Module 1: Conventional Roof Framing Design

In this section we will cover the mechanics of roof loading on structural members. We will show how the designer can determine the  dead loads of typical building materials. Additionally, we will show how roof and ceiling live loads are determined from the residential building code. Additionally, we will also review the code limits for deflection of rafters and ceiling joists and how these limits affect the design process.

This Section covers the sizing and framing of rafters, ceiling joists, rafter ties, collar ties and ridge straps. We will cover all the fastening and connector requirements including connectors needed to resist wind uplift loads.

In this section, we will show that the code requires designers to provide lateral support to the rafter and ceiling joists at bearing points.

We also will cover the guidelines for bridging including the location where bridging is required, the types of bridging and the conditions under which bridging is required.

Additionally, we will look at the limits on notches, cuts and holes on roof framing members. We will also discuss the code requirements for conventional framing of openings.

Finally, we will cover wood structural panels from conformance standards, structural properties, construction specifications and grade stamps.

In this section, we will start the conventional structural design of a two story residential structure in Seismic Design Category D2 (Very high seismic hazard risk) and a wind speed of 120 miles per hour.

Since the scope of this module is on roof framing, our design work will be limited to roof framing. We will design the rafters, ceiling joists, ridge straps (in lieu of collar ties) and all framing connections. We will also design the roof diaphragm and the rood diaphragm connections with respect to the required loads. Additionally, we will develop the structural drawings as is typically required for permit issuance and construction.

The drawings will include roof layout plans, details drawings and material specifications drawings.

In this section we will look at how designers can review manufactured/engineered trusses for conformance with the overall design intent. Additionally, we will look at a design project where will show how the designer can integrate manufactured trusses into a conventional framing design. We will also develop the structural drawings for the project.

There are cases where designers will prefer to use engineered trusses instead of conventional roof framing. Engineered trusses have the advantage of flexibility in terms of the roof configuration or type and are do not take as much time to install since they are manufactured offsite and therefore overall construction time for the project is reduced.