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Broken roof joist mystery

Discussion in 'Roofing and Guttering' started by NicKarla, 20 Jan 2021.

  1. NicKarla

    NicKarla

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    I have no idea what the thinking was. All the rafters are two pieces for whatever reason. This is the only one that is bent like this.

    The house has sold 3 times over the 20 years including to us. I know the previous owners had an inspection done 4 years ago and nothing was raised.

    While I don’t mind putting things right I don’t want to be the mug who pays to put it right when no one else has felt the need over 20 years and where no apparent problem has presented itself. Sistering all of them sounds good but is it, in reality, an unnecessary expense?
     
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  3. NicKarla

    NicKarla

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    Just wondering, does the fact that it is half a bungalow make a difference? I’m wondering if they did this due to the length of beam/roof etc.
     

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  4. Harry Bloomfield

    Harry Bloomfield

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    As I said above, I'm seeing exactly the same thing too - all of the rest appear to have one of those metal joints in them to extend them. My assumption was it was maybe just normal practice to extend them in that way these days. Then the builder damaged that one and did a (very) botched and poor repair. I'm rather hoping a modern builder might add his comments on the practice of jointing roof timbers in that way.
     
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  5. Harry Bloomfield

    Harry Bloomfield

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    Mmm it does appear to need long timbers, have you any idea of the length?

    I would expect them to have been made on site, were it me designing it and there simply had to be joints - I would have staggered the joints, to avoid a 'running failure' across the roof in a line.
     
  6. NicKarla

    NicKarla

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    That would make sense to stagger. I may be worrying over nothing as nothings moved for 2 decades but I like being cautious to avoid a bigger problem down the line.

    We’re doing a garage conversion so when they’re doing it in a few months I may get them to take a look before I start adding more bodge to another bodge
     
  7. JohnD

    JohnD

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    the design looks to me unsound, though there "should" be no bending force on the timbers.

    Maybe a fat builder swung on it?

    if there is some reason it might happen again, I'd be tempted to run horizontal braces between the timbers at the mid-point, reaching the gable walls.

    Easier and cheaper than sistering them all, and I think a more sound design.
     
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  8. NicKarla

    NicKarla

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    That sound easy and straight forward. They’ve done that on the other end. Is this what you suggest? Also would you do A or B or both?
     

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  9. Harry Bloomfield

    Harry Bloomfield

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    A helps take the compressive force at the joint, B stops the timbers moving sideways, although I would suggest B up near the apex is serving little purpose. I wonder why they have done a partial reinforce at that just that location, rather than reinforcing all of the roof timbers?

    I wonder who if anyone inspected that timber structure and passed it, particularly where it is damaged and displaced? Perhaps it was damaged after inspection?
     
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  11. JohnD

    JohnD

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    no, I would run it along the height of the join, all along the length of the roof, and braced to the gable walls.

    Better positioned than "A" to prevent that break, because it is at the point of weakness.

    "B" would not help prevent another break.
     
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  12. JohnD

    JohnD

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    "A" looks like the kind of thing the carpenters use to stop the trusses falling over while they assemble the roof. The ridge, and battens, do the job after build.
     
  13. Lower

    Lower

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    I'd be inclined to cut the nails where the battens are nailed into the rafter with something like a multi tool to enable you to pull it straight from underneath. You might be lucky and find that not many battens are actually nailed into the wonky rafter. In fact, thinking about it, is it possible that this rafter isn't nailed to the battens and that's why its been able to snap a toothplate and move sideways?

    You should be able to lever the battens off the rafter one by one to create enough of a gap to see if a nail is present and cut it. If the membrane gets damaged in the process it should be possible to repair it as the damage would only be in the areas of the nails.

    Then i'd sister it properly from underneath and use small screwed in L brackets to reattach the battens to the rafter.

    What is there will probably be fine for years, but i wouldn't be able to sleep knowing its how it is.
     
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  14. ^woody^

    ^woody^

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    It looks like the truss was damaged somehow , and as there are no spares in a truss pack, it was installed.

    It's all fixed in place now and can't be moved, and one truss does not matter too much to the roof as a whole. If the whole roof is otherwise braced (diagonal timbers across all trusses) then it will be fine

    You'd need to assess the truss in context of the others around it, is it the ridge/centre that's out of plumb, or the bottom of the rafter that's out of line? And then decide if bracing is required. Some packing timber and a nail plate will sort out the joint if need be.
     
    Last edited: 21 Jan 2021
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  15. NicKarla

    NicKarla

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    I’m guessing the reinforcement is there as that is the corner that gets the wind. It would be a coincidence if it was for any other reason.
     
  16. NicKarla

    NicKarla

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    Looking at it again the beam coming up is perfectly square the the walls. The attached point in the apex is not in line. I hope that makes sense as I can’t get a good enough photo to show it so have done a quick and crude drawing.

    As others have suggested I don’t think it has broken. I think when they were building it someone made a mistake in placement and bent the top bit to fit. A bit shoddy they didn’t reinforce it but it hasn’t moved in 20 years.
     

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  17. datarebal

    datarebal

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    A bit of a sag going on far end the other side of the second velux
     
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