Visual inspection and defect survey

The visual inspection of a building or structure is one of the first steps of an investigation, before which a desktop study to obtain drawings or any other information may be appropriate. A desktop study will enable the survey to be planned in advance, drawing prepared and the survey undertaken using a standard system for recording and measuring of the concrete defects. Guidance is given in the Concrete Society Publication; Diagnosis of Deterioration in Concrete Structures - Identification of defects, evaluation and development of remedial action TR54.

Visual inspection is one of the most versatile and powerful tools to evaluate the condition of a concrete structure. Visual inspection can provide detailed information that may lead to positive identification of the cause of patent distress. Its effectiveness depends on the knowledge and experience of the inspection team and knowledge of structural design, concrete technology, and likely construction methods. This will help the findings obtained from the visual survey of a concrete structure to be fully appreciated, whether it is a floor slab or motorway bridge.

Other than obviously an experienced eye, a camera measuring instrument and note book are required to record defect type and size. Binoculars may be needed if close access cannot be afforded. Optical magnification may allow a more detailed view of local areas of distress. A very useful tool for crack inspection is a small hand-held magnifier with a built-in measuring scale.

A detailed survey should record every defect seen on the concrete surface. The aim of the visual survey is to determine how extensive the defects are and the likely cause of defects. A visual survey is normally only one part of a full concrete condition survey, where testing is used to confirm the cause of patent deterioration and investigate evidence for latent defects.