Getting 4.6m rsj into loft

Discussion in 'Builders' Talk' started by pal123, Jan 31, 2019.

  1. pal123

    pal123 New Member

    I'm looking at a loft conversion, which needs two 4.6m (which includes 150mm overhand on each side) long RSJs' to be somehow pushed up to the 1st floor then pushed through a loft hatch, maneuvred into place then overhang by 150mm onto each side.
    I'm not a builder but have a few ideas on how to physically get the RSJ through the loft, but first I need to get an idea of the RSJ sizing. The RSJs are only for loft conversion and are not holding up any beams. Can I please get some advice on how to work out the sizing for the RSJs', and how to get them into the loft? Thanks
  2. DIY womble

    DIY womble Well-Known Member

    Remove some tiles , or bricks in gable get metal hoisted by cherry picker or lorry with grab
    SteveMJ likes this.
  3. KIAB

    KIAB Well-Known Member

    Last loft conversion I helped with, owner hired a spider crawler crane for day, only thing narrow enough to get down footpath & close enought to house to lift rsj's through window in loft,ordinary crane would needed to be large & have a long jib to get the reach needed.
    Last edited: Jan 31, 2019
  4. CGN

    CGN Well-Known Member

    Don’t take chances, pay for a crane if that’s the only feasible way.
    KIAB likes this.
  5. gas monkey

    gas monkey Well-Known Member

    Last crane I had was 250/day about 2002 but atnthe time was quated 2,000 from one firm for the job as they would do all the risk assessments etc
    Can you weld
    Can you do up flanges
    reson cut them up weld them to gether
    if you do not like welding in doors weld the flanges on and bolt them up after fitting
    If you cant do ither get a shop in
    have you though about floor beams onto wall plates
  6. sospan

    sospan Well-Known Member

    dont think you will be able to lift it manually into the attic even if the roof was off and there was access. The best thing would be crane, scaffold and remove some tiles. Other than that ask you structural engineer to redesign / re-specify using smaller sections that can be assembled in situ
  7. Isitreally

    Isitreally Well-Known Member

    A few years back, my last day working for a complete cowboy was because of steels in a loft, I wasn't working on this particular job but was called to it along with 8 others plus those already working there, 12 in total.

    They had set up a ladder type effect out of scaffold towers with 4 different platforms and expected us to carry these steel up them and into the loft via a 2' square hole in the roof.

    The steels were something like 8"x 4" , 5 metres long with cranked ends fitted, weight?? Bloody heavy.

    Needless to say I wished them well a made a hasty exit.
    rogerk101 likes this.
  8. stevie22

    stevie22 Active Member

    If you don't know the size you need I assume you've had no design yet? It is certainly not a given that loft conversions need steels!!

    Many of my jobs have none at all and some years ago I redesigned one for a builder from 2.5 tonnes of steel down to 50kg. It often just needs a bit of thought from someone who knows their job.

    If you do need steel then you either plan how to physically fit it in in 1 piece (eg hole through external gable) or if it needs a splice which you then need properly designed.

    Getting it in place? A lot depends on where you are. Many steel suppliers run trucks with long reach Hiabs and this is probably the best option because you have one vehicle to deal with and no crane waiting for steel to arrive or vice versa. If you're in the countryside you might find a friendly farmer with a telehandler.
    Jimmycloutnail likes this.
  9. pal123

    pal123 New Member

    I could convert the loft by using

    1) Very deep structural timbers, each embedded into the wall at set spacings
    2) 2 x RSJs' with joist hangers for 8 deep"x3 deep" at spacings
    3) Place 4" deep x 2" deep joists on top of the existing 3" deep x 2" deep joists to make the combined joist 7" x 3".

    Overall 3) is cheaper, 2) is the preferred method by building control. Which one is easier?
  10. sospan

    sospan Well-Known Member

    So many factors come into play; design, loadings, access, capability to fit them. What does the structural engineer suggest - or isn't there one ?
  11. stevie22

    stevie22 Active Member

    4x2 on top of 3x2 will make a piece of wood 7x2 (not 7x3) but it will not behave as a 7x2

    Building control will have no preference between 1) & 2) it will depend on the job and the design.
  12. HappyHacker

    HappyHacker Active Member

  13. pal123

    pal123 New Member

    Here's a plan view (A4, 1:100 scale) of the house. I've put a proposed 2 x RSJ 4.6m long in the loft. Before sending this to a structural engineer I'd like to get (free!) advice on how a 4.6m RSJ could be put into the loft. I could split each 4.6m RSJ into 2 x 2.3m RSJs and use adapters to connect the centres. Any thoughts please?
  14. Jimmycloutnail

    Jimmycloutnail Active Member

    Steve already told you the beams can be spliced but the connection detail needs to be designed by a structural engineer and who will provide a drawing that the fabricator will work off
    KIAB likes this.
  15. Powerelec

    Powerelec Member

    If you have no SE no BC, risky proposition. However to get steels up you could use man power and an electric winch and cable .
  16. pal123

    pal123 New Member

    Please bear in mind that I'm doing some PRELIMINARY CALCULATIONS WITH NO NECESSARY INTENTION OF PROCEEDING. This is just my thoughts.

    I've used the rule of thumb of 'RSJ depth = span/20' on a 4.6m span to work out that I need 2 x 254mm x 146mm x 4.6m RSJ (31kg/m) with a lindapter at the midpoint. Each RSJ's total weight is 30kg/m x 4.6m = 138kg. Dividing this into two means transporting a 69kg RSJ into the loft at a time before using a lindapter to connect the two together. A UK metals4u weblink for the RSJ is at:

    Moving a 69kg RSJ is 'doable' without using a crane provided the loft is braced using planks of wood so that the 2 x 69kg beams + weight of 2 people (assume 80kg each = 160kg) so about 300kg, is spread evenly over the loft. I'm wondering if 3x2 can take this load? Using this method I would install the padstones prior to moving the RSJs into the loft.
  17. KIAB

    KIAB Well-Known Member

    A accident waiting to happen...
    stevie22 likes this.
  18. sospan

    sospan Well-Known Member

    Hmm, two guys lifting a 70kg beam through a narrow opening balancing on 3x2s. How is the guy at the bottom going to lift it high enough for the guy (s) in the attic to be able to grab it. You may be able to "bear hug" a vertical 70kg RSJ and lift it a little bit, but not enough to reach the attic. As a minimum you are going to need 4-6 big guys whom like taking risks

    You do realise that if you cause an accident or damage your neighbours property you will be personally liable and possibly face prosecution .....

    Why is it you won't take the advice here - get a structural engineer and a proper risk assessment ???
    stevie22 and KIAB like this.
  19. pal123

    pal123 New Member

    No reason, I've paid for a structural engineer before but it's around £200 a pop. So I'd prefer to work out if it's feasible before paying for anything.
  20. Jimmycloutnail

    Jimmycloutnail Active Member

    Building regs will cost you about a £800 and they won’t accept rule of thumb calcs

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