Calculating Roof Pitch And Roof Pitch Tables
Roof pitch is a common term in construction and one that you'll see a lot if you're searching for information on roofing. If you decide to construct almost any part of the roofing yourself -- making the rafters or trusses for example -- you'll need to know the roof pitch. If you're working with an architect or another professional, you may be able to get the measurements from them. Otherwise, how do you calculate the roof pitch? In this article we'll look at the basics of roof pitch tables and figuring it out on your own.
What is Roof Pitch?
The roof pitch is the slope of the roof or the angle of the roof. Knowing the roof pitch is vital to cutting rafters properly. Roof pitch tables have standard measurements and you'll often see numbers like 7/12 or 7-12 or 12,7 or 7 and so forth. But what do these numbers mean? Using the example of 7/12, 7 means that the roof rises 7 inches for every 12 inches it runs horizontally. The number 12 is the standard number of inches that all roof slopes are gauged by. Figuring out your roof's pitch or slope is not quite as complicated as it may sound.
Measuring Your Roof Pitch
There are many variations of how to calculate roof pitch on your own. For the method discussed here, you'll need a level, a ladder, a tape measure, and a grease pencil. Before you start climbing up to the roof, mark your carpenter's level at the 12 inch line with a grease pencil. There is more than one part of the roof where you can measure the pitch. You can, of course, climb up to the outside of the roof and do this. But shingles or other irregular roofing will prevent you from getting accurate results. An alternative method of getting roof pitch is to measure the underside of a rafter either in the attic or one that overhangs your house. Generally, this alternative method will get you the most accurate results, which will help you to use roof pitch tables to determine the correct rafter length for your roof.
Once you've picked your measuring spot, hold the level straight either so one end touches the edge of the roof or so it's up against the underside of a rafter. Take your tape measure and measure from the ceiling or roof surface to where you marked your level on the 12 inch line. This measurement tells you the rise of your roof. So if your tape measure says 5 inches then according to roof pitch tables the pitch of your roof is 5/12. A 5 inch rise for every 12 inches it runs. Roof pitch examples include 7/12, 6/12, 5/12. A pitch-and-angle calculator can also help you get the pitch of your roof.
When you have the measurements for your roof pitch, use roof pitch tables to help you figure out how to cut your rafters properly. They can give you the standard pitch equivalents in degrees to make cutting your rafters right the first time a bit easier without having to do all the extra math. If you just happen to want to do this on your own, you can find instructions on how to convert the pitch to degrees online as well.
