air ducts

Rafter Design: An Integral Part of the Construction Process

The rafter design of a structure is an integral part of any new roof construction. Rafters serve as the aesthetic framework of a roof as well as structural supports for the building. Roof designs are generally sorted into two categories: vented or non-vented.

Vented roofs are used to adjust the roof temperature to prevent melting snow and ice from damaging the structure. They can also release hot air trapped in the attic of a structure to help provide a cooler living environment beneath the attic space. Ventilation openings are also useful for releasing built-up condensation in the structure.

It can also help equalize the pressure between the inside of the structure and the outdoor environment. Insulation and rafter placement also play an important role in controlling condensation and interior climate.

Proper placement of insulating layers can limit or eradicate the growth of mold, corrosion of the structure’s elements, and decay of the wooden supports. Rafter design should not only be crafted to support the structure’s roof and provide a visually appealing exterior, but it should take proper ventilation and insulation procedures into consideration as well.

The vented roof space should not be connected to the interior living space of a structure. This would encourage airflow and condensation. This is accomplished by installing an air barrier in the ceiling line of the structure and limiting the free space between ceiling and essential internal components such as sprinkler systems and air ducts to two inches. This is necessary in cold or very cold climates.

Rafter spacing must be adjusted in heavy snowfall areas to prevent undue deflection and warping of the roofing surface. Adjustments for the natural climate must be made to ensure proper stability and ensure integrity of the structure.

The pitch of the roof also aids in proper heating, cooling and moisture control for a structure. Utilizing a designing software program to calculate the proper pitch and rafter placement is recommended. Not only must the structural design meet the specifications of the client while adhering to building codes, but it must be built for practicality and longevity as well.

Rafter design involves:

  • combining the structural needs of the building
  • the building codes for the geographic area
  • environmental and climate considerations
  • and the design preferences of the consumer

These complex factors make roof and rafter design one of the major vital elements of any new roof construction.

December 17, 2007

Roof Rafter Design