Advanced Framing is Pretty Simple
To the untrained eye, this image may look fairly conventional. However, this home, and many others, are the product of the quickly advancing industry of building science. You’re looking at a growing trend called advanced framing, also called (OVE) optimum value engineering, that is responsible for lowering construction cost and improving building performance. Developed in the 1960’s by the Department of Housing and Urban Development, advanced framing is finally starting to become integrated into an overall building performance strategy. Here’s how:
First, conventional framing uses 2×4 studs spaced 12″ or 16″ on center, and rafters typically fall out of alignment with the wall studs and land on a double top plate. You’re house is probably built this way. One advantage is that every framer and contractor out there knows how to do this in their sleep.
Advanced framing swaps the 2×4 for a more robust 2×6 and is spaced at 24″ on center on a single top plate. Rafters now must fall on the 24″ spacing and align with the wall studs. This approach immediately saves on material, however, not everyone out there knows how it works, as there are some critical details that are required in order to make it safe.
A defining characteristic of this technique is at the openings. Windows in conventional framing usually requires a large header held up by jack studs, yet again more material. Advanced framing uses header hangers instead, eliminating the jack studs. With the 2×6 studs, if you use a built-up header, you’re left with at least 2″ to the inside of the gyp. which allows for insulation at the header. Headers and rim joists are typically a weak point for insulation in conventional framing.
Another detail that adds to building performance is how the corners of the building are framed. Most houses have a 3-stud corner with an airspace that is poorly insulated. While this may not be a deal-breaker for energy conservation, when used as a part of a larger strategy, it can significantly reduce energy loads year round. Advanced framing uses a 2-stud corner, and still can use a 3-stud corner, however, the 3rd stud is rotated to allow insulation to flow around and inside. You can still make a 3-stud corner energy efficient by layering in rigid insulation, but this is not always done.
Here’s a look at some pros and cons:
-Lower material costs
-Lower labor costs (however there is a learning curve)
-Fewer trees cut for lumber
-Reduction in thermal bridging due to fewer studs and insulated headers
-Fewer drywall problems like nail pops and cracking (attributed to the use of drywall clips)
-Design / engineering costs are probably higher
-More planning time for more accurate drawings
-Local code official my raise an eyebrow at your details, but a clear explanation and a competent contract will help
-If framers are unfamiliar, there will be a training period
-Single top plate will require longer stock material
-Some siding types require 16″ o.c. and will not work with 24″
-R-value is not a shocking increase.
-Interior gyp. should be 5/8″ rather than 1/2″ due to the longer spans between studs.
Have you used the technique on your jobs or home? How did it work, are you satisfied with the result?