In Manufactured We Truss

While stick building remains the standard, remodelers are taking a cue from new home builders' use of pre-assembled trusses when it comes to big jobs. Manufactured roof and floor trusses can ease and expedite the process of installing the roof and floor systems in an addition, and more importantly, provide time, labor and material savings in the process.

March 31, 2006

While no specific training is necessary to install manufactured trusses, it is important to have an understanding of framing and carpentry.  Photo courtesy of Wood Truss Council of America

While stick building remains the standard, remodelers are taking a cue from new home builders' use of pre-assembled trusses when it comes to big jobs. Manufactured roof and floor trusses can ease and expedite the process of installing the roof and floor systems in an addition, and more importantly, provide time, labor and material savings in the process.

"We always use pre-manufactured trusses. It is substantially faster," says Gary Potmich, a project manager with Kirk Development Co. The Phoenix-based remodeling firm typically works on homes built in the mid-1980s or earlier.

The ease of installation makes it easier for less-experienced workers to do the framing.

"Labor costs being what they are, this is a really good option. Also, we are finding that the professional expertise for stick building these trusses is rapidly disappearing," says Simon Evans, owner of Bay Truss, a San Francisco-area manufacturer.

In a 1996 project called "Framing the American Dream," the Wood Truss Council of America and the NAHB's Building Systems Council built two identical, 2,600-square-feet, multilevel homes in Houston. They discovered that using roof trusses saved 156.5 man hours and more than 4,000 board feet of lumber. For the floor trusses, the home with manufactured components required 26 fewer man-hours and 1,108 fewer board feet of lumber.

According to manufacturers, prefabricated trusses:

  • Are structurally efficient. High-strength lumber is optimized by placing only where it is needed for large chord or web forces.
  • Are capable of supporting heavy loads without interior bearing walls.
  • Can be used in applications requiring longer spans.
  • Are available in architectural grades, which can be left exposed.

This means you can order trusses to fit practically any addition.

Instead of placing systems in the home after it is built, organize the utilities within central pathways in the home, such as open web trusses underneath the floors.
Photo courtesy of Wood Truss Council of America

Order up

Trusses are generally designed to fit a specific project. When ordering, provide all of the necessary dimensions and pitches, and identify whether you want a gable, hip or flat style on the plan.

"When getting ready to use prefab wood trusses in a structure, it's important to bring together design, installation and material specification," says William Plant, owner of American Pole & Timber in Houston. For material specification, a remodeler should not only consider high-quality plywood, spruce, and pine, but also decide on grade, treatment and finish.

It's also important to notify the manufacturer or supplier in advance. The amount of lead-time is often minimal, but make the call to be sure you will receive the trusses on time.

"From a local manufacturer, we can usually get them the same week, but as a practice we usually give them two weeks to be delivered," Potmich says. "In a pinch, we can order them Friday or even Monday and get them by Wednesday or Thursday."

As with any pre-manufactured element, it is important for the remodeler to get accurate plans to the supplier. However, for remodelers who have fickle clients or are dealing with large quantities, providing specific plans may be easier said than done. In these cases, you may want to consider using trimmable open-web floor trusses.

Codes generally do not permit prefabricated trusses to be altered on site. Trimmable floor trusses are the exception. They come in two types. The first is a hybrid of truss and I-joist technology. The main part of the truss has steel webs with top and bottom chords made from LVL or 2-by lumber. The web material for a short distance on each end is OSB, effectively forming an I-joist on each end that can be trimmed as needed.

The second type is an all-wood truss. This product has a section of dimensional lumber on the ends rather than an I-joist. The all-wood type does not rely on truss plates for connections like most open-web wood trusses. Rather, the chords and webs are connected using finger-jointing technology.

The trimmable end can be cut in the field up to 12 inches on each I-joist truss and up to 51/2 inches on each solid wood truss.

