1. Roof and Ceiling Framing
Chapter 21
Roof and Ceiling Framing

2. Objectives
After reading the chapter and reviewing the materials presented the students will be able to:
Identify different types of roofs
Describe the components of W trusses
Identify the parts of a roof and ceiling frame
Explain how roof sheathing is installed

3. Introduction
In multistory buildings, the floor frame of the upper floors also supports the ceiling of the floor below.
The ceiling of the top floor is built in conjunction with the roof frame.
Most roofs use triangular frames.
These frames include two sloping members to support the roof and a horizontal member that ties the lower ends of the roof supports together and provides support for the ceiling of the floor below.
Rafter is a structural member of a roof designed to support roof and ceiling loads.
Truss is a premade engineered assembly of framing members designed to support roof loads (fig 21-1, page 357).
Trusses are normally delivered to the building site on trucks and are installed using a crane.

4. Types of Roofs
Four commonly seen roof types are flat, shed, gable, and hip roofs.
Flat roofs have one horizontal surface. Steel reinforced concrete structures often have flat roofs.
Shed roofs have one sloping surface.
Gable roofs have two sloping surfaces and a triangular shaped wall. Gable roofs are common on residential structures. Using trusses often eliminates the need for a center load bearing wall.
Hip roofs have four sloping surfaces. Hip roofs typically have a low slope. Manufactured trusses are typically used to frame hip roofs.

5. Building Gable Roofs with Trusses
The W-truss is commonly used in residential construction (fig 21-8, page 360).
The top chords and the bottom chords form a rigid triangle.
Roof sheathing is nailed to the top chord.
Drywall for the ceiling is attached to the bottom chord.
The compression webs and the tension webs work together to reduce the tendency of the top and bottom chords to bend under load.
A tail is included as part of the truss if the roof overhangs the outside walls of the building.
The optional return is used to support material that enclosed the roof overhang.
Gang-nail plates are steel plates that have nail like projections on one side, are placed on each side of a joint form a solid connection.

6. Layout for Trusses
Roof framing begins after the walls are constructed.
The first step in roof framing is to layout the trusses.
Trusses are often designed to be spaced 24” on center and to run parallel to the short wall of a rectangular floor plan.
Sheathing overhang can be 2”.

7. Installing Trusses
Before beginning the installation of manufactured trusses, erect temporary supports (fig 21-10, page 363).
The next step is to lift the first truss in position.
A crane is typically used to make this task easier.
In addition to being aligned to the mark on the double plates (fig 21-9, page 362), The ends of the truss must extend the correct distance beyond the wall frame on each side of the building (fig 21-11, page 363).
Once the truss is in the correct position, nail it to the top plate and to the temporary vertical support.
To hold the trusses in a vertical position, nail a 2x4 horizontally across the trusses near the top.

8. Custom Built Gable Roof and Ceiling Frames
In some designs, premade trusses are not used to frame the roof and ceiling.
Figure 21-12, page 364 illustrates terms used in rafter layout.
Span is the total distance from the outside of one wall to the outside of the opposite wall.
Run is the horizontal distance measured from the outside of the wall framing to the centerline of the ridge.
The line length of the rafter is the hypotenuse of the triangle formed by the run and the rise.
The bird’s mouth is a wedge-shaped notch that is cut from the rafter so it seats on top of the double plate.
Rise is the vertical distance from the top of the double plate to the point where the line length intersects the centerline of the ridge board.
Slope is the incline of the roof and is expressed as a ratio between the vertical rise for each 12” of the horizontal run.

9. Installing Fascia and Sheathing
Fascia is a vertical board that is attached to the tail of each rafter.
It covers the end of the rafters, provides a base for attaching gutters, and gives a finished appearance to the roof’s edge.
If a rafter is short, a shim can be inserted between the end of the rafter and the back of the fascia to correct the error.
The fascia is nailed to the rafter end using rust resistant nails.
Roof sheathing strengthens and stiffens the roof frame.
It provides a base for nailing shingles or other roofing materials.
The first row of roof sheathing should overlap the fascia slightly (fig 21-13, page 365).

10. Summary
In multistory buildings, the floor frame of the upper floors also supports the ceiling of the floor below.
The ceiling of the top floor is built in conjunction with the roof frame.
Rafter is a structural member of a roof designed to support roof and ceiling loads.
Truss is a premade engineered assembly of framing members designed to support roof loads.
Flat roofs have one horizontal surface.
Shed roofs have one sloping surface.
Gable roofs have two sloping surfaces and a triangular shaped wall.
Hip roofs have four sloping surfaces.
The W-truss is commonly used in residential construction.
The top chords and the bottom chords form a rigid triangle.
The compression webs and the tension webs work together to reduce the tendency of the top and bottom chords to bend under load.
Gang-nail plates are steel plates that have nail like projections on one side, are placed on each side of a joint form a solid connection.
Trusses are often designed to be spaced 24” on center and to run parallel to the short wall of a rectangular floor plan.
Span is the total distance from the outside of one wall to the outside of the opposite wall.
Slope is the incline of the roof and is expressed as a ratio between the vertical rise for each 12” of the horizontal run.
Fascia is a vertical board that is attached to the tail of each rafter.
If a rafter is short, a shim can be inserted between the end of the rafter and the back of the fascia to correct the error.
Roof sheathing strengthens and stiffens the roof frame.
It provides a base for nailing shingles or other roofing materials.

11. Home Work
1. Why are compression webs and tension webs added to W-trusses?
2. Why are gang-nail plates pressed into boards of a truss being joined?