Advanced framing takes some planning
Here are some rules:
Frame walls with 2x6s on 24-inch centers rather than 2x4s every 16 inches can save a lot of wood and increase the energy performance of a house because it makes more room for insulation.
Stack the framing
Aligning framing members between floors transfers loads efficiently. This means that you can omit the double top plate in favor of a single one. It also means a better-quality nailing job of the plywood that spans these transitions.
Place doors and windows on the grid
Moving door and window openings so that they line up on the 2-foot grid reduces waste and, again, leaves more room for insulation.
Use less wood in the corners
Exterior corners can do well with fewer studs and more insulation in them. The same goes for where interior partition walls meet exterior walls — less wood, more insulation.
Omit unnecessary headers
Walls that don’t carry roof loads — for example, most gable-end walls — don’t require structural headers over windows or doors.
MORE ABOUT ADVANCED FRAMING
Load paths must line up
The main principle of advanced framing is to eliminate unnecessary lumber. For example, double top plates can be eliminated as long as each joist and rafter is lined up with a stud and partition walls are tied into intersecting walls with steel strapping.
Lining up framing materials in this way may require the designer to draw up a framing plan for each wall and floor.
Use more engineered wood
OSB, finger-jointed studs, laminated veneer lumber, and I-joists are all examples of reliable building products that can replace conventional plywood and large-dimension sawn lumber. Pressure on old-growth forests is reduced, waste is reduced, and better performance often results.
Omit needless wood
Using two studs instead of four in outside corners saves a lot of lumber. Instead of using the same header size over all openings, engineer each header for the load it will actually carry. Headers in non-bearing walls can be eliminated entirely.
Consider insulating sheathing
Building scientists recommend replacing OSB or plywood sheathing with rigid foam insulation. This reduces the transfer of heat and cold through wood framing, a phenomenon known as thermal bridging. Diagonal bracing and shear panels can provide racking strength.
The current industry standard wall – a 2×4 frame at 16-inch centers with double top plates, three studcorners, jack studs, cripples and double headers – is being replaced by a 2×6 frame at 24-inch centers with single top plates, two stud corners, no jack studs, no cripples and single headers (and in many cases no headers at all).
It is cheaper and faster to build and saves energy. What is not to like? It is cheaper because it uses 5 to 10 percent less lumber (board-feet) and it is faster because it uses 30 percent fewer pieces. It saves energy because it provides a 60 percent deeper cavity (which allows 60 percent more cavityinsulation) and because it reduces the framing factor from 25 percent to 15 percent.1
The framing elements are farther apart allowing easier installation of services – everything fits easier making the plumber and tin-basher happier – the electrician drills fewer holes and the insulator insulates faster because there are fewer cavities even though the cavities are wider and deeper. Everything lines up so the load paths are direct leading to fewer but stronger connections and the lines are cleaner so it just looks and feels better.
Some of the advanced frame technology goes back to the very beginnings of framing – “in-line” framing or “stack” framing where everything lines up is not new (Figure 1). But the real innovations came from a magnificent collaboration between The US Department of Housing and Urban Development (HUD) and the National Association of Home Builders Research Foundation (NAHBResearch Foundation) in the 1970’s. HUD actually did research in those days.2 Out of a HUD initiative called “Operation Breakthrough” the NAHB Research Foundation delivered “optimum value engineering framing” or “OVE framing.” Today we call it “advanced framing.” Why the name changed no one knows.
Figure 1: In-line Framing – Image from “The American Cottage Builder,” John Bullock, Stringer and Townsend, New York, NY, 1854. Great, great granddad figured this out way back when.
Figure 2: Advanced Framing – 2×6 frame at 24 inch centers with single top plates, two stud corners, no jack studs, no cripples and single headers in load bearing walls and no headers in non-load bearing walls.
