How is formwork used on floor slabs? 6 factors to take into account to choose correctly

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When beginning the concrete structure phase of any building project, whether residential or not, this is the time to ask ourselves: What is the best shoring system for floor slabs?

How to choose the best one? What factors should be taken into account?

The formwork market offers different floor slab systems and solutions, but what criteria should be taken into account when choosing the best system according to the project requirements?

To help you make this decision we have established 6 fundamental criteria:

 

1- Type of structure

Before choosing which system to use, it is important that you understand the type of structure that is being created, primarily analyzing the following factors:

The type of floor slabs and the height between floors.

The type of floor slab will give us the load when concreting, therefore determining the number of shores that must be used, both for the floor slab being concreted and for the ones below.

The height between floors is linked to the type of shores, taking the height and admissible load into account. This will also determine the correct formwork system, especially when dealing with larger heights.

In general, when you have a trusted formwork rental supplier, their technical department will identify the correct shores and the optimal system, taking the loads and the heights of the floor slabs into account.

2- Productivity

Each floor slab formwork system has an “associated productivity”, that is to say an amount of output for the time and labor used. For example, an interesting indicator could be the number of square meters formed every day by the same number of workers (generally a team of 4-5 people).

It is important to consider that the productivity may vary considerably depending on the training and/or experience of the workers who are erecting the system. Therefore, it is highly advisable to be present on the job site and do training, especially during the first days of assembly.

3- Volume/handling

Have you ever wondered about the transport cost associated with your floor slab formwork system, and how many crane maneuvers are required to move the different elements?

To compare the different systems from this perspective, we can compare the number of square meters of formwork transported by a trailer, or the number of pallets that need to be maneuvered per square meter. In this way we can assess the transport costs and the cost of using the crane, which is always useful in construction projects.

4- Partial stripping/re-forming

One basic element that should be considered when comparing different formwork systems is the possibility of recovering part or all of the formwork a few days after concreting.

Systems that allow for partial stripping (of which there are only a few) can generate great savings in terms of material and labor, eliminating the need re-shore the floor slab. It is important to perform an in-depth analysis of the cost impact €/m2 of the material that is shored under the slab.

 

5- Price

In price comparisons it is very important to stick to a single unit of measurement: generally the best measurement to evaluate is the €/m2/month.

You have to consider how many shored floors are included in the price (in addition to the floor being concreted), or in other words, the impact of the material that remains shored after stripping (point 4).

Finally, you have to check that the price corresponds to a list of materials that is in accordance with the surface area of the floor and the specific project. In some cases, the material budget provided by the supplier company will include a technical study in the form of a redesign.

6- Safety

The last, but certainly not the least important point, is job site safety. Every formwork system for floor slabs has built-in security measures that considerably reduce the risk of falling from heights (which is the most frequent cause of construction accidents).

It is important to verify that there are well-defined procedures for all assembly and disassembly operations, and that every person receives the devices necessary to be able to use them correctly.

By reducing risks as far as possible to ensure greater on-site worker safety represents a cost reduction for the construction company and improves its image. However, it is often thought of as an added cost. Luckily, this is now a much less frequent misconception.

To summarize, we have seen that choosing the right formwork system for floor slabs is an important factor in determining the productivity, cost effectiveness and safety of your project.

Don’t leave it to chance!

Engineer from the Alsina technical department who has been at the group for 13 years. His career has included projects at a national and international level, and he also boasts experience working for architecture and engineering firms.
Xavi Quer
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