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Wind post - is there another method?

Discussion in 'Building' started by oxfordite, 16 Aug 2018.

  1. oxfordite

    oxfordite

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    Removing the non-supporting wall (red lines) which meets front, single-brick, tile-clad wall, between the 2 front windows..

    image.jpeg

    SE initially agrees removal of wall up to front wall.. Then, in report, requires a 50cm stub to remain..
    ..after querying this, he suggests a windpost design might suffice.

    Our aim is to have a nice large bedroom - not an archway between 2 adjoining rooms.

    Is there another way -- maybe we can suggest to this SE or a different SE?
    Eg. Brace the entire inside of the wall, down to lintel below (the ground floor wall is a cavity wall), with 15mm ply, screw fixed at 400mm centres, horizontal and vertical, with suitable steel straps to screw fix to joists with noggins to interlink the 3 or 4 floor joists nearest wall (they are parallel to front wall), then insert a 4x5 timber/glulam at ceiling height fixed to remaining wall by doorway, and fixed to ply+front wall with wide steel bracket. Add a 10mm (?) steel right-angle strap at floor joist height, screw-fixed to joist(s) and screw-fixed to ply/wall with resin fixed bolts...
    Something like this?

    I'd guess the 1" battens fixed externally for the cladding tiles are a significant part of the wind resistance of the front wall currently..

    Any thoughts?
     

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  2. tomfe

    tomfe

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    What construction is the house?
     
  3. oxfordite

    oxfordite

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    1960 semi-detached brick cavity, 9" party wall. The odd-one out is the front 1st floor wall, which is brick, single-skin, with ~1" battens and concrete cladding tiles.

    I suspect it originally had metal crittal windows.. the tell-tale signs of superficial cracking to plaster suggest later UPVC windows did not give the same structural support as those crittal ones.
    I further suspect the tile battens to exterior of the front wall are lending it some lateral strength.
     
  4. John D v2.0

    John D v2.0

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    A wind post will be a bit more costly but much narrower than a stub buttress. You might be allowed to chase the channel section into the wall to reduce the impact further, and by that time you'll be able to lose the remaining protrusion in the finishes.
    I guess the se has seen the construction and decided there isn't enough stability in the effective single thickness of external masonry wall. This could be especially true if it has windows in it as effectively there's no return on the wall either.
    The extreme option would be to rebuild that part of the house using timber posts and framework on the inner leaf but the se is trying to design the most efficiency solution for you based on budget and requirements. I'm not a pro just had a load of work done designed by an experienced se.
     
  5. wessex101

    wessex101

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    That seems like overkill to me. Maybe you should just get a new structural engineer.
     
  6. tomfe

    tomfe

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    It seems bonkers to me. A 50mm buttress will do very little. You're tied in at the top and bottom of the wall.
    You can use angle iron and gun ties in, that will be cheaper than a windpost.

    What is the total length of the wall? What are your ceiling heights?
     
  7. John D v2.0

    John D v2.0

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    Just in case it's a misread, he said 50cm so 500mm;)
     
  8. freddiemercurystwin

    freddiemercurystwin

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    Maybe its catching, some clown seemed to miss two 0's off the cost of an outline planning application the other day.
     
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  9. oxfordite

    oxfordite

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    Sorry, intended sticking with mm.
    Small room is 2.1m wide, large room is 3.4m wide...
    ..the width of the single brick wall, once the internal wall is removed, will be 5.6m

    Room is approx 2.3m ceiling height.
    -----
    Longer term insulation plan:
    1. Strip cladding and battens, attach vertical 100mm I-beams or equivalent (likely adapt some I-beams), cover with breather membrane and suitable 10mm weather-stable board, blow gEPS behind breather membrane. Batten and re-tile exterior to satisfy local planners.
    But, maybe also..
    2. Glue attach 4mm gEPS insulating lining from BASF (via Toolstation etc). Screw-fix fermacell through the insulation.. Which is where I arrive at pondering 4mm gEPS, 15mm ply, 10mm fermacell.. Just add angle irons and that front wall gains a lot of lateral wind resisting strength.

    ---
    Not sure I'd be convinced that chopping a Windpost in to a 4" brick wall has much margin for error, nor that it would not lessen the integrity of the wall.
    I suspect this was SE in a hurry.

    "Angle iron and gun ties in.." - what size angle iron? Gun = glue/bond? ties = ceiling ties?
    (And, I agree! - could even use angle irons at 1.4m intervals across the width of the room?)

    Thanks for all comments.
     
  10. tony1851

    tony1851

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    Scan0010.jpg Your SE has correctly identified the fact that the single-skin brickwork is not suitable to span vertically between the top of the cavity wall and the underside of the roof structure. The critical weak point will be the full-height wall between the windows, because that will be taking wind load on part of the windows each side, as well as its own area.
    The wind load induces bending in the brick skin, resulting in tension on the room-side, which brickwork is not capable of resisting. Rather than a chunky wind post, why not consider screwing two (or better, three) strips of steel, say 5mm thick and 100mm wide, to the bit between the windows. These should be suitably fixed to at least two floor joist at the bottom, and to the roof structure (via the wall plate?) at the top.
    These would not be true wind posts, but if fixed with sufficient screws, will add some tensile strength to the brick skin as a whole and so improve resistance to lateral wind load.
     
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  11. wessex101

    wessex101

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    I read "single brick" as a 9 inch solid wall and the drawing certainly seems to suggest that. It would make more sense for the engineer to ask for a windpost if it was actually half brick single skin?
     
  12. ^woody^

    ^woody^

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    The engineer is not one. The wall is braced by the roof FFS
     
  13. tony1851

    tony1851

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    You may actually be right. I've always thought of a single-brick wall as 102mm but even for 1960s build, such a thickness - even clad with tiles - would seem to be a bit flimsy (though the plan shows the structure as cross-wall type).

    BTW; "9 inch solid wall" - you're showing your age!
     
  14. tony1851

    tony1851

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    It will of course be braced by the roof, but would the narrow pier between the windows be capable of spanning as a beam between the level of the first floor joists and the roof? I suspect not, considering the fact that it will be picking up wind load from the windows either side.
    If the wall being removed is masonry of some type rather than studwork or a Paramount partition, I would think it is there to support the outer wall..
     
  15. ^woody^

    ^woody^

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    If it's a 9" wall - it holds itself up, and the roof above it.

    If its a 1/2 brick wall, not only would that be unlikely, but there would be a beam across the whole top as a 1/2 brick wall wont be taking that roof load.
     
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