Temporary Works in London Home Construction: Shoring, Propping, and What They Cost

Temporary works are the engineering structures or measures that are needed during construction to support existing or new elements until permanent works are completed. In London residential construction, temporary works are encountered in virtually every project that involves structural alteration — and because London's Victorian and Edwardian housing stock was built without the foundations, connections, and structural continuity that modern building design assumes, the temporary works requirements for seemingly simple alterations can be more demanding than homeowners expect.

This guide explains the common types of temporary works, when they are needed, and what they cost.

Temporary works are typically needed in London residential projects when:

Structural openings are being formed — removing a wall or forming a new opening in an existing wall requires the load above the opening to be temporarily supported while the beam and padstones are installed. This is the most common temporary works scenario in London residential work.

Floors or roofs are being temporarily weakened — loft conversions that involve replacing or strengthening the floor structure require the existing floor to be supported while the new structure is introduced. Similarly, roof alterations for dormers may require temporary roof support to maintain structural stability during the works.

Basements are being excavated — basement excavation adjacent to existing foundations requires the existing foundations to be supported to prevent differential settlement during excavation. This may involve underpinning, contiguous piling, or ground anchor systems as permanent works with temporary propping and shoring during the transition.

Demolition of structural elements — any demolition of load-bearing walls, columns, or beams requires the loads they carry to be temporarily re-routed before removal.

Party walls are exposed — works that temporarily expose or weaken a party wall (the shared wall between two properties) may require temporary support to prevent movement affecting the neighbouring property.

Dead shoring — vertical props (typically adjustable steel acrow props) that support horizontal needle beams through a wall or under a floor. Dead shoring is used to transfer vertical loads downward and is the most common temporary support method for forming openings in London terraced houses. The props sit on a strong floor (typically the ground floor slab or a spreader board) and bear against a needle beam threaded through the wall above the proposed opening.

Raking shores — inclined props that lean against the face of a wall to provide lateral support. Raking shores are used where a wall has become unsupported laterally (e.g., where an adjacent structure has been demolished) or where there is a risk of outward movement during excavation. Less common in typical London residential work than dead shoring.

Propping systems for excavation — where basement excavation is carried out adjacent to existing foundations, horizontal props or ground anchors may be required to support the excavation face and prevent movement of the surrounding ground. This is more specialised and is typically designed and specified by the structural engineer.

Scaffold-based temporary roofs — for roof alterations or where the existing roof must remain weathertight during construction of a new structure, temporary waterproofing or a temporary roof structure may be required. This is relevant to some loft conversion schemes where the existing roof is removed before the new dormer and roof structure are in place.

CDM 2015 requires that temporary works are properly designed, checked, and supervised. The key roles are:

Temporary Works Designer — a competent person (typically the structural engineer or a specialist contractor) who designs the temporary works scheme for a specific project. For most London residential projects, the structural engineer designs the temporary propping scheme for openings as part of their structural package.

Temporary Works Coordinator — under BS 5975:2019 (the British Standard for temporary works), a Temporary Works Coordinator should be appointed on projects where temporary works have significant risk. On smaller London residential projects, this role is often combined with the structural engineer or the site manager. On larger or more complex projects (particularly basement conversions or significant structural alterations), a dedicated TWC appointment may be appropriate.

For London homeowners, the key practical point is that temporary works schemes for structural openings and similar work should always be signed off by the structural engineer before the works proceed — not improvised by the contractor on site.

Temporary works costs depend heavily on the complexity and duration of the works:

Standard opening formation (acrow props and needles): typically included within the structural alteration cost — labour to set up and strike propping for a standard single opening is typically £300–£800, with materials (props and timbers) adding a similar amount. For large openings or multiple simultaneous openings, props can be hired for the duration of the works.

Basement temporary propping: for basement excavation adjacent to existing foundations, temporary propping design and installation can range from £3,000–£15,000 depending on the depth and extent of excavation and the ground conditions.

Temporary roof structure: a temporary weather protection structure for a roof alteration can range from £2,000–£8,000 depending on the size of the roof area and the duration required.

rcbGroup coordinates temporary works with our structural engineering partners on all London residential projects involving structural alteration. We never form structural openings without an engineer-approved propping scheme in place. Contact our team to discuss the temporary works requirements of your London project.