One-Sided Wall Formwork: When to Use It and Why Planning Matters

Whether you're constructing a retaining wall, basement, tunnel or another below-ground structure, one-sided wall formwork provides an effective solution when access to both sides of a concrete wall simply isn't possible.

While the concept may appear straightforward, successful one-sided pours require careful engineering, quality equipment and experienced planning to ensure structural integrity, safety and an exceptional concrete finish.

Here's what you need to know.

What is One-Sided Wall Formwork?

Unlike conventional wall formwork, which is supported from both sides, one-sided wall formwork is designed for situations where only one face of the wall is accessible during construction.

This commonly occurs when constructing:

• Retaining walls

• Basement walls

• Underground structures

• Tunnels

• Lift shafts

• Walls built directly against existing structures or excavations

Because the opposite side cannot be accessed, the entire pressure created by freshly poured concrete must be resisted from one side alone.

This requires a specialised support system capable of transferring those loads safely into the foundation or supporting slab.

How Does One-Sided Formwork Work?

The system consists of robust formwork panels installed on the accessible side of the wall and supported by engineered steel A-Frame brackets.

Diagram of the loads on the concrete structure in one-side formwork.

These A-Frames absorb the significant lateral pressure generated by wet concrete and transfer those forces safely into the foundation through engineered anchor points.

The process generally follows four key stages:

1. Installation

Formwork panels are erected on the pour side of the wall and connected to the A-Frame support system. The configuration is designed to suit the wall height, thickness and engineering requirements.

2. Anchoring

The support system is securely fixed to the slab or foundation using engineered anchors. These anchors prevent movement, lifting or overturning as concrete pressure increases during the pour.

3. Concrete Placement

Concrete is poured from one side only. Careful sequencing and placement ensure the wall fills evenly while maintaining consistent pressure across the formwork.

4. Curing

Throughout the curing process, the formwork and support system continue carrying the concrete loads until sufficient strength has developed for safe stripping.

Choosing the Right Anchoring System

Every one-sided wall project is different, which means the anchoring solution must be selected to suit both the engineering design and site conditions.

Common options include:

• Foundation Anchors – Fixed directly into the slab or footing for high-load applications.

• Mechanical Screw Anchors – Suitable for lighter-duty applications where rapid installation is required.

• Chemical Anchors – Epoxy or resin-based systems used where drilling conditions require additional holding strength.

• Geotechnical Anchors – Used on complex projects where soil conditions require additional engineering support.

Selecting the correct anchoring system is critical to both safety and structural performance.

Seven Factors That Influence a Successful One-Sided Pour

Delivering a quality concrete wall involves far more than simply erecting formwork and pouring concrete.

Several variables must be carefully managed throughout construction.

Concrete Consistency

Concrete that is too fluid creates excessive pressure on the formwork, while concrete that is too stiff may not consolidate properly.

Achieving the correct mix design is essential.

Wall Height

As wall height increases, so does the pressure exerted on the formwork system.

Higher walls require stronger support structures and more robust anchoring solutions.

Pour Rate

The speed of the concrete pour directly affects formwork pressure.

Pouring too quickly can overload the support system, while pouring too slowly may lead to cold joints or inconsistent finishes.

Ambient Temperature

Temperature influences curing times and concrete behaviour.

Hot weather accelerates curing, while colder conditions slow strength development, requiring adjustments to both planning and scheduling.

Reinforcement and Wall Thickness

Heavier reinforcement and thicker walls influence concrete flow, placement techniques and formwork loading.

These factors should always be considered during the design stage.

Concrete Vibration

Proper vibration removes trapped air and ensures a dense, high-quality finish.

However, excessive vibration can cause segregation, reducing both strength and appearance.

Planning and Engineering

Perhaps the most important factor is planning.

Every one-sided wall should be engineered according to its unique loading conditions, construction sequence and site constraints.

When the correct formwork system is combined with careful planning and experienced installation, projects are completed more efficiently, more safely and with consistently high-quality results.

Why Choosing the Right Formwork Partner Matters

One-sided wall formwork is one of the most demanding applications in modern concrete construction.

Success depends on more than just equipment, it relies on experience, engineering knowledge and selecting the right solution for each project.

At Willis Construction Group, we work closely alongside Alsina, contractors, engineers and project teams to provide practical formwork solutions for challenging construction environments throughout New Zealand.

Whether you're building retaining walls, infrastructure, commercial developments or complex concrete structures, our team can help you select the right system to maximise safety, efficiency and project performance.

Planning a one-sided wall project? We'd be happy to discuss the best solution for your next build.