I-JOISTS, WOOD ROOF, FLOOR - CONTENTS:
Definitions & photos of wood I-Joists used in roof and floor framing. Examples of I-Joist framing mistakes and defects. Wood I-joist framing connectors & nailing details to connect I-Joists to walls, beams, rim joists, girders. Examples of avoiding cutting the I-joist center web to pass plumbing or HVAC . Components, Photos of I-Joist hangers
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Wood I Joist Installation & Inspection Guide:
This article defines "wood I-Joists" and illustrates the uses and installation of wood I-Joists used in residential building floor and roof construction. We illustrate the use of wood I-joists with a plywood or OSB center used in floor and roof structures and we include illustrated details of the use of framing connectors to tie I-Joists to rim joists, beams, girders, steel girders, and also I-joist roofs to a wood-framed wall.
This article series describes wood products used in construction including engineered lumber, OSB, and Plywood products.
Above: wooden I-joists set atopo a built-up laminate wood beam supporting a roof.The 2x4 blocking along the beam sides was added to permit covering this beam with drywall. We later removed the blocking and left the beam exposed as an architectural feature in this home addition. Below you can see the finished laminate girder as it was left exposed in the finished space. The building inspector thought we were nuts but I like it and so do the building occupants.
Wood I-Joist Applications: Floors & Roofs
Our photo (below left) illustrates wood I-joists used in construction of building floors and roofs. You will observe that the center web of the I-joist is constructed of OSB sheathing material that we illustrated just above. Our second photo (below right) shows common lumber markings found on the solid wood top and bottom chords of wood I-joists. [Click any image to see an enlarged, detailed version]
Engineered wood floor trusses (photos above and below) such as I-Joists originally were constructed using a plywood web beginning in 1977, and modified by by Trus-Joist in 1969 to use laminated veneer lumber (LVL) and OSB-like laminated wood fiber web (shown in photos above left and below in combination with a steel beam).
Above: view of stampings on the chord of wood I-trusses used in both floors and roofs.
Connections of Wood I-Joist Floor Structure to Rim Joist & Corner Connnections
Click to enlarge the image above for a sharper view of the I-joist hanger used to connect the end of the roof or floor I-joist to the rim joist of this building. At the bottom of the photo you'll also see the bolted corner connection specified by both the architect and the local building inspector. Notice that we include solid blocking at the end of the I-joist behind the joist hanger. Where the floor was cantilevered and occasionally for other structural reasons we also added solid wood blocking between I-joists, visible in the top of the photo.
Below you can see the connection of I-joists at a supporting floor girder over a garage.
Connections of Wood I-Joist Roof Structure to Wood-Framed Stud Walls
Above you can see the use of cut I-joists as solid in-fill or blocking between the roof I-joists where they sit atop the wall top plate.
Connection of Roof Wood I-Joists to Supporting Walls
Above you see part of our steel tie-strap nailed to the top of the I-joists that will support the roof. This connecting strap must wrap the top of the I-joist and is also nailed to the side of the I-joist before it is carried down past any blocking for nailing to the structural supporting wall framing as well. Below you can see some of the nails through the framing connector to the side of the I-joist top chord as well as to the solid blocking in-fill at the end of the roof I-joist.
Below we illustrate the completion of connections for the metal strapping tying the wood I-joist roof structure to the wood-framed stud wall of this building. You can see that I nailed the connecting strap to both the double top plate of the supporting stud wall and then down past thte top plate to the stud itself.
These framing connections assure both the connection of the I-Joist to the stud wall and also the connection of the building's stud wall top plate to the vertical studs in the wall body. I can testify it was a hell of a lot of nailing, all by hand. I don't like trying to shoot framing connector nails through a power nailer. The chance of a backfire and a nail in the eye are just too great.
Below Eric Galow is starting to nail down the roof sheathing to our now personally-secured wood I-joists.
Connection of Wood I-Joists to Supporting Beam or Girder
Below you can see more framing connectors used to tie these roof I-joists to a built-up laminate beam that supports a canti-levered portion of the roof structure. We tied all of these framing straps to the back or less-viewed side of the laminate beam to permit the beam to be left exposed in the room below.
Below you can see how this same framing connector runs up and is nailed to the side of the wooden roof I-Joist. Click to enlarge these photos to count the number of nails used.
