Most structural failures during construction happen not to the finished structure but to the partially completed one. Temporary works — propping, needling, shoring, façade retention, excavation support, falsework and edge protection — hold a building up while the permanent structure is altered or built. This guide explains what temporary works cover, why they need design rather than improvisation, who is responsible under UK practice, and how the temporary and permanent designs relate to one another.
What temporary works actually are
Temporary works are any parts of the works that support or protect an existing or permanent structure, or the people working on it, and which are removed once they are no longer needed. They are engineered structures in their own right, even though nobody sees them once the project is finished.
On a domestic project temporary works might be a pair of Acrow props and a needle beam through a wall. On a city centre development they might be a full façade retention scheme, a propped basement box and a tower crane base. The scale differs; the engineering principle does not.
- Vertical propping to floors, roofs and walls during alteration
- Needling — temporary beams passed through a wall to support the masonry above
- Raking and flying shores stabilising walls laterally
- Façade retention where only the front elevation is kept
- Excavation support, trench boxes and sheet piling
- Falsework supporting wet concrete until it gains strength
- Temporary bracing of steel frames before the permanent bracing is installed
- Crane bases, hoist ties, loading platforms and edge protection
Why they matter more than most people expect
A completed building has redundancy: floors act as diaphragms, walls restrain one another, and load has several routes to the ground. Part-way through an alteration, that redundancy is deliberately removed. The moment a load-bearing wall is opened up, the structure above is being held by whatever the contractor has installed — and by nothing else.
Temporary conditions are also short-lived and often unrecorded, which is precisely why they are under-analysed. Wind can be a more onerous action on a freestanding retained façade than on the finished building. Construction plant can impose loads on a floor far exceeding its design imposed load. Neither situation appears in the permanent design.
Who is responsible for temporary works
In UK practice, temporary works are normally the contractor's responsibility, because they follow from the construction method the contractor chooses. Larger organisations appoint a Temporary Works Coordinator to manage the process, maintain a temporary works register and ensure that designs are checked before use, in line with BS 5975.
That does not remove the permanent works designer from the picture. The engineer designing the alteration must identify where the permanent design assumes a particular sequence, where stability depends on elements not yet built, and where the existing structure is sensitive to being propped or loaded. Those assumptions belong on the drawings and in the calculations.
Under the CDM Regulations, the client, principal designer and principal contractor all have duties to plan and manage construction so that it can be carried out safely. Temporary works sit squarely within that.
Propping and needling on domestic alterations
On house alterations the most common temporary works are propping and needling. Needles are temporary beams driven through the wall above the proposed opening, supported on props each side, so the masonry and any floor or roof load above is carried while the opening is cut and the new beam installed.
The details that matter are rarely the props themselves. They are what the props stand on, how loads spread into the floor below, whether propping continues down through every storey to a solid bearing, and whether the props are positioned close enough to the wall face to control the masonry.
- Props must be founded on something capable of carrying the load — not on a suspended timber floor or a thin screed
- Multi-storey propping must line through vertically, storey by storey
- Needle spacing depends on the strength and condition of the masonry above, not on convenience
- Props must be plumb, correctly pinned and not overextended
- Nothing should be removed until the permanent structure has been installed, bedded and is capable of carrying load
Loads on temporary works
Temporary works are designed for the loads present during construction, which are not the same as the design loads for the finished building. Permanent load may be lower because finishes are absent; construction load may be far higher because of stacked materials, plant and impact.
Wind is often the critical action on temporary conditions. A retained façade, a partially braced frame or a freestanding gable can be far more exposed than the completed structure, and the design must consider that exposure for the whole period it exists.
Sequence and removal
Temporary works are inseparable from sequence. The order in which elements are removed, installed and loaded determines what needs propping and for how long. A clear sequence stated on the drawings is the cheapest form of risk control available on a project.
Removal deserves the same care as installation. Props should be released gradually and in a defined order, so that the permanent structure takes up load progressively rather than suddenly. Mortar bedding, grouting and concrete all need to reach adequate strength before they are relied upon.
Temporary works on existing and industrial buildings
Existing buildings introduce uncertainty. Masonry may be lime-mortared and weak in shear, floors may not act as diaphragms, and previous alterations may already have removed load paths. Temporary works design in these situations is as much about appraisal as calculation.
In operational industrial facilities, temporary works must also accommodate continued production: access routes, exclusion zones, crane operations, plant vibration and the practical reality that the client cannot simply stop work while the structure is opened up.
What good temporary works documentation looks like
- A stated design brief — what is being supported, for how long, and under what loading
- Calculations for the props, needles, beams, foundations and bearings
- A drawing showing prop positions, sizes and bearing arrangements
- A written sequence for installation, alteration and removal
- A named designer and an independent check appropriate to the risk
- Inspection and sign-off before the permanent structure is disturbed
Key considerations
- Temporary works are engineered structures and should be designed, not improvised on site.
- The construction stage frequently governs — wind and plant loads can exceed permanent design actions.
- Propping must reach a competent bearing, continuously, through every level.
- Sequence is part of the design; state it on the drawings and follow it on site.
- Remove props progressively, only once the permanent structure can carry load.
- On existing buildings, appraise before propping — assumed load paths are often absent.
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Important limitations
This publication provides general information only and does not constitute structural engineering advice, design or assessment. Project-specific engineering requirements should be established by an appropriately qualified structural engineer.
BES-TG-008 · Version 1.0 · Reviewed August 2026 · Next scheduled review August 2027