One-side Formwork: 4 concepts to consider


Are you about to start a construction project, and you know that you have to build one-side walls, but you don’t quite know how to do it?

In this article we will try to explain what one-side formwork is, what are its characteristics, and above all what are the critical points to take into account when concreting a one-side wall.

What is One-Side Formwork?

One-side formwork is a construction technique used for concreting concrete walls when access to both sides of the wall is not feasible. This situation can arise in many scenarios, including the construction of retaining walls, tunnels, renovations where an existing structure impedes access, or the construction of basements and basement floors.

Operation of One-Side Formwork

Understanding how one-side formwork works is key to appreciate its versatility and its contribution to modern construction. This technique is based on the use of a system of formwork panels on only one side of the wall you are building with a supporting structure (‘bracket’) to transmit the pressure of the concrete to the ground.

The first stage of the process is the installation of the formwork panels, coupled with this structure, formed by metal ‘brackets’. Depending on the design and specifications of the wall, a suitable formwork system is selected and installed.

In all cases, these panels are secured with anchors or temporary supports to keep them in place during concrete pouring. The anchors are key elements since they support all the pressure of the concrete, preventing the formwork system from being lifted.

Once the formwork panels are in place, the concrete is poured. Here lies the uniqueness of one-side formwork: all concrete is poured from one side only. This requires careful planning and meticulous execution to ensure that the concrete is evenly distributed and reaches all parts of the formwork.

While the concrete cures, the formwork system needs to resist the pressure exerted by the concrete. This is a critical aspect of the process, as the strength and stability of the formwork determines the quality and safety of the final structure. Formwork systems, usually made of steel or aluminum, are designed to withstand this pressure.

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

In summary, the operation of one-side formwork involves a number of well-defined steps, from the installation of the formwork panels to the positioning of the anchors and the pouring of the concrete. Each step is key and helps to ensure that the one-side formwork technique is effective and safe.

Factors to Consider in One-Side Formwork: Adapting to Circumstances

When applying the formwork technique to a side, there are a number of key factors that must be taken into account to ensure an optimal result. Each project is unique, so it is key to tailor the approach to the specific circumstances.

Here are some of the most important aspects:

  • Concrete consistency: Concrete is the foundation of any one -side formwork project. Therefore, the consistency of the concrete is key. Concrete that is too fluid may generate excessive pressures in the formwork, while concrete that is too dry may not fill the formwork properly and lead to imperfections in the final structure.
  • Wall height: The height of the wall affects the pressure that the concrete exerts on the formwork. The higher it is, the higher the pressure. Therefore, formwork (and its anchors!) must be strong enough to withstand these pressures.
  • Pouring speed: The speed at which concrete is poured into the formwork can have a significant impact on the pressure exerted on the formwork. Pouring too fast can generate excessive pressures, while pouring too slow can cause the concrete to start hardening before the filling is completed.
  • Outside temperature: Temperature can affect the speed of concrete curing. In cold conditions, concrete may take longer to cure, which may require the formwork to remain in place longer. On the other hand, in hot conditions, concrete may cure faster than expected.
  • Wall thickness and reinforcement: The thickness of the wall and the reinforcement used can affect both the pressure exerted on the formwork and the amount of concrete required. It is key to take these characteristics into account when planning the project.
  • Correct vibrating of the concrete: Last but not least, the concrete must be properly vibrated to remove any air bubbles and ensure that it is evenly distributed in the formwork. However, excessive vibrating can cause segregation of the concrete, affecting the quality of the final wall.

These are just some of the many factors to consider when applying the formwork technique to a side. Proper planning and careful execution that is adapted to the specific circumstances of each project are essential to ensure the quality and safety of the final structure.

Anchor types

Anchors at the base of the formwork for one-side walls are essential to ensure the stability of the structure during the concrete pouring phase and during concrete curing. These anchors vary depending on the type of formwork used and the project specifications, but some of the common types of anchors are:

  • Standard anchors: They may include steel brackets or plates that are attached to the base of the formwork and firmly anchored to the foundation by means of pre-installed elements with embedded heads.
  • Screw anchors: They are large screws, similar to helicoids, which are screwed into the ground to provide a solid anchorage to the base of the formwork.
  • Chemical anchors: These are chemical materials such as epoxy resins or special cements that are injected into the soil or into specifically created boreholes to provide solid anchorage.
  • Geotechnical anchors: They are used in situations where soil stability is especially critical and include reinforced concrete piles or steel piles that are driven into the underlying soil.

It is important to always check the project plans and specifications to determine the most appropriate type of anchorage for the formwork being used and for the specific conditions of the construction site. Moreover, anchors must be properly dimensioned and installed correctly to ensure the safety and stability of the structure throughout the construction process.



One-side formwork is a key resource in modern construction. With its versatility and adaptability, this technique offers unique solutions to the challenges posed by different kinds of projects, from the construction of retaining walls and tunnels to the creation of basements or underground floors.

To ensure the safety and quality of the final structure, it is key to select high quality formwork materials and use appropriate techniques. Iron formwork, for example, is an excellent choice due to its strength and durability.

As we move into the future of construction, one-side formwork will continue to play an essential role in helping us build stronger, safer and more efficient structures.

Industrial Engineer and Technical Architect, with over 5 years' experience at Alsina, my main duties are oriented to the calculation of singular elements, technical assistance and development of new solutions.
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