Tunnel Formwork or Panel Formwork? A Decision Table

On a housing project the formwork decision sets one of the largest lines in the cost table. The question is usually this: tunnel formwork or panel formwork (conventional steel/aluminium)? The answer lies in the number of repetitions and in the layout.

The basic difference

With panel formwork, wall and slab are separate operations: the wall is cast, left to cure, then the slab formwork is erected and cast. With tunnel formwork the two are a single pour. That one sentence is the source of every difference below.

Decision table

	Tunnel formwork	Panel formwork
Storey cycle	1–2 days	5–10 days
Pours per storey	1	2 (wall + slab)
Labour	Small, trained crew	Large number of formworkers
Crane	Mandatory, high capacity	Small crane is enough
Initial investment	High	Moderate
Layout flexibility	Low — the plan must repeat	High — every floor can differ
Surface quality	Exposed concrete, no render needed	Joints visible, usually rendered
Economic threshold	~100+ repetitions	Any scale
Stripping risk	Controlled, form stays as one unit	Piece by piece, higher fall risk
Site area	Needs manoeuvring space for the form	More flexible

Which project calls for which

Choose tunnel formwork when:

The same floor plan repeats at least 60–100 times (multi-block housing estates, social housing projects)
The delivery period is short and structural speed is decisive
There is a tower crane of adequate capacity on site
Exposed concrete is acceptable (saving on render and plaster labour)

Choose panel formwork when:

There are few blocks and the layout changes on every floor
Crane capacity is limited, or there is no crane
The work involves complex geometry (asymmetric walls, stepped levels)
The investment budget cannot allocate a large share to formwork

Where the cost actually moves

Tunnel formwork increases the formwork line and reduces the labour and time lines. Comparing on formwork price alone is misleading; the same table has to include:

Formworker man-days
The financing cost of the structural programme (interest, lost rent)
Render and plaster labour, which falls substantially with tunnel formwork
Crane hire or depreciation
The residual value of the formwork at the end of the project — tunnel forms are reused on the next job

On high-repetition projects the increase in the formwork line is offset by the reduction in time and labour, and the net result is usually favourable. With few repetitions it is the other way round.

The hybrid solution

In practice the most common third route is mixed use: typical floors are cast with tunnel formwork, while ground floor commercial areas, the roof level and asymmetric sections are cast with panel formwork. This covers the flexibility weakness of tunnel formwork. If a hybrid approach is planned, the interface detail with panel formwork must be considered while the tunnel set is being designed; improvised joints added later leave marks on the surface.

The structural side

A structure built with tunnel formwork is a wall-slab bearing system: no columns or beams, with high lateral stiffness. Panel formwork can build either a frame or a shear wall system. So the choice is not only a construction method but a structural system decision — it has to be taken together with the structural design. Formwork is not a detail chosen afterwards.

What we need to decide

When working out a formwork configuration for a project we ask for:

Typical floor plan, number of storeys and number of blocks
Wall thicknesses and storey height
Slab thickness
Crane make/capacity on site, or the planned crane
Target storey cycle in days
Concrete class, consistency and casting season

With those six items we can show, with figures, which system is economical.

In short

Tunnel formwork brings speed and surface quality; panel formwork brings flexibility and a lower entry cost. The threshold is the number of repetitions. In high-repetition housing production tunnel formwork almost always comes out ahead; for one-off work with variable layouts, panel formwork is the right call.