7.3 Temporary Works Management: Formwork, Falsework & Support Structures (CR 12)
Key Takeaways
CR 1 defines temporary works as any falsework, formwork, support work, scaffold, shoring or other temporary structure designed to provide support or means of access during construction work.
CR 12(1) requires a temporary works designer appointed in writing to design, inspect and approve erected temporary works before use; CR 12(2) requires all operations to be supervised by a competent person appointed in writing.
CR 12(3)(f) requires inspection immediately before, during and after placing concrete, after inclement weather or other imposed loads, and at least daily, with results recorded in a register.
CR 12(3)(g) bars casting concrete until the competent person gives written authorisation, and CR 12(3)(k) bars removal until written authorisation once the concrete can safely carry its own weight and imposed loads.
The Tongaat Mall (2013) and Grayston Drive bridge (2015) collapses each killed two people and led to Section 32 inquiries; both reinforce clear design ownership, conformity with drawings and lateral stability.
7.3 Temporary Works Management: Formwork, Falsework & Support Structures (CR 12)
1. What Counts as Temporary Works
Until concrete gains strength, the permanent structure depends entirely on temporary works. Failures are among the most devastating construction disasters, often killing several people at once. Construction Regulation 1 defines "temporary works" as:
"any falsework, formwork, support work, scaffold, shoring or other temporary structure designed to provide support or means of access during construction work"
The 2017 guideline notes explain that falsework is a combined system of formwork and support work, and formwork is the temporary or permanent shutters used to form wet concrete into structural elements, horizontal or vertical. Scaffolds, trench shoring, propping of existing structures and crane bases built for construction all fall within the definition.
2. Appointments under CR 12(1)–(2)
- CR 12(1): the contractor must appoint a temporary works designer in writing to design, inspect and approve the erected temporary works on site before use.
- CR 12(2): all temporary works operations must be carried out under the supervision of a competent person appointed in writing for that purpose.
The guideline notes add that CR 12(1) is a three-function appointment: designing, inspecting and approving may be done by one person or by different persons, but each must be mandated by the client or contractor to perform the function. Competency should follow a risk-based approach. The Regulation does not require the designer to be a registered professional engineer, but for complex or high-consequence temporary works clients commonly specify one, and many require an independent design check.
The Temporary Works Designer's Own Duties (CR 6(2))
The designer of temporary works must ensure that the works are adequately designed to support all anticipated vertical and lateral loads; that the design is done with close reference to the structural drawings issued by the contractor (consulting the contractor where uncertain); that all drawings and calculations are kept at the designer's office and made available to an inspector on request; and that the loads caused by the temporary works and any imposed loads are clearly indicated in the design.
3. The Contractor's Duties under CR 12(3)–(4)
The contractor must ensure, among other things, that:
- (a) temporary works are adequately erected, supported, braced and maintained by a competent person to carry all anticipated vertical and lateral loads, and are not loaded beyond their design;
- (b) they are erected with close reference to the structural design drawings (consulting the structural designer where uncertain);
- (c) detailed, activity-specific drawings are kept on site and available to the inspector, other contractors, the client, its agent and employees;
- (d) everyone who erects, moves or dismantles them is adequately trained and instructed;
- (e) all equipment is examined for suitability by a competent person before use;
- (f) they are inspected by a competent person immediately before, during and after the placement of concrete, after inclement weather or any other imposed load, and at least daily until removed, with results recorded in a register on site;
- (g) no person casts concrete until written authorisation has been given by the competent person;
- (h) damaged or weakened temporary works are removed or reinforced immediately;
- (i)–(j) deck panels are secured, release agents do not create slip hazards, and solvents or oils do not harm health;
- (k) after casting, temporary works stay in place until the concrete can safely carry its own weight and any imposed load, and are not removed until written authorisation is given by the competent person;
- (l) foundation conditions can withstand the loads in accordance with the design;
- (m) safe access is provided by secured ladders or staircases;
- (n) drawings or other documents include construction sequences and method statements;
- (o) the designer has the latest revision of the structural drawings;
- (p) each design and drawing is used only for its intended purpose and the specific part of the site; and
- (q) temporary works drawings are approved by the temporary works designer before erection.
CR 12(4) repeats that no contractor may use a temporary works design and drawing for any other purpose.
4. Design Loads and Stability
Temporary works are designed using the actions in SANS 10160: the self-weight of formwork and falsework, wet concrete (about 24–25 kN/m³) and reinforcement, construction live loads from people and equipment, impact and heaping during placement, wind on exposed formwork, and a notional horizontal load to cover out-of-plumb erection. Common failure causes are:
- Foundations: props on unprepared or saturated ground punch through; soleplates and verified bearing capacity are needed (CR 12(3)(l)).
- Lateral stability: props carry vertical load well but resist sway poorly, so falsework needs diagonal bracing in both directions or a positive connection to stable permanent structure.
- Prop extension and pins: an adjustable steel prop is a slender column whose buckling capacity falls with the square of its effective length:
so capacity drops sharply as props are extended, and only the manufacturer's high-tensile pins may be used (reinforcing bar off-cuts shear or bend under load). Use the manufacturer's load tables for the actual extension.
