Double Wall House Framing Details: wall placement vs. floor joist ends
Double wall framing detail for super insulated buildings
Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.
This article discusses the question of exactly where to locate the outer edge of a wood-framed double wall for super-insulated building construction. Added details discuss structural load capability of an offset wood framed wall, and insulation and vapor barrier placement on a wood framed wall. Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Readers interested in building framing for optimum insulation and energy efficiency should also see FRAMING DETAILS for BETTER INSULATION. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
The text below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Four Detailed Questions & Answers About Double Wall Framing
What is the exact placement of the double wood framed exterior wall with respect to the ends of the floor joists?
How does the offset in a double-wall framed exterior wall affect the load bearing capabilities of the joists?
What thickness foundation wall is used for double-wall wood framed buildings?
What changes are needed to double-wall framed houses when a brick exterior veneer wall is used?
The questions above referred to "Double-Wall Houses," in Solar Age Magazine, December 1982 and were answered the next April. The questions and the detailed answers by Steven Bliss remain current today. Readers should also refer to the wood framed double wall details in the sketch below.
1. In the Hughes double-wall wood frame structure design, the double wall overhangs the floor platform, bringing the outside surface of the exterior wall sheathing in line with the outside of the building's foundation wall below. (See sketch at left.)
The floor framing is set back from the outer edge of the foundation wall by 3 1/2 to 4 inches. The overhanging section of the double wall is supported by short 2x4's (red in the sketch) toenailed between the top of the foundation sill plate and the bottom of the plywood plate (green in the sketch).
Setting the load-bearing (inner wall) back from the band joist (rim joist) a few inches will, in most cases, not affect the sizing (nor load bearing ability) of the joists (and structure).
Hughes uses a treated-wood foundation system, ordinarily framing with 2x6 lumber for one story and 2x8 lumber for two-story construction.
A brick veneer would need to be supported by an additional thickness of foundation, whether the wall itself is wood or masonry. This section of the building foundation is often offset so that the brick wythe veneer can be carried down to or below grade. (Don't forget termite shields where appropriate and don't forget to provide weep openings in the veneer wall).
This double wall framing system allows the air/vapor barrier to run continuously between floors - around band joists and sill plates, reducing building air leakage and simplifying building sealing. The spaces outside the band joists are filled with insulation, keeping the vapor barrier towards the warm side of the insulation.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in buildings, and other topics.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Mobile View
