Knowing the slope of your roof is good for all kinds of things! From knowing if you have to worry about ice dams to wondering if you should really send you kids up to take down the Christmas lights because you don’t want to, or any reason in-between…it’s good to know the pitch of your roof. Although we could break out the ladder, a level, a tape measure, and get ourselves to get on the roof…it’s a lot easier to gather this info from the safety and convenience of the ground. Here’s how! BTW…the tape measure will still be required.
Step 1: Walk away from your house, perpendicular to the wall that is under the roof pitch you’d like to measure. Walking backwards, and watching where you’re going, walk out to the distance where your eye aligns with the plane on the roof pitch. So you should essentially see the top edge of the eve or gutter line up with the peak of the roof pitch. Assuming the ground is relatively flat, measure the height of your eye from the ground. Record this measurement.
Step 2: Measure the distance from where you’re standing to the face of the wall you walked away from. As a tip, if you had hooked the tape measure to the house when you backed away from the wall, you’ll be able to do this without help from someone else! You’ll also need to know (or measure) the distance of your home’s overhang. By subtracting the overhang distance from your standing distance, we will have identified the ‘Run’ value of your roof pitch! Record that value in both inch & foot values!
Step 3: Measure the height from the ground to the edge of your eve or gutter. Then, take that measurement (102” as pictured) and subtract your earlier eye height (60” example pictured). This will give you your rise value! Be aware that a steep sloped ground surface may throw off this value. We are looking to find the distance from your eye height to the eve edge. So feel free to adjust your measured eye height as you see fit to compensate for a higher or lower ground surface under the eve. Since roof pitches are pretty nominal, we’ve got a lot of play here without effecting the accuracy of our measurement, but if you think it has sloped 6” or more, you’ll want to account for it.
Solve for the Answer!: Roof pitch is calculated in a Rise to Run ratio, with the run value being a 12” standard. So basically, the pitch answers the question of, ‘how many inches does the roof rise over the course of 12 horizontal inches?”. To solve this, we simply plug in our values for Rise and Run. In this example, it is 42” to 84”. We then divide both numbers by the dividend that will get the run value to 12. This number is easily found in step 2! When we recorded the measurement in step 2, we recorded the inch & foot values. In our example, we recorded that value of 84” and 7’. By dividing both numbers in our ratio by the recorded foot value of 7, the 42:84 turns into our final 6:12 pitch value!
Easy enough! …but feel free to use the calculator on your phone if you need to.