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Structural Improvements
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Building an addition to your home or making structural changes like moving walls and raising roofs can be costly due to the labor and material involved. And harvesting and extracting the natural resources used to make construction materials takes its toll on the environment. If you plan ahead, you'll find that many green building practices can save you time and money and can conserve wood and other resources.

This article focuses on some common design and construction practices used when framing a new addition or undertaking a major remodeling project. Most of these recommendations represent improvements to, not drastic departures from, standard construction practices. For example, engineered lumber can replace many types of solid-sawn lumber; it is sometimes slightly more expensive, but is typically more dimensionally stable, straighter, lighter and stronger.

Other recommendations describe practices that may be new to you or your building professional but offer considerable benefits. Using structural insulated panels instead of conventional wood-frame construction, for example, offers enhanced structural performance, reduces air infiltration and speeds up construction time.

Advanced framing techniques

A lot of material and money can be saved by designing wood-framed homes or additions with advanced framing techniques (also known in the building industry as optimal value engineering or OVE). These techniques reduce the amount of lumber typically wasted when constructing a building, while maintaining structural integrity and meeting the building code. Advanced framing techniques also allow for more insulation in the walls, which improves energy efficiency and comfort.

Many advanced framing techniques are suitable for residential remodeling projects. These include placing rafters and studs at 24-inch on center framing instead of 16-inch on center, using the right-sized headers for the structural load, using only jack and cripple studs required for the structural load, using insulated headers on exterior walls, and building two-stud corners with drywall clips.

For more information about Advanced Framing, see the Natural Resources Defense Council's publication, "Efficient Wood Use in Residential Construction" and the Wood Framing section at www.toolbase.org.

Energy heels on roof trusses

At the intersection of perimeter walls and the roof framing, there is often increased heat loss, because conventional rafters and roof trusses reduce the area available for insulation to less than 6 inches. An energy heel is a framing technique that raises the height of the truss at exterior wall top plates to accommodate the full depth of insulation at the building's perimeter. This can save energy, improve comfort and reduce utility bills.

Include energy heels wherever conventional trusses are used. Note that the increased height may require modifications to exterior soffit and trim details.

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Engineered lumber

Solid-sawn lumber in dimensions of 2×10 inches and greater typically comes from old-growth forests or large diameter trees. For a more environmentally friendly option, use engineered lumber products. Engineered lumber is manufactured from the wood of small-diameter, fast-growing plantation trees. These common building products include glued laminated timber (glulam), laminated veneer lumber (LVL), laminated strand lumber (LSL), parallel strand lumber (PSL), wood I-joists, wood floor trusses, finger-jointed studs and oriented strand board (OSB).

Reducing demand for large dimensional lumber decreases pressure to harvest old-growth or large-diameter trees. Also, engineered lumber uses wood fiber more efficiently than conventional lumber. Most engineered wood products are straighter and stronger than solid-sawn equivalents, eliminating crooked walls and reducing material waste.

Make sure that engineered lumber is called out on your project's structural building plans. Here are some common uses for engineered lumber:

  • Beams and headers. Engineered beams and headers can easily replace any solid-sawn member of similar size or even larger. In addition, large solid-sawn lumber is often used for headers and beams when smaller dimension lumber would suffice.
  • Insulated engineered headers. Engineered headers with preinstalled insulation are lighter than solid wood headers, do not shrink (reducing cracks in drywall), and insulate better than solid wood.
  • Wood I-joists or web trusses for floors. The typical 2×10 and larger solid lumber used for floor joists can be replaced with engineered lumber in most applications. Not only are I-joists and web trusses stronger than solid beams, they are lighter. Some have knock-outs or cavities that allow ducts, pipes and wires to easily pass through them, resulting in quicker installation.
  • Wood I-joists for roof rafters. For roof rafters, use I-joists instead of solid lumber.
  • Engineered or finger-jointed studs for vertical applications. Use engineered or finger-jointed studs wherever conventional studs are typically used. Finger-jointed studs use short pieces of 2×4 or 2×6 wood glued together to form standard stud lengths, while engineered lumber is typically veneers, strands or flakes of wood glued to form studs. These studs are all dimensionally straight and save on labor and material costs associated with culling crooked lumber, and shimming and straightening crooked walls.
  • Oriented strand board for subfloors and wall and roof sheathing. OSB is a type of engineered wood product manufactured from fast-growing farmed trees. OSB comes in sheets and is used as an alternative to plywood for subfloors, wall sheathing and roof sheathing.

