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Specification is the art of calling out specific product types to meet the project needs.  The designers must pick a product and design the building with it.  With so many engineered wood manufacturers, the designers are often revisiting their efforts once the project is underway.  The most effective specifications can eliminate call backs, extra work, and subsitution questions.  By clearly showing all of the design criteria that was utilized to design the structure on the contract documents, the designer can eliminate a lot of steps.  We call this methodology the "performance spec".
 
Complete load information is required for any supplier of engineered wood products to do their job correctly.  Below is the key information required:
 

Check list for specifying Engineered Wood Products

 

Verify the following information is clearly shown on the contract documents.

  • Loads

 

    1. Show all applicable occupancy (live) loads relevent to project.  Office, Corridor, Storage, etc...(Show loads per ICC in General Structural Notes page)
    2.  
      Show dead load of structure – specific to floor and roof
    3. Snow Drift – Mark as not required, Included in flat roof snow load, or Provide drift diagram.
    4. Other Loads – Axial/Seismic, Parapet brace, Mechanical screen, Towers, Hanging walls, Sprinkler lines greater than 3” shown on plans, details, or in structural notes
    5. Uplift – Note net PSF uplift or an uplift diagram showing the discontinuity.
    6. Mechanical - Coordinate weight & location specifically or Provide a mechanical zone allowance and location (this will provide more flexibility for future mechanical units).
    7. Office Loading – Design for live load of 100 PSF to accommodate future corridors anywhere on the joists (increases cost).
    8. Sprinkler loading – Add 2 PSF to the dead load for an allowance.
    9. Require that all of the loading above is clearly shown on the shop drawing

 

  • Coordination

  1. Show all shafts, Roof access, Openings, in structure. Note on plan “Joist MFR to design support for openings”.

  2. 2 hour walls & shafts – There are 3 accepted solutions:

a.  Frame single wood wall and provide solid blocking which is the full width of the stud then use face mount hangers to support framing off of the blocking.   

b.  Use a double wall. The inner wall is the free-standing rated shaft wall.  The outer wall is a structural wall for the floor and roof structure.

c.  Use a concrete or CMU rated shaft wall and hang floor and roof structure off ledgers 

  • Hardware

  1. Beams – Specify beam hanger or show the load required.

  2. Joists – Note hanger per Manufacture.

  3. Make sure the wood plate on the steel beam is thick enough for hanger nailing.

 

  • Nailing

  1. Nail spacing closer than 3” OC needs to be staggered.

  2. Be sure to specify the correct strap nailing per strap design guide.

  3. If nailing is required closer than 3” OC R-Chord can be used (See SSI Design Manual).

 

  • Specifying Performance Based Design Criteria

  1. FLOORS

Keep span (inches) / Depth (inches) ratio to 12-15.

 

  • Deflection/Perfomance  criteria -

    •  CommercialCommercialResidentialResidential
     Live Load Total Load Live Load Total Load 
    FloorL/600  L/240 L/480L/240 
    RoofL/360  L/240L/360 L/240 
    Optional Limit deflection to 1/2"   Limit deflection to 1/2"

     

    • Detailing

    1. Web Stiffeners - Note on detail that Web Stiffener as required by Manufacture. Show detail where fillers are req’d such as Hold downs, Straps, Outriggers, etc..

    2. Specify axial transfer that is required at bearing.

    3. Show any braces and their attachments/loading.

    4. Uplift bracing to be designed by MFR.

    5. Web Filler for a hold down up to 10,000 lbs (See SSI manual).

    6. Open web truss shear block for lateral tie (See SSW manual).

    7. Open web truss Skew bearing block may be required.

    8. Design hold down clips at bottom bearing I Joists.

    9. Column interference detail when appropriate.

    10. Make note if product is exposed and the owner would like Architectural grade.

     

    A note regarding floor joist spacing.  Ijoist or truss spacing where gypcrete is applied should be kept to a maximum of 19.2" on center;  this is a requirement per the Gypcrete ICC report

     

     

    Download Checklist for structural specification of EWP

     

    Checklist for Structural specification of EWP.doc

     

    Here is a document to assist you in specifying Standard Structures products

     

    how to specify SSI products