Basic Roof Framing Techniques

You can read 10 books on roof framing, hip roof framing or how to cut a roof in general and come away with 10 different techniques for calculating common and hip/valley rafters. Each one will work if you understand the underlying premise. If you've ever read those little books that come with rafting squares, you might want to quit before you begin! After framing roofs for over 25 years, I've put together a set of steps to help clear up some of the confusion.

One thing to bear in mind about my approach is that it goes beyond the notion of "tables", some books are just that, tables, you find the pitch and follow the tables. My approach is a much more dynamic one that will give you the tools to feel confident to tackle any roof framing project. All you will really need is a framing square, tape measure, string and chalk line, but to make life easier I'd recommend a Construction Master Pro Calculator, but any scientific calculator will do.

Before I begin I would like to say that this is in no way a course in "simplifying" roof framing, to the contrary it is an in-depth view of the components that make up roof framing. I employ the use of variables to define and describe the factors that one needs to deal with in any roof. A through understanding of them will make any roof a simple project to design and build.

I will begin by discussing some of the terms of roofing posed as questions. I will then answer each question as in-depth as possible. The purpose of this is so you will be able to perform the necessary calculations to find the common, valley, hip and valley/hip jack rafter lengths.

For the purpose of this discussion we will use an 8-12 roof slope and a roof deck of 75' x 32'  all common rafters will be 2 x 8's the ridge will be a 2 x 8 and hips and valleys will be double 2 x 8's in this example. We will discuss the techniques for framing a conventional roof and one that I refer to as a fixed height ridge.

The term "conventional" roof framing is readily applied to new construction. Many of the simple procedures followed by past craftsmen lend themselves to this type of framing. If you were so inclined you could do any roof on any new construction site with just a rafter square. Even though this type of roof framing is fine, when it comes to remodels, extensions or additions and different approach might be better in most if not all cases. Their are some who might disagree with this claim, but once you understand the differences you can make up your own mind.

The term "fixed ridge height" is best used in systems where the actual ridge height is a variable. Unlike conventional framing where you are given a roof pitch and then you move your ridge up or down to accommodate, fixed ridge height is like someone saying; I want my ridge "this" high or just below that window. Using the techiques in this section will allow you to set the actual ridge height and determine the actual plumb and level cuts needed to have a well fitting roof structure.

Alternatively there is a method of figuring out complex roof framing conditions that will be of great help to those who are truly new to roof framing. I refer to it as the "Block" & "String" method. It's beauty comes from it simplicity and ease of application.