Element land planning . engineering . architecture . beyond

Wood Butchers Beware

“Wood Butcher” is a colloquial name for Builders in general but more properly Framing Contractors.  Poll Framers on whether it is better to have more wood or less in a home and you will get an almost unanimous “more is better.”  In a home that has been properly designed by a Structural Engineer and coordinated with an Architect/Designer and the Builder, this is not always true.  Harkening back to my college days and quoting a famous Architect – sometimes “less is more.”

Mies van der Rohe aside, there is something to advanced framing techniques that make this subject a portion of the NAHB’s Model Green Home Building Guidelines.  This week, our fifth installment, addresses the techniques, principles and benefits of utilizing certain framing concepts.

In the Guidelines, the team must incorporate a few of the following performance requirements:

• 19.2-inch or 24-inch on-center framing/floor systems
• 19.2-inch or 24-inch on-center framing/bearing walls
• 24-inch on-center framing, roof systems
• 24-inch on-center interior partitions
• Single top plate walls, in exterior and bearing walls
• Single top plate walls, in interior non-loadbearing walls
• Right-sized headers or insulated (box) header (where required)
• Eliminate headers in non-load bearing walls
• Doubling the rim joist in lieu of header
• Ladder blocking at interior-wall-to-exterior-wall intersections
• Two-stud corner framing

Yes, the 19.2-inches – interesting, right?  The 19.2-inch is based on using less wood in a framing wall than the traditional 16-inch on center framing.  19.2-inch spacing is one-fifth of a sheet of plywood.  Works out great from a stud savings, it does make things a little interesting for the framer because there isn’t a .2 mark on most tape measures.

The point of the first four items on the above list is saving in the amount of wood in the “frame” of the home and increased R-Value because less wood, more insulation.  With proper load analysis, the Architect/Designer and an Engineer (independent Structural Engineer or, even better, a Structural Engineer within the Truss Company being used to supply the roof/floor trusses).  Generally, the thought is in typical framing conditions (not hurricane loading or seismic design), our stud walls are over built.  The savings on this can be as much as 30% reduction of framing lumber.  That’s significant.

A single top plate on interior and exterior walls is possible when the spacing of the roof and stud walls have the same spacing.  A top plate transfers the load path from the roof to the walls in a bearing wall situation.  The use of two top plates is when the wall and roof members do not line up – it provides a stiffer path for the load.  It is best to employ this methodology only where all the top plates are single.  There could be confusion otherwise as two different stud lengths would be used.  The savings here is simply in wood and a tiny bit of increased R-value.

The next two ideas involve headers.  Headers are the horizontal members above doors, windows and openings.  Most of the time, for simplicity and accuracy, a Builder uses the same header regardless of interior, exterior, two-foot opening or six-foot opening.  The sizing of these headers or, in some instances, the elimination of these headers can reduce the amount of wood – but more importantly, increase the R-value in an exterior wall.  Here is another example of throwing the Bowtie (Architect/Designer), Blue Jeans (Builder) and, our new friend, Pocket Protector (Engineer) into a room to make sure the plans are clear which opening gets what as a header and to determine whether a header (on interior only) can be eliminated.  It may seem like a lot of upfront work, but this exchange of information insures everyone is on the same page and is a team.

Two-stud corners (also called California corners) are a great way to increase the R-value (insulation) of a home.  Typically, three studs are used for a corner, two for structure and one as a nailer for the drywall.  If one of the studs is laid sideways, a portion of it can be used for a nailer and the remaining cavity can be filled with insulation.  If it is more desirable, drywall clips can be used and you will still have a cavity for insulation.

Whew – this got a bit technical and a bit more involved in the actual construction process than normal.  The idea here is not for you to grab a hammer and your local building supply company’s credit card and start nailing two boards together.  The idea is strictly informative so that you are prepared to discuss these topics from the start – these are crucial concepts when talking to Architects/Designers and Builders.  The benefits are very straight forward:  reduced first cost (up to 5% of framing material cost), improved energy efficiency (up to 5% per year), and less wood consumption and less wood waste.  This is not the end all – taking 5% off the cost of framing or 5% increase efficiency may not seem like a lot – and taken alone – it isn’t.  The idea behind sustainable design and building is optimization of each component and summing them to optimize the entire home.