Frequently Asked Questions
This page answers some of the most common questions we've received, organized by their respective fields. If your question isn't included below, please reach out to us, and we will be happy to assist you.
Ground Penetrating Radar
Here, you will find answers to frequently asked questions about Ground Penetrating Radar (GPR). Since site conditions and project requirements are constantly changing, we strive to keep this section updated with the most relevant information.
What is Ground Penetrating Radar?
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Ground Penetrating Radar is a nondestructive method that uses radio waves or pulses to investigate and locate subsurface items.
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How deep can you see with Ground Penetrating Radar?
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While Ground Penetrating Radar is advertised to detect items up to 30 inches, however, its ability to fully penetrate the concrete is based on the number of embedded items in the slab, as well as the density and moisture content of the concrete.
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Can you scan walls with Ground Penetrating Radar?
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Yes, Ground Penetrating Radar can scan walls and other vertical surfaces to locate embedded items within.
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The concrete is 24 inches thick; can I still use Ground Penetrating Radar?
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Yes, our equipment can locate items up to 30 inches in one direction. If the slab contains a lot of embedded items, the equipment may not penetrate the full 30 inches. In these cases, we would scan to the greatest depth on one side of the concrete and then scan from the opposite side. This requires access to the other side of the concrete and the exit point of the penetration must be marked so scanning is completed in the right area.
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How accurate is Ground Penetrating Radar?
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Ground Penetrating Radar can be an extremely accurate method to investigate concrete. We've found it to be within 1/2 inch of accuracy when locating the center of objects and their depth. The accuracy is heavily based on the data acquired from the equipment combined with the site conditions. Dense or moist concrete will produce less accurate results that concrete that is dry.
Is Ground Penetrating Radar safe to use around people?
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Yes, Ground Penetrating Radar is a noninvasive method that uses radio waves or pulses to investigate and locate subsurface items. GPR does does not produce radiation or byproducts during its use and presents no dangers to the general public or workers.
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Industrial Radiography
This section addresses common questions we receive regarding Industrial Radiography (XRay). As projects and requirements frequently evolve, we make an effort to update this section whenever new and unique questions arise.
What is Industrial Radiography (XRay)
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Industrial Radiography is a nondestructive testing method that uses ionizing radiation to examine and inspect materials to locate and identify defects or embedded items.
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The building won’t let me drill pilot holes; how can I locate the exit point below?
While pilot holes can be beneficial in locating the underside as well as confirming a slab thickness, we can understand the concern involved. Typically, it’s recommended GPR is completed before pilot holes can be drilled. This also helps find a clear area that can be XRayed instead of completing multiple exposures to find a clear area. If the building still doesn’t allow pilot holes, we recommend a Hilti PX10 Transpointer. This device works off magnetic fields and is non-invasive.
How many floors need evacuated?
We require the floor below your space to be completely vacant. We must manually check this ourselves, even if it is under escort. Unfortunately, we are unable to just take someone’s word that the floor is vacant. We would also prefer your space to be vacant, but at a minimum we will need 50 feet around the area being XRayed.
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The tenant below requires escorted access, can you make an exception?
Due to federal regulations, we are unable to allow any members of the unmonitored public to be around when XRays are taking place. On occasion, we’ve been able to find an area that is safe for them to stand, but they are unable to follow us into radiation areas. In the past, tenants have monitored us using closed circuit video surveillance systems remotely.
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There are drywall ceilings below, how can we XRay?
We must have physical access to the underside of the slab. Any barrier between the source and the detector can produce inaccurate results and void the warranty, if any would be possible. An area, directly below the hole, should be cut in the drywall. We recommend an area two feet by two feet to allow for additional area to be XRayed if embedded items are located.
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Can you XRay through roofs?
Yes, but the roofing materials must be removed to the membrane. The detector must contact the surface of the concrete or tar membrane to produce accurate results.
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Can you XRay through a topping slab?
While it is possible to XRay through a topping slab, in our experience, the results are usually unusable. The air pocket and density changes between substrates attenuates the XRays, deeming the image useless.
Will you lay out my underside/exit points?
Due to the liabilities involved we do not complete underside layouts. Completing underside layouts also decreases our overall production. In the past, we completed underside layouts. Unfortunately, the time required to complete these layouts has had a negative effect on our scheduling. There isn’t an accurate way to determine the time needed to locate the undersides. This has resulted in our teams arriving late to other projects, the inability to complete projects in a single shift, and prevents us from scheduling multiple projects on the same shift. When underside layouts are
completed by the associated trades, obstructions and conflicts can be found and avoided.
There is foil insulation on the ceiling below, does this need to be removed?
The insulation can remain. However, if you marked the underside using the Hilti Transpointer, the marks are likely incorrect. The foil blocks the magnetic signal of the device, resulting in the layouts being off center by as much as 2 feet.
What’s the thickest concrete you can XRay?
This varies on the age, embedment, density, and moisture content. While we’ve had success in 22” in some cases, it’s an unknown parameter until we complete a test shot. We are confident in concrete up to 18” thick.
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Can you XRay anchors? Can you lay these out on the ceiling?
Yes, while every project is unique, the best method will be determined after reviewing the conditions. Sometimes the exposures are completed as normal, the results marked on the floor and then transposed onto the ceiling below.
My project is on the second floor. What can you do in these circumstances?
Depending on the foot traffic and nearby businesses, we may opt to complete the project at a later start time, in the middle of the week. Sometimes, the best option is to complete the XRaying inverted. Unfortunately, this requires a lot more preparation and coordination. In this case, it’s best to complete a site review to determine the best method.
I am unable to complete XRay on my project for various reasons. What are my options?
There are multiple reasons that XRay cannot be completed on a project. While some are avoidable, others have no remedy. We recommend GPR and/or 3D GPR be completed if XRay cannot be done. In this case, we recommend all items located are avoided. We recommend drilling only be completed with a stop-box, so the power to the drill is tripped if the core encounters anything. As a last result, we recommend the areas be chipped or trenched, depending on the purpose of the penetration(s) needed.