Handle with care

To help with safe installation, the Truss Plate Institute and the Wood Truss Council of America have published "The Guide to Good Practice for Handling, Installing & Bracing of Metal Plate Connected Wood Trusses" (BCSI 1-03). The guide stresses the importance of proper handling of trusses on site: checking the banding before moving truss bundles, picking up vertical bundles at the top cord, taking proper precautions when storing trusses more than a week, and allowing no more than 3 inches of deflection in every 10 feet of truss span. The WTCA and TPI cite poor handling as a major contributor to accidents and injuries that occur during truss installation.

After ensuring that the proper safety measures are followed, and the walls are plumb and square, you're ready for the pre-fabricated trusses.

"When you're installing an open-web 2×4 or 2×6 truss, whether it is flat or pitched, there is no special training required as long as you have a basic carpentry background," Potmich says.

The exception is if you are using a proprietary truss product, such as TrusJoist's TJI joists or Microllam LVLs.

"For proprietary trusses, there may be special requirements, but things like that are usually included in shop drawings," Potmich adds.

Manufacturers encourage remodelers to contact them for guidance when needed.

"In the end, our biggest single resource for our clients is the carpenter's pencil with our 800 number on it," says Evans. "We encourage people to call us whenever they get stuck."

Lift on three...

Before raising the trusses, measure and mark on each cap plate where the heel of each truss will land.

Trusses are usually secured 24 inches on center, so start on one end by marking the first truss flush with the outside edge of the cap plate. Mark the subsequent trusses at 24-inch intervals. Then mark the truss positions on the opposing cap plate starting from the same end.

For a roof truss with a gable end, manufacturers often provide end trusses with more vertical members that support the sheathing:

  1. Raise one of these end trusses into position first at one end, either by hand or by hoisting. Once raised, place the end truss flush with the outside edge of the cap plate and then toenail it in place. At this point, you will want to nail a few 2×4 braces from the truss to the ground.
  2. Be sure to add any lateral or vertical bracing required by code in your area to resist high winds. BCSI 1-03 also suggests you always use diagonal bracing to secure the trusses
  3. After securing the end truss, you can raise the other trusses onto the walls.

    On larger projects, contractors often hire a crane to hoist lift the trusses up. On smaller projects, or on a tight lot without room for a crane, you can place them by hand for less expense:

    • Set one end of a truss on one wall plate with the truss upside down.
    • Set the other end on the other plate.
    • Swing the truss into its upright position.
    • Rest it against a secured truss already in place.
  • After putting the first truss into place, the ensuing trusses can be raised with the same method, stacking them against the secured gable truss until they are all on the wall plates.

    Two people can usually handle this routine, but ideally, you would have two laborers on the wall plate and two laborers pushing the trusses from below. BCSI 1-03 recommends using 2×4s by laborers on the ground to help tilt up the trusses. This entire process should take only half a day.

    Buried treasure

    Today's homes have a multitude of mechanicals to consider, including water supply, sewer, electric power, natural gas, communications and security. Often there is little consideration to the management of these services, and the systems are entangled in various wall, floor and roof cavities, leaving a disorganized mess to sort through. Manufactured floor trusses can simplify future remodeling.

    "There are advantages to using open web floor trusses, particularly if we want to run electrical wiring, piping and other mechanicals lines through openings in the floor," Potmich says.

    Organize the utilities within central pathways in the home, such as open web joists underneath the floors. The utilities can then be accessed through removable panels in ceilings and floors. A good design will simplify and speed construction; the utilities will also be more accessible and organized, easing future repairs and upgrades.

    Imagine this: Five years from now, your client hires you to install a zone-controlled heating and cooling system. Normally you'd have to rip through walls to access the ducts. If you've run the utilities carefully and provided easy access, all you need to do is remove a few panels. What could be easier?

    The Partnership for Advancing Technology in Housing (PATH, www.pathnet.org), is administered by the U.S. Department of Housing and Urban Development.

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