I'm not aware of any recognised technique for this. Doesn't it depend on the dynamics of the falling material? A static drop with no relative horizontal movement will follow gravity? If the load is swinging/has a sideways force when released, then the released load will follow a sort of parabolic route. Guess you could use the equations of motion to estimate how far sideways the load will travel as it falls.

Also what about the type of material, is it likely to 'bounce' after first hitting the ground and then make a 2nd impact in a different position. How you predict that is difficult, I would think. Or if loose material spread out in different directions?

This calculator is for predicting dropped objects in the sea and where they might settle on the seabed. Doubt if its suitable for air dropped items on a normal construction site.

Many thanks for the replies.

The dropsonline website has some interesting calculation tables for showing the potential effects of dropping objects based on height and weight that will come in useful for this exercise so thank you for that link.

Unfortunately I don't have the budget to purchase the BS document for this piece of work.

I'm second-guessing what I would have selected as a control measure if asked (I wasn't) and I have concluded that I have insufficient knowledge to establish a safe exclusion zone and would not have been able to obtain knowledge to enable me to work it out in the time available (or at all, it seems) so would have dismissed this as an option from the get go.

Would anyone consider that a drop zone (of any dimension) that would close the pavement and possible a side road a serious option as a control measure for working on a fourth floor balcony replacing decking and in the absence of any other protection from falling objects?

Would more experienced practitioners think that there would be a way of establishing the zone (other than arbitrarily closing the pavement and road over a large area)?

Is there any merit in making an exclusion zone to close the pavement (as an extra layer of control) without calculations to show the benefit?

It's remedial works to a domestic block by a small commercial subcontractor for a large commercial contractor.

This isn't the control measure in place. I'm just trying to ascertain whether the exclusion zone would ever have been an option either by calculating it properly or by judgement and previous experience of another safety advisor.

Replacing decking at 18m is pretty serious Work At Height.

My mind boggles as to how you anticipate the contractor would safely remove and replace the decking operating from what I presume would be the general access door to the balcony.

Planning for a vertical gravitational fall would be fine in a laboratory in the real world there can be sudden air movements which could push a falling item well beyond any limited zone cordoned off at street level.

If you don't have the budget to purchase BS 6817 what chance for suitable and sufficient access controls

Originally Posted by: Roundtuit

Replacing decking at 18m is pretty serious Work At Height.

My mind boggles as to how you anticipate the contractor would safely remove and replace the decking operating from what I presume would be the general access door to the balcony.

Planning for a vertical gravitational fall would be fine in a laboratory in the real world there can be sudden air movements which could push a falling item well beyond any limited zone cordoned off at street level.

If you don't have the budget to purchase BS 6817 what chance for suitable and sufficient access controls

I'm not sure why your mind is boggling. Did I say I was doing it in an unsafe manner? No I did not. I asked a theoretical question about calculating exclusion zones should someone think that this would be a suitable control measure as a reflective exercise in considering and dismissing unsuitable control measures.

I don't have a budget to purchase a £300 document that might or might not answer my theoretical question and satisfy my own musings for my personal amusement. If I spent money on potentially useless documents I wouldn't have the budget to put in place the extensive and correct control meausre that I do use so please don't assume we are some two-bit contractor looking to dodge our obligations. That says more about you than it does about me.

I am surprised it took so long for someone to try virtue-signal their own superior knowledge by implying that I am doing something wrong just because I asked a question. You have no basis for that assumption, so why make it other than as an opportunity to show off?

Lisle, unless I have misread the thread, you haven't actually spelt out what the work involves. You 've stated that it's remedial works to be done from a balcony at 18m above ground but I'm not sure what that work involves - could be e.g. some repair to rendering around the balcony.

Without knowing what is at risk of falling other than the workers's tools it is very difficult to assess what precautions against falling objects might be appropriate.

As example, if it is render then you could reasonably presume that it would fall within a very small distance from the face of the building. In contrast if you were replacing cladding, then any sheet could easily be caught by the wind and we would need to know weight and dimensions to consider the options.

the formula can be adopted..wally