Joists, Rafters, Trimmer and Struts...

Discussion in 'Carpenters' Talk' started by Jimbo, May 14, 2019.

  1. Jimbo

    Jimbo Screwfix Select

    Hello. In the context of roofing, does the term "strut" have a precise definition
     
  2. You would fit a strut onto a purlin to take some of the load.
     
  3. Jimbo

    Jimbo Screwfix Select

    Thank you!

    In my case, BC have asked for "struts" to pass load from a flat roof around a skylight to the joists a foot or so under it to prevent sag (because the rafters are not continuous).

    All is C24 and supported by the same steel both ends.

    It seems to me that it's just vertical bars between the two sections.
     
  4. chippie244

    chippie244 Super Member

    Or a strut as it's sometimes known.
     
    Jimbo likes this.
  5. The rafters would normally be doubled up then trimmed,but if that is what he wants then just comply.
     
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  6. Jimbo

    Jimbo Screwfix Select

    Thanks. I just wondered if strut meant something specific, like perpendicular to the rafter rather than perpendicular to the joists for example.
     
  7. KEVIN NAIRN

    KEVIN NAIRN Member

    Hi Jimbo, a strut is a component or structural member that is in compression (think of a pit prop in a mine) it's being squeezed or squashed. It doesn't matter if it's vertical or at an angle, but at an angle, it's usually called a diagonal brace. A tie is a component in tension (it's being stretched or pulled apart). As Deleted member 11267 says struts are used mostly to stop purlins deflecting in the middle from the weight of the concrete tiles on the roof, for instance, but must be anchored to a ceiling joist over a wall or the ceiling will start to bow. The strut should be as close to 90 degrees from the rafters as possible, as this is structurally stronger to resist the rafters and purlin bending.
     
  8. Jimbo

    Jimbo Screwfix Select

    Thank you Kevin, much appreciated :)
     

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