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Birdmouth on truss?

Discussion in 'Floors, Stairs and Lofts' started by matlob, 20 Sep 2020.

  1. matlob

    matlob

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    Hi

    I have a trussed roof and am going to 'beef' up the rafters in order to eventually remove the truss frame.

    Do I cut a birdsmouth to push into the external wall or just let it sit on top of the wallplate?

    Top image is how it is now

    Bottom is with birds mouth and to the right is just a straight cut.

    Thanks

    https://ibb.co/t2jfk8Z
     
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  3. KenGMac

    KenGMac

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    Have you considered the possibility of roof spread sometime in the future?

    Roughly what dimensions is your roof?

    Ken.
     
  4. JobAndKnock

    JobAndKnock

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    AFAIK birdsmouths always sit onto the wall plate (never the masonry) and are either nailed to it or on larger/heavier roofs are held in place using a pair of truss clips. Wall plates in turn are normally fixed down onto the wall by what we call bat straps (because the wall plate ties we use are made by a company called BAT, I suppose)
     
  5. KenGMac

    KenGMac

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  6. JobAndKnock

    JobAndKnock

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    That's the sort of stuff, yes. It still doesn't get away from the need to tie the walls together (which is what the bottom chord does)
     
  7. matlob

    matlob

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    Thanks all for the replies. Only just seen them

    The roof already in place with straps etc. I am sistering 175mm deep rafters to sit alongside the 100mm ones that are there now.

    I will sit them on top of the wall plate and use the truss clips as shown by Ken.

    I'm not removing the ones that are there now but they sit at 600 centres and SE has said the new ones need to be at 400 so there will be extras going in. Some will be screwed to the originals and some sitting on their own. Can I just use the clips for the ones that aren't being sistered and screw the sistered ones to existing rafters?

    Thanks again
     
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