Figure 2 shows the current expression of advanced framing. Everything lines up so that double top plates are not necessary (Photograph 1). No headers in non-load bearing walls. Window openings are clean without jack studs and cripples (Photograph 2). Exterior corners have two studs (Photograph 3). Gypsum board is supported with “drywall clips” (Photograph 4). And all of this is code accepted by the model building codes courtesy of a whole bunch for foresight by HUD and the NAHB in the early 1980’s. Although it’s in the code most code officials are not aware of it and even fewer builders. And engineers? Talk about an information disconnect. The push back from structural engineers centers mainly around the fact that with advanced framing they would be required to do something they hadn’t done since graduation – a calculation. Yup, now they would have to deal with different values not found in tables. They would have to look at a textbook and re-program the computer.
Photograph 1: Stack Framing – Everything lines up so that double top plates are not necessary.
Photograph 2: Window Opening – Non-load bearing wall window openings are clean without jack studs and cripples.
Photograph 3: Corner Framing – My first advanced frame building in 1982 using a two-stud corner.
Photograph 4: Gypsum Board Support – Drywall clips result in floating corners, a good thing, as drywall cracking is reduced.
One of the biggest pushback’s from builders and code officials comes from corner support for gypsum board and trim (Figure 3 and Figure 4). Explaining that “floating corners” reduce drywall cracking and are therefore an improvement takes a little bit of time. Wood always moves because of changing moisture contents. Gypsum board does not want to move – ever. When you attach something that is always moving to something that does not want to move you get a problem. We call that a crack. They key to reducing drywall cracking is to attach it less. We learned this with truss rise in the early 80’s where we developed floating corners and drywall clips. Back then the easiest drywall clip was to cut a piece of corner bead into 2-inch lengths. Presto, a corner bead. The best way to attach the drywall “less” is to not have wood there to attach it to. Technically this is called adding an extra degree of freedom of movement. The rest of us would just call it smart.
Figure 3: Two-Stud Corner – Gypsum board supported by a corner clip yielding a “floating corner” reducing drywall cracks and call backs.
Figure 4: Trim Support – Note that the trim is installed over the wall cladding. Alternatively, a 2×4 can be added to support the wall cladding and trim; see Photograph 8.
Where interior walls intersect exterior walls we have more controversy with today’s advanced framing. I just don’t understand the issues associated with a plate connection and ladder blocking (Figure 5and Figure 6). Actually, I do understand the issues. Anything new tends to be an issue just because it is new. Even if in this case the “new” is actually decades old.
Figure 5: Intersecting Interior Wall – Metal connector plate is used to connect interior wall to exterior wall.
Figure 6: Ladder Blocking – Horizontal blocking used to support gypsum board and tie interior and exterior wall together.
Single top plates seem to be the biggest problem. Not from a structural perspective or from a constructability perspective but from a perception perspective. There are two ways of making a connection: with a metal plate (Figure 7) or with a wood splice (Figure 8). The approach taken is purely one based on preference by the framer. Some framers love the plate others the splice. It is another one of those Mary Ann vs. Ginger things.
Figure 7: Top Plate Connection – Metal plate is used to connect top plates to one another.
Figure 8: Top Plate Splice – Wood blocking is used as a splice to connect top plates together. Note that the “middle” stud is cut shorter to accommodate the wood splice.
One thing I can say for certain – you do not need a double top plate to straighten out the wall. Give me a break. The floor diaphragm and the roof diaphragm do this. Not an additional top plate. Most us (yes, I used to frame when I was young – in ancient times before the flood and wars…) straightened walls during framing by using something called braces.
The real change involving single top plates is that when you are framing an 8-foot wall the studs have to be 1.5 inches longer. Standard “pre-cuts” don’t work. You need 94 inchers not 92.5 inchers. Easy, take 8 footers and cut them. It takes one guy about 30 minutes with a chop saw to do all of the studs in the typical house. In fact lots of framers do this anyway, because “pre-cuts” cost more to buy than 8 footers. How weird is that.
Load bearing walls need headers and advanced framing typically involves using single headers with the header pushed to the exterior of the wall (Figure 9). This keeps the header away from the gypsum board so that boarders can’t attach to it so that shrinkage in the header does not result in a crack in the drywall.