5. The Hold Points: Cast, Monitor, Strike
| Gate | Requirement | Typical site record |
|---|---|---|
| Before the pour | Inspection immediately before placement (CR 12(3)(f)); drawings approved (12(3)(q)); written authorisation to cast (12(3)(g)) | Signed "Permit to Cast" clipped to the pour record |
| During the pour | Inspection during placement (12(3)(f)); pour sequence and rate controlled to avoid heaping and excess pressure on vertical forms | Watchers below and beside the deck; telltales; evacuation signal agreed |
| After the pour | Inspection after placement, after inclement weather and at least daily (12(3)(f)) | Daily register entries |
| Striking | Kept in place until the concrete can carry its own weight and imposed loads; written authorisation to strike (12(3)(k)) | Cube results against the engineer's striking criteria; signed "Permit to Strike"; back-propping sequence |
In multi-storey work, newly cast slabs cannot carry the next pour alone, so the designer specifies back-propping through one or more floors below.
6. Lessons from South African Collapses
- Tongaat Mall, KwaZulu-Natal (19 November 2013): part of a shopping centre under construction collapsed during construction, killing two workers and injuring 29. The Department held a Section 32 inquiry into the design, construction and approvals.
- Grayston Drive pedestrian bridge, Sandton (14 October 2015): the temporary works supporting a bridge under construction collapsed onto the M1 motorway during afternoon traffic, killing two people and injuring 19. The Department's Section 32 inquiry (February 2016 to September 2017) heard conflicting evidence on who had designed the temporary structure, and witnesses cited a wind gust combined with weaknesses in the structure; its findings were critical of the principal contractor's management of the temporary works.
The common lessons map directly onto CR 12: a clearly appointed and mandated designer who owns the design, erection that matches the approved drawings, attention to lateral stability, inspections and written authorisations at every hold point, and an independent check for high-consequence temporary works, especially over public roads.
7. The CHSM's Role
The CHS Manager checks that the CR 12(1) and (2) appointments exist and are mandated, that approved drawings are on site and current, that the CR 12(3)(f) register is complete, that no pour starts without written authorisation, and that production pressure never brings striking forward without the competent person's written approval.
A principal contractor is casting a 350 mm thick suspended reinforced concrete podium slab on a major commercial mixed-use project in Rosebank. Ready-mix concrete trucks have arrived and are waiting to discharge into a concrete boom pump. However, the site Temporary Works Inspector has not yet arrived to conduct the statutory pre-pour inspection, and the formwork has several adjustable props that appear out of plumb. The construction manager orders the pump operator to begin pouring immediately to avoid concrete batch slumping and delay penalties. As the SACPCMP Construction Health and Safety Manager, what is your statutory obligation under Construction Regulation 12(3)(f)?
Authorize the pour provided additional steel acrow props are hand-held under the slab by laborers during concrete discharge.
Allow the pour to begin provided the pump operator signs an indemnity form acknowledging that the falsework has not been inspected.
Halt the pour: CR 12(3)(f)-(g) require inspection and written authorisation first, and the props must be corrected.
Permit the concrete pour to proceed around the perimeter of the slab while the temporary works supervisor visually inspects the propping underneath.
On a multistory residential development in Umhlanga, the contractor casts a post-tensioned transfer beam and slab structure. Five days after the pour, the site production manager orders the carpentry crew to strike all falsework propping beneath the transfer beam so that the materials can be reused on the floor above, arguing that the concrete surface feels completely hard and passes a rebound hammer (Schmidt hammer) test. No concrete test cubes have been crushed. How is this action evaluated under Construction Regulation 12 and SANS 10100 engineering standards?
It breaches CR 12: supports stay until cube tests show the required strength and the temporary works designer authorises striking.
The contractor may strike the propping after 72 hours provided the ambient temperature has remained above 25 degrees Celsius throughout the curing period.
The action is permitted provided the site supervisor signs a daily safety task instruction confirming that the deck was struck safely.
The action is acceptable because rebound hammer surface tests are legally recognized as definitive proof of internal concrete compressive strength under SANS 10100.
During an internal health and safety audit of heavy falsework propping supporting bridge deck formwork in Polokwane, the CHS Manager inspects the adjustable telescopic steel props. The auditor observes that on over 30 props, the original high-tensile proprietary steel pins are missing and have been replaced with bent lengths of 10 mm mild steel reinforcing rebar off-cuts. Additionally, several props are extended to 4.2 meters with no lateral cross-bracing installed. What are the severe engineering hazards associated with this setup?
Rebar pins lack certified shear capacity, and unbraced 4.2 m props have much lower buckling capacity, risking collapse.
The configuration is completely safe provided the bridge deck concrete is poured using a crane bucket rather than a continuous concrete pump line.
The only concern is that rebar off-cuts may scratch the paintwork of the props, which accelerates atmospheric surface rusting.
The rebar off-cuts are acceptable provided they are wrapped in protective PVC electrical insulation tape to prevent galvanic corrosion.
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