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Acceptable Construction Detail - 1.5 Storey - Block on edge for wall plate

  • 08-10-2014 12:51AM
    #1
    05Mav
    Registered Users, Registered Users 2 Posts: 30 ✭


    I am at the Wallplate level for a 1.5 story house. House is I shaped, the 2 ends have a pitch of 35 dig and the middle section is 38 deg. I am doing to case/concrete barge the gables and put the facia directly onto the wall at the front, no soffit.

    My Engineer originally wanted to close the cavity with a block until i said well you can't do that anymore and then showed him the detail in the TGD. When i said i was putting the facia directly onto the wall he said that closing with the block wouldn't work then as it would be a massive cold bridge.

    I am putting on a trussed roof and originally the manufacturer said the block on the edge was fine and that they were all being done this way. Now he is iffy on the whole thing. Wants the 2 rows to end at the same height. And use a slate to close the cavity on the top row. Roofer says the slate will only break when they go to nail the wall plate on. He also says there could be a 12.5 mm deflection on the roof.

    My roofer was iffy at first and now thinks it will be alright with plenty of strapping - every 900mm.

    My Arch Tech says he is specing all his builds with the block on the edge.

    The block layers want a decision and reckon they done a load of house in Kildare last week signed off by home bond with the block closer.

    So i have 5 opinions and then i read different opinions on here and some say no way would they every use that detail on 1.5 story.

    Have peoples options changed on this over the last few years.

    I have attached a picture of the current undecided make up.
    100mm inner/outer leaf - 150mm full fill insulation
    Second last row finished at same height.
    Slate to close cavity, then 4 inch block to take wall plate.

    I take it the above would be very dodgy as any twisting on the wall plate will cause it to go. But the Engineer says that's fine. But with him not fully knowing the detail I’m iffy on this now myself.

    I was going to use a Quinn Lite on the flat for the rest of the cavity, but Engineer reckons that will only stop it moving one way.

    The trussed roof man would rather see them the same height, but then i can't close the cavity. I was thinking of maybe putting a 4 or 6 inch soap on the outside and a wall tie back to the 4 inch and strap the inner leaf every 900mm. The reason for the soap bar is i can't see the rafter working if the inner/outer leaf are the same height. Trussed man says it will work though.

    Either way the void will be filled with insulation.

    Or take out the slate and tie the 4 inch and soap bar together and run a slate over the soap bar to the 4 inch to close the cavity.

    Has anyone any more opinions to add to this Enigma.

    Not able to upload a picture at the minute


Comments

  • #2
    WhiteWalls
    Registered Users, Registered Users 2 Posts: 945 ✭✭✭WhiteWalls


    If you say three hail marys and then walk around the house twice, that usually works for me


  • #3
    sydthebeat
    Subscribers, Paid Member Posts: 44,924 ✭✭✭✭sydthebeat


    1 the acceptable details do not have any structural merit. They are designed from a thermal and air tightness performance ONLY

    2 the slate WILL break, right down the middle, along the whole cavity.

    3 your structural engineer should work with your truss company to find a solution that suits your specific build.



    I have yet to find a builder or engineer that would stand over that particular detail as designed in the ADs

    its very interesting that in the UK their equivalent "accredited construction details" all contain the following statement:
    The above indicative guidance illustrates good practice for the design and construction of interfaces only in respect to ensuring thermal performance and air barrier continuity. The above guidance must be implemented with due regard to all other requirements imposed by the Building Regulations
    "Structure" is a very important part of the other requirements of the building regulations.

    of course, ireland being ireland, the compilers of the acceptable details didnt think it necessary to input that statement on all the illustrations, even though they blatantly copied the Uk version.


  • #4
    JimmyMW
    Registered Users, Registered Users 2 Posts: 695 ✭✭✭JimmyMW


    Hi 05MAV,

    What Part of the TGD's did you see this? I have looked in Part A 2012 and on Diagram 7 on pg 23 it shows a traditional cavity closer.

    "My Engineer originally wanted to close the cavity with a block until i said well you can't do that anymore and then showed him the detail in the TGD. When i said i was putting the facia directly onto the wall he said that closing with the block wouldn't work then as it would be a massive cold bridge."


  • #5
    05Mav
    Registered Users, Registered Users 2 Posts: 30 ✭05Mav


    Hi Syd,

    Thanks for the response.
    My Engineer told me it is not his responsibility to be designing details, he said it is up to me to use and approved detail, and basically once used he will sign it off.

    The guy making the trussed roof has annoyed me though saying it was fine and now changing his mind. I discussed this months ago so i wouldn't run in to this now.

    Both my Engineer and Arch Tech would stand over that detail and an Engineer my Arch Tech uses would stand over it, and probably because all they have to say is well it was an approved detail at the time.

    Are all the other 1.5 storey houses being closed with a block on the flat.

    Have you designed a detail for this before.