Figure 9: Single Header – Header pushed to the exterior of the wall. This keeps the header away from the gypsum board so that boarders can’t attach to it so that shrinkage in the header does not result in a crack in the drywall.
The most significant change is the fact that the walls are thicker and we have to figure out what to do with 4 inches? Do we make the foundation wider? Do we loose 4 inches to the interior? Do we keep the foundation the same, but cantilever the walls? Decisions. Decisions. These are not trivial. In production housing interior dimensions are a big deal and can mess up kitchen layouts, hallways and stairs. Site set backs as well – no kidding. It typically means that the drawings have to be redone. And that folks is the biggest knock against advanced framing. Taking existing floor plans and redrawing them is a $1,000 to $1,500 hit per plan for a production builder. Of course, this is not a problem if the plans are drawn up from scratch to be “advanced frame.”
What about floors? What about them? The floor framing is now on 24-inch centers and that means the floor sheathing has to be thicker. The savings in the floor framing covers the cost of the thicker floor sheathing. Next.
Folks, the interior walls are also framed on 24-inch centers. But these ones are 2×4’s. And almost all of them are not load bearing so the connections are pretty much non-structural (Photograph 5).
Photograph 5: Interior Wall Framing – Also framed on 24-inch centers. But these ones are 2×4’s. And almost all of them are not load bearing so the connections are pretty much non-structural.
Things get interesting when we add insulating sheathing. Now insulating sheathing is not part of advanced framing. It is just that most folks that use advanced framing today also use insulating sheathing (Photograph 6). With insulating sheathing the water control layer is the exterior face of the insulating sheathing taped. Insulating sheathing provides no “racking resistance” or “shear” properties. For that we need OSB or plywood “braced wall panels” (a.k.a. “shear panels”) – and most builders build them into corners (Photograph 7). This leads to interesting corner construction (Photograph 8). The combination of advanced framing and insulating sheathing leads to deep window openings (Photograph 9). Window returns are typically gypsum board with wood trim only at the bottom.
Photograph 6: Insulating Sheathing – With insulating sheathing the water control layer is the exterior face of the insulating sheathing taped.
Photograph 7: OSB Braced Wall Panels – Insulating sheathing provides no “racking resistance” or “shear” properties. For that we need OSB or plywood braced wall panels – and most builders build them into corners.
Photograph 8: Corner Framing With OSB and Insulating Sheathing – Note that the foam sheathing is reduced over the OSB shear panel so that the thickness of both sheathing layers line up with the thickness of the sheathing in the field of the wall. Also, note the spacer strip between the cladding and the exterior face of the insulating sheathing to provide back ventilation and drainage of the cladding layer and trim.
Photograph 9: Deep Window Openings – The combination of advanced framing and insulating sheathing leads to deep window openings. Window returns are typically gypsum board with wood trim only at the bottom.
So how come we don’t see lots of advanced framing? Mostly institutional inertia. Even change that saves money, saves energy, saves resources and reduces callbacks is slow to be adopted because change in general is hard. In the 1970’s there was not enough reason to change standard framing. I think we will see a different outcome this time around.
Common Advanced Framing Details
Common Advanced Framing Details
Optimum-value engineering (OVE) framing techniques were developed under a Housing and Urban Development (HUD) initiative in the 1960’s to cut the cost of houses by omitting unnecessary lumber. The approaches did not get widely adopted at the time. However, with the passage of time, many of the original OVE techniques have been incorporated in what we today refer to as “advanced framing. Advanced Framing includes OVE framing techniques such as increasing joist, stud, and rafter spacing to 24 in.; placing doors and windows on stud layout; and using stacked framing for direct load transfer. Application of advanced framing not only saves on lumber and labor costs, but also supports betterinsulation detailing and reduces the occurrence of drywall cracking. This information sheet will explain the essential basis for advanced framing and some of the more common advanced framing details.
