Temporary Works — Design, Control and the TWC

The register, the briefs, the checks and the permits that stop formwork, scaffolds and props collapsing — the paperwork that actually prevents failures.

Last updated 2026-07-28 by the BuildPedia Editorial Team.

What is Temporary Works — Design, Control and the TWC?

Temporary works is everything that gets built to build the building and then disappears: formwork, falsework, scaffolds, propping, excavation support, hoardings, site cabins on their foundations, crane bases, loading platforms. It routinely carries more load than the permanent structure around it, it is erected and struck under programme pressure by people who will never see it again, and when it fails it fails with people on it. The UK answer to that is BS 5975 — the code of practice for the control of temporary works — and at its heart sits one role: the Temporary Works Coordinator, the TWC.

The system is not complicated, which is why it works. Every item of temporary works on the site goes on a register. Every item gets a design brief that says what it must carry, for how long, and what it bears on. Every design gets a check proportionate to its risk — the check categories run from a simple standard-detail check up to an independent check by another organisation. And nothing gets loaded, and nothing gets struck, without a permit signed by someone with the authority to say no. In the UAE the same discipline applies through the main contractor's procedures and the approvals regimes of DM, DDA or Trakhees — a formwork collapse on a Dubai tower triggers exactly the same investigation questions as one in Manchester, and the answers live in the same documents.

Most temporary works failures investigated in the last fifty years trace back to the same short list: no design brief, an unchecked design, site changes nobody told the designer about, and loads applied before the concrete could carry them. The control procedures exist to close those four doors. A TWC who actually walks the register, and a permit system that is signed on the slab rather than in the site office, is what stands between a wet slab and a pancake of plywood, rebar and people.

When and why is Temporary Works — Design, Control and the TWC used?

Temporary works control starts before the first item is erected and runs to the last strike. It applies on every build type — a house extension with a single acrow prop needs the same logic as a tower jumpform, scaled to risk. The TWC is appointed under CDM 2015 in the UK and under the contractor's and authority requirements (DM, DDA, Trakhees) in the UAE. The reason to invest in the register, the briefs and the permits is brutally simple: formwork and falsework collapses kill more construction workers in a single event than almost any other activity, and nearly every published collapse had a missing or bypassed control that the code already prescribed.

Types of Temporary Works — Design, Control and the TWC

Check category 0 — standard solutions

Site-applied standard details: a TG20-compliant scaffold, a proprietary trench box used within its tables, standard propping layouts. Checked against the published standard by the site — no bespoke design, but still on the register and still permitted.

Check category 1 — simple designs

Bespoke but simple: a straightforward formwork face, a short run of raking props, a loading platform. The design check is done by another competent person in the same organisation, independent of the designer.

Check category 2 — complex designs

Multi-span falsework, jumpform and climbing systems, heavy back-propping schemes, deep excavation support. Checked by someone not involved in the design and not consulted by the designer — often a checking engineer within the organisation.

Check category 3 — novel or high-risk

Unusual structural behaviour, high consequence of failure, or designs outside current codes: the check goes to another organisation entirely, independent of both designer and site.

Temporary Works — Design, Control and the TWC: step by step

Step 1: Appoint the TWC and open the register

Appoint the TWC and open the register — Temporary Works — Design, Control and the TWC, step 1

Before any temporary works is erected, the organisation appoints a Temporary Works Coordinator with the authority to stop work, supported by Temporary Works Supervisors where the site is big enough to need them. The register opens on day one and every item of temporary works goes on it — formwork, scaffolds, props, excavation support, hoarding, crane bases — with its design brief reference, check category, erection and strike status, and permits. If it is not on the register, it does not get loaded.

Step 2: Write the design brief before anyone designs

Write the design brief before anyone designs — Temporary Works — Design, Control and the TWC, step 2

The brief is where most failures are designed out or designed in. It states the loads — wet concrete pressure, stored materials, plant, wind (including funnelling between towers and the full-height sheeting case) — the bearing conditions, the construction sequence, the striking criteria and the site constraints. Guess the ground bearing or forget the loading bay and the best calculations in the world are answering the wrong question.

