As the basis for a strong but lightweight structure, trusses are used in a variety of applications ranging from floors and roofs to bridge structures and even radio and television towers. Regardless of where they are used, roof trusses are usually either Pitched Trusses or Parallel Chord Trusses.
Primarily used in roof construction, the Pitched Truss has a triangular shape with additional structural members within the triangle. In contrast, the Parallel Chord Truss consists of two parallel chords that make up the top and bottom of the truss, with diagonal and/or perpendicular webbing connecting the two parallel chords. The top parallel chord is usually in compression, while the bottom parallel chord is usually in tension.
Instead of dedicating experienced carpenters to the labor intensive job of building trusses on site, many of today’s home builders prefer the more cost efficient option of ordering prefabricated roof trusses that can be delivered directly to the building site. Prefabricated trusses also possess a longer free span, which cuts down on the number of interior load bearing walls needed for the structural integrity of the building. Finally, prefab trusses are designed and certified by professional engineers and can usually be set in one day, shortening the amount of time the interior of the structure is exposed to the weather.
How To Order Pre-Fabricated Roof Trusses
Prior to ordering roof trusses, several options must be determined. These options include type, number, span, pitch, heel height (height above plate), load, bearing width, and ceiling type of roof trusses.
OPTIONS FOR ORDERING TRUSSES
Type – What type of truss do you want on the building? Common gable truss, hip, gambrel, bowstring, scissor, etc.
Number – How many of each type of truss are needed for this particular building.
Span– Distance between outside walls or bearing points where the trusses will be placed.
Pitch – What is the pitch of the roof to be? 6/12? 8/12? And so forth
Height Above Plate – What is the desired heel height above the wall plates at the outside edge of the building? Would you prefer to use a raised heel truss in order to accommodate more insulation?
Load – What are the required live, dead, and wind speed load requirements in your area? These questions can be answered by your local building inspector.
Bearing Width – How wide are the bearing walls or beams where the roof trusses are to sit?
Ceiling Type – What type of ceiling is required in each room? Cathedral, vaulted, barrel, etc.
TIPS FOR ROOF TRUSSES
Allow plenty of lead time. It can take anywhere from two to eight weeks before the trusses will be delivered.
Don’t deviate from the plan. If you change the dimensions on the building after the roof trusses are built, you will be out of luck.
Trusses can be very heavy and awkward to handle. To minimize the danger to yourself and your employees, consider using an all-terrain fork lift or small crane to set them.
Adequate temporary bracing should be available and correctly installed. If trusses fall over, they usually go like dominos – not a pretty sight.
Last, but not least, let one of our truss experts review your building plans.