It is often necessary to verify construction detail of structures. This could be to ensure compliance with current legislation and standards, proposed modifications, change of use, or simply part of a maintenance regime.
The following are all common scenarios:
- There are no as-built documents for an existing structure. Drawings may have been misplaced or not handed on with a change of ownership.
- The accuracy of as-built construction drawings is unknown.
- Drawings are marked as “Verify-in Field” (VIF).
- Older, historic buildings were often built by craftsmen using traditional construction methods. They used their knowledge to overcome construction difficulties. No records for these buildings are available.
Dimensional verification of drawings is fairly straightforward. For example, a topographic survey or 3D laser scanning will identify dimensional mistakes and variabilities.
But what about the hidden construction detail? How can you determine that without using destructive techniques?
Using GPR to verify construction detail
Ground Penetrating Radar (GPR) can be used to determine or verify construction detail.
GPR detects changes in the sub-surface; therefore, it is not limited to detecting only metallic objects. It offers a rapid means of obtaining subsurface information from a variety of materials used in the construction industry. Examples include concrete, brick, masonry, wood, asphalt and soil. Furthermore, GPR is a non-destructive (NDT) survey method, it makes no noise and emits no odour. It can be used on construction sites or in occupied buildings. Because it is non-intrusive, it is ideal for historic or listed buildings.
The following are just some of the ways GPR can help determine or verify construction detail:
Concrete floor slab surveys
GPR can determine general slab construction detail. Examples include slab thickness, reinforcement distribution and adequate mesh overlap. It can also detect variations in construction detail and determine the position of ground beams and pile caps.
Find out more about concrete floor slab surveys.
Locating Tendon Ducts
GPR has a greater penetration depth and better resolution than many other techniques. Therefore, it is effective in locating tendons and confirming they are positioned as per drawings.
Find out more about locating tendon ducts.
GPR offers excellent rebar mapping and concrete imaging to depths of 400mm (depends on the density of reinforcing steel). It is suitable for scanning smaller areas, such as beams or columns, or large areas, such as floor slabs.
Locating embedded metal in masonry
Buildings are often strengthened using embedded steel. GPR can confirm the presence of structural steel members and determine their location and orientation. It can also detect metal dowels, pins and cramps.
Find out more about locating embedded metal in masonry.
GPR can locate voids beneath slabs, basements and pavements. It can also identify construction elements which incorporate voids such as hollow pot slab construction and hollow-core precast units.
More about void location surveys.
I have never seen as-built drawings showing chimney flue locations. However, architects and engineers often need this information. Are chimney flues present? In which walls? Where do they go?
Find out more about chimney flue location.
GPR detects layer interfaces in construction. It can determine the thickness of slabs, screed, asphalt, brick walls, retaining walls, etc. Variations in thickness and construction can also be detected and mapped.
Find out more about wall and slab thickness measurement surveys.
GPR can determine the plan view geometry of foundations such as pad foundations and pile caps.
Find out more about using GPR to locate and investigate foundations.
The above list includes some of the more popular examples of using GPR to verify construction detail. It is by no means exhaustive.
In the hands of an experienced surveyor, GPR is an efficient and cost-effective method for the determination and verification of construction detail. Most significantly it detects metallic and non-metallic objects and changes in the sub-surface. It also determines depths and thicknesses.
For more information about the GPR surveys we offer, see Ground Penetrating Radar Surveys.
We would love to hear from you. For further information please contact us to discuss your requirements. Above all, find out more about how GPR could help you. If required, we will happily provide a no-obligation quotation.