Strong boys

Discussion in 'Builders' Talk' started by Sam Dingle, Feb 2, 2005.

  1. Sam Dingle

    Sam Dingle New Member

    I'm going to be knocking through to our new extension soon.
    I've got the SE to spec the RSJ's and brick work etc..

    What I'm not sure about is if I can use strong boys to hold both skins of the wall?
    I know I'm supposed to have them 3 feet appart.

    The other thing is I'll be needing to support the floor above. So I'm planning on using scaffold boards and acrow props to push up against the ceiling.
    will doing that provide enough support for the rest of the inner skin on the wall above?
    And if so, What is the maximum distance from the wall that I can I have my scaffold boards and props

    I'm thinking I can have strong boys put through from the outside (which will probably reach through to the inner skin) and push the ceiling up on the inside but a few feet away from the wall to be worked on.
    This would give me enough room to lift the RSJ's in from the inside.

    Any comments / advice?
     
  2. on the moon

    on the moon New Member

    Joists are not designed to be used as "needles"
    I assume you have checked to see that they are "built in"?
    If the two skins of masonry are adequately supported that should be sufficient.
    Where there are two skins I prefer to design 2 lighter steel sections, this way they can be inserted seperately on different days . Less chance of movement and easier to install .
     
  3. Sam Dingle

    Sam Dingle New Member

    The SE has done the calcs using two sections that bolt together.

    So can I support both skins with stronboys coming through from one side?

    I'll still be supporting the ceiling/floor but about 2 feet away from the wall.
     
  4. on the moon

    on the moon New Member

    No , they are about 200mm wide.
    Use acros and needles but only do one side at a time. Put the steel in position on the floor, tight to the wall before you begin.
     
  5. DB Builders

    DB Builders New Member

    Wear a hard hat!
    Not being funny but this type of work is not for the DIY clan. Let your insurers know your doing the work, if anything happens (it won't happen to me) you could be up **** creak without a paddle mate.
    But all in all get a BRE directive on how to support walls floors etc properly. They detail good site practice, and don't read to much into what some of these other amateur DIY'types scibble. Especially the ones who script as though the have just read up on some plastic website..

    Good luck!!

    [Edited by: Forum Moderator]
     
  6. chappers

    chappers Member

    Strong boys are long enough to support a solid 9" wall and if you are supporting the built in floor joists as you described, would put one every meter about 2ft from the wall your taking out, then these should be sufficient to help support the inner leaf.
    The main thing to be careful of is whats under your acrows, they shouldn't be stood onto floorboards over a suspended floor, the joists and boards are not designed to take that sort of weight. to be on the safe side, if you have a suspended floor then lift a couple of boards and stand your acrows on the solid ground below the floor.
     
  7. Sam Dingle

    Sam Dingle New Member

    The floor below is solid.
    Yeah, good point about the insurance, it has crossed my mind a number of times.
    I've had a quote from a builder for about £900 to do the actual work. but unfortunatly I haven't got that sort of money to hand. But then again I most definitly haven't got money to re build the back of the house should the worst happen.

    think I need to re evaluate the situation and look to get a bit of dosh from the mortgage.

    Thanks for your help.
     
  8. on the moon

    on the moon New Member

    Hi Sam,
    As some people seem to think that I am a DIY novice perhaps a brief analysis of my advise is needed.

    1. Do not use joists as needles. What I am sayiny here is that by all means support the floor upstairs but do not rely on this as the only means of supporting a skin of brickwork. For all you know the joist ends could be rotten ( not unheard of).
    2. You asked if the Strong boys would do the job. I said NO because they wont.
    3.I suggest 2 sections as opposed to one heavier section ( before I knew that you were actually using 2) because it would be safer and easier .

    From your question I sensed this was probably your first attempt at this . I have been responsible for the removal of literally dozens of walls over many years and I have never taken a short-cut or any risks what so ever and I have never had a problem and I certainly do not need to read-up on a website for help.
    I wish you luck just take your time .
     
  9. Sam Dingle

    Sam Dingle New Member

    Hi OTM.

    Yep it is my first attempt at this.
    I've done alot of reading up on it and have helped a mate replace a rotten lintel before but that span was alot less.

    I'm not the kind of guy just to take someones advice with out thinking about what it involves.
    I've spent the last 3 months thinking about this phase of work and reading up and getting advice.
    I also want to try and do it with out shagging up the ceiling as it's the only good ceiling in the house.
    But it looks like I'm going to have to cut some holes in it to use the strong boys and enable me to have the RSJ hard up underneith the floor joists.
    Hence the original question of, can strong boys support both skins.

    As it's getting close to crunch time I think I'm going to have to pay someone to do the propping and installing and I'll do the knocking and clearing up in the hope to save some dosh. Plus they'll have PLI which I havent.

    Thanks for your help.
     
  10. dazed5

    dazed5 New Member

    Have just done this very thing in my own house but did not use strongboys for one very good reason. If they are inserted from the outside, then you cannot be sure you have got hold of the inner (loadbearing) skin. They are ok for 9" solid walls as the whole wall takes the load, but I would never use them on a cavity wall.
    My method was to use needles, but what I did was to cut a 120mm hole right through both skins, at the needle locations, with a core drill. Save the chunks of brick/block that come out. Then get hold of 2 pieces of 114 CHS steel tube and these become the needles. They slide through the hole neatly. Use a wooden vee block on top af acrows under each end and as mentioned, make absolutely sure they found on a solid floor. Crank them right up as far as you can. Once the wall is removed, insert the 2 steels your SE has designed, along with any padstones etc. Once this has all gone off, remove your acrows, and needles. The core drilled chunks will slide back in and line up beautifully with some mortar surrounding them. Job done. My brother and I did this over 3 Saturdays, not bad I reckon.
     

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