Planning Tunnel Formwork for Mass Housing Projects

On mass housing projects the most expensive mistake is buying the wrong number of formwork sets. Too few and the structural works stretch out; too many and capital stands idle on site. The right number comes from a few simple calculations.

Start with three numbers

Total number of storeys — blocks × storeys
Target structural programme — the calendar from the works schedule
A realistic storey cycle — days from one storey pour to the next

The required number of sets follows:

Sets = (Total storeys × Storey cycle) ÷ Available working days

Example: 8 blocks × 12 storeys = 96 storeys. Storey cycle 2 days. Target 160 working days. (96 × 2) ÷ 160 = 1.2 → at least 2 sets, and 2–3 against programme pressure.

Is the cycle realistic?

Catalogues say "24-hour cycle"; on site the cycle is set by when the concrete reaches stripping strength:

Condition	Wait before stripping
Summer, C30, no heating	12–16 hours
Spring / autumn	16–24 hours
Winter, no heating	24–48 hours
Winter, heated covers	14–20 hours

On a programme that runs through winter, a 24-hour cycle will not hold without planned heating. Calculate the cycle separately for each season.

Crane capacity

A crane is a precondition for tunnel formwork. Check:

Weight of the heaviest piece — it can be reduced by splitting the form, but a split means a joint
Hook capacity at the furthest point — crane charts fall with radius; the critical figure is at the extreme
Lifts per cycle — every lift is calendar time
Number of cranes — on a multi-block site a single crane becomes the bottleneck

Give the crane make and capacity at the start of formwork design; piece weights are divided accordingly.

Block layout and formwork circulation

How the set moves between blocks is drawn at the outset:

Vertical circulation — finish one block, then move to the next. Simple, but time is lost dismantling for the crane.
Horizontal circulation — complete the same storey across blocks. Efficient for the crane, more complex logistically.

Horizontal circulation usually meets the same programme with fewer sets, provided the blocks share the same floor plan.

If the plan does not repeat

The economics of tunnel formwork depend on repetition. Where the project includes the following, a hybrid is set up:

Ground floor commercial areas → panel formwork
Roof level / terraces → panel formwork
Asymmetric blocks → separate set or panel formwork
Typical floors → tunnel formwork

If working hybrid, the interface detail between tunnel and panel formwork must be resolved in advance; improvised joints leave marks on the face.

Bottlenecks outside the formwork

Buying the right number of sets is not enough on its own. Other items that block the cycle:

Reinforcement preparation — storey reinforcement must be ready while the form waits; mesh shortens the cycle
Concrete supply — do the m³ per storey and the pump output match the programme?
Service voids — electrical and plumbing boxes must be placed before the form closes
Labour — tunnel formwork needs a small but trained crew; allow for training in the first week

The first three storeys are slower

While the crew learns the system, early storeys run behind target. Build a learning allowance into the programme: take 1.5× the cycle for the first two or three storeys. A programme without it slips in the first month.

What we need for planning

To work out a formwork configuration for a project we look at:

Typical floor plan, storey height, wall thicknesses
Slab thickness
Number of blocks and storeys per block
Target structural programme and starting season
Crane make and capacity on site
Concrete class, consistency and pump output

From these, the number of sets, piece weights and the cycle plan are produced together.

In short

In mass housing, the formwork decision is not a purchasing item but a programme decision. Storey cycle, crane capacity and set count are interdependent; they have to be solved together, not separately.