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WEST Builders conducts drone surveys to collect aerial data, enhance the site inspection process, and reduce risk in pouring concrete slabs

Construction firms across the world are bringing drones on-site to solve unique challenges and save time and money. For example, West Builders, a Bay Area general contractor, partnered with 3DR to use drones on-site while building The Aquatic, a four-story mixed use building in Berkeley, California. Together, we identified and implemented two important use cases for drones in this project: speeding up the inspection process and documenting the location of PT cables before pouring concrete.

The opportunity: faster inspections, better documentation

The current inspection process

Contractors frequently inspect the site prior to pouring concrete. They walk the area by foot, make observations and any necessary changes, confirm final layouts and placements, and then begin pouring. They also bring in a city inspector and a special inspector for a final review of rebar and embedded elements. Having accurate aerial data and documentation can help speed up the inspection process and clear up any misunderstandings on-site.

Concrete scanning for PT cables

Before pouring concrete slabs, subcontractors laid the rebar, cans, and PT (post-tension) cables needed in order to support the concrete. For those not familiar with concrete construction, PT cables are important because they enable thinner slabs of concrete to be poured, and allow for greater span lengths between support columns. They’re a vital part of modern concrete construction, with significant cost savings and greater flexibility.

Aerial imagery using drone surveys

However, Since PT cables are tensioned after the concrete is poured, it can cause significant damage if they get hit. Contractors occasionally need to drill, core, or chip concrete, depending on the need. They typically do so to fix the placement of a can, which sometimes are out of place when the concrete gets poured. This is costly and time-consuming enough, but they also run the risk of accidentally hitting a PT cable, which can cause major structural issues, safety risks, and costly delays.

To avoid this, some firms hire a concrete scanner before drilling in order to locate where the PT cables within the slab. However, this is a time consuming fix: concrete scanners typically have a 7 to 14 day lead time, and usually it takes a whole day to complete the scan.

Solutions

1. Pre-pour inspections with 3DR Site Scan

Pre-pour aerial inspections of PT cables

Pre-pour aerial inspections of PT cables

The WEST Builders team discovered that they could streamline their inspection workflow by using drones — and the data and analytics that drone software provides — to collect aerial data and photos and easily share them with various inspectors and other stakeholders. This helped them quickly get a bird’s eye view of their job site, and it enhanced their final inspections to ensure they avoided mistakes.

3DR worked with the construction team to use Site Scan numerous times, capturing imagery that enabled them to analyze the placement of PT cables and rebar on their map and overlay their original blueprint so they could see how placements compared to their initial plan:

PT Cable overlays using Site Scan

PT Cable overlays using Site Scan Manager

2. Post-pour PT cable documentation

The possibility of having to drill or core concrete creates a second key use case for aerial data: documentation of PT cables that can be referenced after the concrete has already been poured. This removes the need for using GPR or any sort of concrete scanning: WEST Builders captured detailed, high-resolution imagery that made it easy for them to document PT cables and know exactly where they would have to drill. The imagery from Site Scan can also be overlaid onto site plans and shop drawings, helping avoid costly errors and omissions in the field.

Significant savings, actionable aerial data

ROI with drones in concrete construction

By regularly collecting useful, actionable aerial data, WEST Builders has made their inspection process simpler and more efficient, and can also safely pour concrete without worrying about having to drill and accidentally hit PT cables. This helps them minimize risk along their critical path and save time and money on-site, from start to finish.