Short answer
Removal in refurbishment and demolition are two jobs that use the same attachments for opposite purposes. In demolition the building is going and damage is not a cost item; in refurbishment the building stays and the structure around every piece removed must not be damaged. That opposition changes three things: the attachment choice, the order of removal, and the value of speed. In demolition speed wins; in refurbishment control wins, and removal done quickly comes back as damage that has to be repaired. So the rule of refurbishment removal is one sentence: nothing is broken before it has been cut.
First, which element is load bearing?
The first job in refurbishment removal is not choosing an attachment but establishing whether the element to be removed carries load. An infill wall and a shear wall look similar from outside; one can be removed, the other cannot.
That distinction is not made by eye on site. It rests on the design, or failing that on a structural assessment. Where a load bearing element does have to be removed, how the load will be transferred has to be resolved before it goes.
The attachment decision comes after that and is actually easy: on non load bearing elements the options are wide, while next to load bearing elements impact attachments are ruled out from the start.
Nothing is broken before it has been cut
That is the one rule of refurbishment removal. Cut the boundary of the area to be removed first and the breaking done inside cannot travel into the structure that stays; the crack stops at the cut line.
Start without cutting the boundary and where the crack stops is decided by the crack planes in the material, and those planes are usually not the boundary you wanted. A crack in the wall that stays produces a repair more expensive than the removal.
The cutting is done with a concrete cutter, a wall saw or a diamond wire; which suits depends on thickness and access. A breaker cannot do this job.
When cutting a slab, the floor below is site too
Cutting and enlarging openings in slabs is common in refurbishment, and the side most often overlooked is the floor below. The cut piece drops; below it there may be people, equipment or a sensitive surface. On slab work the exclusion zone is set not only on the working floor but on the one beneath. That is a safety step that comes before any attachment decision.
The order of removal
- 1
Take the non load bearing elements first
Infill walls, finishes, suspended ceilings and services can be removed without touching the structure. This stage opens access and makes the later steps easier.
- 2
Cut the boundary of the area to be removed
Wall, slab or beam; whichever it is, the boundary is cut first. Cutting depth follows the thickness of the element.
- 3
Divide the cut area into pieces
Rather than dropping one large piece, dividing it into handleable pieces is both safer and more practical. Piece size follows the method of handling and lowering.
- 4
Break the inside under control
Once the boundary is cut, the inside can be taken with a breaker or a pulveriser. Approaching the boundary line, the attachment is reduced in size or changed.
- 5
Cut reinforcement to plan
Whether the remaining reinforcement is cut depends on the design. Where it is cut, it is cut with a shear; bending and snapping it with a breaker both cracks the remaining concrete and ruins the bar.
- 6
Check the cut face and the structure that stays
When removal is finished the remaining surface is checked for cracks. Any crack found is assessed before moving to the next stage.
Do and don’t
Do
- Establish from the design whether the element to be removed carries load.
- Always cut the boundary first; breaking is the second step.
- Divide large pieces into handleable ones rather than dropping them.
- On slab work, set an exclusion zone on the floor below as well.
- Where reinforcement is to be cut, cut it with a shear rather than snapping it with a breaker.
Don't
- Do not remove a load bearing element before the load transfer is resolved.
- Do not start breaking before the boundary is cut.
- Do not work with a breaker at the boundary of the structure that stays.
- Do not push a piece off with the breaker to drop it; that is lateral load and the fall direction is uncontrolled.
- Do not pass over a crack seen in the remaining surface on the grounds that "the plaster will cover it".
Vibration: the neighbouring flat is site too
Refurbishment is usually done in an occupied building, and the neighbouring flats are just beyond the boundary of the work. Here vibration becomes a question of relationships before it becomes a technical one.
Removal done with a breaker can produce enough vibration to bring things off a wall in the flat next door. Cutting methods are markedly lower in this respect, and in refurbishment that difference matters more than any difference in speed.
We covered neighbours and vibration measurement in urban demolition in a separate guide; the same logic applies in refurbishment, but the distance is far shorter.