Why it matters

Formwork holds wet concrete until it can carry itself. Wet concrete is very heavy, and it arrives fast. If the shores, bracing or base are wrong, the deck can fold with people on it.

In January 2014 two formwork structures collapsed at Singapore sites on consecutive days. Both gave way while workers were casting a slab. MOM's early findings showed the structures could not carry the load of the pour. The workers got clear with one minor injury. MOM warned that such collapses can kill many people.

Collapse is the worst case. Falls from the deck edge, falling materials, and nails and ties left sticking out cause many more injuries.

What counts as formwork and temporary works

In Singapore law, a formwork structure includes the formwork itself, the falsework, the shores and any other support. Falsework is the frame of supports and bracing under the forms.

Formwork is one kind of temporary works. Others include back-propping, excavation shoring, cantilevered and material platforms, and scaffolds. They share one rule. They must be designed for the loads they will carry, built to that design and checked before use.

One person in charge

UK practice is to appoint a temporary works coordinator. This person makes sure each design is prepared, checked and built correctly, and can stop unsafe work. It works well on any busy site.

Order of controls

  • Eliminate. Use precast elements or permanent formwork so less temporary support is needed at height.
  • Substitute. Use a proven proprietary system, built to the manufacturer's manual. Do not mix parts from different systems.
  • Engineer. PE design where required, a safety factor of at least 2, bracing in both directions, sole plates, edge protection and safe access.
  • Administer. A formwork supervisor on every job, inspection before the pour, a controlled pour sequence, an exclusion zone, and a permit to strike.
  • Personal protection. Helmets, boots, gloves and harnesses where edge protection is not yet in place. None of these help if the deck collapses.

Design and the PE

All formwork must carry the total dead, live and impact loads with a safety factor of at least 2. It must be of sound material, free from defects and properly braced or tied.

A professional engineer must design the formwork if it is more than 9 metres high, has shores in two or more tiers, or carries a slab or beam over 300 mm thick. The design and drawings stay on site. No one alters the structure unless a PE has reviewed and endorsed the change.

MOM has reminded PEs to get the manufacturer's manual when they specify a proprietary system. Avoid mixing systems. If you cannot avoid it, the PE must check the combined structure works as one.

Erecting: the formwork supervisor

The employer must appoint a formwork supervisor with adequate safety and health training for this work. Formwork is only built, changed or taken down under that person's immediate supervision.

The supervisor makes sure every part is properly erected, seated, connected, braced and tied. When the formwork is complete, they inspect it against the drawings. They record the result in a register kept on site and report any unsafe condition to the occupier at once.

  • Horizontal and diagonal bracing in both directions, unless the design says the structure is stable without it.
  • Shores seated firmly top and bottom and fixed so they cannot move.
  • Sole plates under shores that stand on the ground. Check the ground is what the design assumed.
  • Adjustable props locked once set. Shores protected from vehicles and swinging loads.
  • For two or more tiers: tiers connected vertically, and safe, signed access for inspection.

The pour

Before casting into PE-designed formwork, the PE inspects and certifies it, including any changes. MOM expects the PE to inspect jointly with the site engineer or formwork supervisor. Missing, undersized or substituted parts must be fixed before the certificate is issued.

Place concrete so it does not destabilise the formwork. Follow the planned pour sequence and rate. Do not dump a full bucket in one spot.

Only people needed for the concrete work stay near the formwork. The formwork supervisor watches the structure throughout. Look for props moving, decks deflecting, bracing bending or ground settling under sole plates. If you see any of it, stop the pour and get people off.

Watch underneath

In the 2014 Yishun collapse the support structure started to sink before it gave way. Someone must watch below the deck during the pour, from a safe position.

Striking and reshoring

Do not start dismantling until the concrete has set. Good practice is to wait for a competent person to confirm the concrete is strong enough and to authorise striking.

Take shuttering down in a planned order, and keep enough props in to stop parts falling. Remove dismantled materials promptly, or stack them away from work areas and walkways. Pull out, cut or bend over nails, wire ties and other sharp leftovers.

Put in reshores where slabs or beams need support after striking, or will carry loads from work above. Seat and secure reshores the same way as shores. The formwork supervisor inspects them and records the result in the register.

What the rules require (Singapore)

Part IX of the Workplace Safety and Health (Construction) Regulations 2007 covers formwork structures. MOM's advisory for PEs also points to Singapore Standard SS 580 for formwork.

  • Sound, suitable, braced formwork with a minimum safety factor of 2 (reg 58).
  • Bracing in both directions; shores seated and secured; sole plates on ground (reg 59).
  • A trained formwork supervisor appointed and present for all erection, alteration and dismantling (reg 60).
  • Supervisor inspects on completion, keeps a register and reports unsafe conditions (regs 61, 62).
  • PE design for formwork over 9 m, multi-tier shores, or slabs or beams over 300 mm; PE certificate before use (regs 63, 64).
  • PE inspection and certificate before any pour into PE-designed formwork; non-essential people kept away during the pour (reg 65).
  • No striking before the concrete is set; sharp leftovers made safe (reg 66). Reshoring where needed, inspected and recorded (reg 68).
  • Cantilevered platforms, and material platforms loaded to 1,000 kg or more, are PE-designed and certified, and inspected at least every 7 days (regs 46 to 49).
No certificate, no pour

Where a PE designed the formwork, casting must not start until that PE, or another PE the occupier appoints, has inspected it and certified it safe.

Common mistakes

  • Props, braces or base jacks missing or swapped for something "close enough".
  • Mixing frames and props from different systems without a PE check.
  • Changing the layout on site to clear a service run, without telling the PE.
  • Sole plates on soft or backfilled ground.
  • Pouring too fast, or all in one spot.
  • Workers standing under the deck during the pour.
  • Striking early to reuse the forms, or no reshores under fresh slabs.
Built to look right

Formwork can look solid and still be short of props or bracing. Check it against the drawing, part by part, not by eye.

Use it on site: the formwork and temporary works checklist and the toolbox talk to brief your crew.

Sources

  1. Workplace Safety and Health (Construction) Regulations 2007, Singapore Statutes Online (AGC).
  2. Advisory for professional engineers on formwork safety (January 2014), Ministry of Manpower.
  3. Code of practice on safety and health in construction (revised 2022), International Labour Organization.
  4. Temporary works, UK Health and Safety Executive.

This is practical guidance, not legal advice. Laws and codes of practice change; always check the current official text and your site's own procedures.