How to Measure a Roof For Shingles

It’s time for a new roof on your house and you would like to have an idea how many shingles will be needed for your roof replacement. Skilled roofing contractors know how to do this. But perhaps you would like to know yourself. Measuring a roof is not always an easy task. There are a few basic things you will need to know for an accurate measurement.

Roofing Contractors have their own Lingo

The first thing you need to know is that shingles are purchased in what roofing contractors call “squares”. A square is an area that is 10×10 feet or 100 square feet. Normally for basic three tab shingles one square would require three bundles of shingles. Today’s architectural shingles are heavier and thicker. If you are using these it will take four or five bundles to make a square.

First thing to do is to draw what your roof looks like by looking straight down at it from above. Even if you don’t get the exact look a basic drawing will do the trick. The measurements you get will add up to give you the number of squares needed.

Although some are, most roofs are not just two straight sides. Many times there are dormers, valleys, and hip sections. That’s where it gets a little complicated. Seasoned roofing contractors are used to these and should have no problem in delivering the correct amount of shingles to your home.

How to Measure for your Roof Replacement

Let’s take a look first at an easy to measure straight roofing section. Go to the ridge of the roof and measure all the way across. Then measure the length from the ridge to the bottom of the roof. Let’s say the ridge length was 60 and the rafter length is 16. Multiply 60×16 and you will get 3,600. That’s 960 square feet or 9.6 squares.

If you have a hip roof you will measure the top ridge length, the bottom length, and the rafter length. Add together the ridge length and the bottom length and divide by two. Then multiply that number by the rafter length. For example: the ridge length is 20 and the bottom is 35. 20+35=55. 55 divided by 2 is 27.5. If the rafter length is 14 you will multiply 27.5 times 14. That equals 385 square feet. Remember we need squares so it is 3.85 squares.

The end of the hip roof or the triangle shape is an easy one. Measure the length from the top to the bottom and then the bottom edge. Multiply the length by the height and divide by two. Divide that number by 100 to get the amount of squares.

Adding Extra Shingles for Waste, Ridge Cap, Starters, and Valleys

Once you have all the different dimensions you will add those all up together. You then need to account for the extras. You will need to have extra shingles for waste, ridge cap, and starter shingles. One a straight two sided roof you should add 10 percent. For a hip roof add 15 percent.

You may have an even more cut up roof than that with dormers and valleys. These basic instructions will get you through that. Remember though, the more cut up your roof is the more you will need to add for waste.

Residential Roofing Contractors – Keeping them Honest

Roofing contractors regularly measure roofs and know how to accurately figure the size of your roof. Now when your residential roofing contractor comes to give you an estimate you will have a good idea how many shingles you will need…and if the contractor is giving you a precise bid.