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.

Wood I-Joists Used in Floor & Roof Construction

[Click to enlarge any image]

Article Contents

• WOOD I-JOIST APPLICATIONS for FLOORS & ROOFS
• WOOD I-JOIST FLOOR CONNECTIONS
• WOOD I-JOIST ROOF WALL CONNECTIONS
• WOOD I-JOIST to WOOD GIRDER CONNECTIONS
• WOOD I-JOIST to STEEL GIRDER CONNECTIONS

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 above 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.

Definition of I-Joist

Unlike conventional wood or metal trusses that are made of triangular supports between continuous top and bottom members, a web truss or wooden I-Joist uses a solid center member, usually comprised of oriented strand board (OSB).

You can see the OSB center component and flat 2x4 lumber forming the I-joist top and bottom chords in our photo above.

The top and bottom chords of a wood I-joist may be conventional framing lumber such as a 2x4 or the truss chords may be made of laminated veneer lumber (LVL).

Our second photo (below) 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]

Older I-Joists using Plywood

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.

Wood I-Joist Blocking / Bracing

For roofs or floors constructed using I-joists, to increase the structure's stiffness or rigidity, I-joists blocking is used at the center of the I-joist spans. I-joist blocks are best cut and installed during initial framing of the floor or roof system.

Details of I-joist blocking are at WOOD I-JOIST CROSS BLOCKING / BRACING - separate article

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.

Wood I-Joists Atop or Connected to Steel Beams

Wood and steel roof and floor trusses are discussed separately

at TRUSSES, FLOOR & ROOF and also

at TRUSS UPLIFT, ROOF.

Our wood I-joist photo (Minnesota, 2007) 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.

I-Joist to Steel Beam Connectors

Steel joist hangers to connect a wood I-joist to a steel beam or girder are offered by Cullen, Simpson, TriForce, Ozco and other suppliers listed below.

Installation may be as shown in our photo above, with the hangers supported by and welded or bolted to the steel I-beam, or a wood filler may be installed inside the I-beam, bolted to the I-beam, and to which conventional wood-fastener joist hangers may be attached.

Shown below: Triforce Wood-to-Steel connectors joining open-web wood trusses to a steel beam.

• Gauthier, Manon, SPECIAL CONNECTION CONDITIONS FOR A JOIST GIRDER OR STEEL JOIST: VARIOUS SOLUTIONS [PDF] (2011) Canam Buildings, www.canam-construction.com Canam-Buildings 270, chemin Du Tremblay Boucherville (Québec) J4B 5X9 Canada
  Excerpt: -
  Contents: Special connection conditions for a joist girder or steel joist Connection using a joist girder base on the column Connection using a joist girder base facing the column Transverse plate connection Connection of a beam in a joist girder Connection of a joist girder to a joist (or beam)
• Simpson StrongTie, Tel: (866) 252-8606 Email: CSHelp@strongtie.com Web: https://www.strongtie.com/
  
  Including Simpson's EB- beam & glulam top flange hangers, WP welded purlin hangers, etc. also WBAC - wood backing steel connector, Strong Drive TB wood-to-steel screws, and related products for wood-to-steel connections.
• Steel Joist Institute: SIMPLE CONNECTIONS SIMPLIFIED [PDF] (2018) - this is not a wood-to-steel joist to beam document - Ed. - but is useful for steel joist framing
• Triforce, 545, rang St-Malo Trois-Rivières Québec G8V 0A8 Canada, Tel: 1 800 263-7265 Web: https://www.openjoisttriforce.com/
  
  Triforce FRAMING CONNECTOR GUIDE [PDF] - U.S. version
  
  Triforce FRAMING CONNECTOR GUIDE [PDF] - Canadian version

• TSN STIFF-CLIPI JOIST HANGER [PDF] [shown above], TSN, 2012-A Tw Alexander Dr., Durham NC 27709 USA, Web: https://steelnetwork.com/ Tel: 1-888-474-4876, Email: support@steelnetwork.com
  Excerpts:
  The StiffClip® JH, joist hanger connects floor joists to beams. StiffClip JH resists vertical loads. Design loads consider clip strength only. Size and number of fasteners used is based on fastener manufacturer’s allowable load data.
  
  The unique design of MasterClip allows it to be installed either as a vertical deflection connection or a rigid connection. Attachment to the primary structure may be made with a PAF, screw/bolt anchors, or weld and is dependent upon the base material (steel or concrete) and the design configuration.
• NHBC, NHBC Standard 6.4.12 JOISTS CONNECTED to STEEL [PDF] (2022) NHBC, NHBC House, Davy Avenue, Knowlhill, Milton Keynes, Bucks MK5 8FP, UK, For technical help and advice, Call: 0344 633 1000 and ask for ‘Technical’, or Email: technicalsupport@nhbc.co.uk - for fdraming timber & concrete upper floors,
  Additional offices in Edinburgh & Belfast.

Cutting Holes in Joists, Rafters, Studs, or the Web of Wood I-Joists

This discussion has moved

to CUTTING HOLES in WOOD I-JOIST WEBS, JOISTS, RAFTERS, STUDS

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Continue reading at WOOD I-JOIST CROSS BLOCKING / BRACING, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CUTTING HOLES in WOOD I-JOIST WEBS, JOISTS, RAFTERS, STUDS
• DEFINITIONS of ENGINEERED WOOD OSB LVL etc
• FRAMING CONNECTORS & JOIST HANGERS
• FRAMING BLOCKING & BRACING
• FRAMING DAMAGE, INSPECTION, REPAIR
• ROOF STRUCTURE DEFECTS LIST
• TRUSSES, FLOOR & ROOF
• LVL LAMINATED VENEER LUMBER BEAMS
• WOOD I-JOIST CROSS BLOCKING / BRACING

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