Roof Trusses

Building your own home is an exciting event. For many people, it is the realization of a life long dream. While a great deal of attention is paid to the layout of the rooms, placement of windows and doors, and the design of the exterior, it is equally important to address the part of the home that will shelter all that is underneath – the roof.

The roof is supported by a framework referred to as a roof truss. Generally, a roof truss is a frame composed of wood or metal sections that are held together by aluminum or steel connection plates. The purpose of the roof truss is to ensure that the weight of the roof is equitably distributed, and that all sections of the roof are supported properly, thus extending the life of the roof.

When it comes to whether wood or metal trusses are superior, many still prefer the use of wood trusses for homes. Part of the reason is that the individual pieces that make up a wood truss can easily be modified on the building site to ensure a snug fit with the walls of the structure. From a safety perspective, metal appears to have no real advantage over wood trusses that are constructed of properly treated quality lumber. Even in the event of a fire, the general design of the truss is more important that the type of material used. A well constructed truss will not collapse as a whole unit, but would give way incrementally, allowing additional time for persons to escape the structure.

There are over two dozen basic truss designs. The choice of which truss design should be used will depend on what type of roof is required for the structure. As an example, a one story home that is basically rectangular in shape and does not include a finished attic may require nothing more than a simple Kingpost truss. The Kingpost, which is a simple broad a-shaped truss with a center support bar connecting the top and bottom of the truss, is often adequate to handle the type of shingled roofs associated with two and three bedroom homes of this type. In some instances, a Queenpost truss may be used, should there be additional weight to support. The Queenpost adds two additional horizontal bars to the very basic Kingpost, and increases the support for a roof that may be dressed with slate shingles.

When considering the design of a finished attic, a Hip or Scissors truss may be more appropriate. The Scissors truss actually will hug the roofline more closely, allowing more space for installing a drop ceiling within the attic. The Hip truss, with its more elaborate network of connected sections, provides a solid structure that will support not only the roof but a more substantial ceiling.

The overall dimensions of the structure are also important in determining which type of truss is appropriate. Generally speaking, the broader and wider the area to be covered, the more support the truss will need to provide. Two popular trusses for a larger home would b the Double Fink, with its zig zag support across the breadth of the truss, and the Fan truss, with its interwoven pattern. Both of these types of trusses allow the truss to support the weight of a larger roof, while still ensuring that the fit between roof and walls is snug and complete.
For a roof that is more elaborate than a simple A-frame, there are a number of truss styles that may be employed. The Polynesian truss resembles a hat with a brim, and was very popular during the 1970’s. The Cathedral truss is ideal if one wishes to incorporate a rounded design into the ceiling area. Bowstring trusses work well in western styled homes, and there is actually an Attic truss, which allows for maximum space in an unfinished attic.

For designs that call for a relatively flat roof, the Girder truss or the Flat truss work very well. While distributing the weight just as competently as any type of truss, these two require minimal space and tend to be very easily installed. In the event that the roof needs to have a slight pitch, a Monopitch truss allows for the roof to slope in one direction.

When evaluating what type of roof truss is right for your project, it is important to bring in a professional architect and possibly a building engineer. In preparation for your discussions with the builder, make sure you understand that choices you have regarding the type of roof the truss will need to support, the dimensions of your building, the design of the roof itself, and the materials that will be used to cover the roof. Also keep in mind what you wish to do with the space directly under the roof: will the attic space be finished or left unfinished? Your architect will be able to make constructive suggestions on how to achieve the look and the functionality you are seeking.