FSC-certified wood

Forest Stewardship Council (FSC) certification assures that the forest from which the wood was harvested is managed in an environmentally, economically and socially responsible manner. FSC is the only lumber verification rating that maintains chain-of-custody certification throughout the cutting, milling and final delivery of products, thus ensuring that the end product originated from a certified sustainably managed forest.

Use FSC-certified solid wood framing, engineered lumber, oriented strand board and plywood.

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Structural insulated panels and other solid wall systems

Solid wall systems include structural insulated panels (SIPs), insulated pre-cast concrete, insulated concrete forms (ICFs), autoclaved aerated concrete (AAC), and similar systems that are not constructed of wood studs. These panelized walls replace traditional wood stud construction by including structure, sheathing and insulation in a single durable, energy-efficient system.

Most solid wall systems improve home comfort and save significant amounts of wood. Each of these wall systems involves specialized installation techniques. Consult with a building professional with expertise in these systems, and always follow manufacturer specifications.

For more information about panelized wall systems, see the ToolBase TechSpecs at www.toolbase.org.

Earthquake safety

Many older homes in earthquake-prone areas were not built with sufficient structural support to withstand a major earthquake. In most cases, structural retrofitting work can be done to help reduce the risk of earthquake damage.

Homes that are prepared to withstand an earthquake will be safer for residents. Earthquake retrofits may also protect the home from extensive damage and therefore reduce replacement costs and minimize waste from demolition.

Engage a structural engineer for recommendations on how to retrofit the home. Refer to local building code requirements. For more information about earthquake retrofitting, visit the website of the California Seismic Safety Commission.

Recycled flyash or slag in concrete

Flyash is a byproduct of coal-burning power plants. It is typically landfilled, but can be an inexpensive and quality substitute for a portion of the portland cement in concrete. Slag, a byproduct of the steel industry, may also be used like flyash to replace some of the cement.

Flyash and slag improve the performance of concrete by increasing strength, reducing permeability and reducing corrosion of reinforcing steel. Using flyash or slag also reduces the amount of cement and water needed, thereby decreasing the overall environmental impacts of cement production and water sourcing. Cement production is energy intensive; it accounts for more than 6% of the world's carbon dioxide emissions that contribute to global warming.

Up to 50% of cement can be replaced with flyash or slag in many residential concrete mixes. However, high-volume flyash or slag mixes (35% replacement or more) may require longer cure times and different finishing techniques than standard concrete. Consult a structural engineer or concrete contractor for information.

More structural work tips

  • Save those scraps. During construction, save money and material by storing scrap ends and other small pieces in well-organized piles (builders call these "cut piles"). Reuse the materials instead of throwing them away. Properly cover and store reusable materials so that they are not damaged by the weather. Materials that can be readily reused include wood studs, sheathing, joists, drywall, siding, piping, metal products, roofing and even fiberglass insulation.
  • Deconstruct instead of demolish. Keep usable materials out of the waste stream by deconstructing instead of demolishing portions of the home that will be remodeled. Deconstruction involves manually unbuilding and salvaging building materials, trim and fixtures. Reuse them on your current project or a future remodeling project, or sell or donate them.
  • Learn more. For information about other aspects of a home's structure or building envelope, check out our GreenPointers on Insulation and WeatherizationMoisture and Pest ControlRoofing,Siding and Decking, and Windows.


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