Joist Support Advice

Discussion in 'Builders' Talk' started by mackie, May 9, 2016.

  1. mackie

    mackie Member

    Hi Guys and Gals,

    I have started to take down the ceiling in my utility room ready for the wall removal to the kitchen. For this I have had a Structural Engineer out and a report. It is a 1950's ex-council House.

    However taking down the ceiling I have come across a new problem. I have three joist spanning 2.4 meters. All are 7 x 2 in old terms (I am sure some will take offence at the 'old' reference). One end is recessed into a Double skin wall but my issue is at the other end. This joins a single skin wall and because it is single I do not know how far the joist goes into the wall (it does not go through as that would be outside the property. Instead under each of the 3 joists there is a piece of 12mm x 200mm metal inserted into the wall / mortar joint.

    The joists only support a small cupboard on the landing, even this is only 5 foot tall because of the roof pitch.

    Because these 15mm pieces are under the joist this makes the ends lower than the rest of the joists, including those spanning the kitchen I will knock through to. So when I plasterboard it will be flat apart from these joists when it will bend down.

    So any suggestions on how to get round supporting these. Being a single skin wall I am going to frame / insulate and board it. My idea was to use extra-large stud work under these three joists to allow me to remove the excess metal (cut it back so it is flat with the new wall.

    Would this meet Building Regs (who I have booked to come out next week for the initial inspection).

    I have also thought about joist hangers, I can access the wall above the floorboards for the first two joists but cannot for the third.

    I don’t really want to have to go to another SE, this will just more cost money.

    Sorry for the long post but I want to give you as much info.

    PS, in the picture the Plasterboard that you can see will come down but it shows the level of the rest of the ceiling and it is flat with the underside of the metal.
     

    Attached Files:

  2. KIAB

    KIAB Super Member

    Could you not pack out joists to same depth as the steel plate,using 12mm ply, or some 16x50mm ( 5/8" x 2" for the older peeps) PSE,finish size around 12mm, thus saving you a lot of structal work.
    You would need to nail some bearers to side of joists & wall, to provide some fixing area for new plasterboard.
     
    Last edited: May 9, 2016
  3. longboat

    longboat Screwfix Select

    As kiab said, or you could double board the whole ceiling or cut strips of 12.5 board to pack out the joists.
    Even better use insulated boards and cut a little bit out round the metal brackets.
     
    KIAB likes this.
  4. Jitender

    Jitender Screwfix Select

    Not sure about the holes for the pipes/conduit.

    I dont think it's within the zones. BC officer may point this out.
     
    KIAB likes this.
  5. KIAB

    KIAB Super Member

    A bit naughty.:eek:
     
  6. mackie

    mackie Member

    Just measured the metal using an old off cut and packing out the joists sounds like a plan, I guess this would be on every joist in the new 'enlarged' room to make sure ceiling is level for coving, this would take ciurca 1 board extra over the whole room. Using Insulated board sounds expensive (??)

    As for the holes, what do you think the BC will say I have to do?? Sister the joists, Structural Engineer suggested I could do this for 2 joists further down the room (not required but suggested whilst I have ceiling down)
     
  7. You will never find a house of this age that has been rewired or replumbed, with the cables and pipes where it tells you in the book.
     
    KIAB likes this.
  8. KIAB

    KIAB Super Member

    Gyproc Thermaline Basic Insulated plasterboard has a 22mm Celotex insulation layer, usually around £17 a board, but can only find it B&Q for £21:93p a sheet.:(
    Might find it cheaper in your area.


    With 12mm steel plates under the joists, there isn't much risk to the joist with those pipes I would say.

     
  9. Jitender

    Jitender Screwfix Select

    Not sure what BC will say, only been involved with them when I did my replacement windows.

    I dont think the single wall would meet building regs, they may ask for another block wall to be built with cavity?

    is the single wall rendered on the outside?
     
  10. KIAB

    KIAB Super Member

    Good point Jit about the single wall, I overlooked that:oops:, can also see you having to build another wall,to keep BC happy:rolleyes:, all depends on the bod you get on the day, might be a jobs worth type or turn a blind eye to it.
    Better get wifey to make some home made cakes & put the kettle on.:):rolleyes:
     
  11. mackie

    mackie Member


    Oh shoot. I guess that is what a BC Inspection is for though.

    No the wall is not rendered on the outside.
     
  12. mackie

    mackie Member

    Also then I guess the support for the joist is irrespctive then becuase the new skin would be built up to it and would almost be as wide as the plate is long.
     
  13. KIAB

    KIAB Super Member

    The new wall would pick up the joists & serve as support for the joists.
     
  14. longboat

    longboat Screwfix Select

    Why might they insist on another skin to an existing wall that an SE has calculated as satisfactory?
    I thought you only needed to comply with u-value requirement for the new structure?
     
  15. Jitender

    Jitender Screwfix Select

    Seems that the wall supporting wall is external, may want U value.

    If they are happy with the structure than it could be just a case of constructing a stud wall with insulation.
     
    KIAB likes this.
  16. longboat

    longboat Screwfix Select

    Had it in my head that he was knocking through into a kitchen extension?
    If you are just removing an existing wall, I don't think u-values will come into it, as its an existing structure, not 100% sure tho.
     
  17. stevie22

    stevie22 Screwfix Select

    Existing wall will almost certainly have BC saying it needs to be insulated, but the required standard is lower than for a new wall.
     
  18. mackie

    mackie Member

    So the BC came out. The reference he used was to converting a garage as the same rules apply, only two pointers he bought up.

    Single Skin wall - to be 50mm gap / framed / 100mm insulated / boarded. No need to treat inside if I leave the 50mm gap.

    The bigger one though is the floor, the easy bit is that it will have to be painted for damp prevention but then (the tricky bit) needs to be insulated to a U value of .22, this makes it 75mm Insulation. So now I need to decide. Do the whole room and have the 'step-up' from the rest of the house in the doorway. Or do I do it just for the area classed as the 'utility' room, he cannot enforce anything on the existing Kitchen. If I do this though I would have to reduce the height of the plinths to ensure the worktop runs flat down the whole room (otherwise I would have to have a step in the worktop.

    Either way I then have a problem with the back door, only had it replaced a couple of years ago but as it is in the 'utility' area it will need insulation which would then be taller than the threshold.
     
  19. longboat

    longboat Screwfix Select

    Looks like you've got three options.

    Go to huge expenses to end up with a shambles.

    Start digging. Also expensive.

    Inform LABC that its not reasonably practicable and drop the project, wink, wink.
     

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