Interior Walls and Floor Framing

Interior Walls and Floor Framing Affect a Home's Livability

Bird's-Eye View
Key Materials
Design Notes
Builder Tips
The Code

Bird's-Eye View

I-JOISTS MAKE AN ADAPTABLE FLOOR SYSTEM. If a house is framed without load-bearing interior walls, it will be easier to move partitions to meet future needs.

Energy savings and comfort come with smart design

Partition walls affect how much light reaches the interior of a house, and this has a direct bearing on electrical consumption. Because interior walls intersect with outside walls, how the attach is important.

Floor design can make duct runs more efficient and easier to install.

See below for:
OPEN BUILDING IS A FLEXIBLE SYSTEM

Key Materials

Steel studs are lighter than wood, and no drilling is required

Among material choices, light-gauge steel framing is worth considering as a substitute for 2x dimensional lumber in non-load-bearing partition walls. Steel is lighter than wood, comes with prepunched holes for plumbing and wiring, and is consistently straight. Steel studs contain recycled content, and they can be recycled or reused. As long as they are not used on exterior walls, steel studs have some real advantages.

Design Notes

FACTORY-BUILT FLOORS can combine resource efficiency with efficient layout of living spaces and mechanical systems. They were initially only offered by iLevel. With the material, time, and labor savings inherent in this process, look for more lumber manufacturers to offer services such as this.

Place morning rooms on the east side, utility rooms on the north

Floor plans that make the most of natural light (a strategy called “daylighting”) reduce reliance on electricity and thus reduce household operating costs. Thoughtful floor plans also can shorten duct and plumbing runs, lowering construction and operating costs. An interior that has a lot of natural light makes for a pleasant and healthy environment.

Plan room locations around the site’s sun exposure, and frame accordingly. For example, rooms frequently used during morning hours, such as the kitchen or a breakfast nook, should face east or southeast. Major living areas that face south can take advantage of the sun's heat output in winter to reduce lighting and heating bills.

Align skylights over stairwells to introduce natural light deep into the house.

Minimize the length of duct and plumbing runs to lower construction and operating costs. When bathrooms are stacked over one another, for instance, instead of being located at opposite ends of the house, hot water doesn’t have to travel as far. Shorter duct runs offer the same advantage.

Builder Tips

How floors are framed has a significant affect on HVAC systems and comfort

Interior framing should not compromise the integrity of either the thermal barrier or the air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both..

Use drywall clipsMetal or plastic stops that are attached to framing at inside corners. The clips replace framing, thus leaving more room for insulation. Because such a corner floats (acting as a stop, the clip allows the first sheet of drywall to be trapped by the second, perpendicularly installed sheet), cracking of the drywall joint is less common. instead of solid 2x corners to allow more insulation in exterior walls and to avoid popped screws and cracks in the finished walls.

Sloppy or incomplete work at the framing stage can degrade air and thermal barriers, making a house less comfortable and harder to heat and cool. Unless thermal and air barriers are continuous and aligned (in immediate contact with each other), unintentional air currents make thermal insulation much less effective. Typical trouble spots include rim joists, duct and pipe chases, attic kneewalls, soffits, and walls behind tubs and stairs. Once interior finishes go up, it’s too late. Solutions to some of these problems are outlined in the "Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. Thermal Bypass Inspection Checklist Guide."

Air barriers and vapor barriers applied to the ceiling before interior partitions are tipped into place are more effective than those placed after the fact.

How floors are framed can have a significant impact on the overall efficiency of HVAC equipment and, thus, the cost of keeping a house comfortable. Installation costs also are affected.

Floor system framing materials — 2x dimensional lumber versus open-web floor trusses, for instance— affect how easily the mechanical contractor can run air ducts. Ducts can be run between the webs of a floor truss, but they can’t be punched through a solid joist without compromising strength. I-joists have a more forgiving, but not unlimited, capacity for holes. Web designs in floor trusses vary; choose a web that can accommodate the maximum duct size required.

Framing can be adjusted to accommodate ducts. The orientation of major bearing beams, along with the depth and type of floor joists, should be set in conjunction with HVAC plans. Changing floor framing may add cost, but a configuration that doesn't work for the HVAC contractor may, in the end, cost even more.

Ducts that must be routed into complex bends to get under bearing beams will be less efficient than straight runs and may make it impossible to turn a basement into a finished space later.

