Backshoring vs. Reshoring: Know the Difference
When filling forms, concrete shoring involves a system of vertical or inclined supports made of wood, metal, or similar materials. Once the formwork has been removed from the concrete slab, shoring functions as another structural element to deflect and support the weight while the concrete continues to cure. Both backshoring and reshoring look similar, but the difference involves when to use which type of shoring system. In order to maintain structural integrity and avoid potential collapse, you need to use the correct shoring systems to support the weight of newly poured concrete slabs. Knowing the different types of shoring systems and when to use which ones allows construction sites to keep projects safe and in accordance with necessary guidelines and regulations. Here’s what you need to know about the difference between backshoring and reshoring and how different types of concrete shoring apply to various construction projects.
Importance of Shoring Systems
During the concrete forming process, a construction may utilize different traditional forms or gang forms depending on the demands of the job site. Concrete gets poured into these forms, and the faces and framing allow the concrete a place to cure. Proper installation during concrete forming is one key aspect of establishing and maintaining structural integrity on the job site. Concrete forms are temporary structures that function like a mold for the concrete and get removed once the concrete hardens. However, shoring systems go in place next to help bear the load with the added weight of the poured concrete while it continues to strengthen. Shoring systems provide a temporary structure on construction sites to help bear the load of these newly poured slabs of concrete. Shoring systems can also be used to fix unstable walls, change existing walls, or construct new walls. The type of shoring system necessary for a project will depend on several variables, including the site location, proximity to other structures, the environment and weather conditions, and foundational structures. Once original shores are removed, along with the formwork, backshoring vs. reshoring comes into play.
What Is Backshoring?
Backshoring refers to when supports for forms are placed under a concrete slab stripped of its original formwork without allowing the newly formed slap to support its own weight or the weight of existing construction loads. Backshores are intended to have an initial load and be installed before any further stripping of original formwork occurs. When using backshoring, the formwork can be stripped at an earlier stage because of how the large areas of concrete do not need to carry their own weight. The first level of shores remain in place and in contact with the grade so that each tier of shores carries the weight of the loads above it, which can amount to several floors of concrete and construction. Backshoring systems are designed to function as temporary shores that prevent the slab from bending or deflecting under its own weight. Instead, the weight of the slab gets transferred down into the post-shores set by the backshoring system instead of any structural walls or columns in the building. Post shores and cured concrete slabs must be designed for higher loads when using a backshoring system to avoid failure of the slab formwork and falsework along the top of the structure.
What Is Reshoring?
Reshoring refers to when the formwork gets stripped from the concrete slab, and reshores are added beneath the slab or structural elements to deflect and support the weight. A reshoring system is designed so that the concrete slab supports its own weight and the weight of any previously constructed loads. Reshoring also depends on the concrete slab or other structural elements to effectively distribute weight, effectively causing the newly poured slab to work together with other cured concrete slabs to support the weight of new concrete forms. Once a concrete pour gains adequate strength, original shoring gets removed and reshoring is installed. Concrete shoring and reshoring use shores that fit snugly under the concrete slab, typically necessary for any slab that covers more than 10 feet. Keeping reshoring in place at grade levels allows for lessened accumulated shore loads because each slab carried its own weight before the concrete reshoring process began.
Differences Between Reshoring and Backshoring
The timeline for the removal of shoring systems differs depending on whether the project utilizes reshoring or backshoring. Reshoring must remain in place until the concrete slab or structural support beams have sufficient strength to support all current and future loads. However, backshoring only needs to remain in place on the first level in contact with the grade, as long as each tier of shores can carry the weight of the loads above it. The formwork can be stripped at an earlier stage with backshoring because the large areas of concrete do not need to carry their own weight with this system. But reshoring typically requires fewer levels, which frees up more area for other aspects of the project to continue.
When it comes to deciding between reshoring vs. backshoring for your site project, it is important to determine the type of load expected, the formwork required, and the timeline of the stripping process. Choosing backshoring vs. reshoring will impact whether you strip small areas or strip the entire bay and whether you allow the slab to deflect or not. Installation of backshores versus reshores also differs because backshoring gets installed before further stripping, while reshores can be installed without removing deflection. Backshoring involves an initial load, while reshoring does not have an initial load. Finally, it is important to determine whether the project calls for the slab to carry its own weight or not.
Find the Right Shoring System for Your Project
Work with Forming America for all your concrete forming and shoring equipment needs. Forming America offers reliable equipment from a reliable source, so you can get the job done with durable and effective equipment. At Forming America, we are a service-oriented supplier with experts in selling, renting, and renovating formwork and shoring systems. Contact us at Forming America to learn more about what shoring system is right for your project.