Propping and Back-Propping — Safe Work Method Statement
Safe Work Method Statement for installing, adjusting and removing temporary props and back-props under suspended slabs, beams and walls during multi-storey construction and structural alterations, following an engineered propping design.
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Temporary propping holds up loads that the permanent structure can't yet carry on its own. Back-props go under the floors below a new slab pour so that the weight of the formwork, wet concrete and construction loads is shared across several floors that are not yet at full strength. Propping is also used during alterations to hold up walls, beams or slabs while load-bearing elements are removed or replaced. Work that needs temporary support to prevent structural collapse is High Risk Construction Work, so a SWMS is required. Most propping jobs also involve falls of more than 2 metres at slab edges and voids, and work near moving plant.
Propping hazards are mostly about getting the design and sequence right. Props must be installed to an engineered propping design that shows prop type, spacing, capacity, and the floors to be back-propped. They must sit plumb on a sound base, with head and base plates fully bearing and pins and collars engaged. Removing back-props too early, or in the wrong sequence, can overload a young slab and cause cracking or progressive collapse. Back-props are only removed when the engineer says so, usually based on concrete strength and the floors above. Props knocked by plant, pallet jacks or trolleys, or loosened as the slab deflects, can drop out, so they need to be checked and kept tight.
For alterations, the existing structure needs to be assessed before anything is removed: what the wall or beam is carrying, where the load goes, and whether the floor under the props can take the concentrated load. Needle beams, strongbacks and props must be in place and loaded before the element is cut out. Props are heavy and awkward to carry, and adjusting them involves pinch points at the inner tube and pin.
No specific licence is required to install props, but the work must be supervised by someone competent with the propping system and must follow the engineer's design. Any change to prop layout, prop type or removal sequence needs the engineer's approval.
Customise this template with: the structure and levels involved; the propping design reference and engineer's contact; prop types and rated capacities; the back-propping levels and removal criteria; for alterations, the element being removed and the temporary support scheme; how props are protected from plant; the inspection frequency; and who signs off before loading and before removal.
Personal Protective Equipment
High Risk Construction Work Types
- •Risk of a person falling more than 2 metres
- •Structural alterations or repairs that require temporary support to prevent collapse
- •Work in an area with movement of powered mobile plant
Risk Assessment
1.Reviewing the propping design and site conditions
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Props installed to the wrong layout or capacity | Catastrophic | Obtain the engineer's propping design before work starts and brief the crew on it. Check that the props on site match the design type and capacity. Do not substitute props or change spacing without the engineer's written approval. Keep a copy of the design at the work area. | Low | Propping Supervisor / Structural Engineer |
| Props bearing on a base that can't carry the load | High | Confirm what the props will bear on: slab, ground or existing floor. On ground, use sole plates on compacted, level ground as the design specifies. For alterations, check with the engineer that the floor under the props can carry the concentrated load, and prop down through lower floors if required. | Low | Propping Supervisor / Structural Engineer |
2.Moving and handling props
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Strain and crush injuries from carrying and stacking props | Moderate | Move props in stillages by crane, forklift or prop trolley. Carry long props two-person. Stack props in stillages, not loose against walls. Keep the inner tube pinned during carrying so it can't slide out. | Low | Propping Crew |
3.Installing props and back-props
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Prop buckling or dropping out from poor installation | Catastrophic | Install props plumb, with base and head plates fully bearing and centred under the bearer or slab. Use the correct pins, never bolts or rebar, and engage collars fully. Tighten props to the design, not by hammering. Install in the sequence shown on the design. | Low | Propping Crew |
| Pinch and crush injuries adjusting inner tubes and collars | Moderate | Support the inner tube while removing or inserting the pin. Keep fingers clear of pin holes and the collar. Wear gloves. | Low | Propping Crew |
| Falls at slab edges and voids while propping | Catastrophic | Keep edge protection and void covers in place while propping near edges. Do not remove them to place props without an agreed alternative control. Use a mobile scaffold or platform ladder for high props instead of climbing. | Moderate | Propping Supervisor |
4.Temporary support for structural alterations
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Collapse when a load-bearing wall, beam or column is removed | Catastrophic | Install needles, strongbacks and props to the engineer's design, and load them, before any load-bearing element is cut or removed. The engineer or supervisor inspects the temporary support before removal starts. Keep everyone out from under the element during removal. Leave temporary supports in place until the new element is installed and the engineer approves removal. | Moderate | Propping Supervisor / Structural Engineer |
| Disturbing asbestos or silica-containing materials when breaking through walls | High | Check the asbestos register before cutting or breaking existing walls and ceilings in older buildings. Cut masonry and concrete using wet methods or on-tool extraction with an H-class vacuum, and wear a P2 respirator. | Low | Propping Supervisor |
5.Inspection and protection of props in service
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Props knocked out by plant or loosened by slab movement | High | Barricade propped areas or mark them so pallet jacks, trolleys and plant cannot strike props. Inspect props daily and before and after each pour, and retighten loose props. Report any bent, damaged or missing prop to the supervisor immediately. Do not use props as anchor points or to support other loads. | Low | Propping Supervisor / Site Supervisor |
6.Removing props and back-props
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Overloading a young slab by removing props too early or in the wrong order | Catastrophic | Remove props and back-props only when the engineer confirms in writing that removal criteria have been met, such as concrete strength and the number of floors above. Follow the removal sequence on the design, usually releasing evenly across a bay rather than one side at a time. Stop and report any cracking, deflection or noise during release. | Low | Propping Supervisor / Structural Engineer |
| Struck by a prop falling as it is released | Moderate | Hold the prop while releasing it and lower it under control. Keep others clear of the release area. Never knock props out with a hammer. | Low | Propping Crew |
Relevant Codes of Practice
Worker Acknowledgement
By signing below, I confirm that I have read, understood and agree to comply with this Safe Work Method Statement.