Framing questions should be addressed early in the design process through a direct exchange of ideas between the architect and the HVAC contractor. By the time the HVAC contractor arrives at the job site, it’s too late to make major framing changes.

The Code

Lumber grades, loads, joist spans, cantilevers, and fire blocking

The 2006 IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code. includes provisions for wood floor framing in Section 502. Like other sections dedicated to framing, the floor framing section starts with the most general requirements like lumber grading and appropriate design loads. Maximum floor-joist spans (Table 502.3), girder and header spans (Table 502.5), maximum cantilevers (Table 502.3), and drilling and notching rules (Figure 502.8) can be found later in the section. Steel floor framing rules can be found in Section 505.

Wood wall framing is covered in Sections 601 and 602. Figures 602.3(1) and 602.3(2) are helpful for determining where to look for specific rules regarding headers, drilling and notching, and fire blocking. Rules for steel wall framing are found in section 603, which includes material specifications, fastening schedules, and connection details.

OTHER CONSIDERATIONS

Houses on slab foundations often locate ductwork in an unconditioned attic. In a green home, however, all ductwork must be located inside the home's thermal envelope. If ducts will run in interior soffits, ceiling heights must be generous and beams must be located with care.

Look for drywall with recycled content.
An alternative to standard drywall are panels made with recycled content, including by-products derived from stack scrubbers at coal-burning power plants. As is the case when ordering concrete in which fly ashFine particulates consisting primarily of silica, alumina, and iron that are collected from flue gases during coal combustion. Flyash is employed as a substitute for some of the portland cement used in the making of concrete, producing a denser, stronger, and slower-setting material while eliminating a portion of the energy-intensive cement required. More info replaces some of the cement, specifying these products helps recycle industrial waste.

DRAWING LIBRARY CONSTRUCTION DETAILS

Wall-Section Details
Remodeling Details
Mechanical-Systems Details
Advanced-Framing Details

GREEN POINTS

LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -H Up to 4 points available under MR1 (Materials & Resources) for material-efficient framing.

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. Under Chapter 6, "Resource Efficiency": up to 9 points for advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope. (601.2); up to 13 points for modular building dimensions (601.3); up to 14 points for detailed framing plan (601.4); up to 13 points for precut or preassembled framing components (601.5); up to 8 points for stacking floor areas (601.6).

ABOUT PARTITIONS AND FLOOR FRAMING

Think about natural light

Walls on the inside of the house can be either load-bearing parts of the structure or partitions that simply divide the house into rooms. Where interior walls are located, and not just how they are built, has important implications for the amount of natural light that reaches into the house interior. That, in turn, affects lighting needs, solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss., and all-around livability.

Like wall framing, floor framing has an obvious structural purpose, but layout and design can also affect plumbing and duct runs in ways that aren’t immediately obvious. Careful planning can reduce waste and boost efficiency.

MORE ABOUT PARTITIONS AND FLOOR FRAMING

Open building is a flexible system

One of the problems with conventional interior framing is that spaces inside the house are fixed, essentially forever. Moving walls as the needs of occupants change is prohibitively difficult and expensive, in large part because walls are full of pipes and wires. Tedd Benson, who heads a design/build company in New Hampshire called Bensonwood, is an advocate of a design approach that seeks to disentangle the various layers of a house so that future changes, upgrades, and repairs will be easier. This design methodology, called “open building”, would substantially change the way interior framing is undertaken and make houses much more flexible and useful. It has been slow to catch on in the U.S. residential market.

CONSIDER INTERIOR NOISE LEVELS

Some rooms may need extra attention

High noise levels inside the house can make everyone's life miserable. If some rooms will house noisy activities--a room where a band practices, for example, or where a powerful music system will be installed--steps can be taken to limit the sound that spills into the rest of the house. Noise travels by conductionMovement of heat through a material as kinetic energy is transferred from molecule to molecule; the handle of an iron skillet on the stove gets hot due to heat conduction. R-value is a measure of resistance to conductive heat flow. through solid materials or through the air, and there are a variety of steps that can help control it. Using resilient channel on walls and ceilings to isolate drywall from framing is one fairly simple step that will help. Careful air sealing is another. It might make sense to consult an architect or other specialist in situations where activities are going to be especially noisy.

FURTHER RESOURCES

EPA Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners.:
Thermal Bypass Checklist

Green Basics Index

Image Credits:

Justin Fink/Fine Homebuilding #197
Rob Yagid/Fine Homebuilding #189

Interior Walls and Floor Framing