1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

How many acro props ?

Discussion in 'Building' started by george765, 9 Mar 2012.

  1. I am soon going to have a go at installing my first steel lintel. Is there a 'normal' spacing for these ? the span of the opening will be 3350mm.
    It's a cavity wall with good access both sides. Would two be enough (each side) for needles ?
    George
     
  2. Sponsored Links
  3. leew2

    leew2

    Joined:
    13 Dec 2008
    Messages:
    191
    Thanks Received:
    17
    Location:
    Lincolnshire
    Country:
    United Kingdom
    I had a book which recommended 1 pair of props per 900mm (3 feet) of opening width so a 3350mm opening would require 4 pairs (8 props total).
    This is assuming you don't have any joists bearing into the wall just above the opening or other unusual loading conditions which may require extra props.
     
    • Thanks Thanks x 1
  4. tim00

    tim00

    Joined:
    30 Jun 2004
    Messages:
    661
    Thanks Received:
    57
    Country:
    United Kingdom
    Yes, you should be safe at 1100mm spacing. But why not post some pics of, both sides, of the wall in question.? Breakthro's are more than just acrows and removing masonry. In your own inexperienced interest, dont do anything until you've posted pics and picked a few brains.
     
    • Thanks Thanks x 1
  5. thanks guys, very helpfull, I'll try and do some pic's.
    In the meantime, I assume you take up the floorboards and put the acro's direct on to the ground (perhaps on scaffold boards ?) ?
     
  6. joe-90

    joe-90

    Joined:
    28 Oct 2005
    Messages:
    31,284
    Thanks Received:
    1,062
    Country:
    United Kingdom
    The general rule of supporting walls is draw an equilateral triangle above the opening. Only the bricks in that triangle can fall - so the weight isn't massive.

    It's a useful tip to remember.
     
    • Thanks Thanks x 1
  7. noseall

    noseall

    Joined:
    2 Feb 2006
    Messages:
    40,454
    Thanks Received:
    2,536
    Location:
    Staffordshire
    Country:
    United Kingdom
    We would probably be using two each side for that span.

    Spread the load with planks over the floor joists. No need to take up floor boards unless the floor joist configuration is such that you are on one joist as opposed to several.
     
    • Thanks Thanks x 1
  8. Sponsored Links
  9. ^woody^

    ^woody^

    Joined:
    3 Sep 2006
    Messages:
    31,536
    Thanks Received:
    4,224
    Location:
    West Mids
    Country:
    United Kingdom
    If the brickwork is loose (crumbly mortar) then it would mean using more props closer together
     
  10. Symptoms

    Symptoms

    Joined:
    11 Sep 2007
    Messages:
    1,490
    Thanks Received:
    50
    Country:
    United Kingdom
    george - support each side of wall as others have suggested and no need to take-up f/bds if joists are at right-angle to the wall so spead load on scaffold boards. The advantage of using the 'pin' method is that you can use a block & tackle (supported from the pins above) to winch-up that +3m steel if you aren't mob-handed.

    If you don't want to use pins then consider hiring some of strongboy supports to go on top of the acrows, these fit into the mortar joint so 'gripping' the masonry above. A trick we always used pre- strongboy days was to tilt the acrows so the top plate fitted into the mortar joints to grip the wall. The trouble with the pin method is you have to disrupt the wall above when punching through the pin holes and this can cause problems in older building, especially those with lime mortar or other soft mortar.

    Oh, and position the steel at the base of the wall to be chopped out BEFORE you fit the props ... you don't want a huge hole supported by the props and be unable to get the steel in 'cos the props are in the way.
     
    • Thanks Thanks x 1
  11. Some really great tips. I just checked and joist are at 90 degrees so I will put acro's on scaffold boards on floor. Based on your answers I will use 3 each side.
    It's a 1920's house so the mortar is quite crumbly, I will consider using the 'strong boys' rather than disturb loads of brickwork above, but is there going to be room for the beams (2 of 200 x 100 bolted together with spacers) to be placed inside of the acro's when using stongboys ? they look like they cause the acro's to stand quite close to the wall in question ?
     
  12. ^woody^

    ^woody^

    Joined:
    3 Sep 2006
    Messages:
    31,536
    Thanks Received:
    4,224
    Location:
    West Mids
    Country:
    United Kingdom
    Strongboys should only be used for supporting one skin, and do have to stand close to the wall.

    So it can make things tight and awkward

    You need to plan the work so that the beam can me manoeuvred and put in place once the wall is out and the props are in place.

    This may mean putting the beam at the bottom of the wall before placing the props, and cutting out sufficient wall and bearings so that the beam can be lifted up and in - a beam needs more room diagonally than if it is being moved up horizontally
     
    • Thanks Thanks x 1
  13. Thanks for the help guys. I think i'm ready to give it a go. Great forum this !
     
  14. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page