Below you can see a tip for getting along with the building inspector. Even though it was not required to nail the final tip of the framing connector to this side of the I-Joist, we left it exposed so that the building inspector would have no doubt that we had carried each framing connector strap up over the top of the wooden I-Joist for this roof. We also included photos of the nails into the top of the I-joist to document that important connection that was later hidden by the installation of roof sheathing. I showed those photos earlier on this page.
Our wood I-joist photo above illustrates the use of doubled or paired wood I-joists and special steel connectors (I-Joist hangers) designed to support doubled I-joists where they abut a girder or beam.
Cutting Holes in the Web of Wood I-Joists
Generally it is permitted to cut round holes in the center of the web of a wood I-joist, depending on the specific guidelines of the I-joist manufacturer. You should never cut nor notch the top or bottom chord. The rules for allowable hole size depend on the I-joist dimensions and also on where in the run of the wood I-joist the hole is to be cut. For example, no holes may be permitted near the ends of wood I-joists.
Watch out: common construction defects involving wood I-Joists include improper size or placement of holes cut in the I-joist web to permit installation of wiring, plumbing, or ductwork. Improper location or size of holes, notches, or even removal of the center web can cause substantial weakening of the structure and are violations of both the manufacturer's instructions and building codes.
See STRUCTURE, ROOF DEFECTS LIST for details.
Below our photos of I-joists used to support a building floor illustrate how the builder avoided most cuts in the i-joist webs: flex duct and plumbing were laid out to move between I-joists rather than through them, and where an HVAC duct trunk line had to run at right angles to the I-joists the builder suspended it below the I-joists. This was a much better solution than we found at a different job where the builder removed entire sections of I-joist web to run large rectangular HVAC ducts!
Continue reading at FRAMING CONNECTORS & JOIST HANGERS for a discussion of special fasteners used when framing with wood I-joists,or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
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
APA - The Engineered Wood Association, 7011 So. 19th St., PO Box 11700, Tacoma WA 98411-0700, Tel: 253-565-7265. APA provides an HDO/MDO Plywood Product Guide that offers details about these products., provides an HDO/MDO Plywood Product Guide that offers details about these products. Product support help desk: 253-620-7400. Email the APA at firstname.lastname@example.org. Web search 09/13/2010, original source: http://www.pacificwoodlaminates.com/img/PDFs/PlywoodGuide.pdf
John Rudy, Advantage Home Inspections, Flemington N.J. 08822 home inspector, 908-806- 6364, Home, Radon & Termite Inspections, Central & Parts of North New Jersey, email: email@example.com
Laminated Veneer Lumber, Overview of the Product, Manufacturing, Market, Department of Forest Products Marketing, wood-Based Panels Technology, Finland [PDF] web search 09/14/2010, original source: http://www.hochstrate.de/micha/finnland/reports/replvl.html
Malco® Products siding tools are available from that company, including the SideSwiper II SRT2 discussed at Malco's website. Websearch 09/07/2010 http://malcoproducts.com/product/roofing-siding-gutter/siding-vinyl/siding-tools-vinyl/sideswiper-ii. Malco also produces other vinyl siding repair tools such as aprons, awls, hole punches, saw blades, and tools for for fiber cement products including power-assisted cutters
Design of Wood Structures - ASD, Donald E. Breyer, Kenneth Fridley, Kelly Cobeen, David Pollock, McGraw Hill, 2003, ISBN-10: 0071379320, ISBN-13: 978-0071379328
This book is an update of a long-established text dating from at least 1988 (DJF); Quoting: This book is gives a good grasp of seismic design for wood structures. Many of the examples especially near the end are good practice for the California PE Special Seismic Exam design questions. It gives a good grasp of how seismic forces move through a building and how to calculate those forces at various locations.THE CLASSIC TEXT ON WOOD DESIGN UPDATED TO INCLUDE THE LATEST CODES AND DATA. Reflects the most recent provisions of the 2003 International Building Code and 2001 National Design Specification for Wood Construction. Continuing the sterling standard set by earlier editions, this indispensable reference clearly explains the best wood design techniques for the safe handling of gravity and lateral loads. Carefully revised and updated to include the new 2003 International Building Code, ASCE 7-02 Minimum Design Loads for Buildings and Other Structures, the 2001 National Design Specification for Wood Construction, and the most recent Allowable Stress Design.
Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting: A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
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