement will be inaccurate. Hold your level with its side tightly against the side of a rafter to keep the level at right angles to the roof surface.
Or you can make this measurement inside the attic or even inside the building if a cathedral ceiling is installed by holding the level right against the gable end wall as we show at left.
For an outdoor version of this same approach see our example of MEASURING ROOF SLOPE OUTSIDE at the gable end of a building.
Confirm Measurements Before Ordering Materials
As we mentioned, measuring from the ground is a good way to get a rough idea of what youre dealing with when approaching a roofing project. Its also a good way to give an anxious homeowner a ballpark estimate.
Image credit: stonescapesteelroofing.com
What its not good for, however, is accurately ordering roofing materials or bidding jobs. As you can imagine, theres a lot that can be missed with this method since youre not actually getting a look at the roof first.
You can end up paying way too much for material and losing money on the job. Or under-bidding a job and having to work for peanuts. So before you get to this step, youll want to confirm your estimate by either getting up on the roof or ordering a virtual report from a company like EagleView.
If youre measuring by hand, check out this article that walks you through finding square footage step by step. If youre planning to order a virtual report, its as easy as inputting an address and sitting back. Well have a report out to you usually within the hour.
Our measurements are based on patented oblique image capture technology that delivers 4x the detail of standard aerial imagery and 70x that of satellite imagery.
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How To Calculate The Length Of A Common Rafter
To lay out the common rafters, we will need to know
- The building width
- The width of the ridge
If there were no ridge, the run would be half the width from the center to the outside of the wall. In reality, youll need to subtract half the ridge from the measurement.
So, after marking the center line, also mark each edge of the ridge. And don’t forget to include the exterior plywood wall sheathing in the dimensions. It doesn’t always make it up to the top of the wall plates when someone is pulling numbers for rafter measurements.
Hook the outside of the building with your tape and measure to the inside of the ridge. Thats the run, 14 feet, 11-3/16 inches in this case.
Pitch is shown on the plans and is indicated as a fraction, usually with 12 being the denominator. The first number is the rise the second is the run. A 6/12 roof rises 6 inches for every 12 inches of run.
So how do you get from expensive new lumber on the saw horses to a perfect fit on top of the walls?
With a calculator and then a saw. Punch this into your calculator.