HSBC, Goring Road, Worthing
Back in March this year we were approached by our client to price the removal of a walk-in concrete safe in a recently vacated HSBC branch, which had to be returned to its original footprint prior to the bank’s use.
The safe consisted of 300mm thick, heavily reinforced, concrete walls and roof slab. The safe measured 3400mm wide by 3000m deep and 2700mm high overall. The reinforcement ran vertically and then had spiral/helical bars wrapped around each vertical bar.
The complications we faced included no access to the top of the roof slab, as the gap to the floor above was only 150mm, which meant all the drilling and cutting had to done from underneath.
Also, we had occupied flats directly above us so noise was an issue. The residents were not amenable to our presence and we had the task of keeping them informed of our progress throughout the works.
After the removal of the safe door by a specialist sub-contractor, we commenced removal using a Husqvarna DM650 drill motor fitted to a DS50 gyro rig. This enabled us to carry out the inverted drilling to the roof slab.
Holes were drilled to the corners and the intersections with walls in the locations where we intended to track saw the slab into sections. During this operation we discovered that the safe was in fact formed of precast planks/beams which had been installed over three twisted 16mm rebars at close centres and then grouted in.
This discovery made the removal of the top slab even more difficult in terms of support to ensure that we only removed the designated section at a time and that we didn’t suffer any uncontrolled collapse. Once the drilling works were complete we then switched to the Husqvarna WS220 track saw to cut the concrete into sections.
The WS220, although slightly under powered for the concrete we were cutting, was chosen for its size and weight together with it only requiring a 16A 3 phase power supply.
As there was no 3 phase power supply available and nowhere to stand a large generator, we purchased a small Atlas Copco portable 3 phase generator which powered the saw.
We initially removed the front wall to give us better access and enable us to support individual top slab sections. Once again all sawing works to the top slab were carried out upside down (inverted).
This proved tricky with the amount of propping required and very slow due to the level of reinforcement and the intricacy of fitting in between the props.
However our site team persevered and eventually the top slab was removed in sections measuring approximately 600mm x 600mm. The side and rear walls then followed until eventually we were just left with a small section at the base with a rebar sticking out of the floor slab.
We slotted the remaining concrete sections using a DiaquipQHS-400 110V hand held saw and then broke them out with a hand held breaker.
The remaining rebar was cut off using an angle grinder and the works were complete save for removing the numerous concrete blocks which weighed around 35 tonnes.
Although the job ended up taking longer than anticipated all concerned were pleased with the end result and some useful lessons were learnt going forward.