Apr

23

Exposed truss confusion

By izak

When the ceiling is installed below the trusses, the trusses are not visible (or exposed).  When the ceiling is installed on top of the trusses, the trusses are visible (or exposed).  That’s it – that’s the meaning of ‘exposed’!

Say you fax your house plan to a truss plant with the area indicated where the ‘exposed’ trusses must be.  The roof designer phones you and asks what type of ceiling you want on top of your trusses – will it be tongue and groove boards, rhino boards, or isoboard, etc.  You think:  “Wow, this guy knows what type of trusses I want in the lounge!”  NOOO, not true.  He does not yet know!

What the roof designer sees as exposed trusses is that the ceiling is on top – that’s it.  What the architect sees as exposed trusses is:  “Raised tie truss with the tie beam half way up, 50mm SAP PAR, double tie beam, single rafter with tie beams bolted to rafters (using dome nuts!), and cover plates at the connection of the kingpost to the rafters.  Trusses painted Marula Cream and cover plates painted Kiwi black.”

…and you thought the truss designer knew what type of exposed trusses you wanted!

You see, it is the architect’s articles that gets printed in the magazines – and the pictures of the ‘exposed trusses’ are the ones as seen by the architect above.

It is still your responsibility to inform the roof designer about your type of exposed truss, so let me try and give you a few examples:

  1. Normal, standard, gang nail plated truss with ceiling on top
  2. Normal, 38mm SAP gang nail plated raised tie truss with tie 1/4 from bottom
  3. 50mm SAP PAR, gang nail plated with additional tie beams bolted on, tie beams 1/3 up.
  4. 50mm SAP PAR, double tie single rafter, bolted only, raised tie truss, tie 1/3 up.
  5. 70mm CAPE LAM, double rafter single tie, gang nailed king post, bolted, raised tie truss with tie halfway up.
  6. 76mm SAP PAR, double rafter single tie, bolted, raised tie truss with tie beam 2/3 up, truss pinned to concrete ring beam.
  7. Purpose made 100 x 300mm Yellow wood trusses, with webs, bolts and steel plates as per architect’s details.

The list is never-ending, so as you can see when it comes to exposed trusses you need to know exactly what you want and you need to be very specific.

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