Posted By Richard_Sams
I work for a medium sized construction firm who have recently sub-contracted another firm to undertake the demolition work on a building that we are completely refurbishing. Part of the demolition requires removing pre-cast concrete stairs (6 flights). It is not possible to use a crane to lift the stairs out in sections. Propping the stairs from underneath while breaking them up with jack-hammers has been suggested. Concerns however have been raised about the effect the vibration
will have on the stability of the props.
Does anyone have any alternative suggestions from experience with similar situations?
Any suggestions are welcome.

Posted By Richard_Sams
Thanks for the response Bob but how would you propose then getting the cut pieces out of the building keeping in mind that there are 6 flights?

Posted By ddraigice
Will there be a potential fall issue here too?

Posted By Peter MacDonald
First of all find out the supporting mechanism for the stairs. If they are supported only at each floor height then partial dismantling will result in total collapse without propping. Props can be sacrificial and fixed in place and indeed propping up areas during demolition is not uncommon although it is usually done without the input of an engineer, however I would see this input as essential in this case.

If the stairs are supported horizontally they may (subject to enginneering approval be broken out partially without support. In this case you may want to use a Brokk/Robolition machine to break out the stairs working bottom to top (whereby the machine can then be lifted off the roof if possible) or it can climb the stairs and work it's way down. Floors can be welled on the way up to allow material to drop down or holes can be made through the adjacent stairwell walls and the stairs broken out from there.

If the stairs are to be refitted into the existing stairwell then how are the new stairs being put in? The reverse method of construction can be used for demolition. If the stairwell is being removed entirely then prop the surrounding floor and break out the stairwell with the brok from the floor to be retained.

Basically there's a few ways yo can do this but the mode of support for the floor must be established first (by a competent person).

Good luck.

Posted By Peter MacDonald
Robert

I would disagree that hand breaking is a complete no no. You would need to carry out and vibration risk assessment and then control trigger times by regular breaks and job rotation. Also by input from an enginneer you could minimise the amount of breaking out to do. The biggest risk then become stability of partly demolished structures( back to propping)and exposure to a fall through the creation of leading edges. If the stairs are not structurally suitable for robolition machines, then breaking out by hand may become a valid option an option, albeit not ideal, it is far from illegal or unsafe if controlled and managed.

Regards

Peter

Posted By Crim
The spirit of CDM 2007 is to consider the safety of all workers and Designers are required to look beyond what is directly in front of them.

I believe reconsidering removing this staircase is essential and, if not the Designer/s have a responsibility for providing input for the removal.

HSE are now visiting sites looking for safe planning of all work and with this in mind I recommend all necessary safety barriers are put in place prior to removing the staircase and also plan the work to fit the replacement staircase ASAP after removal of the old. (Out with the old and in with the new).

Not very helpful with regard to the original question but I hope I make sense?