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General: Wall plate... If this is the wall plate, it's not all on the wall! Problems?

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    Hi again

    Apologies for another question so soon... Having removed the concrete render from the back of our house, I've also removed the soffits which I'll replace after repointing. I don't know much about building, but I presume the wood on top of the wall is the wall plate? On the right hand side, this seems to be as I would expect - firmly on top of the wall, leaving space in front for ventilation, with small pieces of wood to attach the soffits to. But as it goes along the wall, the wall plate gets further and further away. By the time it reaches the left hand side, it is no longer on the wall at all!

    Aside from potentially being wrong, the other problem is that I plan to install ventilated soffits. In that area they won't be very effective because the timber pretty much spans the gap the soffit will span, so not much air would get passed.

    Bit stuck as to whether I am over worrying, it is totally wrong and needs remedial action, or something in between. Any help would be fantastic.

    The first photo shows the full length.
    The second shows only half the length, looking in the opposite direction, and starting from where the wall plate/timber starts to move away from the wall top. I've put a green line on to help show the timber edge.
    The third is a closer look at the timber off the wall.
    And the fourth is the same, but looking from behind).

    Please ignore all the plastic bags etc which have just been put in to prevent unwanted visitors.

    Many thanks
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    Photo 1
      IMG_20220830_155714259 Smaller.jpg
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    Photo 2
      IMG_20220830_155900964 Amended Smaller.jpg
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    Photo 3
      IMG_20220830_160339240 Smaller.jpg
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    Photo 4
      IMG_20220830_160354021 Smaller.jpg
    • CommentAuthorowlman
    • CommentTimeAug 31st 2022 edited
     
    The inward movement of the wall looks as if it's been going on for a while going by the progressive staining on the timber. If it were mine, I'd be looking at re-instating/ plumbing up, that left hand end. What is that left end, is it a corner? If so what's on the inside?

    P.S. If that left end/corner? is plumb then you may need to inspect the roof on this side. Are the rafters on a purlin? Is that internal roof structure sound or is something causing it to slip? Check the ridge line.
    • CommentAuthortony
    • CommentTimeAug 31st 2022
     
    Looks like the roof is spreading to me, is there another wall plate further inside, or that the only one
    • CommentAuthorCliff Pope
    • CommentTimeAug 31st 2022
     
    How thick is the wall? What is the design of the roof? Are there tie-beams? What holds the ends of each rafter to its pair on the other side?

    I'm only familiar with roofs that have 2 or 3 principal rafters linked by tie-beams, supporting purlins which carry all the common rafters - the ones you see on the outside under the eaves. Only the principal rafters sit on wall plates - or rather on short chunky logs buried lower down inside the wall flush with the inner face.
    The common rafters just sit on boards which project outside creating the eaves. Only the principal rafters with their tie-beams resist the roof spreading - the rest is just a lattice framework sitting on them. The projecting ends of the common rafters don't really do much apart of course from forming the structure carrying the slates.

    But there are other designs of course, which is why I asked about yours.
  9.  
    Posted By: greenfingerpologies for another question so soon... Having removed the concrete render from the back of our house, I've also removed the soffits which I'll replace after repointing. I don't know much about building, but I presume the wood on top of the wall is the wall plate? On the right hand side, this seems to be as I would expect - firmly on top of the wall, leaving space in front for ventilation, with small pieces of wood to attach the soffits to. But as it goes along the wall, the wall plate gets further and further away. By the time it reaches the left hand side, it is no longer on the wall at all!

    The way a roof is built is that the roof timbers - rafters - sit on the wall plate and the wall plate sits on the wall and the wall transfers the weight of the roof to the ground. So if the wall plate is not sitting on the wall - what is supporting the roof?

    Posted By: greenfingerBit stuck as to whether I am over worrying, it is totally wrong and needs remedial action, or something in between.

    You are not over worrying - it is totally wrong and needs remedial action.

    Owlman suggested the wall may have moved inwards, Tony suggested that the roof may be spreading. Either are possible but from my armchair I would favour the spreading of the roof.

    When checking to see if the wall has moved inwards don't forget that stone / rubble walls (that is what it looks like from the photo) are often thicker at the bottom than the top, they are just built like that, so dropping a plumb line down may not give a correct answer, you need to plumb both sides but even then I have seen tapering walls where all of the taper was done on one side only. Plumb this wall and check the results with the other walls for comparison.

    Roofs spread because the weight of the roof causes the rafters to spread outwards if there is nothing or insufficient tying between one side and the other. Usually the ceiling joists tie the rafters together, otherwise tie beams connect the opposing rafters together but these have to be at least 1/3 down from the top of the roof to be effective. Purlins (these are beams end to end in a roof usually about half way down the rafters) can help stop spreading but their function is to help support the rafters and prevent sagging as their main purpose but they are not so good at stopping spreading a tie beams or ceiling joists.

    If the roof is spreading I have fixed such a problem by jacking up the wall plate a bit (to take the load off the wall and then fixing a threaded tie bars between opposing rafters and carefully winding in the rafters to restore the roof positioning. I've done this once and it worked once. The tie bars stayed in place after the job.

    You need to find out why the wall plate is off the wall. careful inspection of the roof timbers to check for out of place joints, missing joists /tie beams may give a clue as to the cause of the problem.
  10.  
    Greenfinger - a photo of the inside showing the roof timbers to see the construction method would be useful
  11.  
    Thank you all so much for all the replies.  Very helpful and very kind.  It may be a day or two before I can get answers and additional photos together, but as soon as I have I'll be back.  

    Thanks again in the meantime
    • CommentAuthorphiledge
    • CommentTimeSep 1st 2022
     
    Id get a roofer/joiner to have a look at that ASAP. If its spread that far theres a fair chance theres something seriously wrong with the roof and you could be heading for further spread/collapse. Someone experienced in roof build will likely be able to tell you straightaway whats wrong. Until you know whats wrong Id not be venturing inside the roof!!
  13.  
    Greenfinger - do you know how long the wall plate has been in this position / condition ?
  14.  
    Sometimes wall plates can warp/twist quite noticeably along the length. I have seen some right wonky ones. that could be contributing to allowing it to spread, especially if it isn't strapped down at regular intervals or bolted to the top of the wall (like wot mine is, long threaded studs drilled into and set into the top of the wall)
    •  
      CommentAuthorfostertom
    • CommentTimeSep 2nd 2022
     
    Posted By: Dominic Cooneystrapped down at regular intervals or bolted to the top of the wall
    Never seen that done on an old (what - pre WW1?) house
  16.  
    Posted By: fostertomNever seen that done on an old (what - pre WW1?) house
    Especially on a stone / rubble wall
    • CommentAuthorMike1
    • CommentTimeSep 3rd 2022 edited
     
    Posted By: Dominic Cooneystrapped down at regular intervals or bolted to the top of the wall
    I'd guess that wasn't common until the popularisation of prefabricated truss rafters (in the 1960s) - probably after someone noticed that they seemed to blew away from time time-to-time due to their light weight. So maybe in the 1970s? At least I don't recall seeing them in buildings earlier than the 70s/80s.
  18.  
    Sorry for the confusion, I wasn't suggesting old buildings would be found in this state, more how it should be done.
    I have long threaded studs drilled into and set into the top of the wall in some places and strapped down in others, (and it's a cut roof with purlins, not prefab trusses).
    The wall plate that the previous owner had fitted to the single-storey part of our barn was very twisted and not strapped down at all, along with grossly undersized purlins meaning that the roof was also spreading as they bent.

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