True Valley Roof Framing

Vertical rise over horizontal run.

True valley roof framing. The run or half the building span is the base of the triangle. This roof valley is a perfect example. 468 chapter 17 basic roof framing. To keep the porch roof framing as simple as possible we installed a structural ridge supported by posts at each end with the common rafters landing on top of the ridge.

Roof pitch the roof pitch is the numerical measure of how steep or shallow a roof is. The main difference between the two is that valley rafters sit on inside corners while hip rafters sit on the outside corners. An example of each is shown in figure 2 1. 4 12 through 9 12 are the most common pitches.

The valley area of a roof the straight lines formed when two different planes of the roof meet is a critical area that handles a tremendous amount of water run off. Installers might feel that continuing the sheathing under the valley framing is not advisable because it is a waste of material or because they want to allow the free flow of air between roof areas. But it doesn t have to be. The framing of a basic gable roof is based on a right angle triangle and the various roof framing components fit the triangle.

Repeat the process on the other side of the hip using the pitch of the hip for the secondary roof 9 5 8 18 13 16. 504 chapter 18 hip valley jack rafters. The general arrangement of rafters shown in the larger drawing. It depends upon several factors including the roof s span run and rise see figure 17 5.

The rise or height of the roof at its peak is the altitude of the triangle. And the line length measurement from the roof peak to the building wall is the hypotenuse. Valleys are typically found where gable dormer roofs meet the main roof or when a house has angled wings or additions where two roof sections in different planes meet. If you begin with accurate as built measurements and use a construction calculator to do the math you can cut all of the rafters for most roofs on the ground in just one shot.

An unequally pitched valley rafter is laid out in the same way as the unequally pitched hip. Regardless the top chord of the supporting trusses beneath the valley set must be properly braced. After installing the rafters we still had to extend the porch roof back over the shed roof creating a valley on either side. Blind valleys simplify framing.

Calculating roof slope the slope of a roof must be calculated before construction can begin. In the u s it is defined by the rise in inches to a 12 run. Gable a gable roof has a ridge at the center and slopes in two directions. Common types of roofs and basic framing terms.

It is the form most commonly used by. Figure 17 3 conventional roof framing basic elements the basic parts of a roof frame. Framing a complex roof is one of the trickiest parts of home building. 3 inch rise per 12 run is a 3 12 pitch roof.