Truss Framing

This topic contains 3 replies, has 3 voices, and was last updated by Jerry Learn JERRY LEARN 1 month, 2 weeks ago.

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  • #23008
    Juan Valdez
    Juan Valdez
    Participant

    I have played around with a plan for house that is 65×32 plus a 10ft porch in the front so really about 65×42 on 9ft pillars. Nothing fancy just a typical ranch style roof and house with a single peak. Is it possible to go the 32ish feet with vaulted ceiling, with the master bedroom being about 20ft. I have looked at the typical truss and I really don’t see anything that would probably work for what I want. I know just about anything can be done. I spend a lot of time over seas and have seen some amazing timber framing. I am also not sure and using SIP I want more of a wood finish in and out. I am guess the SIP isn’t actually the finished product? Thanks for any and all replies not beating me up too bad 🙂

    #23011
    Brice Cochran
    Brice Cochran
    Keymaster

    You can span 32 feet but you will need to bring in an engineer and it may depend on your roof loads where you will be building.  Be ready to include some steel in your connections.  Most people put T&G on top of the timber frame and then add the SIPs on top of it.  That will give you the look you want but still have the insulation the SIP’s provide.

    #24410
    Jerry Learn
    JERRY LEARN
    Participant

    I ruminated for quite a while on how to span 32′ with a truss for a frame I cut and raised for my brother.  Finally the light bulb came on when I attended a Timber Framer’s Guild conference session on historic church truss design.  I figured if they could span 60′ with their designs I could span 32′.

    The key detail is to drop your top chord down off the roof plane so that it can be heavily shouldered into the bottom chord and the kingpost.  Dropping it moves the joint inward at the bottom chord and moves it down on the kingpost.  Then there is timber left on both members beyond the joint’s shoulder to resist the compression that results in the joint.

    I used an 8×12 kingpost and necked it down to 8×8 below the joint with the top chord, then back out to 12″ where the strut meets the kingpost a few inches above the bottom chord.  That gave me a nice 2″ shoulder at the joints in addition to the pegged mortise & tenon.

    I agree that an engineer should be involved in the truss design, and get help if you need it as this is a little advanced beyond beginner level.  You don’t want the roof coming down on your head.

    Hope that helps,

    – jl

    #24411
    Jerry Learn
    JERRY LEARN
    Participant

    One other thing I must emphasize is bulletproof air-sealing of your roof assembly, especially if you are using SIPs on the roof.  Use a fully adhered membrane (but not bituthene) over the T&G or a robust air-sealing membrane that is taped meticulously.

    Air will leak right through the T&G and any pinholes in the SIP joints and rot your roof from the inside out in less than 10 years.  I’ve done the repairs on other’s builds so I know this for a fact.

    I would also definitely vent the roof above the sips and add another layer of sheathing or double strapping so that any moisture-laded air that does get through has a way to escape and not become trapped, leading to the aforementioned rot.

    Best of luck,

    – jl

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