You may be happy to know that there are several ways to measure a roof. If it is very inclined or you don't like climbing stairs or staying high, you can opt for a ground measurement. Although the result is not as accurate as a direct survey of the roof, section by section, this technique allows to obtain a rather accurate estimate. You still need a ladder, but you don't have to climb all the way to the top of the house.
Steps
Method 1 of 4: Draw a Diagram
Step 1. Draw a roof diagram on a piece of paper
Label each section; later you will report the measurements on the drawing to simplify the calculations. Being able to see on paper the elements you have already detected and the points where you have already been makes the process faster.
Step 2. Find the area of the triangular sections
This is not as complex a step as you might think; the area of a triangle is found by multiplying the base by the height and dividing the product by 2 (b x h / 2). Use a measuring wheel to detect the length of the eaves and the distance that separates the midpoint of the same from the opposite eaves; multiply the measured values together and divide by 2. Write the result on the diagram indicating it as the area of this section.
Step 3. Determine the area of the rectangular sections
Always use the wheel to find the length and width of the rectangular portions; multiply these numbers together and obtain the area relating to these sections to be reported on the diagram.
Step 4. Get the total area
Add up the partial surfaces you detected; the total corresponds to the area of the entire roof.
Step 5. Calculate the amount of material you need
Construction products for the construction or repair of the roof are purchased on the basis of the "square meters" of the roof itself. This means that you must take your calculations to the material supplier and procure the necessary quantities, taking care to also include an "extra" to account for errors and possible breakages.
Method 2 of 4: Remote Measurement Services
Step 1. Do some research online
Since 2007, there have been a number of remote measuring instruments that use satellite or aerial images to detect the surface of roofs (in the areas where these images are available). These systems allow you to calculate the area of the roof without having to go up and get the data via e-mail at a low cost.
Step 2. Once you have received the results, remember to also calculate some extra material in stock
This "extra" amount varies based on the complexity of the roof geometry and how you want to arrange the valleys (there are three methods). Do some research online to learn how to calculate materials.
Method 3 of 4: From the Ground
Step 1. Measure the four sides of the house while standing on the ground and using a tape measure
Remember to add to each side an estimated value for the portion of the roof that protrudes beyond the walls; note these findings on the diagram.
Step 2. Get the total area
Add the square meters of each section to find the surface of the house and not the roof.
Step 3. Calculate the amount of material needed taking into account only the area of the house
You can use online calculators based on the very material you plan to use.
Step 4. Determine the slope of the roof
This is the angle formed by the roof with respect to the ground and is calculated as the ratio between height and width. Detect a 30 cm segment parallel to the ground, starting from the edge of the roof and along its base; from this point it measures the perpendicular height up to the hypotenuse of the roof itself. Use the table below which indicates the multiplication coefficient based on the slope (considering a standard width of 30 cm): 5 cm = 1, 102; 7.5 cm = 1.134; 10 cm = 1.159; 12.5 cm = 1.191; 15 cm = 1,230; 17.5 cm = 1.27; 20 cm = 1.322; 22.5 cm = 1.375; 25 cm = 1.432; 27.5 cm = 1.493; 30 cm = 1.554.
Step 5. Get the final values
Take the square figure you got from the ground and multiply the data by the coefficient; in this way, you get the roof surface.
Method 4 of 4: Rough Estimate
The one described below is not a very accurate method, but it gives a pretty accurate idea of the size of the roof, including even those data that you may not have at hand, such as the slope, the size of the garage, and so on; in this way, you come to a fairly realistic estimate.
Step 1. Consider the floor area of the floor plan
Suppose it is about 185m2.
Step 2. If the house is on one floor, add 90m2.
This way, you should get a good estimate. In the previous example, if the house has an internal surface of about 185 m2, it is probable that that of the roof is about 275 m2; this criterion allows you to purchase the necessary building material.
Step 3. If the house has two floors, multiply the floor area by 1, 5
Always taking into account the example described above, you should get a roof area of 277 m2, a value very close to the first result.