Step 3: Design to the brief and assign the check category

Design to the brief and assign the check category — Temporary Works — Design, Control and the TWC, step 3

The temporary works designer works to the brief and current codes, and the TWC assigns the check category 0–3 by risk and complexity, not by programme convenience. The designer must state design life, allowable bearing pressures, tie requirements, and any hold points — the things site must not change without going back to design.

Step 4: Check the design independently of the designer

Check the design independently of the designer — Temporary Works — Design, Control and the TWC, step 4

The checker works from the brief and the drawings, not from the designer's calculations alone — a check that only re-reads the arithmetic never finds the wrong assumption. Category 2 and 3 checks go further from the design team. The check certificate is issued before erection, not discovered missing at the pre-pour inspection.

Step 5: Erect under supervision and issue the permit to load

Erect under supervision and issue the permit to load — Temporary Works — Design, Control and the TWC, step 5

Erection follows the design drawings and sequence, supervised by someone competent who knows what a hold point looks like. Once erected, the TWS or TWC inspects against the design — ties in, bracing in, bearing as assumed, no site improvisations — and only then issues the permit to load. Concrete goes in, materials go on, people go up, only after that signature.

Step 6: Manage change and inspect in service

Manage change and inspect in service — Temporary Works — Design, Control and the TWC, step 6

The commonest silent killer: site adapts the scheme — a tie removed for a hoist, a prop relocated for a skip, a waling swapped for what was in the yard. Every change goes back through the designer before it happens, and the register records it. In-service inspections run weekly and after every event — high wind, impact, adjacent excavation — that could have moved something.

Step 7: Strike only on the permit to strike

Strike only on the permit to strike — Temporary Works — Design, Control and the TWC, step 7

Striking is loading in reverse and kills just as efficiently. The permit to strike is issued only when the evidence says the permanent works can carry itself plus whatever construction load remains — cube or cylinder results, maturity calculations, back-propping confirmed in place. Programme pressure does not sign permits; test results do.

Step 8: Close out and learn

Close out and learn — Temporary Works — Design, Control and the TWC, step 8

Each item closes on the register when struck and cleared, with the permits, certificates and inspection records filed. Near-misses — a displaced prop, a missing tie found at inspection — are recorded and fed back, because the industry's collapses are almost always preceded by near-misses that somebody noticed and nobody logged.

Plant and equipment

Temporary works register and permit documentation system
Design and checking software; current codes (BS 5975, TG20, CIRIA guidance)
Survey kit for verifying founding levels, alignment and deflection
Torque wrenches and coupler gauges for connections
Load test equipment where bearing or anchors must be proved
Inspection tags and scafftag-type status systems at each structure
Camera/tablet for photographic records tied to register entries

Quality control checks

Register live and audited — every physical item traceable to an entry
Design briefs complete and signed before design starts
Check certificates at the correct category issued before erection
Permits to load signed after physical inspection, not desk review
Permits to strike supported by strength evidence (cubes, cylinders, maturity)
In-service inspection records weekly and post-event
Change control: every site modification traceable through the designer

Safety considerations

No loading of any temporary works without a permit to load
Exclusion zones under and around erection and striking operations
Hold points enforced — work stops until the inspector signs
Wind action plan: forecast thresholds that trigger inspections and stoppages
Competence: erectors, supervisors and the TWC trained and appointed in writing
Authority approvals in the UAE (DM/DDA/Trakhees) for façade-adjacent scaffolds, gantries and tower crane bases

Common defects

Items in use that never made it onto the register
Design briefs missing bearing conditions or construction loads
Checks done at a lower category than the risk warranted
Ties and bracing omitted or removed on site without design referral
Striking on programme pressure with no strength evidence
Permits signed retrospectively after the concrete went in

Best suited for

Every site that erects formwork, falsework, scaffolds or propping — which is every site
Tower projects with climbing systems, loading bays and heavy back-propping
Excavation support and basement works where ground loads are temporary and lethal
Refurbishment and demolition where the existing structure is itself an unknown
Multi-contractor sites where one party must hold the whole register

How long does Temporary Works — Design, Control and the TWC take?

Typical duration: Register set-up and first briefs: 1–2 weeks ahead of first erection. Design and check per item: 3 days for a simple scaffold design to 4–6 weeks for a climbing system or major falsework. Permits: same day as inspection. The control regime runs for the whole programme..