Shoring is temporary support used during construction to hold up a structure, or to hold back soil, until the permanent work can support itself. In buildings it usually means the posts and frames that carry formwork and wet concrete. In excavation work it means the system that keeps trench and basement walls from collapsing.
Shoring is also used to support existing buildings during renovation, underpinning or repairs.
Types of shoring
| Type | What it supports | Typical use |
|---|---|---|
| Post shores (adjustable steel or aluminium) | Formwork and slabs | Elevated concrete slabs and beams |
| Frame or tower shoring | Heavier or taller formwork | High floor-to-floor heights, transfer slabs |
| Reshoring and backshoring | Stripped slabs carrying loads from floors above | Multi-storey concrete buildings |
| Raking, flying and dead shores | Existing walls and floors | Renovation, demolition, damaged buildings |
| Hydraulic and timber trench shores | Trench walls | Utility and service trenches |
| Soldier piles and lagging, sheet piles, secant piles | Excavation walls | Basements and deep excavations, often near property lines |
Shoring vs reshoring
Shores carry the formwork and fresh concrete during the pour. Once the concrete has enough strength the forms are stripped, but the slab may still be too young to carry the weight of the next floors being poured above it. Reshores are then installed to share those loads down through several floors. The engineer sets the shoring and reshoring sequence and removal criteria, especially for post-tensioned slabs.
Shoring vs scaffolding
A scaffold is a working platform for people and materials. Shoring carries structural loads. Some frame systems can be set up as either, but a scaffold should never be used to support formwork or structure unless it has been designed and approved for that load.
Shoring in excavations
For trenches, US OSHA rules (29 CFR 1926 Subpart P) recognise three ways to protect workers: sloping or benching the walls, shoring them, or shielding workers with a trench box. Protection is generally required in trenches 5 feet (1.5 m) deep or more unless the excavation is in stable rock, and excavations 20 feet (6.1 m) deep or more need a protective system designed by a registered professional engineer or based on tabulated data approved by one. Canada, the UK and Australia have their own rules, so check your jurisdiction.
Safety and inspection tips
- Install shoring to the approved shoring drawings, not by eye.
- Check mudsills and base plates bear on firm, level ground or slab, and that shores are plumb and braced.
- Inspect before each pour and after any impact, heavy rain or freeze-thaw.
- Have a competent person inspect excavations daily and after rain or other changes.
- Never remove shores or reshores early without the engineer’s approval.
Related terms
Related templates and guides
- General guide for formwork and falsework
- OSHA trenching and excavation guide
- Safety meeting: excavation and trenches
- Work permit: excavation
Frequently asked questions
What is the purpose of shoring?
Shoring holds something up or holds something back while it cannot support itself. In buildings that usually means supporting formwork and new concrete until it gains strength. In excavations it means supporting the soil walls so they do not collapse on workers or undermine nearby structures.
What are the three types of trench protection?
US OSHA recognises sloping or benching the trench walls, shoring them with supports such as hydraulic shores, and shielding workers with trench boxes. Shoring prevents soil movement, while a shield protects workers if the soil does move. A competent person picks the system for the soil and depth.
What is the difference between shoring and reshoring?
Shoring supports formwork and fresh concrete during construction. Reshoring is placed after the forms are stripped, under a slab that can carry its own weight but not yet the loads from the floors being built above it. The engineer specifies when shores and reshores can be removed.
Do you need an engineer to design shoring?
Usually. Formwork shoring, reshoring and most excavation shoring systems are designed by an engineer or follow manufacturer tabulated data. Deeper excavations and those near existing structures normally need a site-specific engineered design. Check your local regulations and the contract requirements.
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