Shared joists and heat coming through shared cavity wall, terrace house

Discussion in 'Builders' Talk' started by BikerChris, Jan 12, 2020.

  1. BikerChris

    BikerChris Active Member

    Hello all,

    I saw someone else mention this here: https://community.screwfix.com/threads/shared-floor-joist-through-party-wall-can-i-cut-them.126537/ only I have a solid floor and this issue at first floor

    I am hammering the forum lately sorry about that lol

    Got a weird one (or may be normal), 1900's terrace with brick cavity wall as party wall. the main house has front to back joists but the rear projection i am sure has left to right and these are one joist being shared across me and neighbours.

    When they are walking around it i can feel it in the floor on our side and i am sure they will feel the same. if we had identical rooms i would not be bothered but my son has the back room while they are using their room as a en suite.i can hear air borne noise but i know that is probably just gaps between shared joists which i know how to fix

    i also borrowed a infrared camera of a mate lately and i can see loads of heat coming from their house and hitting our wall. when i had the floor boards up up stairs i could see and feel wind coming from the cavity.

    i know it is not worth the agg to fix but if i did i wonder if this would be a method

    1. tell them about it and about the heat coming from their house (may be they have hole in their side)
    2. get a party wall thing sorted
    3. take up the flooring on my side along the party wall
    4. take out the brickwork between joists
    5. use a multi tool to cut the joists within the cavity
    6. make good

    i guess a structural engineer would have to be used to check that the new length would be ok for the size of the joists, but i am just wondering really

    pic attached in case this does not make sense, blue circle shows problem area (bottom of image is back of house). red is joist direction

    cheers!

    Chris
     

    Attached Files:

  2. BikerChris

    BikerChris Active Member

    hi all,

    you are normally really gone on here, any thoughts at all much appreciated
     
  3. koolpc

    koolpc Super Member

    Never heard of shared joists
     
  4. BikerChris

    BikerChris Active Member

    me either
     
  5. Thomas Byrne

    Thomas Byrne New Member

    Haven’t got an answer I’m afraid but we have a very similar problem. Live in a terraced house that we’re build around 1880 in pairs. The front of the house had joists running back to front but a back extension built around 1910 has the joists running side to side. The joists run through the party wall and are shared with the neighbour. The room on both sides is about 10 ft wide with side walls supporting the floor. More shockingly the party wall is only one brick wide from the first floor up - not sure what they are doing! If you ever got more advise or a solution I’d be interested to hear! Cheers
     
    BikerChris likes this.
  6. BikerChris

    BikerChris Active Member

    Cheers for commenting, jesus sorry to hear you've only got a single skin between you and neighbour, that must be worse. The bug...problem here is that as terrace houses can be a bit narrow, no one can afford the 4 inch extra wall thickness that's needed to help with sound. Also I think that sometimes terraces were re-subdivided, I've seen some that were 3 unit and converted to 4 by putting up some quick studwork :-/

    About the shared joists though, glad I'm not just imagining things! I know it's been a while but I am intending to speak to the neighbours about it soon, they are very reasonable people and I'm just going to ask if they care about the noise coming from us. Mind you, I think we get more noise from them than the other way round, not their faul though - kid.

    I guess the solution which doesn't exist to my knowledge, is being able to chop the joists in half and then somehow reconnect them with something that provides rigidity but doesn't allow vibration transfer...and I can't imagine that existing! Problem is that if I did what I said, it could pull the walls out sideways. If we're lucky it's only one joist that's shared and the rest of them are done properly...I'll find out soon! Cheers
     

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  7. Jord86

    Jord86 Screwfix Select

    You need to determine that they actually are shared, otherwise you will be wasting lots of time, energy and money into a problem that doesn't exist. More likely they are separate joists but placed side by side and nailed together. Prise off your skirting and see what's on view.
     
    BikerChris likes this.
  8. BikerChris

    BikerChris Active Member

    Completely agree Jord, i really wanted to properly investigate last time boards were up, no skirting boards though as had to replaster that party wall, but not in the area that I think has shared joists. kid going away soon, so I can take a proper look. Cheers mate, good to have perspective put on it, tis a pain though cos lately woke up our kid, though his and next door windows were open which don't help!
     
  9. Jord86

    Jord86 Screwfix Select

    If they are shared then it can be sorted, but you need to determine what's what first.
     
    BikerChris likes this.
  10. BikerChris

    BikerChris Active Member

    Completely agree again mate, I will see what is what and go from there. I've got a few other jobs to get out the way first, but it's getting higher up the list as it's annoying.
     
  11. BikerChris

    BikerChris Active Member

    Just a little update, I've had the flooring up (I hate T&G) and the joists do shoot through to the neighbour. I'm not going to risk cutting them and just put up with the thumps from next door, which it has to be said, ain't that many. Just need to fill the gaps to stop the airborne noise coming through, seems they forgot to brick em up
     
  12. ElecCEng

    ElecCEng Screwfix Select

    Could you not cut the joists flush at your side then attach a new length of joist at one/either side, which extend into the cavity? Leave a 10mm or so gap all round, isolation foam between etc. Done carefully one at a time it’s unlikely your floor will collapse.

    Clearly you’d need to do some structural calcs but noggins would stop the joists twisting.
     
    BikerChris likes this.
  13. BikerChris

    BikerChris Active Member

    Cheers for that mate.

    Like you said I think a structural guy needs to be checked with, as I'm worried about spread, especially as my son is in that room. I think I'll do sound insulation for the moment and if it starts to annoy me too much, I'll ask the structural people I know. :)
     

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