The Evolution of Trusses: How It Affects Ceilings
The wood trusses that we so commonly see today are frames of triangulated lumber joined together with galvanized steel connector plates, commonly referred to as truss plates. The shape of roof trusses has not changed over the years but the make-up, spans possible and the safety has changed.
The truss shape has been in use since man has used pieces of logs and then, centuries later, sawn lumber. In modern times, the first light wood frame trusses were built on the construction site using nailed boards or plywood gusset plates at the joints. Use of these early timber trusses offered longer spans, more cheaply, that un-trussed lumber but took a long time to build on the construction site.
In 1952, in Pompano Beach Florida, after experimenting with plywood gusset plates and varying concoctions and combinations of glue, staples, nails and screws, the metal plate connected engineered wood truss was invented and patented. The inventor, A. Carroll Sanford, founder of Sanford Industries, marked the beginning of the truss industry that is still changing home, apartment and commercial building construction all over the world.
Modern roof and floor trusses, clear-spanning between the perimeter walls, allows larger more open room designs, particularly in areas of great snow or rain loads. This roof system proved to be faster and more cost-effective than earlier practices, much less material and less labor cutting and fitting materials in the field.
Increasing the height of a room without increasing the overall height of the building is becoming ever more popular with developers. Using Raised-Tie trusses (Tail-Bearing trusses) it is possible to raise the room height above the height of the wall top plate. Similar to an attic truss, the lack of triangulation causes the top chord to increase in depth. It is possible to manufacture raised-tie trusses up to 3 ft. above wall top plates, although there are other factors that can affect this.
An alternate option to raised-tie truss is a scissor. Scissor trusses also allow the room height to be increased but only in the center of the truss. In a scissor truss, triangulation is maintained so top chord depths are smaller than a raised tie while still getting a raised sloping ceiling. Therefore, this application usually works where a raised-tie truss would not due to the ceiling-be fixed to the wall top plates.
There are other truss profiles that can be used to raise the room height above the height of the wall top plates such as a coffered ceiling truss. Homebuilders have begun to use a variation of coffered ceilings in some areas of the home to highlight light fixtures, ceiling fans and plant shelves.
The truss component industry has adapted, over time, to the wishes of the building industry and consumers, to produce the many and varied ceiling shapes required by them. We’ve come a long way from flat, low ceilings made from logs or heavy timbers, to the wish list of today’s modern homes and buildings.
What do you think is in store for the future of trusses?
Richard Gould – Design Administrator
Gould Design, Inc.