Whole House Design - Get It Right the First Time
For a number of years, the Wood Truss Council has properly championed the potential benefits of designing the entire house in one seamless package (floor panels, wall panels and roof trusses), Whole House Design (WHD). Now that a builder can order an entire home package made offsite, the time has come for all those concerned with quality, cost and speed of construction to take Whole House Design seriously.
The use of prefabricated roof trusses has been a significant improvement in speed and cost on the jobsite, but has not delivered the benefits of Whole House Design, as the trusses sit on stick/site framed walls that may or may not match the WHD.
Now that it is possible to use structural building components for the entire wood frame structure (house, multifamily, office or commercial), WHD comes into its own. The entire home is designed in CAD, from underfloor framing, to floor panels, wall panels and roof trusses. All structural components such as beams, headers, posts and shearwall are specified in detail, down to the nail pattern. All wall heights and roof detail is laid out with grade changes and stem\walls accounted for. This allows a 3-D model of the home to be constructed in the computer.
With WHD, the entire project (from engineer to HVAC contractor) team can review the 3-D model, identifying conflicts, laying out desirable HVAC chases, confirming window sizes and layout, and spotting architectural and engineering conflicts. If a load bearing wall is 6" off the foundation or a beam is hanging in mid-air (actual examples), the builder using WHD can make a decision about which room is larger or smaller, and how to address the problem in a considered manner rather than on the fly. All these improvements, corrections and enhancements can be made before a single piece of lumber is cut!
Each panel and truss has an individual profile page that details framing, structural components and sheathing, with all materials marked, numbered and specified as to dimension and grade. Leading-edge panel firms will generate machine controls (CAM instructions) to build the panels exactly as approved by the builder; less automated firms will at least generate the saw specifications and controls.
Whole House Design delivers homes that are of superior quality, go together faster and are much lower cost.
Superior Quality - Errors are caught before anything is constructed, and on the fly solutions are eliminated. Floor, wall and roof intersections are clear and as desired, with wall heights established and the trusses seating clear in 3-D.
Faster Construction - Panels go together much faster than stick frame, and there is little or no on-site delay due to errors in design, incorrect wall heights or roof specification.
Lower Cost - The significant portion of on-site cost associated with errors and remediation is eliminated and materials are optimized to reduce waste from 18% to less than 3%.
Whole House Design is here and its value is now fast becoming recognized. Builders who don't move to WHD will be at a clear disadvantage.
For more information, visit www.forma-homes.com.
January 2007 Builder Architect Edition Issue