The installation of forms—sometimes called shuttering—for a slab, when covering an area of more than a thousand square meters, is easier than removing the forms later, after the concrete has been poured and that’s usually called de-shuttering.
You might imagine that is easy to remove the forms, but the truth is: it is very hard and risky.
Before you de-shutter the forms of your concrete slab, you should establish the “Method Statement” or “Methodology” of how to do a safe removal. The process involves risks and hazards, especially in a hi-rise building.
The engineer or consultant might prevent you from removing the forms without their approval and consent, and sometimes they will even ask the contractor to submit the methodology of de-shuttering.
So, here is the methodology on how to safely de-shutter a slab.
1. Preparation prior to de-shuttering
All equipment or apparatus to be used on site must be set before the commencement of work. Site crew and scaffolding should be adequate for the job.
2. De-shuttering works
Not until the concrete has gathered enough strength to support itself should the forms be removed. When members being supported can support themselves as well as the load they carry, props and centers can be removed.
2.2 Once forms are loosened, the concrete should be wetted properly and kept wet while the removal operation is done.
2.3 Extra caution must be observed when removing forms, so as to avoid shocks or stress reversal in the concrete.
2.4 Forms must be carefully removed to avoid concrete damage.
2.5 Formwork can only be removed after the engineer’s approval and a formwork removal permit has been issued.
2.6 All drop heads, which are dropped 20 meters downwards to where the slabs and beam bottom are to be removed, should be done lose. This should be done with the appropriate tool belt. Three wooden planks must be used as platforms, laid safely in the transoms of the scaffolding support, with not more than 150mm oversail at the board ends.
2.6 During the removal process, only ladders should be used to gain access and only the initial and succeeding horizontal props will be provided by wooden planks.
2.7 Plywood beneath the infill beams must be removed manually while appropriate hand tools should be used to remove slabs. To avoid the obstruction, the slabs must be handed down to the third operative, and if used as a platform, the height when stacked should not be above 1.50m.
2.8 The removal of decking beams should follow the handover to the third operative for stacking. This is to be done after the plywood has been removed and stocked properly in the designated stockyard.
2.9 All shuttering nails detached from plywood should be gathered and disposed of properly.
2.10 Part by part, detach all scaffolding support for beam and slabs.
2.11 Any “foreign object debris” or FOD and excess material should be gathered at a designated stockyard to avoid obstruction and the appropriate grouping of the different materials should be done every day.
2.12 Steps 2.1 -2.11 should be followed through for each succeeding slab. Loading and unloading of all removed materials must be brought to the proper stockyard using the right equipment. Suitable load-bearing scaffolds with toe-boards, mid-rails, and top-rail boards, etc., must be used during the entire operation for access/egress.
• The safety recommendations of the local authorities, as well as those of the approved project HSE plan, must be followed.
• It is compulsory that personal protective equipment (PPE) be used. All staff present at the site must make use of PPE.
• Until the project is complete, there must be a hard barricade demarcating the work area.
• Proper signage must be used.
• On a daily basis, pre-job Toolbox talks must be done prior to the start of the day’s tasks.
• Unauthorized access must be prevented by demarcating exclusive zones.
• All training proofs and certifications must be accessible at the site.
• A Permit To Work (PTW) must be implemented for work at height, and only work at a particular level will be permitted.
• It is mandatory for all workers to attend safety induction and training to help them recognize possible hazards related to the job.
• Adequate lighting and appropriate working platforms must be provided.
• A competent supervisor must always be on the ground to ensure proper management and PPE use at all times.
• Before work every morning, a briefing has to be done by a foreman to emphasize all safe working method steps, roles, and responsibilities.
• Clear access and egress routes must be established.
It is important to consider the de-shuttering or removal of forms, especially when the slab level gets higher. If your building is 10 stories or more, the hazards become extremely high, so correct de-shuttering is even more important.