  • #6
    05Mav
    Registered Users, Registered Users 2 Posts: 30 ✭05Mav


    Hi Jimmy,

    Thanks for your reply also.
    I may have slightly misrepresented myself when i said i showed. It was a conversation on the phone where he said to use the block on the flat. That is when i said that it's not allowed as both my Arch Tech and Truss roof supplier said this to me.
    My Engineer then rang back after 10 minutes and said they were right, that he went and checked the detail himself.
    I only looked at you information this morning and seen the traditional block on the flat.
    The detail i was shown is in the Part L supplementary documents - Cavity Wall Insulation - page 13/14. It's from July 2008.


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  • #7
    JimmyMW
    Registered Users, Registered Users 2 Posts: 695 ✭✭✭JimmyMW


    Hi 05Mav,

    I saw this also, but to me that is a suggested detail, in my opinion it does not mean that a cavity closer is not allowed. Id imagine that a Quinn Lite as you suggested earlier would suffice as a thermal break, however I am not sure how a Quinn Lite would be structurally.

    I would be very slow to trust a block on edge like that to hold any load that is not completely vertically. Id say for that detail you would need some sort of a ring beam with steel ect.

    I am looking forward to the opinion of others about this detail


  • #8
    sydthebeat
    Subscribers, Paid Member Posts: 44,924 ✭✭✭✭sydthebeat


    05Mav wrote: »
    My Engineer told me it is not his responsibility to be designing details, he said it is up to me to use and approved detail, and basically once used he will sign it off.
    .

    so.... what is he being paid to do then? if the details is 'pre approved' who has approved it?

    05Mav wrote: »
    Both my Engineer and Arch Tech would stand over that detail and an Engineer my Arch Tech uses would stand over it, and probably because all they have to say is well it was an approved detail at the time.
    .

    actually ive just found the same line above on the very first page of the illustrated details
    http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18751,en.pdf
    second last paragraph
    These diagrams illustrate good practice for design and construction
    of interfaces only in respect to ensuring thermal performance and air
    barrier continuity. The guidance must be implemented with due
    regard to all other requirements imposed by the Building Regulations.

    at the end of the day if your engineer is willing to stand over it, then fine, they know the specifics. but i wouldnt be accepting "oh but looks, it says its an acceptable detail"....


  • #9
    hesker
    Registered Users, Registered Users 2, Paid Member Posts: 1,628 ✭✭✭hesker


    Have you considered a proprietary closer.


  • #10
    sydthebeat
    Subscribers, Paid Member Posts: 44,924 ✭✭✭✭sydthebeat


    hesker wrote: »
    Have you considered a proprietary closer.

    Doesn't solve the structural problem


  • #11
    hesker
    Registered Users, Registered Users 2, Paid Member Posts: 1,628 ✭✭✭hesker


    sydthebeat wrote: »
    Doesn't solve the structural problem

    Found a good discussion on this from a while back.

    http://www.boards.ie/vbulletin/showthread.php?t=2055444995


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  • #12
    05Mav
    Registered Users, Registered Users 2 Posts: 30 ✭05Mav


    Hi Hesker,

    Thanks for the reply. Like Syd i am more interested in the structural element of the inner leaf taking the load of the roof, rather than how to close the cavity. For now at least.

    I'm a bit pissed off at the minute that i am paying professionals for this information yet they have a blasé attitude to it.

    Well this is what i spec, and if it’s an approved detail (as in from the Dept of Environ) then i will sign it off. No good to me when i have crack appearing along every upstairs room.

    Anyway,

    I have seen that link you added and this link here:
    boards.ie/vbulletin/showthread.php?p=65255948
    Both those links are nearly the reason i am here, i just want to make sure i get it right.

    I was thinking of the ring beam being mentioned 100mm wide and 225mm high, and drilling rebar into the block below but after reading another thread it would need to be wider.
    I was also thinking of using long 9x4 lintels but i don't think that would achieve anything.

    Oh the joys of it all.


  • #13
    05Mav
    Registered Users, Registered Users 2 Posts: 30 ✭05Mav


    Hi Hesker,

    Thanks for the reply. Like Syd i am more interested in the structural element of the inner leaf taking the load of the roof, rather than how to close the cavity. For now at least.

    I'm a bit pissed off at the minute that i am paying professionals for this information yet they have a blasé attitude to it.

    Well this is what i spec, and if it’s an approved detail (as in from the Dept of Environ) then i will sign it off. No good to me when i have crack appearing along every upstairs room.

    Anyway,

    I have seen that link you added and this link here:
    www.boards.ie/vbulletin/showthread.php?p=65255948
    Both those links are nearly the reason i am here, i just want to make sure i get it right.

    I was thinking of the ring beam being mentioned 100mm wide and 225mm high, and drilling rebar into the block below but after reading another thread it would need to be wider.
    I was also thinking of using long 9x4 lintels but i don't think that would achieve anything.

    Oh the joys of it all.

    I had to take out the first part of the link as it would not let me post a URL


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