Advanced framing, as the name implies, means using the lumber intelligently in wood framing. The foundations of advanced framing are 1. use common material dimensions (24-inch grid) as a basis for design to maximize material use and minimize waste and 2. efficient load transfer to reduce unnecessary framing members from the home. Some of the techniques used include stack framing allowing for the use of single top plates, elimination of wood beams/headers in non-load bearing walls, and two-stud corners. Framing around openings in exterior walls limited to those framing members needed for vertical load transfer (e.g. jack studs) or horizontal load resistance (e.g. king studs where needed around larger openings in larger buildings or high-wind areas).
Stack framing elevation view
Exterior Wall Openings:
Structural headers are reserved for bearing wall conditions – they are not needed in non-bearing walls and non-bearing partitions. Headers should be sized appropriately for the load. When possible a single header should be used, however for lager openings a double header may be required. At exterior walls the header should be pushed to the exterior to allow for insulation to be installed on the interior. A framing member on the flat should be used below the header to allow for attaching of the interior drywall. Openings should be aligned with stud spacing (at least one side, preferably two) where possible. Cripple studs are not needed to support sill studs where windows are “hung.” Cripple studs are included at the wall stud spacing intervals for siding or interior finish attachment.
Exterior Wall Corners:
Advanced framing uses a two-stud corner as depicted on the following page. A two-stud corner provides the number of framing members necessary for structural support for most residential. Structural continuity between the two intersecting walls is provided by nailing the two studs together, a connector plate at the top of the wall, and nailing into the floor sheathing at the bottom of the wall. Where structural wall sheathing is needed for shear resistance, this can further connect the intersecting wall assemblies.
Corner Framing of Exterior Wall
- Thermal bridging by framing is minimized
- Framing cavity space available to insulation is maximized
- Drywall attachment is to one wall only to reduce cracking resulting from differential wood shrinkage. Alternately, use floating corner for the exterior wall.
Single Top Plate:
With stack framing and structural rim board material transferring loads, a double top plate is not needed for load transfer. The framing members must be centered over the studs with a tolerance of no more than 1”.
Top Plate Splice Over Stud
- Top plate joint aligned over stud
- Connector plate provides structural continuity to top plate
Top Plate Splice Between Studs
Partition Wall Connection:
Similar to exterior corners, adding additional stud framing for drywall support where partition walls intersect exterior walls creates unnecessary material use and unnecessary thermal bridges. The diagram to the right shows how dry wall support at this intersection can be provided by drywall clips or a 1×6 (alternately, a strip of plywood could be used) attached to the back of the partition’s terminal stud. These measures allow insulation of full, or nearly full-, cavity depth to continue past the intersection. Structural connection between the partition wall and the exterior wall can be achieved by a connector plate at the top of the wall and nailing into the floor sheathing at the bottom of the wall.
Partition Wall to Exterior Wall Intersection
- Thermal bridging by framing at intersection is avoided.
- Insulation continues behind intersection.
- Drywall attachment is to partition wall only to reduce cracking resulting from differential wood shrinkage. Alternately, use floating corner for one wall.
FootnotesBuilding Science Insights BSI-030: Advanced Framing By Joseph Lstiburek
- The R-value of the advanced frame assembly is 13.9 and the R-value of the standard frame assembly is 7.7 using the ASHRAE Fundamentals simple parallel paths heat flow calculation procedure and fiberglass batts as the cavity insulation. For you architects this is a 75 percent improvement in thermal resistance. For everyone else, this is a big number.
- HUD established an Office of Research and Technology in 1967. George Romney, Mitt’s father, was Secretary of HUD and promoted “Operation Breakthrough” (1969 to 1978). George Romney placed a strong emphasis on building technology. The early assistant secretary’s running the Office of Research and Technology had technical backgrounds, but by the end of Operation Breakthrough economists were appointed to run the show. HUD research has never recovered. Out of Operation Breakthrough came a seminal document authored by the NAHB Research Foundation and published in November, 1977: “Reducing Home Building Costs With OVE Design and Construction.” I got my hands on a copy in 1981 and had built my first “advanced frame” “OVE” house by 1982. I still get goose bumps when I read it today. Wow. Well-done NAHB. It covered everything, modular dimensioning, minimizing surface areas while maximizing floor areas, stack-framing, two-stud corners, single top plates, no headers, or single headers, it had it all.