Making exposed concrete - you have these possibilities

At the beginning of the concrete construction, no thought was given to the design of the surfaces. Today, exposed concrete is becoming increasingly important - and there are countless design options for the surface. How to make exposed concrete and what is possible, this article reveals.

Exposed concrete and conventional concrete

In the manufacture of exposed concrete, two things are important: the right mix of concrete and the formwork. Conventional concrete can not be used as exposed concrete - it is not suitable for this purpose.

If you want to produce exposed concrete yourself, the following mixing ratio is recommended:

  • 2.5 kg of cement
  • 1.4 liters of water
  • 10 kg surcharge

Particularly important here is the so-called water-cement value (TM value). Especially with exposed concrete, the tool value should be as low as possible. We recommend a water to cement ratio of 0.6 or below.

When adding, it is important that as many fine grains are included. If the fines are too low, it may help to add some fine sand to the aggregate. However, the above-mentioned ratio between aggregate, cement and water should be kept as far as possible.

The formwork

As much scarf oil as possible should be used, but never more than the wood can absorb. For the formwork boards, they have the most significant influence on the structure of the surface.

Depending on how the formwork panels are pretreated and which formwork boards are used, different surface structures can be created.

surface design

There are numerous possibilities for the design of the exposed concrete surface. The washed-out concrete appearance is just one of them. Surfaces can also be textured with rubber matrices.

The use of OSB boards as shuttering boards also gives an impressive appearance. Various objects, such as leaves, can be placed under the formwork boards and thus create an interesting surface. Surfaces can then also be reworked - either by sandblasting or by stonemason treatment.

Tips & Tricks

Be creative when designing your exposed concrete surface - and be inspired by examples of successful designs.

Video Board: Board Formed Concrete - An Architect's Guide